SKRIFTER NR. 183
SVEN A. BACKSTROM and lENO NAGY
Depositional history and fauna of a Jurassic phosphorite conglomerate (the Brentskardhaugen Bed) in Spitsbergen
NORSK POLARINSTITUTT OSLO 1985 SKRIFTER NR. 183
SVEN A. BACKSTROM and JENO NAGY
Depositional history and fauna of a Jurassic phosphorite conglomerate (the Brentskardhaugen Bed) in Spitsbergen
NORSK POLARINSTITUTT OS LO 1985 ISBN 82-90307-36-5 1985 Printed December Contents
Abstract ...... 5
l. Introduction ...... 5
I. l The scope of the study ...... 5
1.2 Previous work ...... 5
1.3 The investigated localities ...... 6
1.4 Sedimentological methods ...... 7 1.5 Paleontological material and methods ...... 7
2. Regional stratigraphy of the conglomerate and adjacent strata ...... 8
2.1 General features of the Brentskardhaugen Bed ...... 8
2.2 De scription of the Marhøgda Bed ...... 9
2.3 Festningen area ...... 9
2.4 Diabasodden area ...... 9
2.5 Brentskardet area ...... 9
2.6 Agardhbukta area ...... 14
3. Fossil content and age ...... 15
3.1 Ammonites and Belemnites ...... 15
3.2 Bivalves ...... 15
3.3 Brachiopods ...... 15
3.4 Dinoflagellates ...... 15
3.5 Faunal comparisons ...... 15
3.6 Age of the Brentskardhaugen Bed and adjacent strata ...... 17
4. Pebble content and origin ...... 18 4.1 Phosphorite pebbles ...... 18
4.2 Chert pebbles ...... 24
4.3 Quartz pebbles ...... 25
5. The matrix of the conglomerate ...... 25
6. Origin of the Marhøgda Bed ...... 25
7. Concluding remarks on depositional history ...... 25
7.1 Source of pebbles ...... 25
7.2 The Ladinian - Pliensbachian interval ...... 25
7.3 The Toarcian - Bajocian interval ...... 26 7.4 TheBa thonian - Callovian interval ...... 27
8. Paleontological part ...... 28
8.1 Introductory notes ...... 28
8.2 List of descriptions ...... 29
8.3 Brachiopoda ...... 30 8.4 Bivalvia ...... 31
8.5 Ammonoidea ...... 36 8.6 Decapoda ...... 41
Acknowledgments ...... 42
References ...... 43
...... �� � Authors' address: Sven A. Backstram lena Nagy Statoil Institute of Geology P. O. Box 300 University of Oslo N-4001 Stavanger P. O. Box 1047, Blindern Norway Osl03 Norway Present: Saga Petroleum al s P. O. Box 9 N-1322 Høvik Norway Abstract This stratigraphical analysis is concentrated on the Brentskardhaugen conglomerate bed, which is a regional marker horizon, separating shallow shelf to marginal marine deposits of the Wilhelmøya Formation (Norian - Toarcian) from deeper shelf deposits of the lanusfjellet Formation (Callovian - Hauterivian). The conglomerate is a remanie deposit containing phosphorite, chert and quartz pebbles in a sandy carbonate matrix. The bed was formed by condensation of Toarcian, Aalenian and Bajocian deposits as shown by its fossil content consisting mainly ofbivalves and ammonites. Based on information derived from the Brentskardhaugen Bed and adjacent strata, the Lower and Middle lurassic development of Spitsbergen may be summarized as follows. After a Lower Jurassic regressive period a transgression culminated in the Toarcian and decreased in effect upwards in the Middle Jurassic. This trans gression introduced shallow shelfto marginal manne conditions to Spitsbergen with formation of the phosphorite pebbles of the Brentskardhaugen Bed. The pebbles were formed by concretionary growth of apatite around sites of organic decay, and contain earl y diagenetic francolite cement and carbonate replacements. These deposits underwent erosion and reworking during a regression culminating probably in the Bathonian. A new reworking, and finaldeposition of the Brentskardhaugen Bed have taken place during the late Bathonian transgression. The paleontological analysis includes fossils from the Brentskardhaugen Bed and Wilhelmøya Formation. Totally 3 brachiopod, 24 bivalve, 10 ammonite and 2 decapod taxa are distinguished. The majonty of these are illustrated.
l. Introduction portance to the present study are included in the following account. 1.1 Thescope of the study Three papers by Frebold (1929a, b; 1930) The present paper is concentrated on the Brent contain extensive faunal descriptions from the skardhaugen conglomerate and adjacent strata Brentskardhaugen Bed which he referred to the in central Spitsbergen (Fig. I). This remanie bed Upper Liassic. The name «Brentskardhaugen has an ave rage thickness of 60 cm in the studied Bed» was introduced by Parker (1967) for the areas, and is characterized by a high content of «Lias Conglomerate» of earlier authors. He in- fossil bearing phosphatic clasts. Its wide regional distribution and characteristic lithology make it C J A HAUTERIVIAN an important marker horizon separating the del R L A o E o N y taic to shallow marine sand-shale sequence of the T W VALANGINIAN RURIKFJELLET U E A E MEMBER 5 N Kapp Toscana Group from the marine dark C R BERRIASIAN F T J D shale succession of the Janusfjellet Formation. U VOLGlAN E A L L p E The Brentskardhaugen Bed is present in its typi p KI!-4MERIDGIAN L AGARDHFJEllET N E MEMBER E cal development in al\ areas of Svalbard where R 'JXFCROIAN T G Cl R the junction between these two units is preserved, F M CAlLOVIAN o U M U except Kong Karls Land and north easternSpits R I Brentskardhau en & Marhegda Beds P D BATHQNIAN A bergen. D 5 L BAJOCIAN The purpose of the present study has been to 5 E K A I AALENIAN throw some new light on the Lower and Middle ri ! III P C TOARCIAN III<5 I� P L WllHElMØVA� Jurassic history of Spitsbergen through a com T PLiENSBACHW. I o I o o IIIII bined sedimentological and paleontological w 5 E SINEMURIAN C analysis of the conglomerate, the dating of the R l A HETTANGIAN N different depositional events, and the origin of A T '1llflllll Mllflllllll Irl I U RHAETIAN the pebbles found within the bed. R I FOR AT ION G I P Il R P A NORIAN - o E 5 2 2 U 5 R CARNIAN p I DE GEERDALEN 1.2 Previouswork C lADINIAN FORMATION � Stratigraphical information on the Brentskard Fig . Lithostratigraphical scherne and age relation haugen Bed is spread in a large number of shipsI. of lurassic and adjacent deposits in central Spits papers, and only those which are of special im- bergen.
5 cluded the bed in the Kapp Toscana Group be of species representing the Toarcian-Bajocian cause of its content of reworked material from interval. that group, and because of its well-marked upper Extensive correlations within the Upper Trias boundary. On the other hand Flood et al. (1971) sic to Middle Jurassic succession of Svalbard are and Birkenmajer (1975) regarded the Brent published by Pcelina (1980). The paper includes skardhaugen Bed as a basal unit of the Janus the Brentskardhaugen Bed and adjacent strata in fj ellet Formation mainly because of the presence westernand central parts of Spitsbergen as well of an extensive hiatus at its base. As seen in more as equivalent deposits in easternar eas. recent literature, there is still a divergence about The faunas of the Brentskardhaugen Bed the formation as sign ment ofthis bed. along the southern coast of Sassenfjorden are A description of the fossil content of the recently treated by Wierzbowski et al. (1981). Brentskardhaugen Bed in southern Spitsbergen Aslo here, the assemblages consist mostly of (SW TorelI Land) is published by Birkenmajer bivalves and ammonites, but some gastropods, & Pugaczewska (1975). The faunas described in serpulids, and crinoids are also present. Accord that paper are dominated by bivalves and am ing to that paper the age of these assemblages is monites, but a few gastropods and brachiopods Middle Toarcian to Early Aalenian. are also reported. The authors concluded that the assemblages found in the bed are mixtures 1.3 Thein vestigated localities The present paper is based on field data and sampl es collected from 22 localities. Detailed field work was made during the summers of 1976, 1977 and 1978 in four areas in central Spits bergen where 12 of the localities are situated. The positions of these localities are shown on Fig. 3. The other localities are seattered over southern and northeasternSpitsbergen, and their positions are marked on Fig. 2. A list of the localities is given below:
'78° 78° Festningen area: Loc. l West of Festningen
» 2 Vardebreen
Diabasodden area: Loc. 3 Deltaneset
» 4 East of Konusdalen .., "- » 77° '" 5 Marhøgda o 77° """"O"" '-- » 6 Wimandalen 15 • U) :--® » 7 Knorringfjellet ._@ JANUSFJELLET • FORMAT ION � l' �@ o 10 20 30 40 50 km Brentskardet area: I I Sørkappøya�' Loc. Juvdalskampen 14° 16° ISO SCALE 20° 8 » 9 Drønbreen Fig. 2. Location map showing the distribution of the Janusfjellet Formation in Spitsbergen. The boxed areas A to D are reproduced on a larger scale in Fig. 3 where Agardhbukta area: the position of localities to 12 is marked. The posi Loc. 10, Il Klementievfjellet. I tion oflocalities 13 to 22 is shown on this map. » 12 Rurikfjellet
