LEIDSE Deel GEOLOGISCHE MEDEDELINGEN, 46, Aflevering 2, pp. 157-235, 17-2-1971

Three Upper Carboniferous, limestone-rich, high-destructive,

delta systems with submarine fan deposits, Cantabrian Mountains,

Spain

BY

W.J.E. van de Graaff

Abstract

Cantabrian northwestern Carboniferous In the eastern part of the Mountains, Spain, Upper strata crop out. In the Pisuerga

Moscovian limestone-rich is in number of structural units. Correlations area an Upper (≈ Westphalian D) sequence exposed a

between the various structural units are based on lithostratigraphic characteristics and paleontological dating with fusulinids

and calcareous algae. The various limestone units show rapid lateral transitions into siliciclastic deposits. The siliciclastic deposits

deltaic are mainly interpreted as deposits.

Three distinct delta like the Rhône all of the systems are distinguished which, recent delta, are wave-dominated, high-destruc- associated with turbidite which indicates that the delta tive type. The oldest delta system is important deposits, prograded into

The second delta is associated with minor but is relatively deep water (i.e. ≥ 125 m). system only turbiditesequences relatively To the NW marine rich in coals. These two delta systems prograded from approximately SW to NE. open deposits with lime-

stones were formed, to the NE fine-grained shelf deposits and limestones were deposited. After deposition of the second delta

of the caused formation of the In system, tectonic tilting in the southwestern part area Vergaño disconformity. the remainder

this level be In the northeastern of the of the area can recognized as a deepeningor transgressive sequence. part area important

slumping movements were caused by the tectonic movements.

this the river the delta diverted another and the ofsiliciclastic After tilting forming was to area only source sediments was a

drift The existence of such drift is the of arenitic competent longshore system. a longshore system proved by presence quartz

pebbles and cobbles in compositionally mature sandstones, as the deltaic deposits do not contain such coarse siliciclastics and

are furthermore of lithic arenitic composition. During this period a zone with shallow marine deposits in the southwestern part

be from submarine and fan in the southern and northeastern of the area can distinguished canyon deposits (turbidites) parts

of the area. The third wave-dominated, high-destructive delta system prograded from SW to NE over these deposits. Open

shelf the NW and NE. After of the third delta marine, shelf and slope deposits are again present to deposition system the

Leonian rise the Leonian and basin resulted. phase gave to disconformity, a new configuration

the interval studied basin to the southwest of the studied be inferred from the facies distributions. The In a margin area can

is of which the from the remainder of the presence proved a synsedimentary fault, separates present Casavegas Syncline area.

This fault influenced thickness and had but little effect the facies distributions. mainly distributions, upon

The limestones in wide of i.e. shelf. The lateral into were deposited a range environments, lagoonal to open rapid transitions

formed in shallower coarse siliciclastics are interpreted as indicating that the limestones were slightly water than the surrounding

siliciclastics. with the the absence of framework and the of all kinds of Together generally muddy character, an organic presence

limestones bank algae, this indicates that the are biogenetic deposits.

The data collected have led to a redefinition of the Vañes Formation and to replacement of the Sierra Corisa Formation by

the Vergaño and Covarres Formations.

Sumario

En la oriental de la Cordillera Cantábrica al Carbonífero En la del parte afloran rocas pertenecientes superior. región Pisuerga edad existe una serie rica en calizas expuesta en distintas unidades estructurales, de Moscoviense superior (≈ Westfaliense D).

Las unidades estructurales basan características dataciones correlaciones entre estas se en litoestratigráficas y en paleontológicas

medio de calcáreas. Las distintas unidades de calizas transiciones laterales por fusulínidas y algas muestran unas rápidas a

depósitos siliciclásticos. Estos últimos han sido interpretados como sedimentos deltaicos.

Se 3 sistemas deltaicos el delta reciente del del dominado el distinguen que, por analogíacon Ródano, son tipo destructivo, por

El sistema deltaico asociado de lo indica el delta ha avanzado oleaje. mas viejo esta a depósitos importantes turbiditas, que que

hacia relativamente En el sistema deltaico turbiditas solamente aguas profundas (≥ 125 m). segundo estas se encuentran esporá-

dicamente, habiendo una abundancia relativamente grande de estratos de carbón. Estos dos sistemas de delta han avanzado

del al En el fueron formados marinos mientras hacia el aproximadamente suroeste noreste. noroeste depósitos con calizas, que

fueron sedimentos de fino calizas. la del deltaico noreste depositados shelf de grano y Despues de deposición segundo sistema

se produjo un basculamientode la parte suroccidental de la región, formándose la disconformidad de Vergaño. En el resto

de la región este nivel puede ser reconocido como unasecuencia transgresiva ode profundización. Hacia el noreste movimientos

tectónicos dieron lugar a la formación de importantes slumps.

del basculamiento el río formaba el delta sedesvió hacia lo los sedimentos siliciclásticos fueron Después que otra región, por que

sistema de corrientes rumbo la La existencia de tal sistema de corrientes de- abastecidos por un con un paralelo a costa. se 158 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

la de cuarzo-areníticos areniscas de mientras muestra por presencia cantos y bloques en composición madura, que los depósitos

deltaicos contienen tales sedimentos siliciclásticos de además de lítica-arenítica. Durante no grano grueso y son composición

se una zona con marinos en la suroccidental de la de- este periodo pueden distinguir depósitos poco profundos parte región y

de cañones submarinos hacia el el El deltaico pósitos y aluviones (turbiditas) que se encuentran sur y noreste. tercer sistema cubriendo últimos desde el hacia el dándose condiciones marinas abiertas de ladera avanzó, estos depósitos, suroeste noreste, y

de la fase Leonesa la dis- shelf en el noroeste y el noreste. Después de la deposición del tercer sistema deltaico dió origen a

de lo resultó de la sedimentaria. conformidadLeonesa, que una nueva configuración cuenca

En el intervalo ha de las distribuciones de facies la existencia de de locali- estudiado se podido deducir un margen cuenca,

zado hacia el de la de estudio. demuestra la de falla el suroeste región Igualmente se presencia una sinsedimentaria, que separa actual sinclinal de del resto de la Esta falla dio a los sedimentarios Casavegas región. principalmente lugar espesores pero tuvo

efecto sobre las distribuciones de facies. poco

Las calizas fueron depositadasen una escala amplia de medios ambientales, desde lagunas hasta un shelf abierto. Las rápidas

laterales siliciclásticas de han sido las calizas fueron transiciones a rocas grano grueso interpretadas como una indicación que

Su la ausencia de construcción formadas en aguas un poco menos profundas que aquellas. carácter generalmente fangoso, una

la de todos los de indican las calizas bancos orgánica y presencia tipos algas, que son biogenéticos.

Los datos han conducido redefinición de la Formación de Vañes de la Formación de Sierra recogidos a una y a un reemplazo

Corisa las Formaciones de Covarres. por Vergaño y

Samenvatting

In het oostelijk deel van het Kantabrisch Gebergte, noordwest Spanje, zijn sedimenten van bovenkarbonische ouderdom goed

ontsloten. In het Pisuerga-gebied is een kalkrijke opeenvolging van Boven Moscovien ouderdom (≈ Westfalien D) aanwezig

in aantal anticlinalen. verschillende structurele eenheden litho- een synchnalen en Correlaties tussen de zijn gebaseerd op

kenmerken fusuliniden De verschillende kalk- stratigrafische en op paleontologische dateringen met behulp van en kalkalgen.

siliciklastische sedimenten. Deze siliciklastische sedimenten afzettingen vertonen vrij abrupte overgangen naar zijn grotendeels afgezet in deltaische milieus.

Drie verschillende deltasystemen zijn te onderscheiden welke, net zoals de recente Rhône delta, van het door golfwerking

gedomineerde,sterk destructieve type zijn. Het oudste deltasysteem is geassocieerd met belangrijke turbidietafzettingen wat dat de delta werd in relatief Het tweede is minder er op wijst gevormd diep water (≥ 125 m). deltasysteem met belangrijke

turbidietafzettingen geassociëerd, maar is relatief rijk aan kolen. Deze twee deltasystemen groeiden van het zuidwesten naar het

In het noordwesten werden kalken mariene in het noordoosten noordoosten toe aan. en ondiep afzettingen gevormd en even-

tesamen met “shelf” Na de het tweede werd in het eenskalken, maar daar fijnkorreligere sedimenten. afzetting van deltasysteem

de delen zuidwestelijke deel vanhet gebied Vergaño-disconformiteit gevormd als gevolg van tektonische opheffing. In andere van

bestudeerde kan niveau herkend worden als of wordende In het het gebied dit een transgressieve dieper sequentie. noordoostelijke

deel van het gebied hadden deze tektonische bewegingen het afglijden van dikke kalklichamen ten gevolge. de rivier die de delta had andere siliciklastische sedimenten Na deze tektonische bewegingen volgde gevormd een loop, en

werden enkel door De kwartsarenietische in toen aangevoerd een stranddriftsysteem. aanwezigheid van rolstenen, qua samen-

stelling rijpe zandstenen, bewijst dat een dergelijke stranddrift bestaan heeft daar in de onderliggende deltaïsche afzettingen

bestanddelen ontbreken de zandstenen bovendien lithies arenietische hebben. dergelijke grove en een samenstelling Gedurende

deze periode werden in het zuidwestelijke deel van het gebied ondiep mariene sedimenten afgezet, terwijl in het zuiden, midden submariene waaier werden en noordoosten canyon en afzettingen (turbidieten) gevormd.

Het derde, door golfwerking gedomineerde,sterk destructieve deltasysteem dat deze afzettingen bedekt, groeide, net zoals de

zuidwest noordoost aan. In het noordwesten en noordoosten werden twee eerste systemen, van naar toe weer ondiep mariene,

“shelf” en “shelf slope” sedimenten afgezet. Na de vorming van dit derde deltasysteem werd ten gevolge van tektonische be- die worden de deze vormde wegingen, aan de Leonese fase toegeschreven, Leonese disconformiteit gevormd. Na bewegingen

zich een nieuw sedimentair bekken.

bestudeerde De verspreiding van de diverse faciëstypen geeft aan dat ten tijde van de afzetting van het sedimentpakket, er

De die de een bekkenrand ten zuidwesten van het bestudeerde gebied lag. aanwezigheid van een synsedimentaire breuk,

huidige Casavegas Synclinale van de rest van het gebied scheidde, wordt aannemelijk gemaakt. Deze breuk beinvloedde voor-

de diktes het bestudeerde had slechts invloed de de namelijk van pakket en geringe op verspreiding van faciëstypen.

De kalken werden in aantal verschillende milieus Deze milieus variëerden marien. een groot afgezet. van lagunair tot open

De snelle sedimenten worden als dat de kalken in iets overgangen naar siliciklastische geïnterpreteerd een aanwijzing ondieper

water werden dan de siliciklastika. met het kwantitatief aandeel van kalk- gevormd aangrenzende Tesamen zeer belangrijke

modder, het ontbreken van een organisch rifgeraamte en de aanwezigheid van vele soorten algen in vaak grote hoeveelheden,

de de kalken als geven deze snelle overgangen aanleiding tot interpretatie van biogenetische bankafzettingen.

de verzamelde bleek het Vafies Sierra Op grond van gegevens wenselijk om de Formatie opnieuw te definiëren, de naam

Corisa Formatie te laten vervallen en de namen Covarres Formatie enVergaño Formatie in te voeren. Contents 159

Contents

160 VI - in I. Introduction Facies group deposits formed (migra-

160 channels 180 General aspects of the Cantabrian Mountains. . ting)

161 Facies VII - and marine Subject of study group deltaic regres-

Previous work the 161 sive 180 on Pisuerga area sequences

interval 161 Facies VIII - 181 Selection and delimitation of studied. . group transgressive sequences . .

used 163 Facies IX - karst 181 Petrographic classification systems .... group infillings

164 Facies X - marine limestones Methods and techniques used group .... 182 Acknowledgements 165 IV. Areal interpretation of lateral and vertical facies

II. Facies descriptions 165 relations 186

South flank of the Castilleria 186 Introduction 165 Syncline .... - Facies I arenites 165 Anticlinorium west of the group graded Verdegosa-Verdiana

Facies II - contorted and fault 192 group fragmented Tremaya sediments 168 Verdegosa-Verdiana Anticlinorium between the and Redondo faults 194 Facies III - siliciclastics 170 group fine-grained . Tremaya

Facies IV - and 194 group commonly rippled Casavegas Syncline cross-bedded siliciclastics . 170 Redondo Syncline 195

with Facies V - siliciclastics group plant rootlets 171 V. Regional interpretation of the observed facies

basin and VI - siliciclastic fill Facies group fining upwards distributions, history comparisons

171 with other delta 199 sequences systems

facies 200 Facies VII - group coarsening upwards se- Qualitative maps 172 Paleogeographic synthesis 204 quences

Facies VIII - Paleocurrent directions 204 group fining upwards sequences with marine fossils and little Provenance of the sediment 204

173 Differential subsidence and basin ... 205 or no cross-bedding margins . . .

Facies IX - arenites on eroded sedimentation 206 group quartz Cyclic

limestones 173 Limestones and their relation to the siliciclastic

206 Facies X - limestones 174 group deposits Comparisons with recent and ancient examples . 207

III. Individual facies interpretations 176 Introduction 176 VI. Lithostratigraphic nomenclature 209

Vanes Formation 210 Facies I - turbidites 176 group 210 Facies II - and mudflow Formation group slump de- Vergano

posits 177 Covarres Formation 211

Facies III - siliciclastics group fine-grained which formed in quiet References 212

waters 178

Facies IV - in group siliciclastics deposited Plates I to IX agitated waters 179

Facies V - with autochtho- group deposits

nous 179 Enclosures 1 to 5 back plant growth .... (in flap) W. J. E. van de Graaff.: Three Upper Carboniferous delta systems, Spain

CHAPTER I

INTRODUCTION

GENERAL ASPECTS OF THE CANTABRIAN A synthesis of the development of the Variscan

MOUNTAINS of which the Cantabrian orogene, present Mountains Cantabrian Mountains in the north of form Matte The Spain only a part, was given by (1968). Wagner

consist of Paleozoic bordered in the and in a outline of Carboniferous a core, east (1970) presented general the south by Mesozoic and Cainozoic deposits. In the stratigraphy in this area. there is transition into the and For of it is sufficient west a Cryptozoic purposes a general background Variscan igneous and metamorphic rocks of Galicia. to state that from the Lower Cambrian until theend of

the Devonian, sedimentationin this area was typical of

a stable shelf environment. Formations can be traced

over tens to hundreds ofkilometres and most sediments

are evidently shallow water deposits. This entire

sedimentary pile has a thickness in the order of 2 to 3

km.

Towards the end of the Devonian, uplift and erosion

(de Sitter, 1965; van Adrichem Boogaert, 1967),

resulted in an important hiatus in the central Asturian and of the line. This area along part Leon uplift was followed another of uniform sedimenta- by period very

tion during which limestones were deposited in most of the Cantabrian Mountains. of northwest Fig. 1. Index map Spain. This relatively uniform picture changed drastically Their is due present topographic expression mainly to during the lower and middle Westphalian, when the

an uplift during the Cainozoic (de Sitter & Boschma, important Curavacas folding phase (Palentian phase of

1966). Wagner & Wagner-Gentis, 1963) occurred. The

Fig. 2. Approximate distribution of preserved Upper Carboniferous strata in the Cantabrian Mountains. Lower Carboniferous and older deposits not differentiated. Modified after de Sitter (1965) and Wagner (1970). Introduction 161

sediments deposited after these tectonic movements are statements on fades associations and their distribution, turbidite partly preserved in a number of so-called "basins" but concentrated on a statistical analysis of These "basins" The latter detailed (de Sitter, 1965). (Fig. 2) are mainly sequences. presented descriptions

tectonic units which are merely fragments of the and interpretations of sedimentary facies but, in view

originally much more extensive sedimentary basins. of the nature of his study, was unable to give aregional

These Upper Carboniferous sediments contrast interpretation of their distribution. Such an inter-

strongly with the earlier ones in that they are typified pretation, however, was attempted by van de Graaff lateral and vertical and their In the other views by great variability by (1970a). papers mentioned, on great thickness. The Westphalian alone, for instance, is stratigraphical relationships and basin development in thick the also over 4000 m in many places. Pisuerga area are presented.

STUDY SUBJECT OF SELECTION AND DELIMITATION OF INTERVAL

STUDIED In these Westphalian deposits marine and non-marine

strata show rapid lateral and vertical transitions into With the published paleontological data available it

one another. In the marine of the select the Moscovian parts sequences was possible to Upper («West-

limestones are common. Some of these limestones can phalian D) strata as the most promising deposits for be traced for several kilometres; others, however, studying the relationships between siliciclastics and

out with siliciclastic abruptly wedge or interfinger limestones. The reasons for this choice were: (1) the

deposits. Isolated lenses, sometimes forming a distinct relative abundance of limestones, (2) the abundant

band, may also occur. The cause(s) of these irregulari- fusulinids and calcareous algae which permit regional ties in the limestone the deposits was (were) original correlations to be quite reliable, (3) the paucity of of this It realized that these ofthe subject study. was soon structural complications outside the central part

could not be understood unless the limestones causes area.

were studied together with the surrounding siliciclastics The approximate distribution and general tectonic which on a regional scale. The Pisuerga area, from setting of the Upper Moscovian deposits is shown in

data were was with the of the published paleontological available, Figure 3 together names respective selected for this study. limestone members.

The lower boundary of the interval studied was

taken at a black shale/mudstone horizon below the PREVIOUS WORK ON THE PISUERGA AREA Socavon and Camasobres Limestone Members. This

The forms the of the is well and to Pisuerga area easternmost part shale/mudstone mappable appears

Paleozoic core of the Cantabrian Mountains (Fig. 2). occupy a relatively constant position in the sequence. General the base of aspects ofthis area were discussed by de Sitter For two reasons the base was not taken at & Boschma Their and constituted the Socavon Limestone Member.First of all because of (1966). map paper useful basis for the the Socavon a present study. Paleontological the interesting facies sequences below data of correlations between which for the permitting stratigraphic Limestone Member, are very important the various structural units have been of the entire because of published by interpretation area. Secondly Ginkel Limestone van (fusulinids, 1959, 1965), Wagner (continen- the discontinuous nature of the Socavon tal floras, 1955, 1960, 1962, 1966) andRacz (calcareous Member, whereas the black shale/mudstone is easy to corals studied de is algae, 1966). Rugose were by Groot trace. Probably the same black shale/mudstone but did data. below Member. (1963), not yield significant stratigraphic present the Agujas Limestone

With view to it should be mentioned Because of section in the a completeness poor exposure, measuring that of the work on continental floras (Wagner, Sheffield), Redondo Syncline was usually begun at the base brachiopods (Winkler Prins, Leiden), conodonts limestone itself. A few of the sections depicted in

(Varker, Leeds), fusulinids (van Ginkel, Leiden), Enclosures 1 and 2 begin below the black shale/ and lamelli- horizon This goniatites (Wagner-Gentis, Sheffield) mudstone (Sections 1, 4, 11, 15). was

to branchs (van Amerom, Heerlen) from this area is still done in order include evidence of lithostratigraphic in progress. As most of these studies are concentrated correlations with the Redondo area. need here. In The of the interval studied on younger deposits they not concern us upper boundary was described the near future theirwork may nevertheless give rise to drawn at the Leonian disconformity, as by further refinements & Winkler Prins and & of correlations in the upper part of Wagner (1970) Wagner Graaff the interval studied. Varker (1970) and accepted by van de (1970a). Other first described Nederlof important papers on the Pisuerga area are by This disconformity was by best Brouwer & van Ginkel (1964), Frets (1965), Nederlof (1959) as a local diastem. Although it is exposed Cabra Mocha hill be & de Sitter (1957), Nederlof (1959), Wagner & SE of the (Section 3) it can

Wagner-Gentis (1963), Wagner & Winkler Prins traced around most of the Castilleria Syncline. The surface (1970), Wagner & Varker (1970) and Reading (1970). locally very irregular disconformity is in most covered well washed and well sorted Of these papers only the ones by Nederlof (1959) and places by quartz of arenites. A seatearth is sometimes in this Reading (1970) attempt an analysis sedimentary present facies. The former author made a number of general sandstone. In the central part of the area the presence 162 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

Fig. 3. Approximate distribution of Upper Moscovian strata in the Pisuerga area. Introduction 163

of such arenitic sandstone it is wellabove the a mature quartz at ap- a true unconformity upper boundary

proximately the presumed horizon in the succession is of the interval studied as defined here.

considered to indicate the disconformity. In the

Casavegas Syncline no clear disconformity was PETROGRAPHIC CLASSIFICATION SYSTEMS

observed, with the possible exception ofSection 11. In USED

this area Wagner & Varker (1970) place the dis- Gilbert's (1954) sandstone classification is used in an conformity at the level ofsome limestone breccias just adapted form as proposed by Dott (1966). As Dun- above the Maldrigo Limestone Member. In the ham's (1962)' classification is used for the carbonates, Redondo Syncline there is a very good exposure of the confusion occur owing to the similarity in the the may disconformity at location at Section 25, but more terminology. In Figure 4 the two classification systems to the north it cannot be traced. The upper boundary are compared. As it only makes sense to compare of the interval studied is there placed at the top of the clastic sediments, boundstones and crystalline car- Abismo Limestone Member or its correlatives. The bonates are omitted from this comparison. correctness of this is indicated by the presence of a A major difference between siliciclastic and cal- reworked tuff a few tens of metres above a lens of the ciclastic sediments is the extrabasinal origin of the Abismo Limestone Member in Section 21. This tuff is former and generally intrabasinal origin of the latter. compositionally very similar to a sill occurring in This intrabasinal origin makes it rather meaningless to Section 3 (447-450 m - not depicted). Although this is consider compositional maturity in addition to a sill and extrusive rock it correlation not an suggests a textural maturity when studying calciclastic instead of between Sections 3 and 21 which was already pre- siliciclastic sediments. For this reason the mud content, sumed by Wagner & Varker (1970) on the basis of the i.e. the textural maturity, is the basis of Dunham's paleontological data. classification. It should be noted here that I do not follow de

Dunham (1962) uses the name grainstone for mud- Sitter & Boschma (1966) in their contention that their free calciclastic sediments. According to him a cal- Figure 7 (p. 214) represents a true unconformity (the Yuso-Cea San Cristobal I unconformity at hill). agree

with Wagner & Winkler Prins (1970) that it is more be fault Which likely to a contact. interpretation i is may In a few cases the name according to Folk (1959, 1962)

be correct is, however, quite immaterial, for even ifit is also used.

Fig. 4. Comparison of the classifications of Gilbert (1954) and Dunham (1962). 164 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

carenite should be called a packstone if containing reliance on measured sections for an understanding of

more than 1% mud. Compared with the 10% matrix the stratigraphic problems in the interval studied, be in Gilbert's arenites the This which may present or up to some mapping had to be done. was partly done matrix which in scale of ofsheets 5% may occur Pettijohn's (1957, p. on enlargements at a 1:10,000 81, 82, this 296) orthoquartzites, 1% boundary seems too 106 and 107 of the Mapa de Espana 1:50,000. As strict. A line is The division these of rather 5% boundary suggested. maps are poor quality, most of the between grain-supported and mud-supported elastics mapping was carried out on aerial photographs with in Gilbert's classification. This has no equivalent an approximate scale of 1:27,000. Control points and be the of boundaries in ofthe boundary cannot accurately fixed, as shape geological most parts area studied

the has influence on the maximum indicated these in the field. The particles so great an were on photographs of sediment. For porosity grain-supported randomly photogeologic map was then projected on the topo- this should be of sketch packed spheres (e.g. oolites) boundary graphical map by means a master. The about mud. For fossiliferous set at 40% some sediments, resulting map at a scale of 1:25,000 was reduced and

however, it might be set at 70 to 80% mud (Dunham, simplified to the form shown in Enclosure 3. ofthis 1962, Plate II). Because variability the boundary Sections were logged at scales varying from 1:10 to is drawn in full line in the The not diagram. boundary 1:1000. The scale used depended on the amount of

between wackestones and mudstones is arbitrarily variation in the interval measured and on whether

taken at facies 10% grains. fundamentally new types were present or not. In

It is obvious from the foregoing that Gilbert's order to save time and to standardize data collecting, wackes the siliciclastic of of the check are equivalents most lists were used when measuring limestones and

packstones andwackestones. The siliciclasticmudstones turbidite sequences. both and mudstones comprise wackestones as Dott Sampling was directed at obtaining representative

(1966) arbitrarily takes the wackes-mudstones bound- samples ofthe coarse siliciclastics and of the limestones.

at Shales and mudstones At ary 25% grains. were neglected. an early

stage in the survey, sampling was relatively intensive limestone clasts the siliciclastics for sections. This done in order Influence of on classification of some was to verify

In Gilbert's classification the abundance of unstable field descriptions of the lithologies. Later, fewer

samples were considered sufficient to check field fragments determines the relative compositional descriptions. maturity of the sediment. Limestone clasts are in

In total about a thousand thin sections were a studied, general very unstable, and ifpresent in sandstone it

halfof which were from limestones. In addition about should, for instance, be classified as a lithic arenite.

a hundred acetate peels and polished surfaces were This is, however, misleading, as the limestone clasts made of limestone of the limestone are commonly of intrabasinal origin. In the area samples. Staining with Alizarine Red-S distin- studied this intrabasinal be samples was helpful in origin can commonly guishing between calcite and dolomite. The relative proved. For this reason the compositional maturity of ofthe various of the limestones sandstones is determined without counting the lime- proportions components estimated with the clasts were aid of charts. The stone present. percentage

composition of the siliciclastics, however, was deter-

mined Three hundred Further remarks by point counting. points per

thin section were counted for over 90 representative The mudstone term will be used in this paper for those samples. siliciclastic deposits which contain a fair amount of The paleontological dating of the samples collected macroscopically visible grains in a fine matrix. Shale was carried out on fusulinids and algae. Van Ginkel will be used for uniformly fine-grained deposits with (Leiden) studied the fusulinid samples and only after few or no macroscopically visible grains. Siltstone will he had assigned a relative age was the stratigraphic be used for deposits of the appropriate grain sizes. It is location of the sample revealed to him. Wishful inter- realized that fully in many cases these distinctions are pretation was thus avoided. The calcareous algae were hard make of the very to on account complete gra- studied by myself. As I did not take the trouble of dations between these categories, but nevertheless it code relative giving the slides a random number the useful seems to make an attempt. to them have been influenced the ages assigned may by Another difficulty when trying to classify such fine- knowledge of the stratigraphic horizon at which they grained sediments is the possibility of extensive collected. Other offossil did not were groups organisms recrystallization at low temperatures, which may be of further refinement of these permit any datings. accompanied by the development of cleavage. As axial

plane cleavage is developed in the northwestern part Storage of collections and additional data of the this area, is a distinct possibility. In some sand- The samples collected and studied were deposited in stones there are also indications that the matrix has to the collectionsof the Afdeling Stratigrafie en Paleonto- some extent been recrystallized. of the Geologisch Instituut, Garenmarkt l b logie ,

Leiden. Most of the macrofossils collected were, METHODS AND TECHNIQUES USED however, put at the disposal ofthe respective specialists As the lateral mentioned the the variability precluded a complete in section on previous work in area. Fades descriptions 165

Additional data such as field maps, Sections 2 and 24, of the Netherlands Organization for the Advancement

thin section descriptions, faunal and floral lists of the of Pure Research (Z.W.O.) for which I am most

various fossiliferous horizons were deposited in the grateful. I thank Dr. R. H. Wagner and Mrs. C. H. T.

files of the Afdeling Stratigrafie en Paleontologie and Wagner-Gentis (Sheffield) for their cooperation in the available interested workers. and for field are to field, putting maps and other unpublished data The discussions with Dr. R. H. at my disposal.