6 South em Spitsbergen : and at localities 18-22, fossils are collected by Loc. 13 Leinryggen D. Worsley.
» 14 Lågryggen
» 15 LidfjelIet 1.4 Sedimentological methods » 16 Liddalen
» 17 Karentoppen The grain-size distribution of the clastic material
» 18 KistefjelIet in the phosphorite pebbles was determined by the conventional sieving method. The apatite Northeastem Spitsbergen: cement of the pebbles was dissovled in dilute Loc. 19 HellwaldfjelIet, 29 m below top of hydrochloric acid. Wilhelmøya Fm. Pulverized samples were analyzed for bulk
» 20 HelIwaldfjellet, at the top of mineralogical content by the X-ray powder dif Wilhelmøya Fm. fraction method. The mineral identitications are
» 21 Wilhelmøya, 7 m above base of bas ed on Berry (1974) and Fang Bloss (1966). & Wilhelmøya Fm. The chemical composition of the phosphorite
» 22 Wilhelmøya, I Om below top of pebbles was determined by X-ray fluorescence Wilhelmøya Fm. spectrometry analyses of samples fused into glass pills. The precision of the procedure is estimated At localities 1-12 and 14, tield data and fos to be better than 4 % of the results achieved. ± sils are colIected by the authors ; at localities 13 The chemical composition of rim cement and 15-17, fo ssils are collected by E. Nysæther; around quartz grains in a phosphorite pebble was studied by energy dispersive analysis of a thin section by means of electron microscope.
A. Festnin en area B. Diabasodden area ISFJORDEN SASSENFJORDEN 1.5 Paleontological material and methods The fo ssil collection discussed in this paper con sists mainly of bivalves and ammonites, but in addition a few belemnites and brachiopods are included. The fossils are preserved in well round ed phosphorite pebbles. Most of the ammonites and bivalves at hand are internal molds, some times with attached fragments of the shell. A few of the specimens are represented only by external mol ds. On the surface of some internal molds of bi valves, muscle scars and the palial line could be observed. On a few internalmol ds of ammonites the sutures were visible without preparation. The methods for preparation and drawing of suture lines are in accordance with the procedu res described by Nagy (1970). Exceptions are two small ammonites of which the sutures were traced by means of a camera lucida mounted on o Investigated locality a stereo-microscope, and one ammonite ofwhich ti n t a�d�a�� n Bed, � � �f� gn tO�e ��n��rj�i� : the sutures were obtained from an enlarged 012345 photograph. Conlour inle-rvol 100 m The whorl sections of the ammonites have Fig . 3. Detail maps of four areas showing position of be en drawn by the following method: A latex localities -12. cast of the ammonite was made, whereafter the I
7 east was cut at the selected cross section. A print that the beds underlying the conglomerate differ of the cross section was obtained by using ordi in lithology from place to place over short dis nary print blacking, and a drawing of the outline tances. of the who ri was then made. The bed contains varying amounts of quartz, The internal and externalmolds figuredon the chert and phosphorite pebbles floating in a plates were coloured with a light grey poster matrix of medium- to coarse-grained quartz and paint to achieve a homogeneous and favourable cemented by microsparitic Fe-rich dolomite. The colour for photographing. Some of the photo quartz and chert pebbles are usually well round graphs shown on the plates are made from latex ed, show an excellent sorting, and have a mean casts of external molds. When making the casts, diameter of about I cm. Thephosphor ite pebbles pulverized co al was mixed into the latex to a are also well rounded, but vary considerably in chieve the same colour as on the naturai molds. size (from less than 0.5 cm to 30 cm), and have a A single-lens reflex camera with a 50 mm macro mean diameter of about 5 cm. Their colour varies lens was used when photographing the fossils. from dark-grey to black on freshly fractured sur faces, and red-hrown to brown when weathered. The amount of pebbles is strongly variable within the unit, both horizontally and vertically. 2. Regional stratigraphy of the conglomerate andladjacent strata At some localities the conglomerate is clast sup ported, while at other places it is matrix support ed with only a minor content of pebbly material. 2.1 Generalfe atures of the Brentskard- The phosphorite pebbles usually contain a com haugen Bed paratively rich marine fauna, while no fossils In the areas studied in central Spitsbergen the have been observed in the matrix, and sedimen thickness of the Brentskardhaugen Bed (Table tary structures (like cross bedding and biotur I) varies from 5 cm (west of Festningen) to 135 bation) are very scarce. cm (east of Konusdalen). The unit rests with an The conglomerate is usually well consolidated, erosive basal contact on the Wilhelmøya Forma but at some localities the pebbles could be picked tion. The erosive nature of this boundary is ex out by hand from a matrix consisting of almost pressed by its uneven surface, and by the fact unconsolidated sand.
Table l. Thethickness of the Brentskardhaugen Bed and the overly ing Marhøgda Bed at the investigated Iocali ties in central Sp itsbergen.
Thickness in cm
Locality Brentskard- I Marhøgda Area number-name haugen Bed Bed Festningen l-West of Festningen 5 40 2-Vardebreen 45 covered 3-DeItaneset 120x) l50x) 4-East of Konusdalen 135 l50x) Marhøgda 5-Marhøgda 40-60 150 6-Wimandalen 45 130 7-Knorringfjellet 45 120 Brentskardet 8-Juvdalskampen covered covered 9-Drønbreen 100-130 30 10-Klementievfjellet covered covered Agardhbukta ll-Klementievfjellet 15x) 100x) l2-Rurikfjellet removed removed x) Upper part covered, or removed by Quaternary erosion.
8 2.2 Description of the Marhøgda Bed The Wilhelmøya Formation is overlain by the Brentskardhaugen Bed which is developed as a In the Diabasodden and Brentskardet areas the 5 cm thick conglomeratic sandstone containing Brentskardhaugen Bed passes gradually up pebbles of quartz, chert and phosphorite. The wards into a 30-150 cm thick microsparitic same bed reaches a thickness of 45 cm at locality limestone, partially dolomitized and sideritized, 2, east ofVardebreen. containing some quartz and chert grains, ooids and glauconite (Fig. 6). The name «Marhøgda Bed» is here proposed for this unit. Its type sec ti on is on Marhøgda, locality 5 (Fig. 3) where its 2.4 Diabasodden area thickness is 1.5 m. Five localities were studied in this area where the On freshly fractured surfaces the ooids appear most complete section was found on Marhøgda. as light grey, rounded structures (1-2 mm in The thickness of the Brentskardhaugen bed diameter) in a dark grey carbonate matrix. Some varies from 40 to 135 cm, and its content of peb bioturbation was observed in the bed, and a few bles shows marked local differences. The lower indeterminable be1emnites were also found. The boundary of the bed is always sharp with the bed weathers into white, light grey and reddish conglomerate resting on an uneven surface of colours which are easy to recognize in the fie1d. shale, sandstone or silty limestone (Fig. 5). Its Scattered pebbles of quartz, chert and phospho upper boundary, toward the Marhøgda car lite occurring in the lower part of the bed accord bonate bed (Fig. 6), is gradational. This car with the gradational contact between this unit bonate bed passes again gradually into the and the underlying Brentskardhaugen conglo overlying silt y shales which are typical for the merate. In the Diabasodden area and at lowermost part of the Agardhfjellet Member. Drønbreen the Marhøgda Bed is overlain by silty The pebbles in the Brentskardhaugen Bed strata which pass upwards into the shales typical were counted and grouped afterlitholo gy at loca of the Agardhfjellet Member. lities 5 and 6 in the lower 30 cm of the bed, and The Marhøgda Bed was recognized in its typi at locality 4 in the interval 75-120 cm above the cal development, with ooids, in the Diabasodden base. At localities 5 and 6 the lower 30 cm of the and Brentskardet are as. A light grey to reddish bed is well consolidated and matrix supported weathering carbonate bed is, however, also pres while the upper 15 cm is unconsolidated and ent at Festningen and on Klementievfjellet just therefore not suitable for pebble counting in the above the Brentskardhaugen conglomerate. At field. This upper portion is cIast supported and both localities it shows the same lithology as in was probably deposited under increased energy the type section, except that ooids were not re conditions. cognizable in the field norin thin sections. As it appears from Figs. 7 and 8, chert pebbles are most common, and are followed (in decreas 2.3 Festningen area ing order) by quartz and phosphorite cIasts. The size of the chert and quartz pebbles is nearly The section measured at locality starts with a I equal and mostly small er than the size of the phosphorite conglomerate regarded as the base phosphorite pebbles. Theexcellent sorting of the of the Wilhelmøya Formation (Fig. 4). This for chert and quartz pebbles and the much poorer mation is 17.5 m thick and consists of cross sorting of the phosphorite pebbles are cIearly bedded, bioturbated sandstones with thick express ed by Fig. 9. mudstone intercalations in the lower half. The marine character of the unit is indicated by its content of saurian bones and marine types of trace fossils. The upper half of the unit consists 2.5 Brentskardet area oftwo coarsening upward sequences interpreted The Brentskardhaugen Bed is extensively ex as barrier sand bodies. The top of the formation posed in the area between Brentskardhaugen contains Rhaetian palynomorphs according to and Drønbreen at locality 9. Here the bed is up T. Bjærke (pers. comm.). to 130 cm thick and consists of two conglomer-