Wagner, which resulted from our sometimes con- and stimulus ACKNOWLEDGEMENTS flicting views, were a constant challenge

to me. I also wish to thank Mr. H. Dupont (formerly

It is a pleasure for me to thank those people and Louvain University) who kindly showed me the

institutions not connected with the Rijksuniversiteit Waulsortian "reefs" ofthe Dinant basin. I am grateful

Leiden, who in one way or another contributed to the to Dr. C. F. Winkler Prins (Leiden) for studying the of the ideas in this thesis. collected the The development presented brachiopods during present survey. thank First of all I should like to Dr. H. G. Reading, comments by Dr. S. van der Heide (Haarlem) and Mr. H. who invited me to spend a couple of months at the W.J. van Amerom (Heerlen) onthe pelecypods

of Oxford, and who contributed to collected have been useful to Mr. A. V. University more very me. education than other Zimmermann contributed the of this my geological any single person. to readability I also wish thank the staff and the Mr. to students of the paper by correcting English. B. van Hoorn Department ofGeology at Oxford for their stimulating kindly translated the abstract into Spanish. And last Mrs. discussions and hospitality. My stay in Oxford would but not least I thank J. E. A. Bergman-van de have been without the financial Kuinder who the main of the impossible assistance typed part manuscript.

CHAPTER II

FACIES DESCRIPTIONS

INTRODUCTION but it also be into weathering may changed rusty

colours (N7 to 5Y7/2 or 10YR7/4). The shales and The various facies groups and types are distinguished either dark mudstones are usually grey to black, or and described on the basis ofcharacteristics thought to light grey to greenish grey. (N2 to N6). be of genetic importance. The grouping together of Limestones are light to dark If dolomitic several facies grey grey. types in this chapter implies a genetic have brown colour when weathered they may a rusty relationship. However, this genesis as interpreted from (N3 toN7, 5YR6/1). the combined properties of a facies will be dealt with dark when fresh Sideritic concretions are grey and, separately from the descriptions in Chapter III. The when weathered reddish brown to dusky red (N3 to facies and differentiated far groups types are, as as 5R3/4, 10R3/4 or 5YR5/6). possible, natural units which should be recognizable in All colour numbers according to Rock-Color Chart the field workers. by subsequent Nevertheless, many of Geological Society of America. arbitrary boundaries had to be drawn where contacts between facies types were gradational or where they

had many properties in common. FACIES GROUP I - GRADED ARENITES

(Plates la, b, c, d, e, Ha, b)

General remarks on the colours the various sediments of Alternations of arenitic to rudaceous beds with shale/ In the studied distinction be area a can made between mudstone beds. The coarse-grained beds have sharp

lithic arenites and lithic wackes on the one hand and bases, often with inorganic, sometimes with organic arenites and quartz quartz wackes on the other. This sole markings. Grading is commonly obvious in the

not is a clearcut distinction, and sandstones of inter- field. The beds are laterally extensive and most mediate composition are common. Taking into account frequently are of a blanket form, although channelling the transitional of the of which nature boundary line, although may occur. A sequence internal structures it is defined in the classification follows: massive interval - laminated sharply system used, runs as (graded)

remarks be made - some can concerning colours offresh interval rippled interval, very rarely with convolu-

and weathered siliciclastic The lithic sand- - laminated be discerned. deposits. tions interval, may This tend stones to be dark grey in fresh condition but sequence is generally incomplete but its order does not brown of the weathering produces greyish green or greyish seem to vary. Sometimes part shale/mudstone

colours to When the this be shown have been (N3 5Y5/2 or 5YR3/2). fresh, overlying sequence can to sandstones quartzose are of a light grey to white deposited during the same single sedimentary event. colour. This colour be somewhat altered may by The inorganic sole markings recognized are flute casts, 166 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

and all ofwhich be 7c.-The sandstones of groove casts rare prod marks, may are a quartz arenitic to

deformed by loading. Load casts which are not quartz wacke composition, or may be transitionalinto of the otherkinds of sole the lithic the deformationsof one markings varieties. In general, maximum grain

are rare. The grading is in general due to a combined size is coarse sand. In this size fraction calcareous

decrease in the maximum and size and an debris is Bed thickness from few mean grain common. ranges a in the of matrix in decimetres increase amount an upward to over two metres. Channelling, though

direction. Apart from rare channelling, no macro rare, does occur. Most beds, however, are of a tabular in this facies. fossils cross-stratification occurs Body are to blanket shape. Generally littleor no shale/mudstone if broken. If the is interbedded with the sandstones of this facies. very rare and, present, normally

fossils had a calcareous shell they are commonly Commonly the sandstone beds are amalgamated. If leached in the Plant be tend have out outcrops. fragments may not amalgamated they to sharp tops. in the lower laminated is often indistinct absent and the very common. Especially Grading or sequence be interval, bedding planes can completely covered of internal structures is incomplete. Upon the massive

with comminuted plant debris. The fragments are interval a thin (10 cm) laminated, and an equally thin

orientatedbut has been made to interval sometimesbe discerned. Included commonly no attempt rippled may of this other beds determine the relation orientation to in this facies are conglomeratic which occur Trace fossils interbedded this facies in Id. These current direction indicators. are not very in or type con- be burrows contain well-rounded common. They may present as and/or glomerates quartzitic pebbles sandstone and cobbles boulders dia- trails (?) at the soles of the beds, as and with rare up to 30 cm in burrows which the bed from above. The and cobbles form frame- penetrate Body meter. pebbles may a and trace fossils rare in the interbedded work "float" in arenitic matrix. are extremely or may a quartz shales/mudstones. Bedding is indistinct and only indicated by the inter-

bedded sandstones. These conglomerates are only

distinguished from other sandy conglomerates on the Several sub-types are distinguished. grounds of the associated facies.

Type la. -The sandstones are of a lithic arenitic to lithic wacke composition. Apart from clay pellets, Type Id. -The sandstones and siltstones are again

of arenitic to wacke which may be several centimetres in diameter, the mainly quartz quartz composition, sand. wackes than in the maximum grain size is coarse to very coarse A although are more common few notable do in the of Ic. Maxi- exceptions, however, occur generally coarser-grained deposits type

size is in the sand - northeastern part of the area. Bed thickness varies mum grain normally coarse grade the calcareous. Thebed from a few decimetres to several metres. Channelling coarse particles are commonly is and is fre- thickness generally varies from thin-beddedto medium- relatively frequent amalgamation very sandstones included in this quent. The sequence of internal structures is incom- bedded, although some

the thick and thick-bedded facies are over one and a halfmetres thick. The layers plete. Especially very sandstones often massive and with extensive and littlethickness variation are ungraded a are laterally very

in bed. in the thicker beds a sharp top. In the medium-bedded sandstones, grading occurs a single Especially

be discerned and lamination of internal structures be can sometimes parallel complete sequence can

be little discerned: massive, basal interval may present. Normally very shale/mudstone graded (often is interbedded between these sandstones which calcareous) - lower parallel laminated interval -

constitute units. in sometimes convoluted interval - some prominent mappable Except rippled, upper

laminated interval - transition into very fresh exposures, spheroidal weathering is charac- parallel overlying teristic of these sandstones. Apart from comminuted shale/mudstone. Beds possessing an incomplete se-

fossils calcareous debris found for instance: interval - plants no body or were quence, as massive, graded in these sandstones. laminated interval - rippled interval - sharp top,

lower laminated interval - rippled interval - upper

laminated interval - gradational top, or rippled Type lb.-The sandstones and siltstones are ofthe same - interval laminated interval - gradational top, are those of wackes composition as type la, although are much more common. The sandstone - shale/mudstone Maximum more commonin these finer-grained elastics. estimated the varies between ratio, as in field, generally grain size is coarse sand. Bed thickness varies from 10:1 and 1:10. IChondrites and Spirodesmos (?) are the laminated to medium-bedded. Individual beds are only determinable trace fossils in this facies. The generally of the blanket type. Sequences of internal former occurs in the sandstone layers, the latter along structures which run as follows: massive graded the soles of the beds. Other of burrows types may interval - parallel laminated interval - rippled inter- occur both in the and the soles of - upper part along val, or parallel laminated interval rippled interval sandstone beds of this facies. are often recognizable. Gradational tops are the rule in this facies The type. sandstone/shale-mudstone ratio, this as estimated in the field, varies in general between Type /tf.-The sandstones and siltstones of type 1:5 and have arenitic 5:1. In most exposures, however, weathering generally a quartz wacke to quartz lithic renders it difficult to make an accurate estimate. composition although transitions into the Fades descriptions 167

varieties are probably common. Maximum grain size

is in the fine to medium sand grade. The small grain

sizes make it difficult to ascertain the precise com-

position. Bed thickness varies from thinly laminated

to thin-bedded. Sometimes it is difficult to see whether

a layer has a distinct, sharp base or not. Grading

is commonly indistinct and the sequence of inter- nal is interval - structures very incomplete: rippled

laminated interval - gradational top, or laminated

- Sandstone - interval gradational top. shale/mud-

stone ratio ranges from 5:1 to 1:30.

laand and and Ie Types lb, types Ic, Id, are gradatio-

nal to each other. Type Ie is also gradational to type These five subdivisions of facies I Ilia. group are The quantitatively very important. following types are less important.

- Medium Type If. to coarse-grained quartz arenitic which medium thick-bedded. sandstones, are to very The beds have which be masked sharp tops may five because ofamalgamation of the beds. In the upper

to ten centimetres of a bed clay clasts and/or well-

rounded quartzitic pebbles occur, which are absent in the lower and middle of the part layer. Grading was observed. Sole be and the not markings may present

only internal structures observed are the peculiar dish

structures as defined by Stauffer (1967) (Plate Ila).

This facies type occurs interbeddedin types Ic and Ie.

/fj.- Commonly graded calcirudites to calcareni- with siliciclastic which tes a fine-grained, matrix, are often overlain by mudstone with "floating" calcareous

debris of the fine sand grade. The lower part of the beds is often of a very localized occurrence in strongly erosive channels. The much upper parts are more extensive. The which complete sequence, was only found be several thick. The once may metres following

sequence could be recognized from bottom to top: rounded cobbles poorly consisting of a calciruditic which in microbreccia, are "floating" shale/mudstone

- interval of an consisting angular limestone fragments

to five centimetres in diameter, which up mainly

"float" in a fine-grained siliciclastic matrix; in this interval contorted shale/mudstone lenses several

decimetres in diameter occur - a graded interval in

which the limestone clasts form a grain-supported

framework (wackestone to packstone) - an interval

consisting of well-graded packstones sometimes with lamination - - interval of parallel sharp top an

greyish green mudstone, often several metres thick, with "floating" silt and sand-sized limestone fragments Fig. 5. Most complete development of facies type Ig. - gradational contact with the overlying blackish Exposure approximately 150 metres above the top of shale/mudstone. Common variations are for instance: Section 20. graded interval with the overlying greyish mudstone,

or an ungraded interval with or without associated mudstone. the Ih.-Graded calcirudites calcarenites with little In former case the sometimes extremely Type to

local occurrence of the graded interval in pockets and fine-grained siliciclastic material as a matrix. The base of the beds is erosive and have channels several decimetres deep, and often only a few commonly may a less the Limestone clasts 10-15 metres or wide, is very striking. Especially as channelling appearance. cm in the basal mudstones can be traced for several hundreds of in diameter may occur part. Stylolitic abundant in the metres. contacts are coarser-grained parts. W. E. de Graaff: Three delta 168 J. van Upper Carboniferous systems, Spain

Bed thickness from medium-bedded to also be but ranges very types may present, they are quantitatively thick-bedded. bed consist of thick A may one graded unimportant. In some cases it may be shown that the of which is in the limestones forms interval, upper part normally a coarse bedding an acute angle to the This calcarenite. massive, graded interval, however, original depositional surface, or geopetal structures be followed lower laminated interval parallel that the blocks are overturned. 7 is a may by: prove Figure map

- interval - laminated interval- of few of these limestones rippled upper parallel a "floating" on and in type few the ruditic gradational top. In a cases coarse part I la and covered by relatively undisturbed sediments absent. offacies Id and soft sediment is ill-developed or types Ie. No deformation of A few more rare variations graded calcarenites of the limestones has ever been observed. The lower-

described. will not be most Sierra Corisa limestone tongue in Section 4 is also included in this facies type, although it is still continu-

FACIES GROUP II - CONTORTED AND ous with the limestone in situ. The reason for this is the FRAGMENTED SEDIMENTS (Plates If, IIc, d, f) e, fact that it is imbeddedin facies lib (see Plate lie, d,

Shales, mudstones, sandstones and limestones which and Fig. 6). At the locality ofSection 4 this lowermost broken and are deformed, contorted, or fragmented, limestone tongue has an extremely sharp and irregular

often in a chaotic manner. Folding and breaking are lower surface. In the lowermost few metres of this

the of slicken- cracks which filled with not accompanied by presence cleavage, limestone, occur are quartzose filled with vein calcite. sides or fractures quartz or sandstone. These sand-filled cracks are absent in the Folding, if developed, is irregular, and pull-apart, remainder of this limestone.

hook-shaped and roll-up structures are often present.

associated with - Small unconformities are sometimes Type Hd. Limestone breccias with a shale/mudstone these matrix. The limestone which deposits. fragments, are very "float" in the but angular to angular, may matrix,

-Sandstone - shale alternations of Ic or a Maximum Ha. type may also form grain-supported framework.

Id, deformed in a chaotic manner. The thickness of diameterof the limestone fragments is normally in the

the involved in deformation from cobble Other sequence may range pebble to range. components are frag- of sideritic a few decimetres to several tens metres. ments of concretions and clay pebbles. Quartz

6. Small-scale unconformities of the lowermost of Corisa Member Fig. on top tongue the Sierra Limestone (Section 4; approx. 1590-1620 m).

Type lib.-Sandstones, siltstones, shales, calcareous arenitic pebbles rarely occur. The maximum lateral shales de- of facies type Hid, which are chaotically extension of these breccias is a few hundred metres.

and which exhibit small-scale unconfor- Thickness be to several of few formed, may may up tens metres. In a

mities (Plate lid and Fig. 6) This type was only ob- cases their basis was observed to be erosive, and served associated with similar breccias in older in Section 4, where it is closely slightly deposits exposed near the lowermost Sierra Corisa limestone San Martin de of the tongue. Perapertii (east map area) are

channel fills. Plate I If shows a very coarse example of this facies from Contorted Type He-Isolated limestone blocks varying in dia- slightly younger deposits. sandblocks occurring associated with these limestone meter from 0.5 to 250 m which "float" in or on shale/

breccias are included in this facies. mudstone or in facies I la and lib. These lime- types stones consist mainly of facies types Xb, c (massive or

poorly-bedded mudstones to wackestones with occasio- Type He.- Channel fill consisting of a sandstone

nal The much limestone breccia with lithic boundstones). other, rarer a shale/mudstone or quartz to Fades descriptions 169

Fig. 7. Isolated limestone knolls east of Piedrasluengas. 170 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

wacke matrix. The lithic arenitic and Sometimes abundant drifted very angular plant fragments occur.

shale clasts form a framework. In instance marine lamellibranchs locally grain-supported one occur in great several centimetres diameter. The fragments are in No numbers. (Section 7, 1011 m). Pyrite is common in this imbrication observed in this facies This facies is the few bedding, grading or was type. type at utmost only a fill. channel channel The was cut at least 8 to 10 m metres thick and commonly grades into another down into facies Id. Lateral observed. extent was not coarsening upwards sequence.

- Type ///".-Lenses of cobble to boulder-sized con- Type IIIc. Indistinctly bedded to homogeneous, argil- with matrix. The cobbles laceous sandstones and and often glomerates a shale/mudstone siltstones, somewhat "float" form framework. calcareous mudstones. may or a grain-supported Spheroidal weathering may which of The cobbles, are a quartz arenitic com- mask any bedding structure present. Marine fossils well rounded. Maximum thickness such crinoid position, are very as bryozoans, brachiopods, ossicles often of the lenses from one metre to about 5-10 In surfaces bioturbation be ranges m. occur. polished may

Lateral extent is in the order of a few tens of metres. visible.

The latter while the others two types are very rare, Type Hid.- Calcareous shales, mudstones, siltstones in several sections. lie and lid be occur Types may and argillaceous, fine-grained sandstones, which are gradational to each other. Type lid is also gradational generally intensively bioturbated. The only determin-

to type Ig. able forms are Spreitenbauten of the Zpophycos group. have Although complete homogenization may occured, bedding is usually still discernable. At the main FACIES GROUP III - FINE-GRAINED occurrenceofthis facies type (Section 4 and eastwards) SILICICLASTICS (Plates IIg, h) the lowermost few metres of mudstone, which im-

overlie the lower Sierra Corisa limestone Shales, mudstones, argillaceous siltstones and/or fine- mediately

sediments tongue, are red The transition grained sandstones. These fine-grained are locally dusky (5R3/4). into the is often difficult to distinguish in the field. It is proved overlying greenish grey deposits very irregular. This facies is exceptionally fossiliferous by the associated facies types that superficially very type similar sediments have been at the location of Section 4. The most remarkable argillaceous may deposited

fossils are the de in widely differing environments. Because of this, most sphinctozoan sponges (van Graaff, 1969), but brachiopods, crinoids, solitary corals, of the types of this group are distinguished primarily rugose the basis of the associated facies In bryozoans, fusulinids, trilobites, lamellibranchs, gastro- on types. general, nautiloids and calcareous also bedding is difficult to discern in this facies. It is often pods, algae occur.

only recognizable because of the interbedded sideritic concretions silt and sand laminae. The Type Hie.-Dark to light calcareous mudstones or quantitative grey

with abundant marine fossils such as brachio- a locally importance ofthis group is obvious after glance at the sections, especially taking into account the fact that pods, solitary rugose corals, gastropods, bryozoans and, of the rarely, sphinctozoan Bedding is indistinct and most unexposed parts are largely argillaceous. sponges. varies from thin medium. Furthermore, about \ to \ of the total thickness of to facies group I is occupied by these fine-grained deposits.

FACIES GROUP IV - COMMONLY RIPPLED AND

CROSS-BEDDED SILICICLASTICS

Ilia.-Dark grey shale/mudstone with sometimes abundant sideritic concretions which indicate the Generally well-bedded or laminated mudstones,

bedding plane. These concretions are flat spheroids siltstones and sandstones which do not form part of a with diameter about a maximum of 30 cm. They fining upwards or coarsening upwards sequence (Allen, occasionally form a nearly continuous bed but nor- 1965; Oomkens, 1967). Bedding contacts are usually

isolated from each other. Sand silt but erosive In the mally they are or gradational contacts may occur. laminae with be and sharp or gradational bases may fine-grained sandstones ripple cross-lamination but if the ratio drift features. laminat- present, sandstone-shale/mudstone ripple are common Bedding or

not exceeds 1:30 the deposit is, for instance described as ion planes can usually be traced for more than a Thin calcarenitic beds also differentiated type Ie. graded may occur. few metres. This facies group, too, is Bioturbation ascertained. This facies is of the associated facies b was rarely type because types. Types IVa, associated with sediments of I. It is form associated with arenitic closely group a sub-group quartz and gradational to types Hid, IVa and c. Lenses and beds coarsening upwards or fining upwards sequences, of marine limestones be intercalated. with limestones. d form second sub- may sometimes Types IVc, a

group associated with lithic arenitic coarsening up-

Type IHb. Well-bedded or laminated to homogene- wards and fining upwards sequences. dark shales mudstones which overlie ous, grey or of Vb IVa. -Laminated siltstones and coarsening upwards sequences type or e, or type Type to thinly-bedded wacke Va. Bioturbation can sometimes be recognized in the fine-grained sandstones of quartz arenitic to fill of the burrows. often with lower part because of the sandy composition. Bedding planes are covered Fades descriptions 171

micas and/or finely comminuted plant debris. Ripple are normally not more than a few decimetres thick,

cross-lamination and ripple drift are common. Sandy are often characterized by brownish weathering

et concretions of sideritic or silty streak (de Raaf al., 1967) rarely occur. Both (limonite?) probably composi-

and fossils tion Often a distinct marine body fossils trace occur. (Hemingway, 1968). sequence can be distinguished in these deposits. If they form the

thick-bedded arenitic of of VIb Type IVb.-Thin to quartz upper part a fining upwards sequence type or

sandstones. Bed shape ranges from tabular to blanket. if they form a thin fining upwards sequence of their bed be included in this facies In some cases a sharp base to a may discerned, own they are type. They are but dominate. A bed be also included in this if no clear be gradational contacts may type sequence can

laminated in itself and occasionally low-angle macro discerned. Marine fossils sometimes cross-bedding occurs. occur

in this facies type. Type FA.-This type differs only from type Va in that the rootlet exhibits bearing deposit a coarsening up-

IVc. -Laminated wards decimetre scale. It Type to thinly-bedded mudstones, sequence on a to metre may

siltstones and fine-grained sandstones of lithic arenitic contain slightly coarser and better sorted sandstones Micas and than which has fine sand its to lithic wacke composition. finely com- type Va, as coarsest minuted remains the plant may cover bedding planes. component.

Rippling is common in this type. Sandstones oftype lb N.B. and or channel fills of type VI occasionally occur in this Fining upwards coarsening upwards se- facies. quences are here used in a slightly different sense than facies VI and VII. In Va and b in groups types they

to metre Rippled, laminated to medium-bedded are on a decimetre scale while in the other scale. lithic arenitic sandstones of fine to medium grain size. examples they are on a larger Furthermore, in of the channel Contacts are usually gradational but sharp erosive the case fining upwards sequence no

do and cross-stratifi- fill is meant but based contacts occur low-angle macro (cf. type Villa), a gradationally discerned. with increase in cation can sometimes be Although many sequence an upward argillaceous borderline cases exist, channel fill with or without material which is eitherinterbeddedor homogeneously fining upwards sequences is described as type VIb. distributed in coarser sediments. Usually the only

depositional structures recognizable are rippling and -Thick-bedded lamination. In the of to massive, very coarse- case a coarsening upwards the channel fills grained quartz wackes. Especially larger grains sequence no macro cross-bedding or well rounded. No in the and laminations are very sedimentary structures occur upper part. Only ripples apart from indistinctive bedding planes were observed. are to be expected.

This facies type occurs as intercalations in limestones in Sections 20 and 21. Pi;.-The of the well- Type upper part well-washed,

sorted quartz arenitic sandstones of types VIIc and

IXa, if penetrated by rootlets and/or Stigmaria. No FACIES GROUP V - SILICICLASTICS WITH PLANT small-scale fining upwards or coarsening upwards ROOTLETS associated sequences are with the occurrence ofrootlets in Va and b. This facies is characterized the of as types by presence plant sheaths. rootlets which are preserved as carbonaceous These rootlets pierce the sedimentary laminations and FACIES GROUP VI - SILICICLASTIC FINING UP- be in out- bedding. Stigmaria may recognizable good WARDS SEQUENCES (Plate IIIa) crops. Apart from rootlets, burrows may also pierce the and it be hard Sandstones and sandstones which do sedimentary layering may to conglomeratic

distinguish the two, especially if the sediment is not form part of a definite coarsening upwards se- and which exhibit homogenized. Bedding contacts are usually gradational quence of facies group VII, macro

in these deposits. Sometimes coal laminae or beds cross-bedding and erosive bases. A channel fill shape overlie such a rootlet containing horizon. Determinable and/or fining upwards sequence are recognizable.

if above the coal two be The first plant fossils, present, occur or directly Again sub-groups may distinguished.

on top of the rootlet bearing layer. Again, two sub- consists of type Via and is associated with quartz of IVa and b, Vc, and groups may be distinguished. The first comprises arenitic deposits types VII c and

types Va and b and is associated with lithic arenitic d. The second consists of Type VIb and is associated of and coarsening upwards and fining upwards sequences of with lithic arenitic deposits types IVc d, Va and Vila and VIb. The consists of Vc and Vila and b. types second type b, and is associated with arenitic quartz coarsening A is called upwards sequences of type VIIc and with type IXa. sequence a fining upwards sequence if the

following features can be distinguished in the field.