9 o L ® ® U--:i u.. eID A DRØNBREEN KLEM ENTIEVFUELLET o- lJJ M RHØGDA ---' �CD ---' lJJ
I l2
M RURIKf1JELLET � - o I" t - - m c AA�- Q� "JV\ � lf + JV\�iJ, HfV\"Å,.... 711 Py.A.l; IV\� li I 711 :i ' U- � . "2 <{ >- / w, � -,-, CSI / MSivffmcvc � L Sandstone --' r····c�:::J lJJ "H I --'
10 L10 I I I � 3: lo.·,t--MSivff mc I/C Sands tone
MSivffmcl/c 15 @�(] � Sands tone Sandstone ______LEGEN like .Shale ISS:lSide rite --<' Cro�s Load east @ Spiral Bivalves cement lemmotion l.J blOturbation Q a lY Ball and 19 � Lim sto ne 1fDisptocraterion (9 Ammonites e � ����z �bles ll\. f:g���·, pillow Phosphorite l Siltstone [OiiJ Weak Rhizocorallium M: MA RHØGDA BED �pebles ��S.in 'led 'r bloturbation � 'V" Belemnites [J] '\'\'\ g B: BRENSKARDHAUGEN Sandstone �Ooids Wave generated e A Chondrites 'VBrachiopods D � ripple marks "" �git r�\�on BED Calcite pc;q Plant remains Crinoids r:::L::d cement � Mud-clasts � Flaser bedding 1H �i��� gation � * ���,ile fUl � �Ll ::::::/ eane-jn-eone ���bW�����dding C==(\Bones Gastropods
Fig, 4, Stratigraphical sections from central Spitsbergen covering the Brentskardhaugen and Marhogda beds with adjacent strata, atic horizons separated by a sandy intercalation They show the same lithology as the sandstone (Fig. lO). bed just below, indicating that the top of the The lower boundary is sharp, with the conglo Wilhelmøya Formation was eroded contempora merate resting on a 4 to 8 m thick bioturbated ry with the development of the conglomerate. sandstone forming the top of the Wilhelmøya In the Brentskardhaugen Bed at locality 9, Formation (Fig. 4). This sandstone contains plant oblong phosphorite pebbles rest with their long remains, scattered pebbles of quartz, chert and est axis paralleI to the bedding plane. The orien phosphorite, and locally a conglomerate is devel tation of the longest axis was measured in 200 oped at its base. The lithology of the pebbles pebbles to obtain information about the direc found in this conglomerate is strongly variable tion of the paleocurrent during deposition. The within the area: phosphorite, quartz, shale and results presented in Fig. I1 show a maximum at silt c\asts have been observed. Below the conglo 118° suggesting a water movement from 28° or merate is a mudstone sequence of which the 208°. In this connection it must be noted that upper 7 m is exposed at locality 9. Both the cross laminae in the sandy intercalation in the mudstone and sandstone sequences are correla middle of the Brentskardhaugen Bed show a tive on palynological evidence with similar lithol current flowroughly towards the south. ogies forming the upper part of the Wilhelmøya At locality 9 a total of 135 phosphorite pebbles Formation in the Diabasodden area (T. Bjærke have been examined for their fossil content by pers. comm.). crushing; 56% of the crushed pebbles contained In the lower part of the Brentskardhaugen Bed macrofossils (Fig. 12). It is, however, highly numerous sandstone c\asts are present. They are probable that this amount is toa low because the mostly angular and less commonly rounded in pebbles were usually broken into only two shape, and can have diameters of up to 30 cm. pieces.
Fig. The contact between the Brentskardhaugen Bed and the underlying silt y limestone on Marhøgda, Diabas· 5. odden area. W = Wilhelmøya Formation, B = Brentskardhaugen Bed.
I1 Fig. 6. The Brentskardhaugen Bed and adjacent strata on Marhøgda, locality 5. W = Wilhelmøya Formation,
B = Brentskardhaugen Bed, M = Marhøgda Bed, J = Janusfjellet Formation.
115-120 1 \.. 'Y' 101 115 / ' , , � 1 /\ / " Phosphorite / 'r /iF -- 10 5 1 01 ---Quartz I 25-30 "O 100-105- , �--- Chert .// , Pj !,' ] 20·25 '/ .1 --Phosphorite U, ---(luartz "O \ li/ li 95001 ' '�j -- - I -----C 15-20 \ hert � l d i, ' � 90-9 5' '. � : '. ' .8 lO-IS '�\ V1I > � l / 85-90- '\ i i d 5-10 I I: .8 \',_ " 1, \ � , /;' -g I 5 0-5 ,il,,'--,- 'i--,-- ---';\\i'-,---,--, 80-85- 10 20 30 40 50 + 1 2 3 4 � V\ Number of pebbles Average diameter, cm 75-80 �.1T--T'--;Ir--Ir--+j�-,-:\\:.-.40 o I Num10 ber of20 pebbles30 Average diameter,2 3 cm Fig. 7. The amount of pebbles and their size distribu tion in the Brentskardhaugen Bed at localities 5 and 6. Fig 8. The amount of pebbles and their size distribution At both localities the counts were made on a 30 cm high in the Brentskardhaugen Bed at locality 4. The counts and 70 cm broad vertical surface starting at the base were made on a 45 cm broad vertical surface 75-120 of the bed. cm from the base of the bed.
12 % Fig. Sorting of the three groups of pebbles in the 100 Phosphorite 9. - --- Brentskardhaugen Bed expressed by size frequency \ ---Quartz curves based on counts at locality 4, 5 and 6. 90 �I ------Chert \1 80 � On Juvdalskampen (locality 8) the Brentskard , haugen Bed is scree-covered except for a few 70 , incomplete exposures. The position of the con glomerate is usually marked by large amounts of 60 \ , loose chert, quartz and phosphorite pebbles just above a sandstone horizon. 50 I In the area at the front of Drønbreen the - \ Brentskardhaugen conglomerate passes gradual 40 ly upwards into the Marhøgda Bed which shows the same lithology as in the Diabasodden area. 30 Its thickness is 30 cm at locality 9. The shale sequence forming the bulk of the Agardhfjellet 20 \\ '\I Member has an upwards tining, silty develop ment in its lowermost portion on Brentskard 10 \\I- - haugen, at the front of Drønbreen (locality 9), on \�\� "'------Flexurfjellet and on the western slope of Fonn hetta. 1 2 4 5 6 >6 O 3 Average diameterJ cm
Fig. Exposure of the upper 25 cm of the Brentskardhaugen Bed at locality 9. JO. 13 Fig . Orientation of the 900 longestIl. axis of 200 phos phorite pebbles in the Brentskardhaugen Bed at locality 9.
o O�-4--+-�--�1..
2700 2.6 Agardhbukta area Locality 10 is situat(:d on Klementievfjellet, on size of the pebbles varied from 2.4 to 13 cm with the westem side of the Lomfjorden fault zone. an average of 5. 1 cm. Their roundness was decid The Brentskardhaugen Bed is covered, but its ed visually by comparison with Power's scale. position is marked by large numbers of pebbles As it appears from Fig. 13 the pebbles are gener weathered loose from the bed. At this locality the ally well rounded, with the size group 5. 1 cm < size and roundness of 160 pebbles were measur more rounded than the size gro up 5.1 cm. � ed and their fossil content was registered. 51 % Locality II lies on the eastem slope of Kle of the pebbles were fossil bearing (Fig. 12). The mentievfjellet, east of the Lomfjorden fault zone. The top of the Wilhelmøya Formation here is formed by a 3 m thick, cross-Iaminated and strongly bioturbated sandstone contammg Frequency of pebbles Fossil conlenl Chondrites, Rhizocorallium and Thalassinoides. Locality 9 Locality 10 Above it the lower cm of the Brentskard 10 20 30 40% 10 20 30 40% IS haugen Bed is exposed. The conglomerate rests Barren
6elemniles � -
Wood I of � Roundness Frequency pebbles Bivolves � Diameter< Diameter � IS sea (Power le) 5,1c m(62'10) ;o5,lcm(38'1o) Shell fragmenIs � - 20 40 60% 20 40 60% Ammoniles � • 3 '" �
Brochiopods 4 Unidenlified organic remains 5 �
Fig . 12. Frequency of phosphorite pebbles with and Fig . 13. Roundness of pebbles of the Brentskardhau without macrofossils in the Brentskardhaugen Bed. gen Bed at Locality 10. The diagram is based on 160 The diagram is based on 135 pebbles from locality 9, pebbles. These are divided into two groups at a diame and 160 pebbles from locality 10. ter of 5.1 cm which is the average pebble diameter.
14 on the eroded surface of the Wilhelmøya Forma ammonites in the conglomerate (Fig. IS). The tion and shows a lithology similar to that of the num ber ofbivalve species decreases slightly from preceding localities. Above the conglomerate the Toarcian to the Aalenian but shows a marked 100 cm of the Marhøgda Bed is visible. increase in the Bajocian and Bathonian. Totally, At locality 12, on Rurikfjellet, the Brentskard ten bivalve species are identified with known haugen Bed overlies a 6 m thick cross laminated species, and five of these occur in Bajocian or and strongly bioturbated sandstone. The basal younger strata outside Svalbard. The presence part of the conglomerate is preserved in depres of these five species suggests that the fo ssil con sions of this sandstone ; the rest is removed by tent of the Brentskardhaugen Bed has been de Quaternary erosion. A shale intercalation 4.5 m rived not only from the Toarcian and Aalenian, below the top of the sandstone contained Toarc but also from yonger stages, at least Bajocian. ian palynomorphs identical to those found in the topmost beds of the Wilhelmøya Formation on Marhøgda (T. Bjærke pers. comm.). In a partly 3.3 Brachiopods phosphorized horizon 4 m below the top of the Two inarticulate brachiopod species, Lingulina sandstone a specimen of Porpoceras polare was cf. beani and Discinisca cf. rejlexa are locally found, indicating the presence of Middle Toarc common in the Brentskardhaugen Bed. Both are ian. In the upper two metres of the sandstone, referred to the Bajocian. scattered phosphorite pebbles are present. The palynomorph assemblages occurring in these dasts are similar to those found in the phospho 3.4 Dinojlagellates rite pebbles of the Brentskardhaugen Bed in the Bj ærke (1980) recorded 18 dinoflagellate species Diabasodden area (T. Bjærke pers. comm.). from the phosphorite pebbles of the Brentskard haugen Bed on Knorringfjellet. The stratigraphi cal occurrence of four of these species in other areas is reported to be Late Pliensbachian - 3. Fossil content and age Bajocian, Bajocian?, Toarcian - Bajocian, and Toarcian - Bathonian. SeveraI of the species 3. 1 Ammonites and Belemnites reported by Bjærke are found in Toarcian and The majority of the ammonites found in the Aalenian (opalinum Zone) deposits in England. phosphorite pebbles of the Brentskardhaugen Based on our present knowledge of the strati Bed represents three zones of the Toarcian: the graphical distribution of these dinoflagellates it bifrons Zone, the variabilis Zone and the thou can be conduded that their occurrence in the arsense Zone (Fig. 14). In addition the fa lciferum Brentskardhaugen Bed suggests the presenee of and levesquei Zones of the Toarcian, and the the Toarcian, Aalenian and possibly Bajocian, a opalinum and murchisonae Zones of the Aalen time range in general agreement with that indi ian are each represented by a few ammonite cated by the ammonite and bivalve assemblages. specimens. Belemnites are locally common in the Brent skardhaugen Bed. They are, however, of no stra 3.5. Faunal comparisons tigraphical significance because of their poor The geographical distribution of ammonites and state of preservation, insufficient for doser deter bivalves recorded from the Brentskardhaugen mination. Bed is shown in Fig. 16. Information on the mollusc faunas occurring in regions relevant for comparison are obtained from the papers in 3.2 Bivalves duded in the synonymy lists (paleontological The bivalves found in the Brentskardhaugen Bed part ofthis paper), and from the following publi extend the time range of the pebbles to parts of cations : Frebold (\ 958b), Ravn (19 I2), Rosen the Middle Jurassic younger than the Aalenian, krantz (1934) and Spath (1947). which is the youngest stage represented by As it appears from Fig. 16, all the bivalve spe-
15 Fig . 14. Stratigraphical j distribution of ammonites '"E o occurring in the phospho S :i<:() 'N... � o c: Ti rite pebbles of the Brent Ej Ej ... ro � (1) T AMMONITE ZONATION 13ro ... '" skardhaugen Bed. es ro E .5 � ro.... c: � Co "C c: (1) Co j .a :i (1) '" "C (After Cope al., E ro 'e ro() ro o (1) oE ... j '" A & 1980) >< ro Ol Co ai es c: () E e () .8 æ '" '" o �ro '"ro ro ro'" ro '" '" (5Co '5.'" ro G ro ... .o '" '" (1) ai ai ai ai E ai ro ro () () () () () Ero .... () ....ro E ai ai .2 . 2 .2 .2 o, ZONES SUBZONES () () . 2 o .2 o o "C(5 "C(5 (5"C "C (5 "C(5 "C g >.... Co Co j j j j j j S () (1) (1) (1) (1) (1) (1) ro ro es es '" '" '" '" '" '" '(jj Cl Co Co Co Co Co Co Co Co 00 "formosl1m A concavum ___ .D.QQ.Z..9.D2. ------concavum - - --- A "gigantea. h o L ____ ..9!.!� ..!'..:: bradfordensis ------� E murehisonae ------______JL _ murehisonae-- - N ------I haugi A seissum opalinum ------N opalinum- - 1 aalensis ------moorei------T levesquei ------levesquei------�------1------O dispansum fallaciosum thouarsense ---- . - .- - A striatulum------l.l---
variabilis R crassum ------bifrons fibulaturn fo- - C ------'------commune- falciferum I falciferum ------. ______exaratum-- - Jl A semicelatum ------tenuicostatum - - tenuicostatum ------N clevelandicum------paltum------
eies recorded from the Brentskardhaugen con Europe, two in East Greenland, four in Arctic glomerate are known from Western Europe, Canada and two in Alaska. while four are found in East Greenland, one in Thus, the bivalve assemblages of the Brent ArcticCanada, and none in Alaska. skardhaugen Bed show surprisingly high simila The ammonite speeies recorded from the rities to contemporary faun as known from West conglomerate show the following distribution ern Europe. On the other hand, they are much outside Spitsbergen: six speeies occur in Western different from the faunas of East Greenland, and
16 BRACH! BIVALVES
Ul (J) Ul (J) U U (J) a. (J) Ul a. Ul Cl -(J) )( (J) Q! c � STAGES � O 'c E d Cl "- > Q! - E u .Cl .Q d - ...: Cl C u u OL. � III L. ::l (J) (J) Ol Eu .Cl .Cl C III E E ::J --.J O ::J i = Z Z 123456789 12345 67 89 CALLOVIAN ! • • ; • BATHONIAN • • • = ; . BAJOCIAN . = = • ! ! • I AALENIAN = •I I• • ; . � TOARCIAN • ! • • Fig. Stratigraphical distribution of brachiopods and bivalves occurring in the phosphorite pebbles of the Brentskardhaugen15. Bed. The number of ammonite and bivalve speeies shown to the right.