Type Fa.-Laminated and rippled shales, mudstones, 1) A sharp, often erosive base. 2) An upwards de-

siltstones and fine sandstones, the latter of lithic crease in both maximum and median grain size. 3) A arenitic or wacke composition. These deposits, which concomitant decrease in the size of cross-bedding, if W. E. de Graaff: delta 172 J. van Three Upper Carboniferous systems, Spain

from lateral accretion do for instance in the form of silt laminae present, large-scale sets to occur, clay or of that medium-scale (dm-m) cross-stratification, generally in sandstones. In case, however, the sand/shale thence smaller scoop/trough type, and to ripples. A ratio will still increase upwards. 2) Concomitant with the the kind type may occur superimposed on preceding larger these changes are changes in of sedimentary

lineation occur associated with the structures In the lower ofthe the type. Parting may present. part sequence

of laminations to two larger types cross-bedding. Ordinary deposits are generally laminated medium-bedded. for alternations of silt and fine consisting of, instance, Bedding contacts are gradational. Seemingly unbedded, sand associated with the small-scale A intervals also occur ripples. 4) homogeneous may, however, occur. which characteristic be masked gradational top, may Higher up, rippling and ripple drift may occur. Still

by later erosion. Such fining upwards sequences differ higher, well-bedded to well-laminated, fine to medium- for Ic in that from graded beds of, instance, type or d, grained sandstones may be present. Bedding and lami-

have of a fore-set nations and can oftenbe traced for they large-scale cross-bedding type; are very regular sev- clear association for facies eral Several of in their with, instance, metres. types macro cross-bedding begin

lateral also to at their smaller extensions, etc. (see occur this level. Small channels (dm-m group V; scale) and tabular Allen, 1965). low-angle cross-bedding are most common. The end with sequence may a gradational top, a sharp sandstones with occasional Type Via. -Quartz arenitic top or it may be unconformably covered by a channel The of of conglomerates. pebbles are dominantly quartz fill or fining upwards sequence type Via or b. The arenitic but and thickness of these varies from few composition too, lydite pebbles clay sequences a metres to Some of the sandstones galls may also occur. coarser over a hundred metres. Their lateral extension ranges

have lithic arenitic to arenitic few hundred several of this facies a quartz from a metres to kilometres.

composition. The content of unstable fragments,

is around 10-15%, while in the true lithic however, Type F/7a.-Lithic arenitic sandstones, siltstones and arenites of comparable size grades the unstable frag- shales/mudstones showing a coarsening upwards

ments form of the rock sediments of 20-35% (e.g. on a scale from a few may sequence varying metres to over

la or VIb). Channel fills and more tabular types a hundred metres. Ifthe size exceeds 25 m they may be both deposits exhibiting a fining upwards sequence called if minor Not major c.u.s., not, c.u.s. considering

The channel fills do not necessarily show a clear occur. clay galls and comminuted plant debris, the coarsest

One of channel cuts fining upwards type coarse to sequence. deposits are in the very coarse sand grades. down into facies IVb for over a metre and is type Because of weathering effects, small structures like

cross-strata. completely filled by low-angle (

strata and structures could surrounding sedimentary the case in some of the major examples. (Section 4,

not be used because of the poor exposure. 510 m, Section 13, 355 m). In this well-bedded part,

low-angle, tabular cross-stratification on a dm-m Type VIb.— Medium to coarse-grained sandstones of scale may begin to occur, and small channels may also lithic arenitic Clay galls and drifted plant composition. be present. Both phenomena become more frequent in

form the only coarser Scoop to fragments components. upward direction. This sequence is typically covered,

to trough cross-stratification on a dm m scale are the with an erosive contact, by a channel fill or a fining commonest types of cross-bedding. Low angle to high of thickness from upwards sequence a varying a

tabular cross-stratification on a 2-5 m scale also angle few decimetres to a few metres. This channel fill or If it is below the smaller and occurs. present so, scoop fining upwards sequence is still included in this cross-stratification. III. In trough facies type for reasons explained in Chapter

one case (Section 7, 1040 m) no distinct erosive and base could be discerned below the scoop trough FACIES GROUP VII - COARSENING UPWARDS in- cross-bedded part. There seems to be a gradual SEQUENCES (Plates IIIb, c, d, IVa, b, c) the number of and In crease in scoops troughs. tabular Shales, mudstones, siltstones and sandstones, which the upper part of this example, low-angle, show definite 10-20 m scale with a coarsening upwards sequence. Again cross-bedding on a occurs super-

One character- and metre two subgroups may be distinguished. imposed scoop through cross-bedding on a ized lithic arenitic the other scale This is cut off by sandstones, by quartz (Plate IVa, b). cross-bedding which of facies arenitic sandstones. sharply by finer-grained deposits are

IVc. tabular on type Low-angle, cross-bedding a A called if similar but without smaller sequence is a coarsening upwards sequence scale, superimposed cross- in Section it shows the following characteristics from base to top: stratification, occurs 13 (360 m) (Plate IVc). A both maximumand median In few it be observed that the lower 1) progressive increase in a cases may only

with and of a is grain size, beginning argillaceous deposits part coarsening upwards sequence developed, fill is ending with sandstones. Minor reversals of this trend i.e. the channel or fining upwards sequence Fades descriptions 173

absent and the then either but of sequence may gradually or common, larger types cross-bedding are rare or

sharply be covered by fine-grained deposits. Laterally, absent. In a few cases the ripples were observed to have channel fill the sometimes cross-sections. Marine fossils found however, a forming top may symmetrical are

be observed (Section 4, 730 m). occasionally. Burrowing may occur especially in the lower These have parts. sequences may a sharp top

VHb.- which but in a number of Type Coarsening upwards sequences cases (Sections 12, 13) a gradational differ from Vila type in that the sandstones are top is observed. In the latter case they are covered by transitional from lithic arenites into arenites. sediments of Ilia i.e. the facies quartz type or c, same type Furthermore they are closely associated with facies in which these sequences began. VIIc and d and other with marine types deposits

faunas. The upper part of one example (Section 10,

FACIES GROUP - FINING 590 formed of VIII UPWARDS m) is actually by deposits type VIIc. In SEQUENCES WITH MARINE FOSSILS AND the middle ofthis number of part particular sequence a LITTLE OR NO CROSS-BEDDING (Plate IVd) peculiar channel fills occur. They consist of sandstone bodies about lateral and 5 to 50 m in extent up to one Type Villa.-Sometimes calcareous, quartz arenitic metre in thickness. differ from other channel They sandstones to siltstones of a tabular to blanket shape.

fills in these not because of this sequences only greater These sandstones have sharp bases and vary in thick-

lateral but also to the fact that the thin from than extent, owing ness less one metre to over thirty metres.

sandstone beds composing the channel fill are in- Marine fossils are in the common, especially upper A tabular tensively rippled. low-angle (<5°) cross- part, as is burrowing. Upwards this facies commonly

on a metre scale can sometimes be discerned. into either black of bedding grades shale/mudstone type Ilia Some of these and (Plate Hid). regularly thinly- or into limestones. A combination of an upward bedded sandstones show sole Another decrease and median markings. in maximum grain size, a difference from type Vila is that in the fining upwards decrease in distinctness of bedding and the restriction which forms the sequence top, conglomerates may of major cross-bedding or rippling to the lower part

occur. warrant the The name fining upwards sequence.

common presence of marine fossils and the much

VIIc. — siltstones and sandstones sho- Type Mudstones, greater possible thickness indicate, however, that this

wing a coarsening upwards on a scale varying is different from those of VI. sequence type fundamentally group from 5 20 The sandstones of arenitic to m. are a quartz composition and the maximum grain size rarely

exceeds the fine FACIES GROUP IX - QUARTZ ARENITES ON sand grade. This type of coarsening ERODED LIMESTONES (Plates IIIe, f, IVe, f) is furthermore characterized upwards sequence by a

sharp top which may be penetrated by plant rootlets IXa.- Sometimes arenitic Type calcareous, quartz and/or burrows. Complete homogenization of the sandstones overlying an often strongly erosive contact few centimetres have occurred. Tree upper may with limestones. The sandstones fill pockets and pipes five trunks, to metres long and half a metre wide, up which penetrate the limestone. In one example already which floated in, were observed in a few examples of described Nederlof these by (1959, p. 662), pipes, this facies type. Characteristically the lower part which 50 in the are up to cm diameter, penetrate consists of rippled and laminated mudstones to sand- underlying limestone for at least seven metres in a

stones. The middle is well-laminated and most part direction perpendicular to the bedding. Normally, shows distinct tabular frequently low-angle or trough/ however, the pockets are only a few decimetres or less scoop cross-stratification on a dm-m scale. Lamination in Associated with these and depth. pipes pockets may planes are sometimes covered with fine plant frag- be cracks and in the limestone numerous vugs which ments and/or micas. In the bedding and/or also filled with These upper part, are quartz arenitic sand. cracks lamination is less easily recognized. This is often and few centimetres in diameter. vugs are usually a accompanied by the of rootlets and/or presence Limestone conglomerates occur locally in this facies burrows. In a few examples the surface shows Sometimes upper type. a fining upwards sequence of type smooth ripples on a metre scale. Fossil debris is Villa is present, but a sharp top penetrated by plant occasionally recognizable in these deposits. rootlets burrows also and/or may occur. These sand- which than few stones, are normally not more a N.B. The of of this parts deposits type are metres upper thick, are generally verywell washed and sorted. described as Vc if penetrated by rootlets. type Not counting some dissolved carbonate(?) material, of the sandstones consist for of some over 95% quartz.

Vlld. - siltstones and arenitic The drawback is that has Type Mudstones, quartz only overgrowth occurred of fine sandstones showing a coarsening upwards se- the originally well rounded grains. Nevertheless these 10 The sandstones the the quence on a to 50 m scale. deposits are gene- are most mature in entire area rally laminated to thin-bedded, and individual beds studied. Lateral tracing of different examples showed are tabular to blanket shaped. Bed thickness and that some of them grade laterally into quartz sand

distinctness of individual beds show a slight increase in bearing lime grainstone after a few hundred metres.

upward direction. Rippling on a centimetre scale is Others, however, can be traced for kilometres. 174 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

FACIES GROUP X - LIMESTONES It is this facies with (Plates V, VI, VII, type that, together type Xb,

VIII, most IX) constitutes of the limestone bodies in this area.

This shows transitional contacts with Although the relationships of the various limestone type, too, many other facies such members with the surrounding siliciclastic deposits types as Xa, Xb, Xd, Xe, Xf, Xh, theme of this limestone Xh, Xj, Xk. form a main paper, only one

body was studied in detail. This is the Agujas Lime-

Member Type Xd. -Light or dark coloured sparite patches of stone which crops out in the Redondo Syn- but smooth The dark colour of cline. The following facies descriptions, with the irregular shapes. some of these is caused the of exception of Xn, are all based on observations on the patches by presence organic

Member. material. Single patches in diameter from a few Agujas Limestone During a cursory exami- vary about 10 In nation of the other limestones, however, it appeared mm to cm. one example radiating tube-

most to like structures are visible in the sparite The that in aspects these are very similar the Agujas patches. Member. Their facies either consist of fibrous calcite Limestone patterns, however, sparite patches (dark

variety) or of a fibrous calcite rim with more equidi- are much less complicated. The causes of these differ-

mensional in the centre. In few ences will be dealt with in Chapter V. crystals a examples no

From the following facies descriptions it will be obvi- fibrous calcite crystals can be recognized. In some

that several similar specimens undulating fronds of codiacean ous types distinguished are very to platy algae

can be In thin section the fibrous calcite each other. In some cases the only difference is the recognized.

rim as well as the are seen direction in which a certain trend changes. As the equidimensional sparite from these fronds In the genetic significance of such changes is still obscure, it to emanate (Plate VIb). of these fronds is seems important to note these minor differences depressions mudstone/wackestone

difficult sometimes a clear structure. although they are as yet to interpret. present, forming geopetal

In most specimens collected, however, codiacean or

other are not in a form. In Irregularly bedded limestones with a brec- algae present recognizable

ciated nodular in the In thin those examples the sediment in between the sparite to appearance outcrop. consists of seen to patches mudstone, wackestone, packstone sections the clasts may be have pressure

contacts. and rare grainstones and boundstones. In rare exam- solution Along the pressure solution seams the fill is overlie thin fibrous dolomitizationis frequent. Texturally these limestones ples geopetal seen to a

calcite rim. In most studied brittle de- are at present coarse cm) wackestones to pack- specimens This is fossiliferous. Brachio- formationand fragmentation occurred of the sediment stones. type locally very surrounding the sparite patches. If this is the the pods, crinoids, echinoids, solitary rugose corals, case, fragments are seen to rest each other and the sphinctozoan and other sponges, goniatites, nautiloids, upon the trilobites, bryozoans, ostracods, gastropods, radio- sparry cement in fractures belongs to the same

generation as the cement in the larger patches. This larians, calcareous algae and oncolites were recognized.

facies is but never- In Section 21 (530 m) a few phosphatic nodules occur type quantitatively unimportant theless in this This facies is in the fairly common. It is transitional into Xc type. type most common type

and occurs most surrounded this facies Redondo Syncline, where it occurs at the base of the frequently by

Agujas and Abismo Limestone Members. It also type. occurs in isolated lenses in Sections 1 and 4. Laterally and it shows transitions into Xe and -Facies Xb and Xc often show vertically shale/mudstone Types Xf. types of types Ilia or Hie. very gradational transitions into one another. In a

number of cases a clear trend-like change was observed

Xb.- bedded in the number of dolomitized solution Type Indistinctly, irregularly mudstones, pressure seams wackestones and rare packstones. Bedding is most which are the main characteristic of type Xb. Ifsuch a indicated solution from Xb occurred direc- frequently by pressure seams along change to Xc in an upward which dolomitizationoccurred. Fossils abun- tion the called Xe. Ifit occurred in are not sequence was type dant but crinoid If the and echinoid fragments, fusulinids a downward direction it was called type Xf. and other foraminifera, dasyclads and other calcareous transition is relatively sharp, only Xb and Xc are algae, chaetetid, "lithostrotionid", auloporid and differentiated. solitary rugose corals occur. Crinoids and fusulinids are often somewhat concentrated the - Massive-bedded to well-beddedoolite along pressure Type Xg. pack- solution Chert nodules This and with sometimes seams. occur locally. type stones grainstones a sharp, clearly is Clasts quantitatively very important in nearly all the erosive base. of underlying limestone deposits limestone abraded fossils such be units of this area. It is transitional into most and as coral fragments may other facies of this i.e. Xc, Xe, Sometimes "mottled" types group, Xa, Xf, present. pelsparitic grainstones

Xi, Xj, XI, Xo, and Xp. and packstones occur. The "mottled" appearance of

these pelsparites is due to minor differences in the

Type Xc. -Indistinctly to massive bedded mudstones, proportion of matrix and cement. These differences wackestones with some boundstones and rare pack- are accentuated by pressure solution phenomena. stones. Crinoid "mottles" in from Fossils are rare. ossicles, foraminifera, These range shape equidimensional algae (mainly Komia) and fenestrate bryozoans occur. spots to platelike layers which may have a thickness- Fades descriptions 175

width ratio of least 1:20. These "mottled" Xk.-This is combinationof Xb at pel- Type type a types and in the of this facies The The basal of called Xk consists of sparites occur upper part type. Xj. part a sequence this facies Xb which coarse-grained part of type contains a facies type grades upwards into regularly rich flora and fauna. Fusulinids and other and well-bedded and of relatively packstones grainstones type foraminifera, crinoids, echinoids, bellerophonid and Xj. Apart from the upward increase in median and other gastropods, dasycladacean and codiacean algae maximum grain size, a decrease and eventual dis-

all A in this of and other be are very common. peculiar phenomenon appearance dasycladacean algae can Member the observed. the number facies type in the Agujas Limestone is Furthermore, of dolomitized occasional of arenitic The solution and the of insoluble occurrence quartz pebbles. pressure seams amount

largest pebble observed was about 20 centimetres in material decreases in upward direction. In the pack- and of the chert diameter. All pebbles are spherical superbly stone-grainstone part sequence is rare. rounded. The occurrence of these pebbles is all the few siliciclastics more surprising as or no fine-grained XL- Regularly and thinly-bedded mudstones and

were observed as an admixture in the limestone. Only wackestones which contain few macroscopic fossils. In

in Sections 20 and 21 does a coarse-grained quartz thin section sponge spicules can sometimes be recogni- thick intercalation the limestone zed but other fossils Chertification wacke occur as a in are rare. along but here little or no mixing of the two lithologies took bedding planes is common. Due to discontinuous of be place. The upper boundary this facies type may exposures, the lateral equivalents of this type are

sharp or gradational. difficult to ascertain. Nevertheless, it seems likely that

it into f the hand and grades types Xj, Xb, e, on one

Xm on the other. Type A"A.-Gradationally based, massive to well- bedded packstones and grainstones while "mottled" Type Xm. -Dark coloured, laminated to thinly bedded, also in the In pelsparites may occur upper parts. fact, fetid mudstones and wackestones which are completely base the of this apart from the sharp description type non-fossiliferous. Laminae and bedding planes are identical that of The lower however is to type Xg. part, extremely regular and can in some cases be traced for is transitional from mudstones and wackestones of

several metres. No indications of bioturbation Xc Xe. The mudstones and wackestones were types Xb, or observed. Low angle cross-bedding on a cm to dm scale change, in an upward direction, into packstones and sometimes these occurs. In cross-bedded parts few grainstones which gradually become oolitic. In the erosional features are visible. The dark colour is do Both and Xh lower parts oncolites occur. type Xg caused by a relatively high content of organic material. are commonly overlain, with a sharp contact, by type Chertification sometimes occurred along bedding Xi. planes. In thin section this type consists of microspar to

pseudospar (Folk, 1965). Laterally this facies type AY.-Irregularly but distinctly bedded mudstones, into XI Xb. In Sections 20 and 21 grades types or

wackestones and rare and of packstones boundstones, quartz wackes type IVe are associated with this which often rich in insoluble material. are fine-grained facies.

Pressure solution seams with attendant concentration of insolubles and dolomitization are common. Big Type An.-Beds of mudstones and wackestones with auloporid colonies (up to 1.5 m in diameterand 40 cm abundant codiacean algae and furthermore crinoids, in height), chaetetid and "lithostrotionid" colonies, brachiopods and lamellibranchs. Some of these fossils solitary rugose corals, oncolites, dasycladacean and are pyritized. These beds occur intercalated in dark codiacean characteristic of this facies algae are type. grey shale/mudstones of type Ilia or Illb (Section 7, Although sometimes transported, the corals, especially 1013 m). Lateral tracing of this bed indicated its close the colonial ones, are often in position of growth as association with a seatearth/coal horizon. faunal crinoids are the algae. Although elements like and fusulinids also be present, the above-mentio- may Xo.-Limestone breccias rounded Type to poorly con- ned association is characteristic especially if all the glomerates which occur in facies types Xb or Xp. The elements This is transitional in are present. type clasts be may up to 30 cm in diameter and have the upward direction into types Xb or Xe, and commonly same composition as the immediately underlying overlies Xh with Xg or a sharp contact. deposits. The lateralextension ofthese breccias is in the order of few of the thickness a tens metres, is up to

Type Xj. -Wackestones, packstones and rare grain- about 1.5 m. Texturally they are wackestones to of stones, which show distinct and regular bedding on a packstones. Some grading the maximum grain size medium scale. Chertification often occurred along the may be present. bedding planes. Crinoid ossicles, echinoid spines and

and foraminifera the most facies those plates, algal fragments are Type Xp.-This type comprises sequences important fossils present. Bioturbation was observed characterized by an upward increase in the number of of indications of dolomite which do in a number exposures. Indistinct partings, not start in type Xc like channeling are present in Section 17. Laterally this Xe, but in XI. In its upper part it is in places similar to type seems to be transitional into type XI. Xa or Xi. Three 176 W. J. E. van de Graaff: Upper Carboniferous delta systems, Spain

CHAPTER III

INDIVIDUAL FACIES INTERPRETATIONS

INTRODUCTION sandstones are considered to have been deposited by

immatureturbidity currents in which grainsegregation In order to keep the more factual observations as had not yet occurred (Walker, 1965). As the character from presented in Chapter II as separate as possible the of a turbidity current and the resulting deposit is a more subjective interpretations, these interpretations function of number of viz. of a factors, magnitude will be given here in a separate chapter. In this chapter the current, character of sediment load, time of of the individual facies and the interpretations types of travel, distance to source, rate deceleration, groups will be presented without attempting any areal Reading (1970) is followed in his contention that interpretations. Areal and regional interpretations the terms mature and immature turbidites are to which can only be made after further subjective assess- be prefered to distal and proximal turbidites. The ment ofthe basic data will be presented in the following relative proximity to the source point can only be two chapters. This grouping into three chapters is deduced from a regional analysis of a turbidite se- really a grouping on the basis of the number and from the character of quence, not a deposit at any importance of the uncertainties, inaccuracies and the single place. Reading (1970) also mentions the possibi- subjectiveness of the various levels of interpretation. lity that a number of these sandstones were emplaced In this facies and the inter- chapter some groups types different mechanism like flow by a grain (cf. type If). pretation of which is considered to be fairly straight- forward will be be touched Other only upon. groupsor Type lb.-This facies conforms much better to des- which difficult to or which types are more interpret are criptions of well developed flysch-type sand beds (e.g. of paramount importance for establishing the environ- Bouma, 1962) and it is therefore interpreted as having ment ofdeposition, willbe dealtwith more exhaustively. formed by the action of mature turbidity currents

which entered an environment of quiet clay deposition.

FACIES GROUP I - TURBIDITES

the Sandstones of this differ from those of The features enumerated such as grading, presence type of of the entire ABCDE ofBouma la in their and in attendant features part of, or sequence type composition characteristics (1962), the presence of solemarks, great lateral ex- such as spheroidal weathering. All other of the finer varieties of this tension, etc., are characteristic of what may be called grained type are quite

with sand beds. Kuenen similar to those of la. Because of this sequences flysch-type (1967) type similarity reviewed the possible interpretations of these deposits these sandstones, too, are interpreted as immature and concluded that turbidites. The sandstones in deposition by turbidity currents conglomeratic present

entering a realm ofclay sedimentationis the most like- Section 5 (570m) are included in this fades solely on ly interpretation for these, often graded, sand beds. the ground of their close association with the sand- features of Ic Id and the lack of features Admittedly (see Kuenen, 1967) some are stones typical type or difficult to understand in the light of this hypothesis permitting of their recognition as type If. Their be the but any other mechanism of deposition postulated genesis, however, is much more likely to one far inconsistencies. With the inferred for boulders 30 in dia- presents greater exception type If, as up to cm of all in this considered have meter to have been in type If, types group are to are unlikely transported sus- The association of been deposited, at least partly, by turbidity currents, pension (Dott, 1963, p. 123).

not i.e. they are turbidites. coarse conglomerates with flysch-type sand beds is

unusual. A recent example in the La Jolla fan valley difficult described al. Type la. -These, often massive, sandstones are was by Shepard et (1969). if in isolated The to interpret they occur exposures. Id. -Like la and and this main reason for including sandstones of this type in types Ic, type lb type with lb and the differ in the and the attendant group I is their close association type mainly composition lack of features like In behaviour of the sandstone beds. This macro cross-bedding. some weathering type,

been mature exposures sole markings, indistinct grading and too is interpreted as having deposited by of in of gradational tops are recognizable. Amalgamation turbidity currents an area clay deposition. several beds is feature. In this thick a common way very beds In some Type /e.-The characteristics of this indicate that may originate. exceptional exposures type

amalgamation is indicated by multiple grading. The the sandstones were deposited by very mature turbi-

close association of this with characteristic currents. if becomes indistinct type more dity However, grading and the interbedded material becomes it is flysch-type sand beds and the presence of part of their silty very

typical features indicate a similar but not completely difficult to differentiatebetween turbidites and normal arenitic identical depositional mechanism. Similar sandstones current deposits. This type has no lithic or like Ic Id. The for this is have been called fluxoturbidites (Dzulynski et al., wacke equivalent or reason These that because of effects the thin bedded 1959) or proximal turbidites (Walker, 1967). weathering Individualfades interpretations 177

sandstones of lithic composition often have a much interpretation for this fades type. Van Hoorn (1970) massive Because of this arrived such lime- more appearance. difficulty of at a similar conclusion for graded

recognition these thinner sandstone beds were included stone breccias. in Section type lb (for instance 7: 0-150 m). Thick of the discussed above sequences types are

Type If. -The absence of grading and the occurrence inferred to have been deposited in therecent submarine of sandstone beds fan and fan off the of pebbles in the upper part of of this canyon, valley systems coast California Gorsline & Hand & type preclude interpretation as turbidity current (e.g. Emery, 1959;

deposits. Sandstones with dish structures and big Emery, 1964; Shepard, Dill & Von Rad, 1969 and clasts in the of the bed described The facies discussed top part are by many others). types are thought to

Stauffer (1967) in a sequence which ranges from deep have been deposited in similar environments although turbidites shallow-marine This water to and nonmarine not necessarily at the same depth. applies espec-

deposits. These sandstones with associated conglomer- ially to the laterally and vertically extensive occurrences and ates occur in between the turbidites and the shallow- of these facies types. For the smaller thinner marine Stauffer them different is follow- deposits. interprets as grain sequences a setting more likely (see

flow deposits. Sanders (1965, p. 208) states that in ing chapters). The differences in composition of the inertia due different of the flow layers (= grain flow) larger particles tend various types are to a history the of the flow. Dill describes sediments before resedimentation. The lithic sand- to move to top (1964)

moving sheets of sand flowing down steep submarine stones were resedimented before reworking in a These flows littoral could eliminatethe unstable slopes. start as traction carpets under the zone components.

influence of shoaling waves and once moving down The compositionally more mature sandstones came from lost their slope, continue as flowing-grain layers which are kept either a different source area or in motion the of unstable i.e. rock by tangential component gravity. components, fine-grained frag- The Sanders (op. cit.) argues that such grain flows could ments, during their stay in a littoral zone. facies and the fossils clasts in the keep moving on very gentle slopes. Shepard, Dill & types present as

von Rad (1969) consider sand flow (= grain flow) to limestone-rich varieties of this group indicate that be an important process in both La Jolla submarine they are of very local derivation. and fan In the fan describe canyon valley. valley they sand beds and sand beds the ABC graded showing part

- AND ofthe FACIES GROUP II SLUMP MUDFLOW Bouma sequence. From the foregoing I conclude DEPOSITS that an interpretation as a grain flow deposit does

indeed seem appropriate for this facies type, which The intensive deformations observed in sediments of

occurs interbedded in Ic and Id. types this are not as shown the absence of group tectonic, by cleavage, slickensides, etc. This means that deform-

Type Ig. -This type, too, is difficult to explain as the ation must have occurred shortly after deposition of The when the sediment lithified.This deposit a simple turbidity current. ungraded to was not yet relatively

matrix-rich lower with features of unconsolidated is the deform- poorly graded, part state proved by plastic soft sediment deformation, the sudden jumps in grain ation of the strata. The limestones, however, do not the erosive and indications of deformation but of sizes, strongly channelling appearance show simple plastic

of the lower part, all suggest a different mechanism. brittle fragmentation instead. All varieties can occur, The lower with lime clasts from deformed and very muddy part "floating" barely to completely broken-up

in matrix with contorted shale The whole is considered to a together fragments homogenized. group as a and indicate from and lenses, deposition a viscous sus- have been deposited by slumping (i.e. sliding)

pension (Sanders, 1965) or a mudflow. In this inter- mudflow (plastic mass flow to viscous fluid flow)

pretation the graded parts are thought to have been mechanisms (Dott, 1963). from turbid deposited a suspension associated with the

mudflow. The slightly calcareous shale above the Type Ha. -The general interpretation of this group

coarse-grained part of the turbidites indicates that cannot be amplified for this facies type. of the from part shale/mudstone was also deposited in the turbidity current. The great thickness ofthe graded Type lib.-The small-scale unconformities depicted and its of the deposit relatively great lateral extension suggest Figure 6, Plate lid constitute the best proof

that this suspension cloud was a true turbidity current synsedimentary origin of the associated soft sediment and not a mere cloud hovering on top of the mudflow. deformation. These unconformities are definitely not

The mudflow deposits are sometimes clear channel of tectonic origin because of the absolutely identical the fills and this proves strong erosion prior to deposition. facies both above and below unconformity surface. Their small distribution in the areal present- Ih. -Sanders that the of shown almost in 6 Type (1965) argues coarse part day outcrops as completely Figure of instead tectonic this type deposit was deposited by grain flow layers also suggests a sedimentary origin of a and that the of these beds The of lib above and below the only upper part graded was one. occurrence type deposited from turbidity currents. Considering the lowermost tongue of the Sierra Corisa Limestone of underwent grain sizes up to 10-15 cm this would seem a likely Member indicates that the limestone itself 178 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

some displacement. Proofs of this interpretation are lateral and vertical extensions of the deposit. Only

shown in Plate lie, where a slump ball is visible below regional correlations can lead to a more definite the base of the of these due sharp, irregularly scoured, limestone, interpretation deposits as to tectonic or to

and in 6 where the unconformities of the local Figure on top causes. The limestone are depicted. sharp, irregular base of

the limestone cannot be interpreted as an erosive

FACIES GROUP III - FINE-GRAINED SILICICLAS- channelling base of a clastic limestone, as the lime- TICS WHICH FORMED IN QUIET WATERS consists of and d. The stone types Xb, c sand-filled

cracks which are restricted the lower of the to part These fine-grained sediments were all deposited in

limestone are tongue interpreted as having originated quiet water. The water depth at which deposition the of the limestone. during displacement During or took place, however, varied greatly. Fossils indicate after these the cracks filled movements were by injected thatall ofthis formed in deposits group were marine to quick sand, i.e. a similar to the formation process very marginally marine environments. of sand dikes. The displacement ofthe limestone which

is still connected limestone in occurred in to lying situ, main clues permitting ofinterpretation

several phases, as is indicated by the ofseveral presence of these deposits are the close associations with lime- unconformities. The total displacement have been may stones of types Xa, b and c, on the one hand and the in the order of few of very small, possibly a tens metres. with d and the gradational relationships types Ic, e on

other. In fact the shale/mudstone interbeddedwith the

Type lie —Limestone blocks, lenses and beds described turbiditic sandstones is identical to deposits of this

lie surrounded associated with These indicate that the of as type are by or types type. relationships depth Ha and b, and can often be shown to have experien- deposition is intermediatebetween that of the shallow- ced movement relative to these strata. A spectacular water limestonesand therelatively deep-water turbidite is shown example in 7. This limestone The sideritic nodules so common in some Figure block, sequences. called the Pico Guillermo, in contrast to the Sierra deposits of this type do not permit of furtherrefinement Corisa has broken off its of this have been formed in example, adjoining deposits interpretation as they may and slid down into differentenvironment. of environments. a completely a great variety

lid.-This is transitional between lie and IHb.-This overlies seatearth horizons with Type type type of this without associated which form the Ig. Normally deposits type are intensively or coals, upper part and contorted, original bedding is rarely recognizable. of coarsening upwards sequences. The seatearth levels Flow lines visible in these formed in shallow above the are occasionally deposits were very water or water The is table These contain (Plate Ilf). homogenization interpreted as being (see types V). shales/mudstones a due to from mudflow. be deposition a The general absen- clearly marine fauna. Such a sequence can only of sand beds sandstone in these In the follow- ce or fragments interpreted as a transgressive sequence. which deposits, are often clearly erosive, is thought to ing pages it will be argued that coarsening upwards be due different factors. to two Firstly, the general sequences of type Vila, were formed by prograding absence of sand beds in the eroded strata and secondly delta distributaries. Taking into account this inter-

the unconsolidated of the sand beds eroded. sediments ofthis are considered have nature pretation, type to the formed in lagoons on delta top (Oomkens, 1967). Z/e.-This and Type type type Ilf, although containing clasts of different IIIc.-The association of this with a very composition, are texturally Type type types Ic,

identical to i.e. the type lid, coarse to very coarse IVa and VI Id indicates intermediateto shallow depths clasts "float" in form The bioturbation observed in a muddy matrix or a grain- of deposition. intensive framework with such matrix. In this indicates that the bedded supported a type polished samples indistinctly the clasts sandstone due this are mainly fragments which are to homogeneous appearance is probably to identical in turbidites of bioturbation. mottled homo- composition to type la occur- Such or secondarily

ring nearby. The one ofthis is are indicative of low rates exposure type interpreted geneous deposits relatively the of The as deposit a mudflow which originated locally of deposition (Moore & Scruton, 1957, fig. 13). and which fills channel Id turbidites. and crinoids a cut into type often fragmentary bryozoans probably also their and bio- owe appearance to scavenging occasional Type ///".-In contrast to type He, the quartz arenitic turbating activity, as is inferred from the cobbles and bouldersofthis have concentrationof fossil debris in distinct burrows. type cannot originated

locally. The superb rounding testifies to a long history of of rich transport the clasts before they were finally Type Hid. -The extremely fauna and flora locally in mudflow. in of this conditions deposited a present deposits type testify to very favourable to life and to the preservation of these The different somewhat types of this group all indicate unstable organisms. The generally preserved but conditions of the Whether indistinct Plate lid lib original depositional slopes. bedding (see depicting types of the this instability was due to sedimentary overloading or and Hid) suggests less intensive reworking tectonic than of IIIc. to movements can be deduced partly from the sediment by organisms in the case type Individualfades interpretations 179

The best depth indicators present are the dasyclada- FACIES GROUP V - DEPOSITS WITH AUTOCHTHO- seatearth level about NOUS PLANT GROWTH cean algae and the 20 to 40 m above this facies (Section 4:1590-1630 m). Both type The of rootlets in sediment of this is presence a type features indicatewater depths ofa few tens of metres at due to autochthonous plant growth. The importance the utmost. The ofZoophycos burrows indicates presence other facies is of this group in interpreting types very relatively quiet conditions at shallow to intermediate for noted who great as, instance, by Reading (1970) depths (Seilacher, 1967). states (p. 22):

"Although limited in amount, this association is of

Hie.-This a fauna similar to the one Type type yields disproportionate importance because it is the one

found in Hid but on the other hand it is transitional certain indicator of depth, proving, if not actual

to Ilia. The main difference with Hid is probably type emergence, very shallow water". the absence of sand-sized siliciclastic indi- material, a below a coal is taken to The presence of seatearth cating quiet conditions. The latter inference is very indicate an autochthonous origin of the coal. If no the observation that supported by solitary rugose seatearth was observed below a coally bed, this was corals sometimes in are preserved an upright position, considered to be of allochthounous origin.

i.e. probably in a position of growth.

often Type Pa.-The fining upwards sequence re- this is cognized in deposits of type interpreted as a FACIES GROUP IV - SILICICLASTICS DEPOSITED decrease in of currents to IN AGITATED WATERS gradual competency carry and deposit sand-sized material. Reading (op. cit.) This of the sediments group comprises a large part states the following concerning this feature :

included in (1970) agitated basin association. "In the of rootlets in Reading's some cases presence rippled The body fossils found indicate that most, if not all, sandstone and the decreasing grain size upward of this in marine strata were deposited fully to the seatearth that group through suggests plant growth marine environments. The distinctionof two decreased marginal began under water and current competence of is based on the established". sub-groups compositional maturity as plants became should be noted that the the sandstones. It rare The of sideritic concretions does not presence marine faunas in the marginal pelecypod occur mainly permit of further refinement of the interpretation of and of IVc and d. mudstones siltstones types the depositional environment.

IVa. -This type is associated with mature sand- of Type Fi.-This type coarsening upwards sequence,

stones and is considered to have been in an marine deposited with a seatearth on top, yielded marginally environment characterized by slightly agitated water. in This pelecypods one outcrop (Section 1,807 m).

Extensive of the sediments waves and reworking by that such is or means a sequence a shoaling regressive of the absence of unstable currents is the cause com- Cavaroc show the sequence. Ferm & (1969) possible ponents (fine-grained rock fragments) in the sand- of such in their 9. The development a sequence Fig. stones. of this facies is thus to be lower part type interpreted a

marine bay fill deposit, whereas the upper part was side of levee in Type IVb. -This type is closely associated with type deposited on the bay a or a coarse

IVa and is interpreted as having formed in the same overbank environment. In either case subaerial

environment but under conditions. to of autochthonous more agitated exposure was long enough permit plant growth.

Types IVc and (/.-The environment inferred for these

is similar to the invoked for IVa and Vc. - In contrast to Va and the sandstones two types ones b, Type types b, well sorted and washed.The i.e. shallow and slightly agitated to agitated waters. of this type are very that the of The main difference is the immature character of the associated marine fossils suggest maturity

sandstones. This is probably due to a difference in the sandstones is due to intensivereworking by marine

This that this is to be marine influences as the more marginally marine waves and currents. means type

faunas in these or associated with them. considered a formed in beaches occur types are as deposit emergent or barriers. Anotherfeaturesupporting this interpretation abraded 7F«.-This is difficult is the occasional presence of very big, tree Type type very to interpret as no stems size observed 5 X 0.5 m) in this facies sedimentary structures have been observed in these (max. type, beaches. this have which is a common phenomenon on recent deposits. In outcrop deposits of type a mas- In thin section the sive, homogeneous appearance. claimed be facies of salient features are the superb rounding ofsome of the Recent environments to analogues sand in and the of character for grains, up to 2.5 mm size, poor sorting. ancient coal measures paralic are, the of Its marine origin is proved by the limestones in which instance, coastal mangrove swamps, Everglades 1969, and the it is intercalated. Its homogeneous appearance may be Florida (Spackman et al., Scholl, 1969) due either bioturbation delta for formed the to very rapid deposition or to systems as, instance, by Mississippi (Moore & Scruton, 1957). River (Frazier & Osanik, 1969). 180 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

FACIES GROUP VI - DEPOSITS FORMED IN this facies would be much Now it type more common. CHANNELS (MIGRATING) is mainly restricted to Section 1, 750-860 m and Section 4, 1100-1145m. Fining upwards sequences showing upward decreases in maximum and median grain size, combined with

changes in the size and kind of the associated sedi- FACIES GROUP VII - DELTAIC AND MARINE mentary structures, have been interpreted for by, REGRESSIVE SEQUENCES

instance, Allen (1965a, b) and Visher (1965a, b) as The increase in size with the attendant representing the deposits of migrating rivers. Similar upward grain also be formed channels change in the kinds ofsedimentary structures deposits can by migrating in present, can be interpreted in terms of an increase in water marine environments. The sequences observed can be

agitation. Such a is either a interpreted in terms of flow regime and of position sequence regressive marine deltaic relative to the channel. The parting lineationhas been sequence or a sequence (Visher, 1965b).

to Both are due a predominance ofsedimentationover formed in the lower part of the upper flow regime, the subsidence which and cross-stratification in the causes shoaling eventually large upper part of the lower because of the of the i.e. flow regime and the laminated and rippled sands and emergence prograding coast,

ofthe these are A marine silts in the lower part lower flow regime and by regressive sequences. simple regressive usually contains well washed vertical accretion. The macro cross-bedded sands and sequence littoral deposits and lagoonal sediments, whilst the the sands with parting lineation are both in-channel deltaic is characterized by the of deposits. The micro cross-bedded sands and silts are sequence presence fluvial deposits. partly in-channel and vertical accretion deposits. The

overlying laminatedsands, silts and mudstones are also Vila.-This of vertical accretion deposits. A lag deposit is sometimes Type type coarsening upwards sequence the base of these The character of (c.u.s.), which locally contains marine fossils at the present at sequences. is channel fills these lag deposits, together with the faunas of the base, usually topped by or fining up- of VIb. wards identical to the deposits type associated facies types and the presence or absence of sequences In other these fluviatile which autochthonous plant growth in the vertical accretion words, are deposits form the of the The sandstones below deposits, form the most important clues for deciding top part c.u.s. also the distinctly fluvial part of the are upon a fluvial or a marine environment respectively. sequence

lithic arenites which means that these sandstones were

not reworked by waves or currents. The deltaic Via.- of this associated Type Deposits type are closely has been discussed sequence by, among others, with facies types containing marine fossils (Section 3, Scruton (1960), Visher (1965b), Fisher et al. (1969). 152 Section and 407 Section m; 5, 304 m; 12, 390 m). With their data available it is possible to differentiate This association indicates an origin in a marine en- between the of these various parts sequences according vironment for this facies. This would also agree with the to the respective depositional environments. This relatively mature composition of the sandstones. The for differentiationis only feasible for the major c.u.s., lower parts of these sometimes conglo- sequences, the minor different have be sequences slightly settings to meratic, indicate that competent currents must have invoked. The pro-delta environmentis characterized by occurred. In a marine environment such strong cur- shales/mudstones and silts which may show lamination, rents are likely to be at least partly due to tides. The rippling, some graded bedding and some burrowing. presence of this facies type is one ofthe few indications When measuring a section, the selection of the horizon of the influence of tides in the entire interval studied at which a c.u.s. is considered to begin is arbitrary as features like herring-bone cross-stratification or because of the gradational nature of this contact. In flaser und linsen structures have not been identified. general graded beds were not considered to belong to of type Vila. The delta-front deposits consist rippled VIb.- of this and laminated tabular cross-bedded Type Fining upwards sequences type can sands, low-angle be identifiedas being offluvial origin by the absence of sands, sands deposited in minor channels, and trough marine organisms in the lag deposits, by the presence cross-bedded sands. These sediments were deposited by ofrootlets the and the in upperpart ofthe sequences by migrating distributary mouth bars, subaqueous levees, abundant transported plant fragments (Visher, 1965b). distal bars and marginal sheet sands. The only delta Notable this included this in facies type is the immaturecomposition top deposits in type are the fining up- of the sands which is feature of fluviatile wards in the of the a common sequences upper part sequences. sands. The of several centimetres in These included in this their formation presence clay galls are type as on diameter and of tree logs up to a metre in length, top of a c.u.s. is the logical consequence of a single that the rivers the of delta be- proves were able to transport coarse process, i.e. extension a distributary the material. Nevertheless, the coarsest quartz grains and cause of sedimentation at its mouth. Although lithic fragments are not over 2 mm in maximum dia- bases of these fining upwards sequences are erosive, meter. This is taken to indicate that no coarse material extensive erosion ofthe underlying mouth bar deposits was supplied by the rivers to the depositional basin. is rare. The water depth in which these major c.u.s. If considered fining upwards sequences on top of coarsening were formed is to have been of the same included the order the of the The for upwards sequences were not in latter, as length sequence. reason Individualfades interpretations 181

this assumption is the dominance ofsand and silt sized thick. The recognition of the various forms is ex-

material in these sequences, which materials do not tremely difficult in stratigraphic sections as the lateral much finer sediments. The of these seldom be observed. compact as as grained major equivalents deposits can

coarsening upwards sequences are considered to have Even if exposures are favourable, the exact time formed because of the of of has be prograding major delta equivalence strata yet to proved. Considering

distributaries into a relatively deep hydrographic only the thickness it seems likely that the examples basin. The included minor sequences in this type only present in Section 10, 598-643 m, are chenier deposits. above This indicates that For all other ofthis facies each ofthe occur major sequences. they occurrences type,

were formed in one of the delta-top environments. The alternatives mentioned seems equally likely to me.

prograding of minor distributaries into delta-top

lagoons, or crevassing of major distributaries are Type VIId. -The absence of seatearth levels indicates

invoked to explain their presence. that the upper part of this facies type was never for The alternation with the emergent long periods. fossiliferous of Ilie Type Vllb.-The mature composition of the sandstones relatively deposits suggests open

and the association with sediments with marine faunas marine conditions. Because of these features this type is formed offshore bars. the main differences Vila. The reduced interpreted as having as are to type of unstable in the sands importance fragments suggests

ofthe sands FACIES GROUP VIII - TRANSGRESSIVE reworking by waves and currents. Seatearth levels be in associated sediments. SEQUENCES may present closely If this the is case, however, especially the sandstones Type Villa.-The. upward decrease in grain size of this are different from those inferred to be offluviatile very decrease type is interpreted as a gradual in water origin. The main occurrence of this (Section 10, type In the best of this facies agitation. two exposures type 500-597 m) can only be interpreted as a regressive (Section 4, 1148-1190m; Section 10, 643-646 m) it marine Only in the next chapter will a sequence. overlies sediments with seatearth horizons and in turn more detailed interpretation be possible. Another is overlain by sediments containing marine fossils. In ofthis differs occurrence type (Section 12, 255-280 m) other words, these sediments form a deepening se- from the first in that channel fills at the are present top. former land surfaces quence. As they begin on (the This is The more like the normal deltaic sequence. seatearth also be called trans- horizons) they may marine fauna at 295 m and the mature character ofthe discussed the gressive sequences. Visher (1965b) sandstones indicate, however, that this is not a normal forms of aspects of different transgressive sequences. fluviatile delta. The features mentioned are best Fisher (1961) described the sequences at present explained ifthis example is interpreted as a tidal delta. With developing on the Atlantic coast of New Jersey. their data the under discussion be inter- type can VIIc.-This of Type type coarsening upwards sequence preted. Fisher considers that in basins with tides of comprises compositionally mature sandstones which limited magnitude and not too great wave energy a are commonly well sorted. Further characteristics are transgression would leave the following record: the often evenly laminated and the close aspect such "A stratigraphic section through a trans- association with marine faunas. The of a presence would show transition from gressive sequence a lagoo- seatearth is indicative of This (Vc) emergence. nal shoreline deposits to deeper lagoonal deposits, combination of features is characteristic of recent disconforma- then up into lagoonal shoreline deposits, beach In delta number deposits. recent systems a of bly overlain by the sediments of the beach and of the beach forms can be distinguished (Todd, 1968; open sea". Hails & Hoyt, 1968; Hoyt, 1969). The forms of sandy In the examples observed, lagoonal deposits beaches relevant for this facies interpreting type are: thin This indicates instance Illb) are or absent. (1) barrier beaches which, according to Hoyt, are of of the This extensive erosion part sequence. means formed by slow submergence of pre-existing beach that the sharp bases of some of these sandstones are ridges. These form extensive deposits which may very surfaces which be of disconformity can regional are up to several tens of metres thick; importance (Oomkens, 1967). formed and (2) spits are by longshore currents may A transgressive sequence is not necessarily developed rise barrier. give to a Hardly distinguishable from 1) siliciclastic dealt with above. Lime- as a sequence as in stratigraphic sections; lower stones may also occur in the part (Section 5, (3) cheniers are formed by periodic reworking of a 580 of these 200-280 m; Section 12, m ??). Aspects do form prograding muddy coast. They not very various developments will be dealt with in the following extensive sand deposits. The thickness of the Lousiana chapter. examples does not exceed 8 m (Hoyt, 1969);

"normal" beach deltaic here (4) ridges in areas are FACIES GROUP IX - KARST INFILLINGS considered to be those sandy beaches which form due delicate balance of and sediment IXa. -The of vertical of to a waves, currents Type presence originally pipes

at and which to seven metres in limestones with associated supply a specific place are not produced up depth These limestone and of by reworking of a pre-existing muddy shore. conglomerates, development se-

also and can only be explained by inferring deposits may be quite extensive relatively condary porosity E. de GraafF: Three delta 182 W. J. van Upper Carboniferous systems, Spain

and solution meteoric As nodular of these Adnet Beds is due subaerial erosion by waters. appearance to a the ofthis facies is indicative of combinationof solution ofthe such, presence prolon- subaqueous fine-grained which it is carbonate with ged emergence of the limestones on present. muds, alternating subaqueous lithi-

The karst holes are filled with sands containing a fication and possible shrinkage-cracking of these sediments. Their contention is that these marine fauna not present in the limestones. This processes indicates that erosion probably occurred in near- produced a rubble ofsemi-consolidated to consolidated

littoral environments (cf. Newell & Rigby, 1957, nodules which were embedded in an insoluble residue. the evidence in this Plate XX, Fig. 1). The sequences observed in Paleontological proves particular case of Villa the that the of low. from sandstones are commonly type or VIIc, rate deposition was very Apart with without indications of autochthonous the the of latter or pure paleontological evidence, preservation follows: after the of and hematite plant growth (Vc). This is interpreted as ammonites, presence manganese

the karstified also indicate low sedimentationrates. In the a more of less prolonged emergence crusts case limestone surface was transgressed by the sea. In this of type Xa, relatively low sedimentation rates are not the sands reworked is indicated the of few shallow sea were extensively unlikely as by presence a phos- before deposition as is proved by the extremely phatic nodules and by the preservation of a goniatite These undeterminable mature composition of the sandstones. newly found in Section 21 (532 m). This the of the lower side and deposited sands first filled in depressions goniatite had a fairly well preserved a surface and of the corroded side. Most other part secondary porosity. Locally upper fossils, however, are could emergent beaches developed which support well preserved, which is due to an oncolitic coating on after time collected. The oncolitic and plant growth but some these, too, were most specimens coatings submerged and deposits of type Villa, developed. the divers fauna, in addition to the calcareous algae

In where limestone was not the found in this facies indicate an areas emerging type, important contact with the overlying sands of this facies is either difference to the environment of deposition invoked

but for the Adnet Beds. While the latter to sharp, not clearly erosive, or gradual. are thought the have been deposited at depths of up to 4,500 m,

former were certainly formedin much shallower water.

FACIES GROUP X - MARINE LIMESTONES The of makes 50 presence algae waterdepths exceeding

to 100 m most The of The fossils found in all limestone deposits in this area unlikely. presence diagenetic dolomite in the insoluble-rich of this in are all marine limestones. parts type, prove that these deposits The which in in combination with interpenetrating contacts between algae, are present great quantities facies and which in "clasts", makes it likely that post-depositional pressure most types general occur through- solution Nevertheless, I out that the limestones phenomena were important. the entire section, prove were in shallow the of consider it likely that the mechanisms invoked by deposited water. Especially presence

Garrison & Fisher an in water. played important part dasycladacean algae indicates very shallow pro- the rock fabric observed. The of With the data and interpretations presented by Racz ducing occurrence this the base of the and Abismo Lime- b) available it be concluded that the type at Agujas (1966a, may Members isolated lenses in the southern algal assemblages observed in the various limestone stone or as

flank of the Castilleria Syncline indicates, that it was members indicate waterdepths not exceeding 50 to

to form as the first carbonate deposit in areas 100 m. If dasycladacean algae and oncolites are likely with of siliciclastic material. present, they indicate waterdepths not greater than a diminishing supply

10-25 m. From sedimentological evidence presented

Xb.-Th.is facies is considered to have been later it even becomes obvious that waterdepths in the Type type under conditions order of a few metres were common. From the mere deposited relatively quiet because of

de- the high carbonate mud content. The poorly bedded presence of the generally fairly pure limestone

and often are posits one more general conclusion can be drawn: in apparently homogeneous appearance

due to extensive bioturbationon both this area the supply of siliciclastics at many points and possibly a macro

and micro scale. In the same moments was negligible. a manner, scavenging

activity of some of the faunal elements causing homo- the sediment is invoked the Type Xa.-The complete lateral and vertical gradation genization of to explain scattered of crinoid broken with siliciclastic mudstones with approximately the widely occurrences ossicles, The is in same fossil content, the highly characteristic fossil shells, etc.. only problem that, except type distinct burrows tracks have been ob- content itself, the lack of current-induced sedimentary Xj, or rarely served in of the limestone facies structures, the fine-grained matrix in between the any types. However, from the flora and fauna it is obvious that "clasts" cannot be explained satisfactorily by assuming present facies conditions suitable for the of rich a normal, i.e. clastic mode of deposition of this were occurrence a All these characteristics consider benthonic fauna both and in the sediments. type. obliged me to upon other interpretations. Garrison & Fisher (1969), in Moore & Scruton (1957) showed that in recent their siliciclastic description of the Jurassic Adnet Beds, figure a deposits complete homogenization may number of specimens of these nodular limestones. occur as aresult of the burrowing activity oforganisms

These similar to which do not leave other trace of their photographs (Figs. 5, 6, 7(1) are very any presence also of The dolomitizat- our Plate Va. Garrison & Fisher argue, that the (see interpretation type Xm). Individualfades interpretations 183

ion observed in this facies is connected with that the "leaves" formed framework type proof an open solution and such considerd could filter down. pressure seams as is to be through which overlying sediments

That it is of = The remainder of the then filled with diagenetic. not synsedimentary ( pri- pore space was void- mary) origin is also indicated by the fact that the fibrous and equant sparry calcite, i.e. typical dolomitized fine medium It is obvious that the of parts are to crystalline, filling sequences. proportion whilst primary dolomites tend to be much more fine- crystalline calcite cement and original carbonate Furthermore dolomites much sediment be grained. primary are may vary greatly. Furthermore, it can

more extensive than the dolomite streaks of this facies seen that even in the specimen shown on Plate VIb which are at best a few decimetres long. Nevertheless, the fine structures and textures which make the algae

the restriction of this dolomitization to laterally recognizable as such, are ill-preserved. In the other

extensive association with and the sequences suggests an some examples depicted, algae are not recognizable primary factor influencing the composition of the amount of sediment in relation to the amount of sediment. is much In crystalline cement greater. some examples

of fibrous calcite (Plate Vila) only vague masses are

Ax.-This facies considered have a On Plates Type type, too, is to present, pervading mudstone/wackestone. and almost brecciated been deposited under relatively quiet conditions Vlf, g partly completely exam- because of this facies shown. This brecciation is of the predominance of carbonate mud. The ples type are

massive character indicate a to more is thought to more interpreted as synsedimentary early diagenetic continuous of and ofsediments of this underthe influence of processes deposition homogenization. collapse type sediments. That brecciation is indeed However, the local presence of non-bedded, algal overlying a very boundstones that the massive is the fact that the suggests homogeneous early phenomenon proved by only least be feature. sediment and the calcite is brecciated. appearance may at partly an original not crystalline The The of the breccia and the rare occurrences of birdseye structures with very sharp edges fragments fills that lack of indications of deformation that geopetal prove organic or inorganic con- plastic prove solidationof the sediment occurred locally immediately this sediment was consolidated and possibly lithified

after Shinn soon after The example pictured on deposition. (1968) argues that birdseye very deposition. Plate Vh is of different because of the structures are good evidence of a supratidal or intrati- a slightly type

dal depositional environment. Whether this holds radiating tube-like structures in the sparite filled

for kind of be cavities. Furthermore, the cavities have much good every birdseye remains to proved greater but their further corroborates the dimensions than in other presence argument any example.

in favour of shallow water a origin of the limestones However different the various occurrences of these under discussion. sparite patches may look at first sight, they nevertheless De (1969) the of have common that associated Meijer proved presence non- in they all occur closely calcareous in similar algae limestones from the slightly with or surrounded by facies type Xc. Furthermore, older Formation. He also found these Lois-Ciguera any single occurrence shows complete gradations to non-calcareous in from this facies facies Xc. such series be ob- algae a sample type. type Although no can He considers these non-calcareous collected algae, which were served in the field, from the samples a also observed in other facies have been continuous be types, to series can arranged showing gradations

important agents in the entrapment and consolidation from one form to another. This strongly suggests a of these carbonate sediments. generally similar mode of formation with minor

differences in environment for most occurrences,

Xd. -The the Type sample showing most important which caused the different aspects of this type.

clues as to the mode of formation of this in have been type was not Organisms, some cases proved to algae, collected from Member the Agujas Limestone but played an important role in the formation of these from the Sierra Corisa Limestone Member. This filled and the of sparite cavities attendant entrapment sample was collected about 150 m west of the line sediment. Although it has been shown that the algae which Section along 4 was measured, at the point are probably no longer in position of life, the indicat- where the limestone interfingers with fine-grained ions of early consolidation of the entrapped sediment siliciclastics. This sample is shown on Plate Via, b. In and the occurrence of specimens as depicted on Plate these it be that the be photographs can seen "primary" Vh lead me to consider the rocks ofthis facies type to components of the rock are the undulating fronds or boundstones. Admittedly, it is possible to prove this "leaves" of codiacean algae (phylloid algae in the interpretation for only a minority of the examples terminology of Pray & Wray, 1963). According to studied. Therefore it is wiser to mention the inter-