still more from the faunas of Canada and Alaska. accordance with the presence of the narrow Ju These differences are probably caused by diver rassic shelf sea that connected the Barents Shelf geneies in facies which might have a marked directly with the North Sea along the Norwegian influence on the distribution of this benthic coast. group. The ammonite assemblages of the conglom 3.6. Age o/the Brentskardhaugen Bed erate show the greatest similarities to Western Europe, but they are also c!early like the faunas and adjacent strata of Arctic Canada and Alaska. The most probable The composition of the ammonite, bivalve and reason for this regional similarity is the pelagic dinoflagellate assemblages found in the phos mode of life of this group. phorite pebbles demonstrates that the fossil con Based on the relations presented above we can tent of the Brentskardhaugen Bed was formed conc!ude that in the Toarcian-Bathonian interval by mixing of elements of different ages. The as a pelagic faunal communication has existed di semblages contain Toarcian, Aalenian and Bajo rectly between Western Europe and Spitsbergen, cian species, while presence of Bathonian forms and from here to north-western North-Arnerica. cannot be totally exc!uded. The marked similarity between the benthic On the basis of palynological analyses the faunas of Spitsbergen and Western Europe is in beds just below the Brentskardhaugen conglom-
17 Fig. 16. Bivalves and am o Z 0--':'--' monites recorded from the Wu - Z CLe 01"' - � W 00 c:r-.I d Brentskardhaugen Bed 2,nd 0::- ::JOl Z Q) U On·i: L their occurrence in other <.9o::: W ,� C '--o Z "O from Spitsbergen in earlier (f) w1uO�c øCl:: � CL'� ::i ..... U.��«(]) I publications). f- o f- � .... CL (f)l-_eE6�Q;·�o (f) u'C � � (f) i:5 4�<{ Oxytoma inequivalvis* �
erate (Fig. I) are referred to the Toarcian in the before the deposition of the basal shales of the Diabasodden, Brentskardet and Agardhbukta Janusfjellet Formation. It seems most probable are as (Bjærke Dypvik 1977.) This dating in the that the bed reached its finaldevelopment in the & Agardhbukta area is confirm ed by finds of Por late Bathonian, an assumption supported by the poceras polare on Rurikfjellet 4 m below the transitional relation between this bed, the Brentskardhaugen Bed. At Festningen the Marhøgda Bed and the shales of the Agardhfjel Brentskardhaugen Bed rests on Rhaetian depo let Member. sits (T. Bjærke pers. comm.). The basal siltstones of the Agardhfjellet Member on Marhøgda contain cf. Kepplerites 4. Pebble content and origin tychonis Ravn 1912 at two places, only 3 m above the Marhøgda Bed. The presence of this am 4. 1. Phosphoritepebbles monite indicates an uppermost Bathonian - X-ray diffraction (Fig. 17) and thin section analy basal Callovian age. ses have shown that the phosphorite pebbles The age of the Brentskardhaugen Bed can only essentially contain carbonate-fluorapatite and be determined indirectly because no fossils have quartz, and lesser amounts of pyrite, c\ay mine been found in its matrix. The deposition of the rals, rock fragments and glauconite. The apatite bed must have taken place after the fomlation occurs as cement between the clastic grains. Shell of its phosphorite pebbles (see next chapter), but fragments and plant remains have been replaced
18 by phosphorite. The cement in the pebbles can sented in Table 3 have been obtained by a visual be recognized optically as a microcrystalline, comparison of the shape of 144 pebbles with the anisotropi c variety of apatite, collophane (KeIT enclosed macrofossils. Pebbles containing bi 1959). X-ray fluorescence analyses have con valves which have the same length as height are firrned that the cement is a fluoride-rich variety often almost circular in outline. If the bivalves of apatite, probably francolite. According to are oval in outline, then the pebbles will also McConnell (1958) francolite is a carbonate have this shape. The pebbles containing am fluorapatite with F-content greater than 1%. monites have their shortest axis oriented paralle1 Analysis of the grain-size frequency distribu to the umbilical axis of the ammonite shells. tion of the clastic material in nine phosphorite Pebbles containing pieces ofwood or belemnites pebbles was carried out by dissolving the pebbles are oval, or even cigar-forrned. in dilute hydrochloric acid (Fig. 18 and Table 2). In cross sections the phosphorite pebbles often The results show that the original sediment in show internalconcentric structures (Fig. 19). This which the pebbles were fo rrned,was a well sorted is also reflected by the fact that the pebbles, when quartz sand. The average amount of the clastic dissolved in dilute acid, seem to peel off in con material is 53 weight-%, which means that the centric flakes. apatite cement constitutes on average 47 In thin sections of the pebbles a rim of phos weight-% of the phosphorite pebbles. Both the phorite cement around the clastic particles can quartz content of the pebbles and the average often be observed (Fig. 20). The composition of grain-size show a rather homogeneous distribu the rim-cement is confirrnedby energy dispersive tion throughout Spitsbergen. analysis of thin sections using e1ectron micro Severai phosphorite pebbles show internal scope (Fig. 21). The individual phosphorite crys bioturbation features fo rrnedwhile the sediment tals (length up to 10 [lm)are oriented radially out was still unconsolidated (Fig. 19). The bivalves from the c1astic partic1es. The remaining pore found in the pebbles are often closed, showing space is filled with microsparitic phosphorite. that they were protected within the sediment The rim-cement, however, is not always devel until lithification. oped; sometimes the microsparitic phosphorite Pebbles containing macrofossils clearly show cement is to tall y dominating. a cOITelation between their shape and the shape In re cent literature severai theories are pre of the fossils enclosed in them. The results pre- sented in order to explain the forrnation of
2.79,1
>-� it: w " >
>- Cf: 2,70 "A w > >- " a. " w 3 .• d > >-
55 50 45 40 35 30 25 20 15 10 5 Degrees 29 Fig . 17. X-ray diffractogram of a phosphorite pebble from the Brentskardhaugen Bed. 19 marine phosphatic sediments. A model is based ries by replacement of previously formed car on the hypothesis that phosphorite is formed by bonate deposits. Kennedy Garrison (1975) & replacement of already existing materials, usual interpreted Cenomanian phosphatic nodules as ly carbonates. D' Anglejan (1967) reported formed by replacement of lithified carbonates, phosphorite deposits fo rmed by replacement of either prefossilized internal mol ds or reworked calcareous shell debrls from the sea floor off carbonate concretions. southem California. This region is characterized Another theory is based on Kazakov's (1937) by upwelling of phosphate-rich water and a low mode! of direct inorganic precipitation of marine rate of c1astic sedimentation. Peaver (1966) in apatite from sea-water. Dietz et al. (1942) and terpreted Tertiary phosphorite sediments from Emery (1960) assumed that the phosphorite de the United States as formed in productive estua- posits off the California coast were formed in this way. Atlas (1975) conc1uded that apatite is formed 2mm Imm 0,5 mm 250�m 125�m 63�m 99.9 ��-�------,------,--, from the pore-water of anoxic sediments, rather '---r ,-'- -,"- +- than from the overlying sea-water. Burnett (1977) 99.5 reported phosphorite deposits from the shelf off 99 Peru and Chile formed by a direct inorganic 98 97 precipitation of apatite in such an environment. 95 95 This precipitation took place about 15 cm be!ow 90 the sediment surface. 84 The results achieved from the study of the 80 75 phosphorite pebbles of the Brentskardhaugen 70 60 Bed indicate a c10se relationship between the 50 50 formation of these pebbles and the phosphorite 40 pebbles found off Peru and Chile. The character 30 25 istic rim cement around the c1astic grains in the 20 16 Spitsbergen pebbles indicates a direct inorganic 10 precipitation of the phosphorite cement. Internal bioturbation occurring in the sandy matrix of the 5 5 3 pebbles c\early shows that this precipitation must 2 have taken place within a still unconsolidated 1 sandy sediment. Any evidence that the phospho 0.5 rite cement has replaced an already lithifiedsedi 0.1 ment (e.g. carbonate) has not been observed, -I 2 3 4 units however, shell material and plant remains have O) - been phosphatized by an apatite replacement Fig. 18. Grain·size frequency distribution of the clastic material in 9 phosphorite pebbles from the Brentskard proeess. haugen Bed. The fossils found in the pebbles c1early indi- Table 2. Average cp values and weight-percent of quartz in 9 phosphorite pebb/es determined aft er disso/ution of eement. I S. Brent- Sp its- SpN.its-E. Area Diabasodden skardet bergen bergen Locality 3 4 5 6 7 8 9 14 22 Sample no. 78-76 103-76 13-76 51-76 62-76 4-77 23-77 S5 pl-6- 4 Average cp 2.8 2.4 2.4 2.7 2.8 3.0 2.7 3.3 3.0 Quartz I weight 61 46 43 53 59 56 50 46 60 % I I 20 cate that the sediment was deposited under precipitation of