Pray & Wray, these phylloid algae probably grew as pretation of very similar deposits presented by Pray & The for this be upright plants (p. 216). reason assumption Wray (1963). They consider their examples to is thebilateralsymmetry ofthe internalstructures. This biostromal deposits formed by essentially in situ clastic that the means sub-horizontal position of the "leaves" accumulation of algal fragments in a relatively indicates that have fallen Because of the turbulent environment. In the of the they over. case Agujas small quantity of sediment present in the sample Limestone Member and the other limestones studied, the formed that depicted, fronds necessarily a grain- however, I consider it most unlikely these deposits supported framework. The geopetal structures are were formed in a relatively turbulent environment 184 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

of their association with mudstones and Included in this facies and in the because type type Xg are

wackestones. Packstones and oolitic grainstones truely peculiar "mottled" pelsparitic grainstones which are associated Plates d. As shown in indicating agitated water are not closely depicted on Vllh, Villa, b, c, with this facies these the "mottles" sub-horizontal type. photographs, are discussed with the rods and of various dimensions. The Someof the sparite patches agree blebs, plates

definitionof the term stromatactis given by Chilingar difference in composition between the rounded

& Bissell (1967, p. 167), and this term has been used "mottles", which are slightly more sparitic, and the loosely during fieldwork and in Fig. 12. intervening sediment, which contains more matrix, is

primary. It is only accentuated by the presence of and For the the lithological characteristics of pressure solution seams stylolites. inter- identical those of of the environment of these these two types are nearly to types pretation depositional

Xb and Xc, the interpretation is identical too. The pelsparitic grainstones the genesis of the pellets is of

transitional contacts which characterize these two importance. This origin, however, is quite difficult to be due the lateral ofthe establish. The and the types are thought to to shifting subspherical shape good realms of Xb and Xc. There clues of the do definite clues. types are as yet no sorting pellets not provide any Xf for Folk des- as to whether Xe or represent, instance, a (1962), although using pellets as a purely difference in nevertheless considers ofthose shoaling sequence or a wave energy. criptive term, a majority of fecal He bases pellets to be very probably origin. this the and the packstones and grainstones ofthis fades view on generally constant size, shape

content originated in a strongly agitated water environment extra high of organic matter. Beales (1965)

(Plumley et al., 1962). This is indicatedby the presence states that pellets may be formed by organic ag- of overturned and and of oolites, the occasional presence glutination, inorganic precipitation cementat-

rounded fragments ofchaetetid corals, of well rounded ion, recrystallization, or by a combination of these of pebbles of grainstone, and of quartz arenitic pebbles. processes. Although such a variety processes may role in the remarkable The presence of a few very angular fragments of the play a pellet formation,

underlying mudstone also suggests strong currents similarity and uniformity of ancient pelletiferous

which could erode consolidated sediment. In the best limestones suggest similar depositional and diagenetic these in histories. If the of fecal exposed example deposits seem to grade pellets are origin very complete direction into Xb Xi. Those of the sediment have occurred. Beales upward or two types reworking must the this represent a much less agitated environment. In Xg no (p. 52) states following concerning point: distinct definite observed. "A lack of skeletal uniform structures or sequence were coarse debris, pellet size, This is considered have been either and insoluble type to deposited commonly pale coloration, a meagre

by a migrating channel or by a migrating shoal or bar. residue characterize many pelleted limestones. The Other such the of the "mott- fine of debris could be due aspects as interpretation comminution skeletal to led" will be dealt with under Xh. feverish of and parts type activity many scavengers working

reworking the sediments for every last vestige of nutrient material. and upward change from mudstones and Alternatively, perhaps more wackestones into and likely, the shallow to extremely shallow water, which packstones grainstones represents

environmental seem to a change from relatively quiet water deposits into interpretations suggest, may have been of nutrients in the deposits formed in relatively agitated water. In largely stripped marginal

and only a restricted fauna and flora could analogy to siliciclastic deposits, such a sequence is here areas, Under called survive in the sometimes vast interior areas. a coarsening upwards sequence. In siliciclastic be such circumstances mud-ingesting organisms would deposits a coarsening upwards sequence may safely

and amounts of a pellet large interpreted as shoaling sequence and often it can also process predominantly sediment for the little food contained be to a precipitated proved be regressive sequence. In carbonates this is much difficult The evidence for therein. more to prove.

this facies will Whatever the pelleting organisms were, most of interpreting type as a shoaling sequence of be presented in the next chapter, where the areal them left no trace of burrows in the majority facies These facies limestones." relationships are discussed. areal pelleted relationships form the best evidence for this and other This last remark points towards the main difficulty the interpretations. Nevertheless, the oolitic grainstones in interpreting our examples. Although pellets

themselves be formed well be fecal the observed are can interpreted as deposits in may pellets, structures relatively agitated and shallow water. definitely not burrows. Dr. CI. L. V. Monty of Liege

The arenitic which in that non-calcareous quartz pebbles occur type Xg University suggested algae played and additional evidence of role in their formation because of the in this type constitute a numerous but much threads and tubes visible in thin sections under strongly agitated water, a more important algal conclusion can be drawn from their presence. A very high magnifications (lOOx and over) (pers. comm.).

or shallow marine drift Because of the of these non-calcareous algae, competent longshore system presence must have existed at the time of deposition of the whose importance in the production, entrapment and Agujas Limestone Member in order for these pebbles consolidation of sediment has been shown by Monty to be deposited in this place. (1965a, 1965b, 1967), the platy structures shown on Individualfades interpretations 185

Plate Villa, b are considered as algal mats. In the equally well explained by assuming a relatively low

light of this interpretation the possibility that the sedimentation rate of carbonate material, causing less of and of fecal has dilution of the siliciclastics. The pellets, too, are algal not origin, to preservation of the be borne in mind. A third possibility is indicated by chaetetid, auloporid and "lithostrotionid" corals and the of small foraminifera of of of the and also of presence in some samples many dasycladacean possibly the pellet size. The preservation of these foraminifera phylloid codiacean algae in position of growth raises

varies from good to very poor. This indicates that part the question whether these organisms needed a hard of the pellets originated by micritization ( = grain substrate. No indications of early lithification were diminution, Wolf, 1965) of small fossils. observed. The only hard objects available were due dessiccation of these the ofother Disruption to mats seems a probably remains organisms. Although no likely process to explain the occurrence of the dis- special attention was paid to this feature in the field, I continuous plates and the rounded blebs. This dessic- have the impression that the corals and algae could cation subaerial Sub- settle and flourish was not necessarily a process. on a, possibly consolidated, muddy aqueous syneresis may well have produced the rounded substrate (cf. Rich, 1969, p. 353). The number of and the of of these corals and in shapes concretionary aspect some algae present growth position at the "mottles". of of this induce majority occurrences type me to consider be biostromal Compared to the facies types already described the it to a coralgal deposit formed in and Xh of and in occurrence types Xg distinctly quiet water. regularly bedded sequences together with more This fades type with its rich floras and faunas difference. Whether massive parts is an important the commonly occurs right on top of the agitated water of of these of and Xh. These massive, homogeneous appearance parts deposits types Xg two types were facies is due to biogenic homogenization, extremely interpreted as subtidal to intratidal deposits with

or to continuous, in the ofthe rapid deposition a very uninterrupted especially upper part sequence conditions sedimentation process could not be established. The unfavourable to most forms of life. This return to of well-bedded that with presence parts suggests, however, favourable conditions a fairly great variety of life least of these forms is at part sequences were deposited too interpreted as a deepening or a transgressive

for to Because of the the oolitic and rapidly organic homogenization occur. sequence. deepening,

The preceding interpretations can now be combined pelsparitic grainstone shoals "drowned" and their and summarized. The often oolitic surface then covered the corals coarse, packstones upper was by settling in Rich and grainstones were deposited probably sometimes and algae. (1969) also considers Chaetetes to have shoals and in channels. A in and than where emergent migrating relatively grown slightly deeper quieter water rich and varied flora could flourish in these environ- the oolites and coated grains were formed and deposi- sedimentation ted Areal distribution of facies ments. Relatively high rates are (Fig. 10, p. 357). characteristic of part of these deposits. On top of these supporting this interpretation will be dealt with in the shoals the water was less agitated as is deduced from next chapter. the decreasing amount of oolites. Most agitated conditions assumed have occurred at the rims are to Type Xj.-The clastic wackestones, packstones and of the shoals where the broke. Conditions oflife waves of this in grainstones type were deposited shallow, furthermore less favourable is inferred from were as water. and fairly agitated Bedding vague channelling absence of fauna. this the common a preserved In that are preserved, indicating burrowing organisms environment huge amounts of pellets were formed by unable rework and though present, were to homogenize some mechanism (a fecal, algal or micritization origin all of the sediment. The genetic significance of the

considered the most The are likely). pelletiferous chertification along bedding planes is not clear. From sediment was trapped and consolidated in algal mats. observations made on thin sections it seems likely that

The algal mats have been preserved as such or were porosity differences played an important role in broken dessiccation in either subaerial sub- by a or a determining the location of the concretions. environment. The of which aqueous depth water in these formed is considered have been deposits were to Xk.-TYm shows Type type, too, a coarsening upwards in the subtidal to intratidal range. sequence like type Xh. It differs from Xh in that it of Xb instead of begins on deposits type type Xc and

Xi.-The rich coral fauna and the rich that it does not contain oolites in its Type equally upper part. Like with the of other faunal Xh it is for algal flora, together presence type considered, reasons discussed in the indicate conditions favourable life. The elements, to next chapter, to represent a shoaling sequence. presence of oncolites points towards a shallow, subtidal environment with Xl.-Thb, facies formed in sluggish currents (Logan, Rezak, Type type was quiet waters

The latter is also in environment not favourable life. The & Ginsburg, 1964). interpretation an very to the of mudstone in between the main in favour of this supported by presence argument interpretation is the corals. The of siliciclastic observation that this be intermediate relatively high content type seems to insolubles in this facies type may be interpreted in between Xb and Xm. various It somewhat ways. may mean a greater supply of these materials. Its be Type Xm.-These fetid limestones presence may, however, yield a relatively 186 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

of insoluble material. This sizes ofthese sediments difficult but high quantity organic high are to establish, are

content of organics is the main clue for interpreting thought to have been in the clay to silt range. these unfossiliferous and undisturbed deposits. Purdy (1964), in his discussion ofthe influence ofsedimentary Type Xn.-This facies was mainly differentiated be- substrates on benthonic faunas states that ifthe content cause of its close association with shale/mudstone of of matter in a sediment is too high (approx. organic found type Illb, which in turn was overlying a decomposition produces too toxic 3-4%), many of Vila. Further- coarsening upwards sequence type compounds. Especially in poorly permeable, i.e. fine- this facies differs from the similar more, type very deposits this leads to conditions hostile to grained Xb and that types Xi in it contains pelecypods which benthonic organisms. From the complete absence of a found in other limestone were not any type. Type Illb flora or fauna and the undisturbed recognizable aspect formed is interpreted as a lagoonal mudstone after the of even the thinnest sedimentary laminae, I conclude marsh, in which the first Por si Acaso coal formed, was that no benthonic life could be supported by this drowned. Because Xn overlies Illb, and as it is of facies type. shallow water origin, it is interpreted as having been The cross-lamination with few erosional features and in the environment deposited same lagoonal on the top chiefly tangential contacts between the laminae, i.e. of the delta. Such lagoonal limestones are mentioned kappa-cross-stratification (Allen, 1963, Fig. 4a) is by Oomkens (1967). indicative of relatively high deposition rates from Their indicates that the suspended load. presence Xo. -These breccias to in not Type conglomerates occurring water above the depositional interface was types Xb or Xp are products of local erosion and stagnant, at least not all the time, but that sluggish redeposition. This is deduced from the poorly rounded currents occurred from time to time. This favours the forms of the clasts and from their composition which is interpretation that toxic conditions in and upon the similar to that of the underlying strata. Their sediment and not a lack of circulation of the water very occurrence in otherwise relatively quiet water deposits above the sediment, were the main factor responsible that they have originated due to local for the absence of benthonic life in these fine-grained suggests may currents caused by storm (Hayes, 1967). clastic deposits. surge

The relative depth of deposition of these quiet water

deposits can, once more, only be established after Type Xp. -As this type differs only from type Xe, in that the areal facies considering relationships. Nevertheless, it is transitional from XI instead of from Xc, its en-

the of this to ofthe vironment of is considered be the general similarity type some exam- deposition to nearly

ples described by Wilson (1969) suggests an environ- same. The environmental significance of this sequence of least than that of ment deposition at slightly deeper in terms water depth or wave agitation is not yet inferred for the other limestone types. understood. From the combined interpretations of Xb

As extensive recrystallization to microspar or even and XI it is clear that this sequence represents con-

pseudospar (Folk 1965) has occurred, the original grain ditions gradually more favourable to life.

CHAPTER IV

AREAL INTERPRETATION OF LATERAL AND VERTICAL FACIES RELATIONS

Within the various structural units (Fig. 8) litho- Section 4 immature turbidites (type Ic) also occur. stratigraphic correlations are easy to make. Corre- Tracing this interval laterally from Sections 1 to 4 lations their between the various structural units are based proved that these immature turbidites make data. These first south of Section and in mainly on paleontological regional aspects appearance 2 increase will be dealt with in the following chapter. Only importance towards Section 4. More to the east they of the obvious Muda some more lithostratigraphic corre- disappear again, and north of San Cebrian de lations will be mentionedin this chapter and the facies only mature turbidites have been observed. The sole relationships will be discussed in their stratigraphic markings indicate current directions from SW to NE The This of sequence. approximate distribution of the major (Fig. 14a). direction is oblique to the plane a facies is shown Enclosure section Sections and indicates groups in 3. cross through 1 4. This

that the basal part of Section 4 cannot be considered

to be more proximal than the equivalent deposits in SOUTH FLANK OF THE CASTILLERÍA SYNCLINE Section 1. It is for this reason that I the and interpret (Figures 8, 9a, b, c Enclosures 1, 3, 5) of this interval somewhat present-day outcrop as a

The lowermost part of Sections 1 and 4 consists of oblique transverse section through submarine fan quartz arenitic turbidites. In Section 1 only mature valley deposits. Menard (1955) and Shepard et al. turbidites (types Id and e) are present, whilst in (1969), among others, describe recent fan valleys in Areal interpretation offades relations 187

8. Structural of the studied Fig. map area. W. E. de Graaff: Rhree delta 188 J. van Upper Carboniferous systems, Spain

which sands in the axial Above the limestone horizon another interval coarser were deposited parts from the differences with deltaic which than on the levees. Apart in grain follows, deposits are considered to sizes, differences in sedimentary structures were also have formed in bays and sounds on the delta. Crevasse noted. These differences, if translated into terms of splay deposits are probably important in this interval. indicate the of The lenses of the second levelofthe Socavon Limestone relative maturity, presence more in the axial of the In Member overlie this interval. This limestone horizon immature currents parts valleys. traced far the lower the axial parts, sand flow, creep and slumping may cannot be as west as one. Mapping also be important. In this interpretation Section 4 is evidence indicates that the two limestone lenses below Cebrian located somewhere near the axis of the valley whilst the San coals in Section 5 probably correlate

Section 1 and the deposits north of San Cebrian were with this second limestone level. In Section 4 (approx.

on the levees. 800 and near San well deposited nearer to or even m) Cebrian, washed, compo- sandstones The overlying shale/mudstone sequence indicates sitionally mature are present above the that the supply of coarse siliciclastics was negligible limestone. This is most probably the same sandstone for considerable time. is between the limestone lenses of Section 5 a as present These arenitic sandstones The succeeding lithic arenitic turbidites are com- (100-132 m). quartz are

as of the destructional of positionally identical to the deltaic and fluviatile(?) interpreted deposits phase delta sandstones above them. In Section 4 graded sand beds the underlying system. This interpretation means that the lower limestone lens in Section 5 to the base of the deltaic only (80- are present up coarsening The currents 95 m) correlates with the second level of the Socavon upwards sequence, (c.u.s.). turbidity Limestone Member. The second limestone lens of which deposited these turbidites are therefore inferred

the delta front where Section 5 is therefore considered as the to have originated right on the (132-140 m) third level of the Socavon Limestone Member sediment was not reworked by marine waves and (see also the discussion of currents. The absence of slumping phenomena in the stratigraphical nomenclature). of the In Section 4 the lower parts coarsening upwards sequences transgressive sequence overlying brings to mind the possibility that turbidity currents the Socavon Limestone Member is followed by lithic originated at the river mouth during flood stages, as arenitic turbidites. Laterally this turbidite sequence Heezen al. be traced far. The small areal extension for instance suggested by et (1964), cannot very

Houbolt & Jonker (1968), Nesterof et al. (1969) and of these turbidites may be explained by interpreting van Straaten (1959). Reading (1970), discussing these deposits as having formed in a delta front gully his river generated sandstone association, also con- (van Straaten, 1959; Shepard, 1956). The turbidite cluded that turbidity currents may originate from sequence is overlain by deltaic deposits which in their The sole marks measured these contain minable coals. These the San rivers in flood. on upper part are turbidites indicate derivation from the west (cf. Fig. Cebrian coals which are mined near the village of the

14a). This constitutes a fairly marked difference to the same name. These coals were formed on the delta direction of of the arenitic turbidites. and intercalated with fluviatile sandstones supply quartz plain are

This difference is an indication of the important and fine-grained overbank and probable bay fill changes in the general setting of the area during the deposits. the interval. time represented by shale/mudstone These San Cebrian coals are overlain by marine

The deltaic and fluviatile sandstones immediately sediments deposited after a transgression (Section 4: of the succeeding the lithic arenitic turbidites are mainly 1145 m; Section 5: 222 m). Good exposures

distributary mouth bar and channel deposits. At the actual contact between the coal measures and the shore of the Vanes reservoir (Spanish: Pantano de overlying transgressive sediments are rare, but the map Requejada; also Pantano de Vanes) where the only configuration west of Vergano definitely indicates im- distinct fluviatile erosion below the surface deposits were recognized, cross- portant transgression (Fig. Cebrian stratificationindicates a westerly derivation (Fig. 14a). 9a). Although the disappearance of the San

The well-developed seatearth levels occurring in coals west of Vergano is partly due to facies changes, Section 1 800 the the coal horizon such is eroded (approx. m) were not recognized at bearing as probably corresponding horizon in Section 4 (approx. 530 m), and overstepped by the overlying marine strata. In autochthonous Section 4 these marine although Reading (1970) reports plant (1145-1150 m) transgressive

in this level 3 - Section have a erosive with the under- growth (his Fig. 9, approx. deposits clearly contact This does 450 m; N.B. as indicated by the explanation of Fig. 3 lying delta plain deposits. exposure, however, - and - and the erosive of the base of the trans- Fig. 7, Fig. 3 Section 9 Fig. 3 Section 10 not prove nature

have been reversed, i.e. in Fig. 3 Section 9 should be gressive deposits, as at this locality the quartz arenitic

Section metres 10 and vice versa). A few hundred to sandstones only fill in the upper part of a 12 m deep the observed seatearth this level. These channel. The lower of this channel is filled with west I a good at part

contact the deltaic deposits are overlain by marine mudstones lithic arenitic sandstones and the between with varieties of sandstone is This fill a few limestone lenses (lower level of Socavon two sharp. channel Limestone which become and that the channel delta distri- Member) more frequent suggests was cut by a channel thicker towards the east. The directions of supply and butary which eroded delta plain deposits. The the fades indicate before the occurred and of both siliciclastics and carbonates was cut shortly transgression of the channel filled with marine more marine conditions towards the east. the upper part was Areal interpretation offades relations 189

Fig. 9. A. Map of the southern flank ofthe Castilleria Syncline. Some intervals are drawn on anexaggerated scale. B. Interfinger- ing of the Sierra Corisa Limestone Member with siliciclastic deposits. C. Interpretation of 9B. Graaff: Three 190 W. J. E. van de Upper Carboniferous delta systems, Spain

sandstones. Further to the west the actual contact and cobbles the existence of pebbles proves a compe- the deltaic sediments and the between transgressive tent longshore drift system as no pebbles of this

marine deposits seems to be a rather featureless composition occur in the underlying deltaic deposits with little erosional relief. The surface overstepping (see Chapter II, types VIb and Vila). It is assumed

and onlapping relationships of the post-transgression that together with the pebbles this longshore drift

deposits are shown on the map (Fig. 9a.). system also supplied finer-grained siliciclastics to the

The thickness distributionof the sediments between basin.

surface and the Leonian discon- Sedimentation did with subsidence this transgression not keep up and,

formity (Section 3: 440 m; Section 4: 700 m; Sec- somewhat east of the location of Section 3, a relatively 5: 910 lateral distance between Sections tion m; 3 deep hydrographic basin came into being. Slump and and 5 about 5.5 km) indicates that this transgression mudflow deposits together with turbidites were formed

with attendant erosion of the underlying strata is at the location of Section 4. These deposits correlate

not due to a simple change in sea level or a mere with mature and immature turbidites in Section 5.

cut-off of sediment supply. Tectonic tilting is con- Cursory mapping north of Section 5 suggests that this sidered be the of the features observed. to cause interval gains in relative importance towards the

This is the more for the between north. A sole mark indicates likely as sequence single reading transport

the second level of the Socavon Limestone Member directions towards the north at the location of Section and the of the San Gebrian coals the is in 4. The orientation of the of balls the top thinning axes slump at

the opposite direction (Section 4: 350 m; Section 5: same locality suggests movements from W to E. This between 115 m; lateral distance Sections 4 and 5 turbidite bearing interval is tentatively interpreted as about 4.5 For the of the submarine fill with associated fan de- km). underlying part sequence a canyon valley insufficient data have been collected to ascertain posits. In this interpretation the slump and mudflow whether such of the The ofSection constitute the thinning strata occurs. map deposits 4 canyon fill, whereas from San the immature turbidites and flow of configuration, however, suggests thinning grain deposits Cebrian towards the north. Section 5 constitute the fan valley deposits.

The features enumerated warrant the terms low- After deposition of these turbidites the relative rate and diastem for increased and angle unconformity disconformity to of sedimentation a shoaling sequence

the transgressed surface. In the following parts this was formed. Beaches formed locally in the upper part referred surface will be to as the Vergano discon- of this sequence (Section 5).

formity. A thick limestone was then deposited at the location

The sandstones above the Vergafio disconformity of Section 5. To the southwest this limestone splits up

are of a quartz arenitic composition, and as the fossils into several tongues which interfinger with siliciclastic

indicate a marine environment this relative maturity deposits. At the location of Section 4 the lowermost of the sandstones is considered to be due to reworking tongue experienced synsedimentary displacement and Cross-stratification and the Further the this by waves currents. (Fig. 6, Plates lie, d). to west tongue

local development of limestone (Section 5) indicate is developed as isolated limestone lenses. Between

that the water in which sedimentation occurred re- Section 4 and the top of the Sierra Corisa hill this mained shallow. A few sandstones has surface conglomeratic are lower tongue a very irregular upper (Figs. in these shallow marine E of The in the limestone filled with present deposits (Fig. 9a, 6, 10). depressions are which the Vergafio). The presence of these quartz arenitic shales/mudstones (types IIIc, d and e), at

10. surface of the lower of the Sierra Corisa Limestone Member. Fields and wooded situated Fig. Irregular upper tongue parts on siliciclastic deposits, sst-quartz arenitic sandstones; symbols as used on the enclosures 1 and 2. AreaI interpretation offades relations 191

actual contact often have a dusky red colour (5R 3/4). stones as calciclastic deposits even less likely. For this The these lime relation between the following tongues and the reason I interpret mudstones, wackestones,

siliciclastics with which they interfinger is depicted in packstones with rare grainstones and boundstones as

Figure 9. The interpretation of the coarse siliciclastics biogenetic banks, i.e. essentially in situ accumulations in Section 3 deltaic of debris from benthonic and animals. as a coarsening upwards sequence organic plants consisting of mouth bar and channel deposits is Baars (1963), in his discussion of the distinctive

straightforward (Chapter III). The seatearth level in properties of reefs, banks, bioherms and biostromes, the Section forms the of follows Lowenstam and Nelson al. poorly exposed 3a, top a c.u.s. mainly (1950) et of Vb. In III it is that this in his Baars the type Chapter argued type (1962) terminology. states following formed subaerial levee such about banks was as a or very near to a biogenetic (p. 112): levee. At approximately 500 m to the east of this levee "The other biogenetic carbonate deposit, which is marine limestones formed fault the of reef is the deposit fully were (the quite opposite a deposit, aggregational

in between Section and Section 4 is considered not 3a, build-up, or biogenetic bank. These accumulations of

to have affected this The found in the distance). fine-grained skeletal debris commonly are more pro-

siliciclastic deposits between Section 3a, and Section 4 tected waters of the back shelf, in marked contrast to

marine fill The relative and be carbonate sediments are interpreted as bay deposits. reefs, appear to ordinary mud abruptness of the limestone-siliciclastics contact and with varying amounts of lime and skeletal mate- the small lateral distance between limestone rial. For this considered be pure and reason they usually are to sand-sized siliciclastic deposits is taken to indicate "poorly sorted" clastic deposits, but this is wrong, for that the limestones of sediment and originally formed slight elevations no transport no dynamic sorting of relative to the bay fill deposits. If the limestones had particles has been involved in their formation. The been deposited at the same level as, or lower than the deposit results wholly from prolific in situ production siliciclastic bay fill deposits, they would have been and accumulation ofskeletal material in all size-grades

to much more diluted by these siliciclastics and the zone from mud pebbles. The sediments normally consist ofmixing of the two lithologies would have been much of unsorted calcareous mud and skeletal particles,

extensive. Freeland describes coral which have accumulated in a low more (1969) recent together energy unaffected reefs on the shelf near Veracruz (Mexico), which are environment completely by vigorous wave

completely surrounded by siliciclastics. From the reefs action. All or most of the sediment is produced by Much to the surrounding deeper areas with siliciclastic de- organisms at the site of deposition. ofthe skeletal the of sediment consists of rather than posits, percentage CaCOs may drop from 100% fragmental particles

to within a lateral distance of 200 Maxwell & whole shells because the and mud feeders 5% m. scavengers Swinchatt efficient (1970) also mention the presence of coarse are usually very at their job of making small sands within mile of individual of Textures for the quartz one coral reefs particles out large ones. are, most of the Great Barrier Reef. In both examples the differ- part, mud-supported with a fairly high amount of ence in topographic elevation of the two facies realms skeletal and pelletal particles "floating" in the fine- is the probable cause of the abrupt facies differentia- grained matrix. But near the margins of the accumu- tion. lation, grain-supported textures become more com-

In the under discussion scattered mon. This be due to belts of example only pat- change may fringing

or to the action of ches of boundstone of type Xd are present in the specialized organisms winnowing

and tidal currents to both." otherwise mainly micritic limestone, and no trace ofa waves or reef in the Marine are in the framework, as occurs recent examples grasses important agents entrap- is In III it and consolidation mentioned, present. Chapter is argued that ment of sediment (Ginsburg & it is that Xd was formed in Lowenstam, and are as such unlikely type agitated 1958) very important waters. This the of contention is mainly based on the ob- in construction recent biogenetic banks in servation that oolitic and Florida Other like also be packstones grainstones are Bay. organisms, algae, may not closely associated with type Xd. For this reason important. A few recent examples are described by I conclude that these boundstones were not originally Baars (1963, p. 120): wave resistant, nor did the constructing organisms "Three prominent mounds of carbonate sediment

the to have been constructed in situ the have ecological potential produce a wave re- along inshore, sistant structure. The early diagenetic compactional well-protected margin ofthe shallow reef tract (Florida

of of Xd the from northeast to Rodri- collapse many examples type supports Keys). They are, southwest, contention that this Tavernier and Snake Creek type was not a wave resistant quez Bank, Bank, Bank boundstone. Consequently the limestones under dis- (Fig. 11). All are composed of mud-size carbonate cussion cannot be considered to be true reefs. Never- sediments with varying amounts of skeletal debris theless organisms preserved in situ, or nearly in situ, derived from organisms that live on the banks. Rodri-

in their formation. Further- and Tavernier Banks not related to tidal played an important part quez are any the the be more, geometry of these micritic limestones as passes through keys, so they cannot considered shown in Figure 9 precludes interpretation as simple deltaic in origin. Snake Creek Bank is traversed by clastic tidal channels which least have altered deposits. The general absence of calcareous two at its con- debris in those deposits which formed under influence figuration, but the internal construction of the bank is of There of longshore drift makes interpretation of these lime- not suggestive current deposition. is no appa- W. E. de Graaff: Three delta 192 J. van Upper Carboniferous systems, Spain

rent external source for the sediments found on the which, however, interfinger with shales/mudstones of

and some of the that have Ilia and turbidites. The discontinuous of banks, indeed, organisms type nature debris the contributedskeletal to the banks are not found limestones may also partly be caused by tectonics in other localities. It that living any seems likely, then, and/or slumping.

these banks were built in place by the prolific life of there functions organisms; is, however, no rigid VERDEGOSA-VERDIANA ANTICLINORIUM organic frame to promote growth of the mound into WEST OF THE TREMAYA FAULT (Figure 8 and the of the surf zone, as in case reefs. In fact, there is no Enclosures 1, 3, 5) surf although the waters are shallow, and there are no - potential framebuilders nothing but muddy sedi- The in this be correlated sequence area can easily ments." with the south flank of the one exposed in the Castille- three of (p. 125) "Here, then, are examples biogene- ria Syncline, with the aid of only lithostratigraphic

tic banks in the shallow carbonate seas. modern, They criteria. No single section covers the entire interval constructed of skeletal were muddy debris in the very studied and because of the tectonic complications few environment of the quiet, well-protected back-shelf, data on thickness distributions in this structural unit

and, most important, they have no rigid framebuilding were collected.

or binding as do the coral reefs of at the base components agents Section 10 begins approximate of very the shelf. Yet these banks fringing strangely enough, thick, lithic arenitic turbidites which overlie a thick

withstood the of a hurricane of with recently onslaught major shale/mudstone sequence type Ilia, some better than the coral reefs and turbidites of Id and Ie. This (Ball, Shinn, Stockman, types shale/mudstone modern biohermal banks 1963). Although are being sequence is considered to be the equivalent ofthe shale/ constructed in situ differ by biologic processes, they mudstone which is intercalated between the quartz markedly from coral reefs in their internal make-up, arenitic and lithic arenitic turbidites of the south flank kind of constructional organisms, and geometric con- of the Castilleria Syncline. This correlation implies

and most differ that the turbidites of the Castilleria figuration, important, they radically quartz arenitic in environment of deposition." Syncline are the lateral equivalents of the Curavacas

These quotations should suffice to convey the bio- Conglomerate Beds exposed to the NE of Los Llazos bank genetic concept. and in the Casavegas Syncline. The immature, lithic

Therecent described Baars differ examples by (1963) arenitic turbidites form a prominent sandstone body

from the limestones under discussion in at least one, which is an excellently mappable unit. In the In Sections 7 and 10 the turbidites followed possibly important, aspect. Carboniferous, are by

marine which an on the a c.u.s. of Vila Vllb. Vila and grasses play important part type or Type type

had not come into exis- in this recent biogenetic banks, yet Vllb are each other's lateral equivalent area. have been the im- tence. Algae are thought to most In Chapter III it is argued that the more mature in the formationof these Carboniferous portant agents composition of the sandstones of facies type Vllb is

banks de not due and The absence biogenetic (cf. Meijer, 1969). They only to reworking by waves currents. in the and played an important trapping con- of a channel fill in the of this of part upper part example solidation of the but most also sediment, probably type Vllb provides further evidence that this c.u.s. is

produced most ofthe fine carbonate mud. Lowenstam not normal deltaic As lithic arenitic sands a sequence.

and Stockman et al. have shown how (1955) (1967) were supplied to the basin at the location of Section 7 recent such as Penicillus death Section 10 is algae disintegrate upon (type Vila), the c.u.s. of type Vllb in and of lime mud. Similar the of produce great quantities interpreted as deposit a prograding coast (Visher,

considered to have been in the processes are important 1965b). The coast could prograde because of a plenti-

Carboniferous. ful supply of sand and finer-grained siliciclastics which Tavernier Bank and the other banks described eroded from delta by were nearby distributary deposits. Baars stand about 2 3 above the In the oferosion and marine (1963) to m surroun- process transportation by

ding sea floor and rise to about low-tide level. Differ- waves and currents the unstable components were in elevation of the order of eliminated. Such ences same magnitude partly or entirely contemporaneous destructive fa- are considered sufficient to explain the facies distri- development of both constructive and butions of delta characteristic of delta depicted in Figure 9. cies a is high-destructive The which fill in the of which the Rhone delta is shales/mudstones depressions systems a recent example in the upper surface of the lower limestone tongue (Fisher, 1969). similar those of their above the lithic arenitic (Fig. 10) are very to interpreted as bay Because position fill in Because of this these deposits Figures 9b, c. similarity turbidites, coarsening upwards sequences are and because of their approximate equivalence to considered to be the correlatives of the lowermost deltaic and 4. In deposits in Section 7 (950-1010 m) these de- coarsening upwards sequences in Sections 1 which pression fills are tentatively interpreted as bay fills too. Sections 7 and 10, chiefly mature sandstones North littoral environ- of Section 5, the interval studied is poorly were deposited in a shallow marine to and this exposed part of the area only received a ment overlie these c.u.s. deposits. Beaches (see Chapter examination. It that often autochthonous cursory seems likely there, too, III, type Vc), supporting plant coal the limestone splits up into several tongues and lenses growth formed locally. A number of seams Areal interpretation offades relations 193

(Perniana coals) were formed in these strand plain 1957), these 10 m may originally have been some 20 the show little deposits. The migration of various types ofbeaches to 30 m of sediment. Sandstones normally combined with subsidence and sedimenta- and volume is reduced from continuing compaction pore usually

tion produced a number of minor transgressive and 35-40% to 10-20% by cementation (Pettijohn, 1957). regressive cycles. In Section 10 a major transgression In thin sections of this interval compaction effects are

surface be 643 where facies this have resulted in can recognized at m, type plentiful. Suppose compaction to sandstone with and of would Villa, overlies a seatearth, is a loss of volume 15%. This mean an original overlain limestone and of thickness of about 90 for the 78 of sandstone by shales/mudstones type m m and sand- Ilia. Lithic arenitic turbidites, and a poorly exposed preserved. The overlying 10 m of limestone of follow. The of the is after subsidence had al- c.u.s. type Vila, top c.u.s. not stone were deposited some

exposed but a major transgression must have occurred ready occurred, but this will be neglected as the after its thin followed of this This formation, as a marine limestone seatearth is in the upper part sequence.

at not by clean sandstones with a seatearth and a thick means that the turbidites were deposited a depth

sequence of shales and mudstones overlie this deltaic exceeding 125 m and possibly as little as 100 m. The deposit. limestone is interpreted as a lagoonal West of Section 10 a hill named Pefla Tremaya

deposit, the overlying sandstones as the deposits of a (Fig. 8, Enclosure 3), which consists of thick lime- barrier beach the of which did migrating migration stones, constitutes a tectonic and stratigraphic problem. erosive base the The not produce a strongly to deposit. Nederlof (1959) and de Sitter & Boschma (1966)

not actual transgression surface below the limestone is considered this limestone hill as an anticlinal core.

the surface on exposed, only secondary transgression Although dip and strike readings give some support the seaward side of the barrier is well and for this it exposed interpretation, was easily disproved as top indicated in the section. and bottom criteria in sandstones exposed NE and both In Section 7 no lithic arenitic turbidites or deltaic SW of the limestone indicated that sides younged

sediments were observed at this level. Only marine towards the SW. The aberrant dip and strike readings

sandstones and siltstones ofa relatively mature compo- can therefore only be explained by interpreting an sition found. In other the constructive fault in the limestone. A were words, important strongly recrystal- found in the facies of the delta in Section 10 had its destructive lized zone with slickensides was actually middle of the and this the equivalent at the location of Section 7. This further limestone, zone connects

corroborates the of this delta of siliciclastic material which to the interpretation system as two wedges point of the a high-destructive one. middle of the limestone hill. This doubling is confirmed the of fusulinids of The transgression surface at 808 m of Section 10 limestone by presence the Fusulinella in the can be traced laterally into transgressive deposits of Bi zone (van Ginkel, pers. comm.) of the limestone and the type Villa in Section 7 at 650 m. This transgression upper parts two bodies, by of D flora surface is followed above by a thick shale/mudstone finding a Westphalian (Wagner, pers. in the sandstones SW of Pena Such sequence which contains turbidites and calcareous comm.) Tremaya.

mudflow This establishes the flora indicates that this sandstone is the same as the deposits. sequence corre- the lation of the transgression surface discussed above sandstones in Section 10 (600-645 m) and not

with the Vergafio disconformity. This also establishes continuation of the sandstones connected with the

the correlation between the deltaic deposits of the Aurora coal seams of Caniabrian age. This sandstone stated constructive facies below the Vergafio disconformity in sequence is overlain by Cantabrian strata, as by Sections 1, 4, 5 and the deltaic and shallow marine Wagner and Varker (1970), who interpret the contact another deposits of the destructive facies in Sections 7 and 10. as a sedimentary one. However, I interpret

to the west of the D This correlation renders the conclusion that we are fault Westphalian sandstones,

which is a direct continuation of the Los dealing with the deposits of a high-destructive delta probably Llazos fault. This structural accounts system inescapable. interpretation the of the for of the Pena Tremaya structure. In this inter- From presence turbidites in upper part part however, the northeastern of Pena of Section 10 inferences can be made concerning the pretation, part the depth of deposition of these sandstones. The turbidites Tremaya is in its original position with respect to

succession of Section 10. in this ex- are overlain of Mapping poorly by a coarsening upwards sequence indicated that this northeastern limestone deltaic origin. These deltaic deposits are predominant- posed area and overlain and barrier block is the lateral of the interval ly sandy are by lagoonal equivalent approxi- 10. No beach deposits. The seatearth in the barrier beach mately between 450 and 650 m of Section between limestone and deposit provides a datum with regard to water depth. interfingering relationships siliciclastics observed. In view of the limestone Taking into account compaction of the various sedi- were the turbidites be facies and the small distance between lime- ments, depth of deposition of the can types pure

stone and siliciclastics these limestones are calculated the formation of a deltaic is interpreted as c.u.s. pro-

too as bank deposits which at form a bably fast a process to permit of important subsi- biogenetic present dence ofthe basin floor. Above the bioherm. or uplift uppermost which the turbidites in Section 10 (710-720 m), no more than Above the transgression surface, is equi-

of As consoli- valent of the the of a about 10 m shale/mudstone are present. Vergano disconformity, presence dated have of thick clays an average porosity 50% (Pettijohn, shale/mudstone sequence containing quartz 194 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

arenitic turbidites and calcareous mudflow deposits stratigraphic correlations prove that in the remainder the lower of the interval has been mentioned. The turbidites disappear to the of the sub-area only part of Section 7. studied is the NW present. Although corresponding to

If is accepted that in analogy with most recent lower 300 m of Section 8, the sequence exposed may

turbidites, the turbidites in Section 7 (760-880 m) well be thicker. North of San Juan de Redondo even

the foot of the shelf the dark lower of the interval studied than those were deposited at slope, parts exposed Near the Redondo shales/mudstones oftype Ilia, in which they are inter- in Section 8 are cropping out. fault be shelf number of less isolated limestones calated, may interpreted as slope deposits. a more or crop out Moro limestones This shale/mudstone interval with turbidites, corre- in the woods (Pefia del of Nederlof, with the turbidite of Sections Their lates bearing sequences 1959, p. 627). surroundings are very poorly

4 and 5. The slump and mudflow deposits together exposed, but their occurrence as isolated lenses and of be slide with the turbidites Sections 4 and 5 were interpreted blocks suggests that they may deposits. The submarine and fan The indicates that these limestones as canyon valley deposits. map configuration may

turbidites of Section 7 are in this interpretation be the lateral equivalent of the shale/mudstone interval

considered as deposits formed on the fan or in the fan below the lithic arenitic turbidites.

valley. Towards the northwest, i.e. towards Section 10, In Section 8 lithic arenitic turbidites are succeeded

the hydrographic basin was probably shallower than by cross-bedded sandstones which are also of lithic ofSection 7 and this is considered be These at the location to arenitic composition. are interpreted as deltaic the for the absence of turbidites in this This of the correlates with the reason part. deposits. part sequence

This interval is followed above by coarsening up- lowermost coarsening upwards sequences in Sections 1, of which of the wards sequences type Vila, are coal bearing 4 and 7. The overlying limestone consists same The coal inter- the limestones which form the (Por si Acaso coals). bearing parts are facies types as upper delta Limestones of the of Sections 4 and 5 and is therefore also inter- preted as plain deposits. same part 3, above facies as those in the upper parts of Sections 3, 4, and 5 preted as a biogenetic bank deposit. Its position

are intercalated with these deltaic deposits and the lithic arenitic turbidites and a deltaic c.u.s. indicates associated shallow marine deposits (Sections 6 and 7). that it is the lateral equivalent of the Socavon Lime- Member. few They are also interpreted as biogenetic banks and they stone In its upper part it contains a

are the lateral equivalents and continuation of the cross-bedded, calcareous sandstones which permit of

biogenetic bank deposits in the south flank of the correlation with the limestone of Section 9. This se- overlain and mudflow Castilleria Syncline. quence is by slump deposits.

The destructive facies equivalents of these deposits Limestone blocks of over 20 metres in diameter occur

belonging to the constructive facies of the delta system in this interval. The presence ofthese deposits indicates of since are distinctly developed north of the location of instability sedimentary slopes and, also, they

Section 6, and the beach deposits at 770 m in Section are overlain by shales/mudstones with turbidites, im- This 5 probably also belong to this delta. portant deepening of the basin. deepening se- The considered correlate with the most remarkable feature of this delta system quence is to transgressive is the close association and the relation- which overlies the in interfingering sequence Vergafio disconformity

ship with fully marine limestones which formed as the Castilleria Syncline. In other words the instability this which biogenetic banks. Although the older delta systems of of the sedimentary slopes at location, re-

this of the also associated with bio- sulted in is related to tectonic part area were slump movements, interval genetic banks, no such interfingering was observed. tilting in an area to the southwest. Above an

with distinct turbidites, which correlates with the

turbidites in Sections 4 (1340-1460 m), 5 (530-650 m) VERDEGOSA-VERDIANA ANTICLINORIUM and 7 (750-875 m), follows a poorly exposed sequence BETWEEN THE TREMAYA AND REDONDO FAULTS consisting mainly of shallow marine deposits. These (Figure 8 and Enclosures 1, 3, 5) shallow are interpreted as the lateral equivalent of the

marine and beach in Section 5 (650-780 m). Both Nederlof (1959) and de Sitter & Boschma (1966, deposits The overlying limestones form the most impressive Fig. 10) presented too simplified an interpretation of feature of the Celada Syncline. Because of the consti- the structures of this part of the area. Top and bottom tuent facies these limestones as criteria (cross-bedding; seatearth; corals and algae in types are interpreted bank with the of that the limestones biogenetic deposits correlating upper position growth) prove forming of Sections 5 and 6. the La Frechilla and Verdiana hills do not form the parts 3, 4,

eastern flank of a simple syncline. Instead, the lime- stones forming these two hills belong to the opposite CASAVEGAS SYNCLINE (Figure 8 and Enclosures 1, 3, 5) sides of a syncline which have shifted in such a way as criteria to constitute each others continuation (Enclosure 3). Correlations based only on lithostratigraphic between the This new structural interpretation has of course an are difficult to make Casavegas Syncline and the Castilleria the important effect on any attempt at an palinspastic Syncline or Verdegosa-Verdiana of the Anticlinorium. for the lower ofthe reconstruction area (Chapter V). Only part sequence be used with confidence. The Only in the Celada Syncline could a fairly complete can they some shale/ section of the interval studied be measured. Litho- mudstone interval underlying lithic arenitic turbi- Areal interpretation offacies relations 195

dites be traced from based the of of Vllb can Tremaya (Section 10) to is upon presence deposits type

as tidal the road-cut north of Camasobres (Section 13). In (Section 12, 250-275 m) which are interpreted this turbidites visible in In Section 11 dis- road-cut a few very mature are delta deposits Chapter III. a this in the shale/mudstone. Further to the west this shale/ continuous limestone is present at approximately mudstone be interval, though poorly exposed, can level. This limestone, too, is interpreted as a biogenetic

traced as far as the location of Section 11. At this bank deposit.

it has become thin. The environ- This is followed of bioturbated mud- point very general by a sequence of this inter- and siltstones better sorted sand- ment deposition in which shale/mudstone stones with locally

val formed be inferred from the as which are in III bar was can sequence stones interpreted Chapter as Here in Sections 12 exposed between Sections 10 and 13. the shales/ deposits. This sequence, which is cyclic

mudstones overlie the Curavacas Beds. formed marine en- Conglomerate and 13, was in a shallow, open enabled These conglomerates interfinger with lenticular lime- vironment. Periodically low rates of deposition contain the stones lying in situ. As the limestones algae, burrowing organisms to rework and homogenize the sand this indicates a shallow water origin for the conglom- sediment. This does not necessarily mean that

erates. The overlain lithic much the of shales/mudstones are by bars were deposited faster, as presence

arenitic indicates that the on the turbidites. This sequence burrowing organisms is largely dependent these shale/mudstone interval is a shelf slope deposit as it is characteristics of the substrate (Purdy, 1964). As enclosed which is by shallow water and relatively deep water bars formed in at least slightly agitated water, deposits. inferred from their comparatively good sorting, the

and silt sized food were also In Section 13 no distinct lithic arenitic turbidites commonly clay particles

were observed. The interval is immedi- winnowed The result of this winnowing is that shale/mudstone away. unattractive to mud ately overlain by a c.u.s. which contains a few slumped the sediments deposited are

limestone blocks at the base. The composition of the ingesting organisms, i.e. the sediment will be relatively sandstones of this indicates that the lower undisturbed such c.u.s. part by organisms. has is overlain thick lime- to be included in type Vila, whereas the upper This sequence by locally very

This is which thin to absent between part belongs to type Vllb. upper part very stones (Enclosure 3) are number of isolated limestone much distorted by tectonics. Laterally this c.u.s. cannot Sections 12 and 13. A turbid- be traced far. blocks which are overlain by a few calcareous

that this out is due to Both east and west of the location of Section 13 the ites indicate wedging probably

in this These limestones, too, are succeeding limestone unit seems to rest immediately deeper water zone. because of the is considered to be biogenetic bank deposits upon shale/mudstone interval. (Section 13 not of the situation the thick lime- the constituent facies types and also on account of the very representative as lateral transitions into siliciclastic deposits. stone units wedge out on either sides of the valley in rapid which the A minor increase in thickness of the interval studied section was measured). The limestones are

east to This trend is paral- lenticular and the maximum thickness of the lenses seems to occur from west.

a transition from a containing decreases to the west (Enclosure 3). Their facies indi- lelled by sequence

deltaic into a containing cates that they are biogenetic bank deposits. fluviatile (?) deposits sequence marine deposits. These limestone lenses are overlain by shales/mud- only

stones which contain turbidites. In Section 13 these

are lithic arenitic turbidites (270-300 m), whereas in REDONDO SYNCLINE (Figures 8, 11, 12 and Enclosures Section 11 quartz arenitic turbidites occur. Their 1, 2, 3, 4, 5) indicates that considerable presence deepening occur- red after of the limestones. In Section 12 of the interval studied is deposition The lower part very poorly turbidites occur at two levels between shallow marine exposed, largely covered as it is with scree of the un-

deposits. This interbedding indicates that thin tur- conformable Permo-Triassic or with the Permo- bidite sequences may have originated in comparatively Triassic itself. The oldest part of the sequence is shallow the sides of the main water. relatively well exposed on road

The overlying deltaic c.u.s. in Section 13 has a small from Cervera de Pisuerga to Potes about 1 km south lateral extension. and Halfway in between Sections 12 of the village of Piedrasluengas (due west of Section 13 found of lithic arenitic sandstones of arenitic no trace was 16). Mature and immature quartz turbidites,

deltaic west origin, and further only compositionally which are quite intensively folded, are exposed there.

more mature sandstones of marine are exposed. This turbidite is overlain a origin sequence by poorly exposed This is one more proof in favour of the interpre- shale/mudstone interval, which in turn is overlain by

tation of these deltas as delta ofvariable thickness. This of high-destructive sys- a limestone unit sequence

tems. The occasional of sediments presence conglomeratic relatively deep water (turbidites) overlain sandstones in the of the and shallow western part Casavegas by shale/mudstone water limestones (al-

is in with sand- to Syncline analogy the conglomeratic gae) leads once more the interpretation of the

stones of the Castilleria as interval shelf Syncline, interpreted shale/mudstone as a slope deposit. of proof the existence of drift If we trace this of the from competent longshore part sequence the SE In these affected systems. areas by longshore drift, (Section 27) to the NW and around the synclinal nose tidal currents This contention were locally important. up to Section 14 it is possible, despite the poor exposure Three 196 W. J. E. van de Graaff: Upper Carboniferous delta systems, Spain

to observe important facies changes. At the base of positional environment already existed before the main

Section 27 a few metres of shale/mudstone are exposed slumping occurred. The limestones, however, were and the contact with the limestones seems undisturbed. formed in relatively shallow waters on the shelf. They

From here up to the location of Section 23 the lime- were already lithified when displaced by sliding move- itself is continuous is indicated the soft sediment deformation observed in stone as by presence ments, as no was of sinkholes in the scree-covered At the location these allochthonous blocks. parts. Only breaking occurred, of Section 23 the limestone overlies a distorted se- resulting in smaller or larger fragments. As the dis- of Ila. The itself is undisturbed. and broken limestone unit least 200 quence type contact placed was at

For Section 22 the same description holds good. About metres thick before the process began (Section 18), km NNW of Section 22 better considerable of the has be 1.5 exposures are instability slope to assumed avaiable of the sequence below the limestone. About in order to set such a limestone in motion. This in- been caused 100 to 150 m below the base of the limestone, slump stability may either have by tectonic and mudflow He and backward deposits are present (types Ila, movements, sedimentary overloading, ero-

IIf) together with mature and immature turbidites. sional valley cutting or by a combination of these turbidites the the Upwards more mature are more frequent factors. Considering magnitude of resedimenta- and although the siliciclastics are somewhat distorted tion phenomena, tectonic movements seem to be a

the limestone conformably overlies the shales with likely cause. That such movements indeed played a sandstones. East of Sections and the will be in the this 20 21 sequence part argued following chapter as can

discussed is again poorly exposed but the few out- only be deduced from regional relationships.

crops permit of recognition of immature and mature On the basis of the preceding inferences the features

turbidites and slump deposits. The siliciclastics-lime- observed are interpreted as follows. In an area with

is in this of the but limestone in shelf environ- stone contact not exposed part area, predominantly deposition a abandoned submarine as sinkholes are generally absent in the scree-covered ment, an active or canyon (or that the reaches of fan formed parts it is likely limestone outcrops in this area upper a valley) a deeper zone.

20 and in fact isolated blocks. How- Due to tectonic movements the of the (Sections 21) are slopes canyon became unstable and the siliciclastics which ever, only in the Pico Guillermo area is definite proof were not available that the lithified slide and flow. Because of this limestone outcrops actually repre- yet began to

sent isolated limestoneblocks (Fig. 7). These limestone slumping and flowing of the slope material the over- lithified blocks "float" on and in slump and mudflow deposits. lying, already limestone unit was losing its Their distribution be likened that of in When sufficient material had flowed and can to currants supports.

a pudding. From the facies relationships depicted in slid into the deeper parts of the depression (canyon or lithified and Figure 7, especially the extremely abrupt contact fan valley), the limestone cover broke up between the limestone blocks and the siliciclastics and was carried along on the moving substrate. Once

the unconformity between the main limestone block started, such a process will probably be kept going for and the time the sheer of the lime- overlying sequence with mature turbidites, I some by weight overlying

conclude that the limestone blocks allochthonous stone which the unconsolidated silici- are presses away

too This that fromSection 27 clastics. Whether the could started (cf. Chapter III). means process get merely

to Sections 18 and 19 we trace a limestone unit which as a result ofsuch overloading is to be doubtedbecause

lies in situ in the south to a zone where the same lime-

stone is broken up and displaced by sliding movements. An intermediate zone where minor displacement with-

out of the limestone occurred also be breaking can distinguished.

Further west it is difficult to decide as to whether the

limestone is in place or displaced on account of the

more complicated tectonics. Section 17 was measured in limestone a block which appears to be in place,

while at the location of Section 16 the limestone

certainly is in place. Further to the south, at the loca- tion of Section 15, the limestone experienced some

displacement as is testified by its eroded base. A few

hundred metres to the south where Section 14 was

measured the limestone is again broken into several blocks.