apatite, took place because of the marine conditions. The correlation between the fo rmation of NH4 + and other nitrogenous bases shape of the pebbles and their fossil content, during the decomposition of proteins and other together with the presence of structures indicat biochemical compounds. ing a concentric growth, suggest that the pebbles The chemical composition of nine phosphorite must have been formed as concretions around pebbles was determined by means ofX-ray tluor the fossils, probably in connection with the decay escence spectrometry (Table 4). The variation in of organic material. Bumett (197 7) assumed that Si02 and P205 content retlects a variation in the the dissolved phosphate mainly came from such amount of clastic materials versus amount of a decay and that a rise in Ph, necessary for the apatite cement. Table 3. Correlation between pebble shape and shape of enc/osedfo ssil based on visual comparison of 144 pebbles with their fo ssil content. Correlation in shape: Pebble - fo ssil Number of Fossil groups pebbles cases - cases + Ammonites 31 29 (94 %) 2 ( 6 %) Belemnites 45 35 (78 %) lO (22 %) Bivalves 53 42 (79 %) I1 (2 1 %) Wood fragments 12 12 O Saurian bones 3 3 O Fig. 19. Intemal structures in phosphorite pebbles from the Brentskardhaugen Bed: a. Bioturbation preserved in a pebble with a belemnite rostrum at the centre (x 1.8). b. Diffuse concentric structures around an ammonite shell (x 1.2). 21 Fig. 20. Thin sections of phosphorite pebbles from the Brentskardhaugen Bed displaying the following details : Q = quartz grain, R = rim cement of Ca-apati te, M = microsparitic phosphorite. a. Clastic grains partially surrounded by rim cement of phosphorite crystals. Crossed nicols (x 160). b. SEM photograph (x 390; = point ofX-ray analysis, see Fig. 21). + Il) C GI - C --Il o F Na Mg AL Si P S Cl K Ca Ti v Cr Mn Fe C o Ni K-alpha Lines Fig. 21. Curve of a qualitative X-ray analysis of thin section made by electron microscope. It shows that the rim-cement int the phosphorite pebbles is Ca-apatite. The point analysed is shown in Fig. 20. 22 The CaO/P20s ratio of the pebbles of the The F /P20S ratios of the Spitsbergen pebbles Brentskardhaugen Bed shows only slight chang are fairly constant (Table 5). In all the samples es and the average value is 1.49 (Table 5). Ac these ratios are somewhat higher than the ideal cording to Burnett (1977), the CaO/P20, ratio of ratio of 0.089 given by Burnett (1977) for a non the phosphorites off Peru and Chile is 1.50 which carbonate-fluorapatite. The samples analysed by is only slightly higher than expected for a pure Burnett show, however, also slightly higher carbonate-fluorapatite phase. He concluded that values. He explains this «excess» of F as probab the CaO not associated with apatite, was probab ly being incorporated into the apatite lattice to ly included in detrital phases, such as plagio balance the excess positive charge created by cIase. Since no other phosphate mineral has been substitution of CO/- for P/ - . recognized in the samples described in the pre The chemical composition of the phosphorite sent paper, it must be assumed that all the P20S pebbles of the Brentskardhaugen Bed is similar is included in the apatite. to the resuIts achieved by Burnett (1977) for the Table 4. Ch emical composition of phosphorite pebbles fr om the Brentskardhaugen Bed. Brent Southern Area I Diabasodden !I skardet Sp itsbergen Locality 5 5 5 ! 7 7 9 9 13 18 Sample no. 8-76 9-76 19-76 32-76 85-76 14-77 23-77 S5- KIS !1 pl-64 Loss on ignition 2.70 3.03 2.77 2.94 1.48 2.35 2.23 1.36 1.00 SiO, I 59.52 46.26 63.11 59.23 62.66 66.66 53.23 60.53 55.46 AI,O, 1.79 4.15 1.32 1.96 1.51 3.19 2.83 1.87 0.98 Fe,O, 1.76 0.93 0.94 0.95 0.70 I 1.00 0.70 1.77 0.52 MgO 0.36 0.06 CaO 18.56 25.02 18.01 19.37 18.45 14.53 22.24 19.07 22.81 Na,O 2.64 2.91 2.12 I 2.40 2.49 1.96 2.77 2.17 2.71 K,O 0.32 0.49 0.17 0.28 I 0.14 0.20 0.30 0. 19 0.13 P,O, 12.48 16.99 11.03 12.60 12.47 9.78 15.47 12.95 16.28 TiO, 0. 12 0.13 0.08 0.12 0.07 0.23 0.15 0.07 0.08 MnO 0.03 0.01 0.01 0.01 0.01 0.03 0.01 0.01 0.01 Cl 0.01 0.01 0.01 0.01 - i 0.01 0.01 0.01 F 1.34 1.98 1.43 1.47 ! 1.50 1.33 I 1.82 1.72 1.95 i I 101.49 101.26 101.76 101.72 I 101.94 Total 101.26 101. 91 101.36 101.40 . -O I 0.56 0.83 0.60 0.49 0.63 0.56 0.77 0.72 0.82 I 101.08 100.76 1 100.91 i 100.86 100.70 100.99 101.00 101.12 Total 100.70 1 1 i Table 5. Ca 0/P2 0j and F/P2 0j ratios of phosphorite pebblesfrom the Brentskardhaugen Bed. I I Brent- Southern Area Diabasodden I skardet Sp itsbergen I I Locality 5 5 I 7 I 7 9 13 18 Sample no. 8-76 9-76 19 76 32-76 85-76 14 77 23-77 S5- KIS ! � � pl-64 1 I! CaO/P,O, 1.49 1.47 1.63 1.54 1.48 1.49 1.44 1.47 I 1.40 F/P,O, 0.107 0.117 0.130 0. 117 0.120 0. 136 0.118 0. 133 0.120 I I I 1 23 pebbles off Pem and Chile (Table 6). It supports Table 6. Average chemical composition of phosphorite the assumption that the pebbles from Spitsber pebbles fr om the Brentskardhaugen Bed (9 analyses) compared to the average values reported off Peru and gen and from the South American shelf have Chile (15 analyses). The values are given in weight been formed under essentially similar condi percent. tions. Off Peru and Spitsbergen Chile (Burnett 1977) (This paper) 4.2. Ch ert pebbles Si02 22.13 58.52 Counting of pebbles at localities 4, 5 and 6 in the AI2O, 5.15 2.18 Diabasodden area showed that chert pebbles are Fe20, 2.85 1.03 the most common clasts in the Brentskardhaugen MgO 1.07 0.05 Bed (Figs. 7 and 8). At these three localities the CaO 33.93 19.78 average frequency of chert pebbles is 57 % of the Na20 0.85 2.46 total pebble content. The chert pebbles are usual K20 1.30 0.25 ly very well rounded, in spite of their resistance P20, 22.61 13.34 Ti02 Not determined 0.12 against wear, and also show an excellent sorting. Thin section studies revealed an assemblage MnO Not determined 0.01 of sponge spicules inside some of the chert peb Cl Not determined 0.01 S 0.16 Not determined bles (Fig. 22a). In the Svalbard archipelago bedded cherts and other cherty lithologies are F 2.22 1.62 Loss on ign. 8.78 2.21 well known from the Upper Permian Kapp Sta Total 101.05 101.57 rostin Formation, but chert to a considerably smaller extent is also present in the Upper Car -O 0.93 0.66 Total 100.12 100.90 boniferous-Lower Permian deposits. Spiculitic CaO/P2O, 1.50 1.49 cherts are common in the Upper Permian as it F/P2O, 0.098 0.109 appears from Siedlecka (1970). It is therefore Fig. 22. a. Thin section of a chert pebble from the Brentskardhaugen Bed showing sponge spicules. Crossed nicols (x 51). b. Thin sectin from the Marhøgda Bed showing ooids with their concentric structure disturbed by sparitic anker ite. Nuc1ei of quartzare visible. Crossed nicols (x 60). 24 likely that the chert pebbles of the Brentskard from adjacent areas affected by periodic high haugen Bed, at least partially, were deri ved from energy currents, e.g. tide dominated environ those strata. ments. Dyed thin sections and X-ray diffraction ana lyses show that the microsparite has been re 4.3. Quartz pebbles placed by siderite, and in some places also by Polycrystalline quartzpebbles are also frequently other Fe-rich carbonates (Fig. 22b). Theconcen found in the Brentskardhaugen Bed. At localities tric structure of the ooids is often destroyed by 4, 5 and 6 this pebble type constitutes on average sparitic Fe-rich dolomite, otherwise the ooids are 29% of the total pebble content of the conglom replaced by siderite. Grains of quartz, chert, erate. These pebbles are also very well round glauconite and kaolinite acted as nucIeation ed, and their sorting is good. Metamorphic po centres for the ooids. Iycrystalline quartz pebbles (often with undulat ing extinction under crossed nicols) were prob ably derived from HecIa Hoek. Birkenmajer 7. Conclu ding remarks on deposi- (1972) described pebbles of vein quartz from the tional histor y Brentskardhaugen Bed, which he recognized as HecIa Hoek material. 7.1. Source of pebbles Sandstone cIasts with lithologies resembling The material which forms the Brentskardhaugen the sandstones of the Kapp Toscana Group must Bed is to a great extent deri ved from the Wil have been eroded from that unit. helmøya Formation through reworking in the Middle Jurassic. This origin is indicated by: the erosional basal contact of the conglomerate ; the presence of angular sandstone c\asts in the lower 5. The matrix of the conglomerate part of the conglomerate ; the occurrence of The material between the pebbles is dominated phosphorite, chert and quartz pebbles both in the by fineto medium grained quartz sand in a car conglomerate and in the Wilhe\møya Formation ; bonate ground mass. At some places this sand is and the exceptionally high sand content of the grain supported, while at other localities it is phosphorite pebbles. more or less floating in the carbonate ground The phosphorite pebbles of the Brentskard mass, but variations are observed also within haugen Bed are mechanically rounded, but a individual sections of the conglomerate bed. The correlation exists between their shape and the sand is probably derived from the Kapp Toscana shape of the encIosed fossils indicating a con Group. Some scattered glauconite grains were cretional origin of the cIasts. In spite of their also observed. greater resistance against mechanical wear, the The cement found in the matrix is a microspa chert and quartz pebbles are more rounded and ritic carbonate. X-ray diffraction analyses and better sortedthan the phosphorite pebbles. This dyed thin sections have shown that this car relation suggests that the chert and quartz peb bonate is an Fe-rich variety of dolornite (anker bles passed through one or severai episodes of ite). mechanical weathering before they became in volved in the same events which rounded the phosphorite pebbles. 