The occurrence of sliding or slumping is indicative

of unstable slopes. The association of such deposits

with pebbly mudstones and immature turbidites and/

or grain flow deposits suggests deposition in a sub- marine canyon or in the proximal parts ofa fan valley. The of such below unbroken lime- presence deposits Fig. 11. Inferred mechanism of resedimentation of the

stones indicates that conditions favouring such a de- Agujas Limestone Member. Areal interpretation offades relations 197

of the magnitude of the phenomena described. The pebbles in Sections 18,21,22 and 24 constitutes some-

process invoked may be likened to the collapse of a thing like a marker horizon. In between Sections 21

dike due to sliding after it has been eroded at its base and 22 it provides a correlation which indicates that

by currents, which is a dreaded phenomenon in facies type Xm is the lateral equivalent of types Xa, Holland Zeeland. and d. is and b, c In Chapter III type Xm interpreted as

The time required for completion of the process having formed in quiet, probably relatively deep

described is difficult to estimate. From the description water, where only sluggish water movements occurred. Yamasaki of the effects of the 1923 earth- of and in the south by (1926) Deposits types Xb, c d, occurring

quake in Japan, it can be gathered that such resedi- flank of the Castilleria Syncline are interpreted as

mentation can take place in a couple of hours. On biogenetic bank deposits, which biogenetic banks were

page 99 he states: slightly elevated above their surroundings. The facies

"One of the most remarkable local disturbances is relationships, as observed in the lower parts ofSections that which occurred in the 21 and fit well into such model. In this Uraga furrow, an eastern 22, very a

branch of the main trench. The northern flank of the facies Xm formed in a interpretation type was deeper

submarine range which extends to the west of Cape area in between slightly more elevated biogenetic the mouth of the Chan- banks and Such Suno-Saki, embracing Uraga (facies types Xb, c d). a depression

nel, experienced a great slip 10 km long, similar to a may be likened to the lagoons of present day coral

mountain slip on the land surface, filling the floor of reefs, and therefore the term "lagoon" is used in

the furrowwith debris 230 in in other 12. For facies XI the inter- m thickness, or Figure type (Section 25) words, decreasing the depth of the furrow by just that pretation is identical with the minor difference that the

much." sedimentary interface was not completely barren of

life. The differences in elevation between the banks Whether the deposits discussed were indeed sedi- and the is indicated mented so rapidly is difficult to establish and it is a "lagoons" were very slight as by distinct that the of resedimentation the lower of Enclosure 4 where the limestone is possibility process part true to scale. took considerable time. Although the tectonic move- depicted invoked caused local of and of is ments infilling depressions The distribution ofthe quartz wackes types IVe

thus shallowing of the basin at that location, the also easier to understand in this interpretation. As they

overall effect was probably the opposite as the lime- were deposited in pre-existing depressions their lateral overlain turbidite extension is determined the size of these stones are by a sequence. by depressions As the siliciclastic sediments do contain How these wackes still remains not any quartz were emplaced

macrofossils except plant debris, the dating of the a mystery. is based the floras and faunas sequences only on con- As the limestone under discussion is both underlain

tained in the limestones. this lack of definite Despite and overlain by thick turbidite sequences, it evidently data it is considered unlikely that differences in entire Its great forms the shallowest part of the sequence.

between the resedimented strata and the surroun- age setting immediately above slope deposits without any

ding as are associated or coarse- sequence exist, they lithologically very coarsening upwards sequences

similar. This means that these con- shallow marine that it deposits probably grained deposits, suggests stitute borderline between and olisto- a case slumps formed on an open shelf. Being the shallowest part of

stromes. According to Gorier & Reutter (1968), both the of a sequence, culmination a shoaling se-

slumps remain in their original stratigraphic horizon, and the of are quence beginning a deepening sequence while olistostromes contain the limestone. fragments (olistoliths) con- likely to be present and recognizable in older than the and siderably underlying overlying It is on account of this inference that the Xa—>Xb, c Sections sequences. and d—>Xh sequence (well developed in 18, 27 and less Sections 22 and is The distribution of the various facies types in the 23, distinctly in 24)

limestone unit which was involved in the slumping interpreted not only as representing an overall increase

will now be dealt with. The gross facies relationships in wave energy but also as a shoaling sequence. The

are depicted in Enclosure 4. Although Section 18 was inferred development of the limestone unit under dis- shelf of measured in the allochthonous block forming the Pico cussion is as follows. On a shallow supply siliciclastics certain becomes Guillermo, it is included in this diagram as this block at a moment sufficiently

is believed not have been low allow of of limestone at to displaced over great to deposition (type Xa)

distances (a few kilometres at the most). Moreover, its some points. On these first limestone deposits prolific constituent facies be matched built banks types can perfectly with, organic (mainly algal) activity biogenetic which the base. Once the base for instance, Section 22. Nevertheless, it is wiser to base rose slowly to wave wave reached and the interpretations solely on the sections measured in was packstones grainstones were deposited

limestones which are still in situ of nearly in situ. In instead of mudstones and wackestones and in even formed. On the the correlation diagram the top of the limestone has more agitated waters oolites shallowest been taken datum level for of and of these shoals which the arbitrarily as a want a quieter parts "capped"

better marker. Identical facies types were correlated real biogenetic banks, the "mottled" pelsparitic grain-

between the various sections. A few units were actually stones were formed. Sedimentationon these shoals was of traced in the field but most correlation lines were probably so slow that they "drowned" because subsidence and drawn afterwards. The presence of quartz arenitic continuous after deposition of a trans- Three 198 W. J. E. van de Graaff: Upper Carboniferous delta systems, Spain

Facies in the Limestone Member. The of the is cross-section. The Fig. 12. relationships Agujas upper part figure a hypothetical

denote and The lower of the inter- terms turbidite-shale, slump deposits, etc. underlying overlying deposits. part figure is an pretation of facies relationships during deposition of the middle part of the Agujas Limestone Member.

gressive deposit (type Xi) another biogenetic bank and all kinds ofscavenging and boring organisms, and could of sequence develop. redistributed by waves and currents. No trace such this which debris observed in the limestones of the Incidentally, aggradational sequence zones was area does studied. not contain any obvious debris of the underlying limestones is a further proof that these deposits were Few of the second generation biogenetic banks not reefs. Recent reefs are commonly associated with developed an oolite capping (Section 24) and higher great quantities of debris produced by waves, currents in the sequence the facies distribution is much more Regional fades distributions, basin Jill and other delta systems 199

in the lower discussed The thick turbidite monotonous than parts. No "lagoonal" movements previously.

in between the banks is considered to be submarine fan deposits are present biogenetic sequence a deposit and and oolite shoals are rare poorly developed. because of its lateral and vertical extension. In the

That the invoked "drowning" of the shoals was most southern half of the Redondo Syncline immature

due to local and not to turbidites in the of the turbidite probably causes regional occur upper part se- sea-level deduced from the somewhat These changes in is quence (Section 25). are interpreted as proximal

haphazard distribution of the various occurrences of fan valley deposits which formed at the foot of the facies Xh. types Xg and A regional change in sea-level, shelf slope. The overlying shales/mudstones are inter- would be difficult from intercalated however, very to distinguish preted as shelf-slope deposits as they are

the local effects and its occurrence remains a distinct between turbidites and shallow marine limestones. In

possibility. Of course there has been an overall change these shelf-slope deposits lenticular to channel-like

in sea-level as the limestone is overlain by turbidites calcareous mudflow deposits occur (type lid). but this The limestones which form the of the major change is thought to be responsible for upper part the of the for the interval studied lenticular monotonous aspect upper part, not are strongly (Enclosure 3)

in the middle of the limestone and their facies warrants the bio- cyclic sequences part interpretation as unit. banks. These banks also formed the genetic on open of the shelf. In Section 21 these limestones show indications In the greater part Redondo Syncline the limestone unit is overlain by turbidites. Only in the of slumping and resedimentation by grain flow and/or

NW currents. is a shale/mudstone sequence intercalatedbetween immature turbidity the This is From the and the sections it is two. shale/mudstone again interpreted as map (Enclosure 3) that Redondo the interval stud- a shelf slope deposit. The fact that the turbidites obvious in the Syncline

ied thickens fromNW to SE directly overlie the limestones is taken to indicate that very considerably (Section

considerable deepening occurred in a short time. The 14: approx. 400 m; Section 25: approx. 1050 m).

deepening was probably related to the slumping

CHAPTER V

REGIONAL INTERPRETATION OF THE OBSERVED FACIES DISTRIBUTIONS,

BASIN FILL HISTORY AND COMPARISONS WITH OTHER DELTA SYSTEMS

The preceding chapter dealt with the interpretation reasonable estimate based on the available data can of the sedimentary facies within the bounds of the be made. Although the displacement along the faults

main tectonic units. We in the central of the is difficult to may now attempt a regional part area estimate, the observed facies distributions. order of of the interpretation of a shortening in the 30 to 45% original

Their present-day distributionis shown in Enclosure 3. length seems likely. In this estimate the internal de-

As stated in the introduction such a regional inter- formationof the sediments is neglected, as slaty cleav- would be without the detailed is absent in the studied. The pretation not possible age very rare to area SW- correlations presented by van Ginkel (1965) on the orientation of the trend of greatest shortening is basis of fusulinid studies. His data combined with those NE (cf. de Sitter & Boschma, 1966, Fig. 24). It is of Racz (1966) and myself, permitted the following obvious that if these tectonic displacements are not

correlation chart of the various limestones to be drawn taken into account the resulting paleogeographic pic-

(Table I). The locations of these limestone members ture will be in error. are shown in Figure 3. Apart from the shortening, another factor further

complicates the construction of a fence diagram. Al-

From this chart it can be deduced that the main lime- though most sections were measured perpendicularly that stone levels in the various structural units represent to strike and dip of the strata, this does not mean intervals. With this correlation vertical measured. Sections the same knowledge a an originally sequence was

diagram can be madeofthe sections measured. Though are customarily depicted as if they represent a truly correlations influenced vertical In when the as such are not by tectonic sequence. most cases a relatively

displacements, such displacements have to be taken uniform interval is studied this does not lead to great with into account when attempting to reconstruct the paleo- errors. But we are dealing a relatively thick se-

From de Sitter Boschma's and in relation to the size of the geography. & map quence (thick folds), sections and from it which furthermore shows lateralvariations. This (1966) my own map (Enclosure 3) rapid that it is the is evident that considerable shortening of the strata has means no longer permissible to depict occurred. For an accurate determinationofthe amount sections vertically (Fig. 13). For this reason all the of much detailed and tecto- lines of sections rotated around the fold to shortening a more map a were axes nic analysis of the area would be required, but this is determine their original orientation. The fold axes

the of the a around which rotation took first deter- beyond scope present study. Nevertheless, place were 200 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

fusu- South flank Casavegas algal Anticlinorium Redondo linid Verdegosa-Verdiana Syncline Castillena zones Syncline Syncline zones

c

D II C Ib (5 3 —?-

1- Sierra Corisa L.M. Verdegosa L.M., Sosa L.M.(?), Villar L.M. Maldrigo L.M. Abismo L.M. TZb

c o L.M. V) Tejedo I 'b C 2 g

(A

O a r o ' Coterarraso L.M. § 1 c Si ,g II- "5 M f> O S a U_ 15 a l]2a Castrillo L.M.(?) a 1 ,3 3 1 Socavon L.M. Celada L.M. .Verdiana L.M., Matacas - Camasobres L.M. Agujas L.M. Tremaya L.M. tillo L.M.

-*- L c o (J !fi

0 c C 0 E .g C

"o A £ m 1 -c

H a ■A Q *- ■

(C s <1> £ 1 «j 1 1

Table I. Correlation chart of the various limestone units. Mainly after data presented by van Ginkel (1965) and Rácz (1966). Boundaries ofWestphalian C, Westphalian D and Cantabrian after Wagner & Varker (1970).

13. Influence of the orientation of section. Fig. folding on a stratigraphic

mined construction by on a stereographic net. Because 14a, b, c, d, e, f) as the accuracy ofthe paleontological of the limited data the of these correlations does of the construction of available, accuracy not permit determinations is 10° 15° for both strike d and probably to paleographic maps. Nevertheless, Figures 14c, e and The orientations of these fold and the fair dip. axes are probably approximations of such maps. The of which shown in distributionof the various facies areas they are representative are groups as depicted on

Figure 8. If after rotation the sections 70° or these is based distribu- dipped maps, primarily on outcrop Some of the and more, they were depicted vertically. tions, secondly on the inferred continuation of shorter sections were also drawn vertically because in these outcrops. When inferring the continuation of the the projection used it would have been impossible to outcrops the character of the facies group, the direc- depict them clearly in their actual orientation. Al- tions of supply and the general paleogeographic pic- inaccurate in the resul- taken into Inclusion of such data though probably many points ture were account.

correlation diagram as shown in Enclosure 5 is introduces a element in the A ting subjective maps. second, be realistic in its the thought to proportions. probably more important subjective element is

allocation of the siliciclastic sediments to one subzone

lime- or another. As the only dated horizons are the QUALITATIVE FACIES MAPS stone units, the allocation ofa certain interval of silici- With the palinspastic correlation diagram as a base, a clastics to a subzone is largely fortuitous. A third sub- number of of qualitative facies maps were drawn (Figs. jective element in these maps is the subdivision the 14. facies of the interval studied. A. Fusulinella base Fusulinella Fig. Qualitative maps Top Profusulinella B, A, B[ (sub)zones. B. Fusulinella Bi subzone. C. Top Fusulinella Bj, base Fusulinella B2 subzones. D. Base Fusulinella B2, middle Fusulinella B2, sub-

For remainder of 14 203. zone. Fig. see page W. E. de Graaflf: Three delta 202 J. van Upper Carboniferous systems, Spain

subzones. As van Ginkel (pers. comm.) is not able to development of minor coarsening upwards sequences distributaries make such subdivisions, these are based on litho- which were formed by minor in shallow

stratigraphic correlations and inferences as to which bays and lagoons. After deposition of the second level each other's of the Limestone the facies groups are conceivably time equiva- Socavon Member, main trans-

lent. Notwithstanding these subjective elements, Fi- gression took place. After this transgression a second

14a to f a fair of the overall delta over the older gures give impression system prograded submerged one. deltaic facies distributions. The various map configurations The coal-bearing fluviatile deposits (San Ce-

will now be explained and interpreted. brian coals) and the coal-bearing strand plain deposits extend the (upper Perniana coals) over a large part of This delta southern halfof the map. system probably

- This the Figure 14a. map possibly represents upper had a facies distributionand extension identical to the of the B all ofthe Fusulinella A part Profusulinella zone, underlying one. An important difference, however, is zone and probably the lowermost partof the Fusulinella that the first delta is associated with system genetically Bi subzone. No paleontological control is available for a thick sequence of lithic arenitic turbidites, whereas the southern of the the part map. During deposition rise the formation the second delta system only gave to in the northwest ofshallow water conglomerates, which of relatively thin and not very extensive sequences of considered be of the main of the are to tongues body lithic arenitic turbidites. The depth of water in which Curavacas conglomerates to the west of the area stu- the respective deltas formed possibly have been turbidites may died, quartz arenitic were deposited in the the determining factor for this difference. northeastern and in the southern ofthe After part map. this episode supply of coarse elastics to the area was

14c. - On this which halted. A all Figure map deposits are depicted shale/mudstone sequence was deposited formed during uppermost Fusulinella Bi times and over the area. In some ofthe structural units this shale/ lowermost Fusulinella Is 2 times. After deposition of the mudstone sequence can be shown to be a probable second delta high-destructive system an important shelf slope deposit (Chapter IV). In the southern half occurred. In IV it of the this interval is covered transgression Chapter (Fig. 9a) map shale/mudstone by was shown that this transgression was associated with, lithic arenitic turbidites which are also present in the have been due or directly to, quite important extreme northeast. Whetherthese two occurrences form may

tectonic of the southwestern of the area. not tilting part one single lithosome could be established. These

This tilting, which caused some erosion in the south- lithic arenitic turbidites are interpreted as having been of the westernmost part area (Vergano disconformity), deposited on a submarine fan which prograded over apparently caused the delta forming river(s) to flow the underlying deposits. As the overlying deposits are different deltaic into a area, no deposits immediately interpreted as having formed on a delta, the immature overlying the transgressed surface being known. This composition of the turbiditic sandstones warrants the diminished sedi- delta switching, which resulted in a conclusion that delta front sands were resedimented caused in the shallow ment supply, a progressive deepening without being reworked by marine processes. southeastern of the area as sedimentation could part the initial not keep up with subsidence. During stage 14b. - This the entire of this shallow marine Figure map represents nearly transgression deposits were

Fusulinella EU subzone. In the southwestern part of the formed over a large part of the area. Locally (in delta discontinuous area a system developed during lower Bi time. between Sections 5 and 10) limestones The fluviatile of the delta is coal the and beach part bearing at were deposited some ridges supported au- location of Section 1. Further to the east there tochthonous This trans- appears plant growth. important be dated Sections and In Section 5 to more marine influence in this delta system and at gression is well in 5 10. the locations of Sections 7 and 10 these deltaic sedi- the surface transgressed overlies the Socavon Lime- dated ments were contemporaneously reworked by marine stone Member, the lowest level of which was and and strand Cebrian the Fusulinella waves currents, a plain supporting near San as belonging to Bi

turn overlain autochthonous plant growth was formed. subzone. The surface transgressed is in

This delta therefore be classified the Coterarraso Limestone Member which system may as a by was NW subzone. In Section 10 the base high-destructive one. To the (Sections 11, 12, 13) dated as Fusulinella B2 the and to the NE and E (Sections 8, 9 and 14 to 27) thick of the main transgression is situated just below which dated biogenetic bank deposits formed. Depending on the Matacastillo Limestone Member, was as distance the mouth these Fusulinella These that in this to distributary biogenetic Bi subzone. datings prove banks associated with deltafront sands of the the main which is are (Sections 8, part area transgression, occurred 9, 13), shallow marine to littoral deposits (Section 12) associated with the Vergafio disconformity, at

transition of Fusulinella times and most or fine-grained shelf to shelfslope deposits (Sections 11, the Bi to B2

14 to 27). The development of the Tremaya Lime- probably in upper Fusulinella Bi times. The Celada, stone Member in Section 10 and ofthe Socavon Lime- Agujas and Camasobres Limestone Members, which stone Member is of of Fusulinella Bi all three overlain a (Sections 4, 5) proof an important are age, are by this first delta The continua- and de- transgression over system. deepening sequence (turbidites locally slump tion This obvious Sections of deltaic sedimentation on an important scale in posits) . deepening sequence is in

this is indicated the 14 to 27 and less distinct in Sections 12 and 13. nearby areas during period by 8, 11, Regional fades distributions, basin Jill and other delta systems 203

Taking into account the various datings it is logical to in the partly deposited present area. The presence of this which occurred all the interpret deepening, over quartz arenitic pebbles in the Agujas Limestone Mem-

area in probably Fusulinella Bi times upper ,as being ber of Fusulinella Bi age is explained in the same due to the tectonic which caused the tilting Vergano manner. The only difference is that no evidence is disconformity. This correlation of the of deepening available of tectonic tilting of the area at that time.

the basin at the location of Sections 14 to 27 with the The interpretation presented for the occurrence ofthese tectonic which caused the disconformi- tilting Vergano quartz arenitic pebbles implies that the sediment

to also the best evidence that the ty form, provides transported by longshore drift came from western to

slump movements in the Pico Guillermo area were southern directions.

triggered by tectonic movements. An identical con-

clusion was in IV for the already presented Chapter 14d. - On this facies distributions Figure map during slump level above the Gelada Limestone Member in lower and middle Fusulinella B2 times are shown. Section 8. During this time interval the eroded area near the lo- In IV it is that the of Chapter argued presence cation of Section 3 was covered by marine sediments the arenitic pebbles in the a quartz deposits overlying and could no longer be source of sediment. In the

surface the existence ofa transgressed longshore eastern were proves half of the map area mainly turbidites drift system. As at this time no fluviatile deltaic depo- deposited. A proximal facies with immature turbidites, sits formed in the all the were area studied, nearly grain flow and slump deposits, which in Chapter IV

siliciclastics must have been supplied by such a long- submarine and were interpreted as canyon proximal shore drift the small be- system. Considering angle fan valley deposits, can be discerned at the location of

tween the sediments below and above the Vergafio Sections 4 and 5. To the NE an extensive submarine

fan formed 14 Paleocurrent disconformity, it is unlikely that this part of the area was (Sections 8, to 27). much sediment. The arenitic directions in this northern of the indicate supplied quartz pebbles part area derivationfrom the SE. from the SE also provide a clue to the provenance of these post-trans- Supply was found Nederlof for gression deposits. To the west of the area studied the by (1959, p. 690) younger deposits He very thick Curavacas conglomerates of Westphalian in the Redondo Syncline. also noted that, con- The the facies directions from A to Upper Westphalian B age are present. sidering distributions, supply found in the and in these Curava- SW NE be A of this pebbles present area to were to expected. prograding

cas both of arenitic submarine fanand the shelf is indicated conglomerates are quartz compo- adjoining slope sition. the the found, for instance in Section 25, It is considered very likely that tectonic by sequence

movements which resulted in the formation of the where mature turbidites are overlain by immature affected where turbidites which fan Vergafio disconformity also the area are interpreted as valley deposits.

these Curavacas conglomerates originally occurred. These are in turn overlain by shelf slope deposits. To

Because of these tectonic movements the conglomer- the west of, and partly coinciding with this realm of and the erosion turbidite sedimentation in ates could be reworked by the sea relatively deep water,

products were transported by longshore drift and shallow marine deposits were formed. The occasional

base B subzones. For 201. 14. E. Fusulinella B subzone. F. Fusulinella B Fusulinella legend see page Fig. Top 2 Top 2, 3 W. E. de Three delta 204 J. van Graaff: Upper Carboniferous systems, Spain

of that drift shelf and shelf sediments accumul- presence conglomerates proves longshore fine-grained slope

at was still important, but the same time the first ated. Locally thick limestone units, which formed as

fluviatile deltaic deposits after the main transgression biogenetic bank deposits, interfinger with siliciclastic

at the of Section The were formed location 13. small deposits. After the formation of the Vergano dis-

lateral extension of this deltaic deposit and its inter- conformity the same general distribution of land and

with shallow marine is in the fingering relationship deposits sea recognizable: emergence southwest, a rim

indicates that this delta, like the preceding ones, was of shallow marine deposits to the N, NE and E of this

of the high-destructive type. land, and further to the NE relatively deep water in which a submarine fan was formed by turbidity cur-

- This the Figure 14e. map represents upper part ofthe rents. The proximal facies of this submarine fan can be

Fusulinella B2 subzone. In the southwestern corner of in the southern of the recognized part map. During

the map coal-bearing fluviatile deltaic deposits were this period sediment supply to the area took place by formed which with bank de- of drift. This drift interfinger biogenetic means longshore longshore system More posits within comperatively small distances. or transported the sediment from W, SW or S to the

less continuous biogenetic bank deposits formed over area studied.

most of the area during this period. To the N, NE and

E of the fluviatile part of the delta (i.e. constructive PALEOCURRENT DIRECTIONS facies), strand plain ( = beach plain) and adjoining

shallow marine deposits were formed (destructive The measurements of paleocurrent directions are too

facies). The strand plain deposits are locally coal to few in number permit any other conclusion than

bearing. In the northeastern of the area fine- part that they do not contradict the paleogeographic pic- grained siliciclastics were deposited in shelf and shelf ture presented. For several reasons no exhaustive slope environments in close association with biogenetic survey of sedimentary structures in order to determine banks. directions made. of paleocurrent was First all, folding

in this area is often strongly disharmonic which makes

- This the situation the Figure 14f. map represents at it difficult accurately to determine the orientation of transition of the Fusulinella B2 into the B3 subzone, i.e. the fold axes. Ten Haaf (1959) has shown the effect the time of formation of the Leonian disconformity. such uncertainties will have upon the accuracy of the

Only the areas where more or less unambiguous signs paleocurrent determinations. Secondly, it is relatively

of erosion were observed are indicated. difficult to determinethe current direction from trough

cross-stratification which is the dominant of type cross- bedding in the deltaic deposits. the PALEOGEOGRAPHIC SYNTHESIS Thirdly, variability

of the measurements made indicated the need for a

As stated previously, every single map of Figure 14 statistical survey of large numbers of measurements. contain serious because of inaccuracies in The three factors mentioned indicate that it would be may errors

correlations. Nevertheless, the overall paleogeographic very time consuming to obtain reliable results. Only evolutionofthe entire studied interval is clear from very sedimentary structures were thereforemeasured which the and be summarized follows. encountered foregoing may as were accidentally during section meas- Fusulinella and times of the and which results. During Bi B2 (= large part uring gave unambiguous

Upper Moscovian & Westphalian D) the area studied

formed of less sedi- part a more or rapidly subsiding PROVENANCE OF THE SEDIMENT mentary basin. That it was not a small, independent de Boschma's basin, as according to Sitter & (1966) The facies distributions strongly suggest that the source is the distribution of the facies from which the basin sediment contention, proved by area was supplied with

to to and of the thicknesses. A basin margin the south- was situated the S, SW or W. As a nearly fully of the studied is indicated the formation Fusulinella about west area by marine sequence of B age is known

r three delta the fluviatile of which 40 km the o systems parts are to west (Lois-Ciguera Formation) (van

to mainly restricted this southwestern quadrant, by Ginkel, 1965), it is most likely that the source area was the presence of the Vergaflo disconformity and by the located to the S or SW. That means that the source fact that the Leonian disconformity is most distinct in area is now covered by the Mesozoic and Cainozoic this delta the oldest Castilian dominant minerals area. Of the three systems is of the Meseta. The heavy of the Carboniferous sediments rutile associated with extensive turbidite sequences, the are tourmaline, middle with few minor turbidite and zircon This indicates that system a sequences (Nossin, 1959). only

and the youngest system with none at all. Each single sedimentary rocks were exposed and eroded in the delta has rim of shallow the size deltas system a marine deposits to source area. From of the preserved a the NE and E. The of strand estimate be madeofthe size ofthe delta NNW, N, presence plain very rough can The deposits in this rim, which were formed contemporane- forming river and of the size of its drainage area. with the advance of the and the of deltaic but of the ously delta, rarity preserved deposits are fragments tidally affected sediments indicate that the three delta original deltas. Especially the landward sides with in systems are to be considered as wave-dominated, high- fluviatile deposits are poorly preserved. However, destructive delta Further from the delta 14b it is shown that about km 2 of the sub- systems. away Figure 100 Regional fades distributions, basin Jill and other delta systems 205

second delta aerialpart ofthe system are still preserved. and the Polentinos fault respectively (p. 233, Fig. 21). the subaerial delta The facies observed This means that original was much and thickness distributions prove

larger. An estimate of 200 square kilometres seems a that the two features mentioned did not have the conservative The Ebro which influence sedimentation and therefore very one. recent delta, slightest on

2 has a subaerial area of approximately 250 km probably did not exist. Only to the southwest can the is of (Shirley & Ragsdale, 1966), comparable size. presence of abasin margin be proved as is done above. indicates that fair-sized river the of the interval studied another This comparison a was During upper part responsible for the formation of the deltas in the area ridge, the Celada ridge ( = Los Llazos ridge according studied. & which the Redondo Shirley Ragsdale (1966) presented a num- to Frets, 1965), separated present ber of data the extension of the subaerial of from the remainderof the is considered on parts Syncline area, recent deltas and the associated drainage basins. These to have developed (de Sitter & Boschma, 1966). Neder- of 21 deltas and the lof stated the evidence in favour of the data are given recent drainage (1959, p. 621)

area/subaerial area ratios were calculated. The mini- assumption that a zone of less subsidence (Celada

mum ratio was 5 (Po delta), the maximum 210 (Ebro ridge of de Sitter & Boschma, 1966) existed. This

delta). These values indicate that the drainage area evidence is therapid thinning ofstrata from east to west delta Redondo of these Carboniferous forming rivers was at in the northern part of the Syncline, and the

2 least 1000 km and probably much more. thinning and wedging out of the limestones near

San Juan de Redondo and Celada de Roblecedo. The

latter argument is fallacious, as the wedging of indivi- DIFFERENTIAL SUBSIDENCE AND BASIN dual limestone units merely indicates that they are MARGINS siliciclastics. laterally replaced by Only complete se- the ofthe studied be In their de In the section on paleogeography area quences may compared. Figure 22, it stated that the sediments Sitter & Boschma draw a number of lines was preserved represent (1966) but a fragment of the original sedimentary basin. De which suggest that, apart from the features mentioned,

Sitter & Boschma (1966) contend that the studied basin margins were present immediately north and sediments formed in a east of the De Sitter & Boschma were fairly small, independent present day outcrops. do factual evidence in the basin ofaboutthe same size as the present day outcrops. (1966) not present any

This basin, which they termed the Pisuerga basin, was form of data on thickness or facies distributions to bounded in the south and west by the Rabanal ridge support their ideas. Another major weakness in their

Fig. 15. A. Thicknesses of the whole interval studied. B.