6. Origin of the Marhøgda Bed The microsparitic limestone forming the bulk of the Marhøgda Bed was originally deposited as 7.2. TheLadin ian-Pliensbachian interval carbonate mud. Its content of quartz and chert The Ladinian-Norian period in Svalbard is grains, glauconite and ooids must have been dominated by delta influenced marginal marine derived from areas outside the carbonate mud to shallow marine conditions which led to the environment and then transported into these deposition of the De Geerdalen Formation (Fig. deposits. The ooids have probably been derived 23). In central Spitsbergen the deltaic influence 25 Fig. Depositional histo 23. Depositional of central Spitsbergen conditions fromry Middle Triassic to Upper Jurassic as reflected aJ aJ C C C . . by the Brentskardhaugen o ;: ;: Lithostratig phi al Dominant o o conglomerate and adjacent ra c :;:; units litholo9 Age 'Vio E E strata. Y. aJ c a. o ... o aJ o C -o o VI I .r: C Bajocian � Aalenian oarcian Wilhelmøya. T u Formation DS Ul Ul Pliensbachian [fiJj 'O ::J Sinemurian rJ Hett angian . ..:.:...... :...:.• ....:...:� l-i:::: De Geerdalen Carnian Fo rmation => Ladinian was reduced in comparison to the eastem parts prevailed to the late Pliensbachian. These condi of the archipelago. tions seem to have resulted in a total or partial Shallow shelf conditions of a more normal non-sequence corresponding to the Hettangian marine character were introduced to central Pliensbachian interval, which explains the ab Spitsbergen during a transgression which pro sence of diagnostic fossils from this time period. bably started in the Norian and culminated in the Rhaetian. The lower part of the Wilhelmøya Formation has been deposited by this marine 7.3. TheTo arcian-Bajocian interval ingression as suggested by Bjærke Dypvik A new transgression started probably in late & (1917). Pliensbachian (T. Bjærke pers. comm.) and Regressive conditions started already in the reached its maximum in the Toarcian. This event late Rhaetian or early Hettangian and probably introduced shallow shelf to marginal marine 26 conditions to Spitsbergen, with an extensive ant constituents, among these, the phosphorite reworking of deltaic sediments, resulting in the pebbles. deposition of the upper part of the Wilhelmøya A new transgression started probably near the Formation. end ofthe Bathonian contemporary with a global The Toarcian maximum of marine ingression elevation of the sea level at the transition be is reflected by the fact that most of the ammo tween the Bathonian and Callovian. This event nites found in the Brentskardhaugen Bed belong led to renewed reworking and final deposition to this stage. The regional extent of the trans of the remanie sediments forming the Brent gression must have been as large, or larger, than skardhaugen Bed. In easternand central regions the present distribution of the Brentskardhaugen these Middle Jurassic reworking processes conglomerate which extends from Sørkapp Land reached locally down at least to the Middle through the western outcrop belt, the Isfjorden Toarcian bifrons Zone. The lower parts of the area and Agardhbukta to Wilhelmøya. This Toarcian remained undisturbed as shown by the marine ingression appears to be time correlative relations found in the region between inner Is with the global Toarcian transgression which fj orden and Agardhfjellet, and further northeast. reached its peak near the end of the stage. In the western outcrop belt, e.g. in the Fest The degree of open marine influence seems to ningen area, the Brentskardhaugen conglomer have been reduced al ready in the Aalenian as ate rests on Rhaetian deposits belonging to a very this stage is represented by bivalves and only a thin Wilhelmøya Formation. Thus, in western few ammonites in the Brentskardhaugen Bed. regions the Middle Jurassic erosion might have The Bajocian is represented by bivalves but been more extensive, and removed a larger part shows a total absence of ammonites suggesting a of the Wilhelmøya Formation, than in eastern further reduced open marine tendency upwards areas. In this connection it must be noted, how in the Middle Jurassic. ever, that Mørk et al. (1982) suggest an originally The formation of phosphorite nodules seems thinner and more incomplete development of the to have been promoted by increasing marine Wilhelmøya Formation in areas west of the Bil influence as shown by the fact that the majority lefjorden fault belt. of the phosphorite pebbles apparently belongs to As energy decreased during the Bathonian the Toarcian. The preceding chapters demon Callovian transgression, an ess entially fining strate that the pebbles were developed as con upwards sequence was developed in the Diabas cretions by precipitation of apatite commonly odden and Brentskardet areas. It starts with the initiated by biogenic materials. The precipitation Brentskardhaugen conglomerate which has a has taken place below the bottom surface, direct transitional boundary towards the Marhøgda ly from the pore water of mineralogically mature, Bed. There is also a gradational contact between bioturbated sand deposits. the Marhøgda Bed and the lowermost siltstones of the Agardhfjellet Member, as well as between these siltstones and the black shales higher up in 7.4. TheBat honian-Callovianinterval the member. We can therefore conclude that the The Middle Jurassic regression seems to have Brentskardhaugen Bed and the lower part of the culminated in the Bathonian. Absence of diag Janusfjellet Formation have been deposited dur nostic marine fossils of Bathonian age from the ing a single, continuous, transgressive event. Brentskardhaugen Bed suggests that the sea re In central Spitsbergen the lowermost siltstones treated at least from western and central Spits of the Agardhfjellet Mernberco ntain a Keppler bergen during this stage. (It must be noted here iles fauna of uppermost Bathonian-basal Callov that two Bathonian bivalves are found in the ian age. Based on the fact that the Brentskard uppermost part of the Wilhelmøya Formation on haugen conglomerate and these siltstones were Hellwaldfjellet.) During this regression the shelf deposited during the same transgressive event, became exposed to coastal erosion with energy we may assurne that the final deposition of the high enough to break up parts of the Wilhelmøya Brentskardhaugen Bed has taken place not much Formation and concentrate its coarse and resist- before the end of the Bathonian Stage. 27 8. Paleontological part more detail ed synonymy lists, the reader is refer red to those publications. The classification of 8.1. Introductory notes the brachiopods, bivalves and ammonites corre The synonymy lists given in this paper are not sponds to the Treatise on Invertebrate Paleontolo complete and include on ly the publications used gy. edited by Moore (1957, 1965, 1969, R.e. when identifying the speeies. For more informa 1971). tion about the morphology of the speeies and In the drawings illustrating the ammonites, Table 7. List of speeies with references to the localities where they were fo und. LOCALITIES SPECIES 3 4 , 6 7 • 9 12 13 14 15 16 17 " 19 2. 21 22 Lmgula cf beanl-- :I: c---- - u * * , "" lmgula sp I I ... a: * * * al Dlsclnlsca cf reile •• 1 l * * Buchia sp , 1 * * - � -- Inocer.mus sp I * O.ytoma (O ) m&qUlv.hm - I------* � * O.ytorne sp ----- i � -- - Meleagrlnell. cl echtnata * , I * * * * Propeamusslum ( Parvam leI person.turn -- * Chlamys (e ) sp * f------, Plaglostoma cl subcardlilormlS -- * r-- * Gryphaea ? sp - * f------f---- Llolngonl. )Inganensis - * * f------Trlgonla sp * '" luclnlola cf pumlla * w Mactromya globOsa I * "" ------:;> t- Astarle {A_l elegans * iii Tancredl' (T ) donacrtormls * * * *** * ... f- Pholadomya (P ) cl hemlcardl8 * Pholadomya (P ) klngl ... Pholadomya ,p * ... Gonlomya Iiterata I , Homomya gibbosa * Pleuromya elongala ...... ------? Pleuromya margInala * ------I * * Pleuromya subcompressa -- .