Thicknesses of the interval between the Vergafio and

Leonian For disconformities. geographic names see Fig.

14-p. 201. W. E. de Graaff: Three delta 206 J. van Upper Carboniferous systems, Spain

did scales and in different environments. On the interpretations is that they not attempt a palin- very one

spastic reconstruction, although Nederlof (1959, p. hand there are cyclic turbidite sequences which are of centimetre scale. On the other 685) already mentioned the necessity doing so. cyclic on a to metre With the so-called Celada it be hand there the of the three main delta regard to ridge may are deposits also be considered stated that the thicknesses measured do not indicate systems which may as cyclic deposits which the Re- but scale in the order ofhundreds of These the existence of such a ridge separated on a metres.

dondo Syncline from the remainder of the area. major cycles may be called megacyclothems. In both interval the and destructive facies of the delta Especially in the upper part of the studied, constructive the is considered have the intermediate scale be dis- when ridge to developed, systems cycles on an may

distributions not of its cerned. Deltaic sedimentation with occasional di- thickness are very suggestive

existence. As the facies distributions are not indicative version of the distributaries because of their over-

which the into subbasins combined with of less but ofa ridge separated area two extension, more continuous, of Celada subsidence for the either, evidence of the existence a ridge is possibly irregular, can fully account

I consider it much that the observed. This holds true for the lacking. more likely rapid cyclic sequences even thinning of the interval studied in the Redondo Syn- megacyclothem formed by the first and the second with the between Sec- delta after of the second cline is to be connected zone, system. However, deposition

tions 10 and 13, where important thickness changes delta system tectonic tilting occurred, as was shown in

15a and The remarkable IV. This that at least on this scale occur (Figs. b). most aspect Chapter proves

the sedimentationin this was controlled of this zone is that for the lower part of interval cyclic area partly

sediment thicknesses much to the tectonic movements. In like the studied, are greater by areas present one, the of where lateralfacies it is east than to the west ofthe zone. For upper part rapid changes occur, impossible the differences do eustatic sea-level the interval studied, however, not to distinguish regional or changes The of such seem significant, but for the succeeding, post-Leonian from local effects. occurrence changes therefore be excluded but is sequence sediment thicknesses are much greater to the cannot by no means re-

NW of the zone than to the SE and E. According to quired for explaining the observed cyclicity.

Wagner & Varker (1970), over 2000 m of sediment before sediment- were deposited in the Casavegas area

ation to the east of the zone began. This belt separating

two areas which subsided at different rates was fairly LIMESTONES AND THEIR RELATION TO and If tectonic dis- narrow in between Section 10 13. THE SILICICLASTIC DEPOSITS both sides of the taken into placements on zone are

it that the actual transition zone was account, appears A distinctive feature of these delta systems is their very about kilometre wide. The probably a sedimentary close association with extensive limestone deposits. In

facies on both sides of this belt suggest that IV it shown that in this present Chapter was many cases asso- the lower Fusulinella Bi times was water the eleva- only during ciation was only possible on account of slight of the belt. appreciably deeper immediately east tion of the carbonate facies realms above their silici-

the remainderofthe interval studied there was During clastic surroundings. As their muddy character and the

no surface of this zone. Consider- inter- probably expression absence of an organic framework precludes the of the and the of narrowness zone magnitude considered be ing pretation as reefs, they are to biogenetic the thickness this zone is considered as a formed in differences, bank deposits. These limestones were a active sedi- fault zone which was periodically during and sounds wide variety of environments: in bays on mentation. later tectonic deformation this During zone delta Limestone Mem- a drowning system (Socavon

was reactivated and the contacts are all present day in behind a barrier beach ber) ; protected lagoons

as fault contacts IV-Pena interpreted (cf. Chapter in the sea (Matacastillo Limestone Member); open Tremaya). As the fault zone apparently had little in- after ofthe seaward face of barrier passage a migrating

fluence facies distribution it formed a on never topo- (Tremaya Limestone Member); immediately laterally the basin into graphic ridge separating sedimentary of active distributaries (Sierra Corisa Limestone and ofsediment. two separate areas never was a source Member); laterally of the delta in association with

This fault zone is referred to as the synsedimentary sand-sized sediments which were not reworked by

Los Llazos zone in Figures 15a and b, while the pre- marine agents (Celada, Verdiana Limestone Mem-

sent fault is called the Los Llazos fault in 8. day Figure of the delta in association with re- bers) ; laterally in worked sand-sized sediments which were deposited

marine environments Coterarraso open (Castrillo,

CYCLIC SEDIMENTATION Limestone the shelf in association Members); on open with fine-grained siliciclastics (Camasobres, Abismo, In the preceding chapters it has been shown that deltas Agujas Limestone Members).

in the studied Fusuli- An difference between the limestones were very important area during important nella The the where siliciclastics B times. great variety of fades, especially formed on the open shelf, supply of facies is and those formed the deltas is the cyclic occurrence of various types easy to was low, nearer to in understand when thinking in terms of a delta model. character ofthe sediment which fills the depressions

The cyclicity of sequences occurs on widely different between the biogenetic banks. In the areas sufficiently basin and delta Regional fades distributions, fill other systems 207

near to the deltas to receive considerable amounts of indicated by several cable breaks. From the shape of between the banks filled siliciclastics, the areas are the deltas it seems likely that they are of the wave- with siliciclastic It is in this that the Within few deposits. zone dominated, high-destructive type. a

limestone units may have distinct biohermal shapes kilometres of the gravel deltas and the adjoining spits, On the these de- reefs flourish the island carbonate (Enclosure 3). open shelf, however, coral on shelf. These

pressions in between the biogenetic banks may be filled deposits also contribute sediment to the submarine with carbonate sediments Limestone (Agujas Member) fans in the Yallahs basin. As Jamaica forms part of the Another difference between the Agujas Limestone Caribbean loop it is frequently affected by earth-

Member and the other limestone units is the much quakes. This may be another similarity between the

more frequent occurrence of oolitic grainstones in the Yallahs area and the area studied, as the Vergano and

former. This also be related to its formationin Leonian disconformities that tectonic may an prove tilting shelf environment where had open waves not yet occurred periodically. broken siliciclastic shores. on The limestone deposits which are interpreted as

predominantly biogenetic bank deposits, are somewhat

similar to the Waulsortian "reefs" of Belgium and COMPARISONS WITH RECENT AND Ireland. These Waulsortian "reefs" of Lower Car- ANCIENT EXAMPLES boniferous age were recently described by Dupont and Lees These "reefs" lack Before attempting such comparisons it is useful to (1969) (1961, 1964). an

summarize the main characteristics of these Upper organic framework and are interpreted by Lees as

Carboniferous delta The mudbanks which have a biohermal systems. contemporaneous commonly shape. development of the constructive and destructive facies They differ from the Spanish bank complexes in

of the deltas, and the general rarity of tidally in- several aspects. First of all, the stromatactis cavities in

fluenced sediments that wave-domin- the Waulsortian "reefs" are of a different proves they are very type. faunal element ated, high-destructive delta systems. The oldest and Secondly, bryozoans are an important the middle associated with whereas in the system are genetically algae are more important Spanish it be shown in number of turbidite sequences, which indicates that the deltas examples. Thirdly can a formed that occurred the were in relatively deep water. The delta cases steep depositional slopes on furthermore associated with flanks of the Waulsortian which feature has systems are closely banks, nowhere been noted in the studied. Other extensive limestone deposits which formed as biogenetic area banks in environments of "reefs" of the Waulsortian ranging from lagoonal to open occurrences type were shelf. Between deposition of the second and third described by, for instance, Pray (1958) and Cotter delta in the of the United States. system, tectonic tilting occurred which is (1965, 1966) Mississippian

considered to have caused delta diversion. Conse- In the Pennsylvanian of the southwestern United

quently, only longshore drift systems supplied the States, carbonate mound complexes occur which

basin with coarse siliciclastics. These sands are com- resemble the Spanish examples closer than do the positionally much more mature than the deltaic Waulsortian ones. Elias (1963), Pray & Wray (1963), sandstones. Heckel Because of the tectonic tilting, continuing & Cocke (1969) who, among others, described subsidence and low sediment these the supply, a deepening deposits, stress important part played by and turbidites in the formation of these biostromal sequence developed were deposited on a phylloid algae or submarine fan adjacent to, and overlying shallow biohermal carbonate deposits. Apparently similar marine The various carbonate associated with the deposits. sedimentary processes deposits are closely environments which have and at one time or other Cisco delta systems of Upper Virgilian and Wolf- occurred existed in the be under- in North Texas These or area studied, can campian age (Brown, 1969). stood in the terms of two fairly simple models. These Cisco deltas, however, differ from the Spanish exam- are the delta model and the longshore drift/submarine ples in that they are of elongated to lobate high- canyon/submarine fan model. In both settings bio- constructive type. These deltaic deposits, which grade

genetic banks could form. In Figure 16a and b these laterally into interdeltaic and strand plain deposits, models with limestones formed shelf. two are depicted. interfinger on an open

A recent example of a wave-dominated, high- Near the shelf edge, carbonate banks developed. Shelf destructive delta mudstones with system mentioned by Fisher (1969) slope deposits are predominantly is the Rhone delta. It is subordinate siltstones and sandstones. At a very good example indeed, limestones, associated it sand bodies as is with a large submarine fan (Menard, the foot of the slope thin fan-like were

Smith & Pratt, 1965). If size is taken into account, the deposited. These sandstones were possibly emplaced much less studied Ebro delta would be currents. ancient appear to an by turbidity Although numerous better delta have been and described even example. However, no important lime- deposits recognized as stone deposits are associated with these deltas. In this such, these Cisco deltas and associated environments the Yallahs the best the respect area near Kingston, Jamaica, are ancient analogue to Spanish delta which was described Burke be that I with from literature. by (1967), may a systems am acquainted better recent analogue. Gravel deltas supply the As recent analogues of the sediments deposited in Yallahs basin with sediment which inferred be between the second and third delta is to system, I consider, resedimented slides and for the submarine and fan off by turbidity currents as instance, canyon systems Three 208 W. J. E. van de Graaff: Upper Carboniferous delta systems, Spain

Fig. 16. A. Depositional environments during delta formation. B. Depositional environments after formation of the Vergano disconformity. Although they are approximations of paleogeographic reconstructions these drawings mainly illustrate sedi- - - and b - ch bar barrier - 1st b - banks. mentary processes environments, beaches; cheniers; beaches; sp spits; limestone Lithostratigraphic nomenclature 209

the of California. for the of sediment the coast As, instance, Delgada interception coarse moving along

and Monterey canyons are not associated with major shore by a canyon heading near the shore line is a well- the rivers, sediment transported down the canyons is known process (Hand & Emery, 1964). probably supplied by means of longshore drift. Such

CHAPTER VI

LITHOSTRATIGRAPHIC NOMENCLATURE

Although a set of lithostratigraphic names does not feature (Corisa or Sierra Corisa Formationand Sierra

help in understanding a stratigraphic problem, such Corisa Limestone Member; Maldrigo Formationand

names can be very useful in describing and discussing Maldrigo Limestone; Abismo Formation and Abismo such order a problem. In to render such a set of names Limestone), which is hardly recommendable.

useful have to be defined and used in Table II shows the they precisely a sequence as exposed near Vergano consistent of manner. Because rapid facies changes and with the formation names as used in some ofthe more the In the remainder an inadequate understanding of the sedimentary recent papers on Pisuerga area.

facies of the interval studied, the formations and of the area studied use of these names is even more

members used by previous authors are partly ill- confusing. As I consider the set of formation names in

Nederlof & Wagner & Brouwer & de Sitter & section Wagner Nederlof Frets van Ginkel v.d.Graaff de Sitter Wagn.-Gentis van Ginkel Boschma 1955 1959 1965 1965 1971 Metres 1957 1963 1964 1966

2000 1 Branosera | 1 1 1 f| Formation I 1 1 ' 1 1 I . Leonian 1 diastem Sierra diastem Limestones g non-sequence ■£ ■ =*. Sierra Sierra disconformity Formation — E of Corisa of of of 11 rl S-A £ ~' 0 Cabra nd Sierra | Corisa Cabra Mocha Corisa Limestone °o Cabra 2 tongue tMt D ,S Mocha Member Mocha Sierra Corisa ■z S*E Coriza/ w (Leonian \ 1 1 Limestone Limestone 0 Corisa hase) L i 1 1 1 Alto Sierra 3\ P U mestone c 1 1 Member 2 o o c ll I Sierra .0 O S (J ¥ T i i S 1^ Eirt I** tongue □ I o s 0 1500 o o c u_ o

C ;o | 0 c .0 E _jr_ ry -5 o (J 1 g U ■ & v Vergano a ,1 rrv.' 1/1 disconformity _San Cebridn San — San Cebridn- San Cebridn - San Cebrian — San Cebridn— Cebridn Cebridn— o San San A.A.-Mt § San Cebridn group Formation O coal group coats coal member ~coal measures- a coats

E 0 c b 1000 U u_ O o

a | i

Socavon — Socavon Socavo'n — — Socavon —; Socavon 2™ fens Member Limestone Socavon -SJ5B Limestone Limestone Lmst. Mbr. c Member — Member , Limestone o st ■I 1 lens ZZ o I E i

500

u Lithic u Vanes 1 % c Vanes arenitic ai o

E LT Formation member 1 1

"- — ~~~~ Black shale ;>' Black shales 1 Formation i member tj£ Quartz

arenitic .£ member 1 1 1 1 1 i 1 1 I

Table II. Lithostratigraphic nomenclature of the interval studied as exposed in the southern flank of the Castilleria Syncline.

All terms have been translated into English.

which the chosen. Furthermore, the characteristics on current use in entire Pisuerga area as unsatis- of the various units based and the mappability is factory, a number of changes are proposed. The

to boundaries used are poorly described. In some cases changes proposed arerestricted the interval studied, the name of a formation and one of its constituent but some changes in formation names currently being members were both taken from the same geographical proposed by Wagner & Winkler Prins (1970) and 210 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

Wagner & Varker (1970) for the overlying sequence scale) may herald the succeeding macro cross-bedding have been adopted. Most of the formally introduced of the overlying Vergano Formation. In the preceding members limestone units which these lithic arenitic sandstones are are easily recogniz- chapters are interpreted able in the field. Therefore there is little need as immature turbidites. The of to to mature upper part these this member is the lower of revise most of limestone members. The formal usually part a major informal units have been indicated in unit. This member and recognized coarsening upwards upper was the stratigraphic sections and also partly in the mapped in the Castilleria Syncline, the Verdegosa- correlation diagram. Verdiana Anticlinorium and in Section 13 in the

Casavegas Syncline.

The lower member ofthe Vanes Formation is shown VAÑES FORMATION (Chapter IV, Verdegosa-Verdiana Anticlinorium) to

be the lateral of the Curavacas The name "Series de Varies" was originally proposed equivalent Conglo-

merate Beds of the Casavegas Syncline. A similar by Nederlof & de Sitter (1957). The type section is

correlation was Brouwer & van situated to the northwest ofRabanal de los Caballeros already proposed by Ginkel (1964). This also corroborates the proposed (Brouwer & van Ginkel, 1964), i.e. in between Sections correlation between the Lechada Formation and the 2 and 3. As the type section is not very well exposed,

Vanes Formation & van Section 4 is selected as a reference section. The basal (Boschma Staalduinen, 1968). On the basis of of Ginkel's of the Vanes Formation not studied. The extrapolation van (1965) part was is here redefined data the of the Vanes Formation is considered to upper boundary, however, and age be Lower to Middle Moscovian («Westphalian C to arbitrarily taken at the base of the first macro cross- Lower the Albas to metre in the Westphalian D), as underlying bedding (decimetre scale) sequence Limestone Memberyielded a fauna ofthe Profusulinella exposed in the type section. Even in poorly exposed B and the overlying Socavon Limestone Member areas this is an easily recognizable level and the zone, Fusulinella fauna. boundary with the Vergano Formation is therefore (Vergano Formation) a Bi the easily mappable. Defined as such, Vanes Format- ion forms of the Vanes Formation only a part according VERGAÑO FORMATION to previous authors (Table II). Corisa Sierra Corisa The redefined Varies Formation comprises three in- This formation replaces the or formalmembers. A lower arenitic memberis dis- Formation of authors in the Castilleria quartz previous and tinguished consisting of a sequence of more or less dis- Syncline, the Verdegosa-Verdiana Anticlinorium

tinctly graded sandstones alternating with shale/mud- the Casavegas Syncline. A new name is introduced for

In the these sandstones first of both the and lower stone. preceding chapters are two reasons: all, upper both interpreted as mature and immature turbidites. This boundary are changed considerably, secondly, a

lower member was mapped in the south flank of the member and the formation itself were named after the

Castilleria and in the northern ofthe Re- feature. As the dominant of Syncline part same geographic lithology considered least dondo Syncline near the Piedrasluengas pass. This the Sierra Corisa hill is limestone, it is

lower member grades into the middle member, which confusing if the name Sierra Corisa is retained for the

is called the black shale member. The boundary is limestone member.

drawn where facies type Ie grades into type Ilia. The The formation is named after the village ofVergafio. black shale member consists dark Section measured the road from Valle- of grey shale/mud- 4 was along

stone with rare sideritic concretions, a few burrows spinoso de Cervera to Vergafio and in the valley NNE the and occasionally silty or sandy layers of type Ie. It can of Vergafio. This Section 4 is designated as type be shown locally (Section 10) that this member was section, and because of lateral variability Sections 7

probably formed on a shelfslope. This middle member and 13 are designated as reference sections (Section 4, of the Vanes Formation is the best marker unit of the 491-1845 m; Section 7, 238-1198 m; Section 13,

whole area studied occurring as it does in the Castille- 130-655 m). ria Syncline, the Verdegosa-Verdiana Anticlinorium, The lower boundary of the Vergafio Formation is the the first in Casavegas Syncline and in the Redondo Syncline. taken at the base of macro cross-bedding shale member which horizon is Where Peculiarly enough this black was Section 4, easy to map. no the in one of the earlier & distinct observed, as in distinguished papers(Nederlof macro cross-bedding was de base of the Sitter, 1957) but was not subsequently used as a western part of the Casavegas Syncline, the unit. the taken the base of the map In a large part of the area middle formation is arbitrarily at member is overlain the lithic arenitic Camasobres Limestone Member which in this by upper or area member. In the Castilleria Syncline the contact is directly overlies the black shale member of the Vanes Formation. ofSections 12 and 13 indicates usually sharp, as the black shale/mudstone is abruptly Comparison overlain often massive lithic arenitic sand- that is made in The by thick, no great error doing so. upper at the stones. Some ofthese sandstonebeds are graded, and in boundary of the Vergafio Formation is taken the sandstone of the sandstones offacies which between beds shale/mudstone is inter- base mature type IXa, calated. The of this member does indicate the level of the Leonian (cf. upper part not disconformity contain The In the where the usually any shale/mudstone layers. Chapter I). Casavegas Syncline,

of the is difficult to establish, it presence of small-scale cross-bedding (centimetre position disconformity Lithostratigraphic nomenclature 211

is arbitrarily taken at the top of the Maldrigo Lime- Formation (Boschma & van Staalduinen, 1968) and Defined such the Formation. stone Member (Sections 12 and 13). as Lois-Ciguera

Formation wide of As the rich fusulinid faunas in the various the Vergano comprises a variety present

members to the a limestone belong Fusulinella Bi and lithologies which at many places show distinct several forms, but B2 subzones, the Vergano Formation is of Upper cyclicity. The cyclicity may assume Moscovian collected repetitions of coarsening upwards sequences are the age. Wagner (1970, pers. comm.) flora from cross-bedded most striking. a Westphalian D sandstones

south of the San Cristobal hill. This to be the Limestone units are common in this formation. appears

bound- sandstone level below the first lenses of the Socavon These limestone units commonly possess sharp Limestone Member 1, 770-860 Section aries and clear topographic expressions and because of (Section m; 4, 500-570 i.e. the base of the these characteristics to distinct m), very near Vergano are easy map as mem- the in Formation. In the Casavegas Syncline the Casavegas bers of the Vergano Formation. As sequences several hundreds of metres above the of the coals, top the various structural units are not obviously homo- dated Formation, were as uppermost taxial and because of the discontinuous nature of the Vergano Westphalian D (Wagner, 1970; Wagner & Varker, limestone units, these limestone members have been This that the Formation named in structural unit. Van Ginkel 1970). proves Vergano differently every of the represents only a part Westphalian D. (1965), though not formally proposing them as such, evidently considers the various limestone units mentio-

ned him formal members. it is by as Although likely COVARRES FORMATION

that some of these formal members were formerly Corisa The Corisa or Sierra Formation of previous continuous to each other (Table I, Fig. 14b, c, d, e, authors considered to extend into the Redondo and Enclosure 5) it is considered advantageous to was Syncline. Although the limestones in the lower retain these names as in this manner it is easier to present of the in the Redondo indicate precisely which limestone outcrop is meant. part sequence exposed Syncline similar the limestones of the are to Vergano Van Ginkel (1965) recognizes the following limestone very Formation, the associated siliciclastics are quite members belonging to the Vergano Formation introdu- different. Although the sandstone/shale ced above: Socavon Lst. Mbr., Coterarraso Lst. Mbr. sequences which turbidites with interbedded Sierra Corisa are interpreted as (spelt Cotarazo in van Ginkel, 1965), shales, are cyclical, no rhythms of coarsening upwards Lst. Mbr., Camasobres Lst. Mbr., Castrillo Lst. Mbr.

or fining upwards were observed. The and Maldrigo Lst. Mbr.. sequences

absence of features like c.u.s., f.u.s., macro cross- The following limestone members of the Vergano bedding and seatearth or coal horizons, all characteris- Formation here: Celada Lst. are proposed Mbr., tic ofthe Vergano Formation, indicates that a different Villar Lst. Mbr., Verdiana Lst. Mbr., Verdegosa Lst. formation name is useful. The interval studied as Mbr., Sosa Lst. Mbr., Tremaya Lst. Mbr., and exposed in the RedondoSyncline is therefore considered Matacastillo Lst. Mbr.. All members are indicated in the of the Vanes Formation to comprise upper part Figure 3 and in the stratigraphic sections. Several of and the Covarres Formation formally proposed here. these names were used before in an informal manner This new formation is named after the Covarres hill in by Nederlof (1959), viz. Verdiana (Verdiana-Frechilla) the southern part of the syncline (Enclosure 3), and limestone, Verdegosa limestone, Sosa limestone. is the section. Section 25 designated as type Although Nederlof (1959) does not state precisely The Covarres Formation conformably overlies the which limestone unit is meant by Celada limestone, it shale member of the Vanes Formation in the larger comprises both the Celada Lst. Mbr. and the probably of the and in is overlain discon- part syncline, turn Mbr. Villar Lst. as used in this paper. The Villar Lst. formably by the Branosera Formation. Three formal Mbr. is named after a brooklet that crosses the Celada and two informal members of the Covarres Formation Syncline near its middle. The Tremaya Lst. Mbr. are recognized. At the base of the formation the is named the occurs in Section 10 and after nearby Member Agujas Limestone is present. In the area were of Tremaya. This limestone unit is considered village the limestoneis discontinuous, the underlying contorted

lens or a of the limestones as a possibly tongue com- siliciclastics are arbitrarily included in the Covarres the actual Pena The Matacastillo posing Tremaya. Formation. The Agujas Limestone Member is overlain Lst. Mbr., which is slightly higher in the succession, by a sandstone/shale alternation which is named the named after the flat south ofPena is area Tremaya. sandstone member of the Covarres Formation. The

consider the San Perniana and Por si I Cebrian, sandstones are interpreted as turbiditesin the preceding Acaso coals informal members of the as Vergano chapters. In the northwestern part of the Redondo Formation. Of these three the coal-bearing sequences Syncline a fairly thin, more shaly sequence occurs at

San Cebrian and Perniana coals are at least partly the base of the sandstone member. The sandstone each others is equivalent. member overlain by a shale/mudstone sequence Field evidence and datings (van Ginkel, 1965) which is called the shale member of the Covarres indicate that the Vergano Formation is the lateral Formation. Lenticular limestone breccias occur locally of the Covarres Formation section this shale member. The shale member equivalent (see on in is interpreted

Covarres Formation) and of (parts of) the Lechada in preceding chapters as a shelf slope deposit. The 212 W. J. E. van de Graaff: Three Upper Carboniferous delta systems, Spain

Abismo Lst. Mbr. and the Lst. Mbr. fauna that be intermediate between those Tejedo overly, appears to and partly interfinger with, the shale member. found in the Abismo and Coterarraso Lst. Mbrs.. The and Abismo Mbrs. These names Agujas Lst. were datings prove that the Covarres Formation is

used before in a formal sense by van Ginkel (1965). the lateral equivalent of the Vergano formation. sandstone and shale The the member were already

described by Nederlof (1959), who used them as De Sitter & Boschma (1966) extended the use of the

informal units. The Tejedo Lst. Mbr., which is named names Ruesga Group, Yuso Group and Cea Group to the Pena here after Tejedo, is distinguished as a formal the Pisuerga area. The interval studied, i.e. the

unit. The reason for this is its isolated position, al- redefined Vanes Formation and the newly proposed

though it is probably the equivalent of the Abismo Vergano and Covarres Formations, belongs to the

Lst. Mbr. the Yuso Group as employed by de Sitter & Boschma

The Leonian is These defined disconformity only clearly recogniz- (1966). groups were originally by the of Section able at location 25. Elsewhere the top of Koopmans (1962) as being separated by folding the Covarres Formation is taken the of the The Yuso is considered all at top phases. Group to comprise Abismo Lst. Mbr.. Where the Abismo Lst. Mbr. is sediments deposited after the Sudetic folding phase the is taken the of discontinuous, boundary at top an and before the Asturian phase. This division into three bioturbated sandstone often intensively (Type IIIc to groups may be a useful concept in the area where

tens metres IVa, Plate Ilg), which occurs a few of Koopmans worked, but in the area studied it has led to the below disconformity (Section 25). an illogical subdivision of the sequence (Wagner, The and Abismo Limestone Members the of based Agujas 1970, p. 451). Although use groups on

fusulinid fauna to the Fusulinella subdivision of the tectonic be yielded a belonging sequence by phases may

Bi and B2 subzones respectively (van Ginkel, 1965), practicable in the entire Pisuerga area, this should be which indicates Moscovian for the considered a context which the an Upper age in wider is beyond Covarres Formation. The Lst. Mbr. of this Tejedo yielded a scope study.

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