- Pleuromya sp � I * I Daclylloceras t Olophorurn * Porpoceras polare f---- * * * , Porpoceras splnalum i ... -- - - -, - 1 - Porpoceras cl_ splnalum ------;-*1- r-- -I--- -j-- BraSIlia aH_ bradfordense r -- -- PseudOlloceras compactllE' '" ------W * r---,-1* * f--* - J >- Pseudolloceras gradatum-- z --- - - * - - - O Pseudolloceras cl gradal\,;m - � --- * � "'5]'- * "" �� ��* Pseudolioceras pumilum ;i=------* * r-- - Pseudolloceras cl pumlluln ' One søecimen * Pseudolloceras macllnloc�.1 * - - * Few specimensd= r-- * * * -r--- * PseudollOceras ro senll ran tZI specimens , � * **Several Pseudolloceras spp I * * j-- Pseudogrammoceras lallal;losum 1 ------r--- O- f * 1 "" Haslltes ? sp - U ---+=f w Belemnltldae genus Indet I j- O " = * * * *** �i±=* -� * I * * * 28 reconstructed parts of the sutures and who ri sec Page tions are indicated by dotted lines. Each suture Family Pectinidae is based on a single specimen, and for the re Genus Propeamussium De Gregorio 1884 constructions, adjacent sutures are used. On the Propeamussium (Parvamussium) suture drawings the middle of the venter is cf. personatum (Zieten 1830) ...... 32 marked by a straight line with an arrow pointing adorally, while the umbilical seam is marked by Genus Chlamys ROding 1798 a dashed arc. Small arrows indicate points where Chlamys (Chlamys) sp ...... 32 the figured suture is truncated by the preceding Family Buchiidae suture. Genus Buchia Rouillier 1845 The distribution of the species at the investi Buchia ?sp ...... 32 gated localities is summarized in Table 7. The fossils figured in the present paper are Family Limidae deposited in the Paleontological Museum of the Genus Plagiostoma Bruguiere 1797 University of Oslo. The registration numbers of Plagiostoma cf. subcardiiformis the specimens (e.g. A39420) refer to the collec (Greppin 1870) ...... 32 tions of this museum. Family Gryphaeida 8.2. List of descriptions Genus Gryphaea Lamarck 180 l Page Gryphaea ?sp ...... 32 Phyllum Brachiopoda Class Inarticulata Order Trigonioida Order Lingulida Family Myophoriidae Family Lingulidae Genus Liotrigonia Cox 1952 Genus Lingula Bruguiere 1797 Liotrigonia lingonensis Lingula cf. beaniPhillips 1829 ...... 30 (Dumortier 1869) ...... 33 Lingula sp ...... 31 Family Trigoniidae Order Acrotretida Genus Trigonia Bruguiere 1789 Family Discinidae Trigonia sp ...... 33 Genus Discinisca Dall 1871 Discinisca cf. reflexa Order Veneroida (Sowerby 1829) ...... 31 Fami1y Lucinidae Genus Luciniola Skeat Madsen 1898 Phyllum Mollusca & Luciniola cf. pumila Class Bivalvia (Goldfuss 1840) ...... 33 Order Pterioida Family Inoceramidae Family Mactromyidae Genus Inoceramus Sowerby 1814 Genus Mactromya Agassiz 1843 Inoceramus sp ...... 31 Mactromya globosa Agassiz 1845 .... 33 Family Oxytomidae Family Astartidae Genus Oxytoma Meek 1864 Genus Astarte Sowerby 1816 Oxytoma (Oxytoma) inequivalvis Astarte (A starte) elegans (Sowerby 1819) ...... 31 Sowerby 1816 ...... 33 Oxytoma sp...... 31 Family Tancrediidae Genus Meleagrinella Wh itfield 1 885 Genus Ta ncredia Lycett 1850 Meleagrinellacf. echinata Ta ncredia (Tancredia) donaciformis (Smith 1817) ...... 31 Lycett 1850 ...... 34 29 Page Page Order Pholadomyoida Pseudolioceras pumilum Family Pholadomyidae Buckman 1902 ...... 39 Genus Pholadomya Sowerby 1823 Pseudolioceras cf. pumilum Pholadomya (Pholadomya) cf. Buckman 1902 ...... 39 hemicardia Roemer 1836 ...... 34 Pseudolioceras maclintocki Pholadomya (Pholadomya) kingi (Haughton 1858) ...... 40 Meek 1873 ...... 34 Pseudolioceras rosenkrantzi Pholadomya sp ...... Dagis 1965 ...... 40 35 Pseudolioceras spp ...... 41 Genus Goniomya Agassiz 1841 Goniomya literata Genus PseudogrammocerasBuc kman 1901 (Sowerby 1819) ...... 35 Pseudogrammocerasfa llaciosum (Bayle 1878) ...... 41 Genus Homomya Agassiz 1843 Homomya gibbosa Family Graphoceratidae (Sowerby 1813) ...... 35 Genus Brasilia Buckman 1898 Brasilia aff. bradfordense Family Pleuromyiclae (Buckman 1887) ...... 41 Genus Pleuromya Agassiz 1842 Pleuromya elongata Order Decapoda (Goldfuss 1836) ...... 35 Family Belemnitidae ?Pleuromya marginata Genus Hastites Mayer- Eymar 1883 (Agassiz 1845) ...... 35 Hastiles ? sp ...... 41 Pleuromya subcompressa Belemnitidae genus indet...... 42 (Meek 1873) ...... 36 . Pleuromya sp ...... 36 Class Cephalopoda Order Ammonoidea Family Dactylioceratidae 8.3. Brachiopoda Genus Dactylioceras Hyatt 1867 Lingula cf. beani Phillips 1829 Dactylioceras toxophorum Plate l, Fig. 1 (Buckman 1928) ...... 36 o 1829 cf. Lingula Beanii Phillips, p. 157, pl. l l, fig. 24. Genus POIpocerasBuc kman 1911 o 1900 cf. Lingula heani Phillips - Pompeckj, p. 54, pl. l, Porpoceras olare (Frebold 1929) ..... 3f figs. 2-5. p Porpoceras sp inatum Material and occurrence. - Internaland external (Frebold 1958) ...... 37 mol ds, poorly preserved. Phosphorite pebbles of Porpoceras the Brentskardhaugen Bed at loe. 5 and 7. cf. spinatum (Frebold 1958) ...... 37 Remarks. - The Spitsbergen speeimens resem bIe Pompeckj's (1900) Lingula beani in shape, Family Hildoceratidae size and ornamentation, although his speeimens Genus Pseudolioceras Buckman 1889 have weaker and more numerous radial striae. Pseudolioceras compactile The speeimens described by Phillips (1835) show (Simpson 1855) ...... 37 more parallel lateral margins and a more stumpy Pseudolioceras gradatum area near the frontal margins. Buckman 1904 ...... 37 Pseudolioceras cf. gradatum Stratigraphical range. - Lower Bajocian (Pom Buckman 1904 ...... 38 peckj 1900). 30 Lingula sp. Oxytoma (Oxytoma) inequivalvis Plate l, Fig. 2 (Sowerby 1819) Plate I, Fig. 9 Material and occurrence. - Internalmolds, often o 1819 Avicula inequivalvis Sowerby, p. 78, pl. 244, fig. 2. with attached shell fragments. Phosphorite peb o 1840 Avicula inaequivalvis Sowerby - Go1dfuss, p. 130, bles of the Brentskardhaugen Bed at loe. 5, 8 and pl. 118, fig. l. 17. o 1905 Oxytoma inaequivalvis (Sowerby) - Benecke, p. 91, pl. 4, figI l. Remarks. - The present speeimens fu lly corre o 1975 Oxytoma inaequivalvis (Sowerby) - Birkenmajer & spond in morphology to Lingula sp. described Pugaczewska, p. 61, pl. 3, figs. 1 -6. by Birkenmajer Pugaczewska (1975). They can o 1981 Oxytoma (Oxytomaj inequivalvis (Sowerby) ·· Wierz- & bowski et al., p. 219, pl. 7, figs. 5-7 . be separated from Lingula cf. beani by their small er size and somewhat different omamen Material and occurrence. - Incomplete internal tation. and extemal mol ds, all ofleftvalv es. Phosphorite pebbles of the Brentskardhaugen Bed at Ioc. 6. Discinisca cf. reflexa(S owerby 1829) Stratigraphical range. - Sinemurian to Kim Plate l, Figs. 3-5 meridgian (Birkenmajer Pugaczewska 1975). & o 1829 cf. Orbicula rejlexa Sowerby, p.4, pl. 506, fig. l. o 1900 cf. Diseina rejlexa (Sowerby) - Pompeckj, p. 58, Oxytomasp, pI. 1,figs. 6-9. Plate I, Fig. 10 Material and occurrence. -Internaland extemal Material and occurrence. - Severai more or less molds, poorly preserved. Phosphorite pebbles of complete internalmolds. Lower part of the Wil the Brentskardhaugen Bed at loe. 5 and 7. helmøya Formation at Ioc. 21. Remarks. - The present speeimens are similar Remarks. - The speeimens have a greater size in shape and size to forms usually inc1uded in the than O. (Oxytoma) inequivalvis and the omamen family Discinidae. The morphology and strati tation is somewhat different. graphical distribution of the genus Discinisca re corded by Rowell (in Moore 1965) fit well with that of the Spitsbergen speeimens. They are Meleagrin ellacf. echinata (Smith 1817) Plate 2, Fig. 1 almost identical with Diseina rejlexa recorded by Pompeckj (1900), although poor preservation o 1817 cf. Avicula echinata Smith, pl. 26, fig.8. makes a detailed comparison somewhat difficult. O 1840 cf. Monotis decussata Goldfuss, p. 139, pl. 120, fig. 8. O 1853 cf. Avicula echinata Smith - Morris& Lycett, p. 16, Stratigraphical range. - Lower Bajocian (Pom pl. 2, fig.7. peckj 1900). O 1961 cf. Meleagrinella echinata (Smith) - Sibiriakova, p. 70, pl. 8, figs. 13-15. O 1975 Meleagrinella cf. echinata (Smith) - Birkenmajer & 8.4. Bivalvia Pugaczewska, p. 62, pl. 3, fig. 9. O 1981 Meleagrinella cf. echinata (Smith) - Wierzbowski et Inoceramus sp. al., p. 219, pl . 8, figs.6-8. Plate I, Fig. 8 Material and occurrence. - Severai more or less complete intemal molds, often with attached Material and occurrence. - Incomplete internal shell fragments. Phosphorite pebbles of the mold of a left valve. Phosphorite pebble of the Brentskardhaugen Bed at Ioc. 5, 6, 7 and 8. Brentskardhaugen Bed at Ioc. 9. Remarks.- Our speeimens are c10sely similar to Remarks. - Shape, omamentation and frag the speeimens illustrated by Birkenmajer Pu ments of a postero-dorsal auric1e indicate that & gaczewska (1975) and Wierzbowski et al. (1981). the speeimen belongs to the genus Inoceramus. AmongLower Jurassic subgenera it corresponds Stratigraphical range. - Bajocian to Callovian most to (Inoceramus). (Birkenmajer Pugaczewska, op. cit.). 1. & 31 Propeamussium (Parvamussium) cf. persona Buchia ?sp. tum (Zieten 1830) Plate I, Figs. 6, 7 Plate 2, Fig. 2 Material and occurrence. - Severai internal and o 1830 cf. Peclen persona/us Zieten, p. 68, pl. 52, fig. 2. extemal molds. Phosphorite pebbles from the O 1840 cf. Peclen persona/us Zieten - Goldfuss, p. 75, pl. 99, upperrnostpar t of the Wilhelmøya Forrnation at fig. 5. Ioc. 20 and 22. O 1905 cf. Peclen (Variamussium) pumilus (Lamarek) - Be necke, p. 1 12, pl. 3, figs.20 -22. Remarks. - Poor preservation does not allow O 1961 cf. Va riamussium personalum (Zieten) - Sibiriakova, deterrnination at the specificlevel, but shape and p. 85, pl. 10, figs. 14- 17. O 1975 cf. Variamussium personalum (Zieten) - Birken rib pattem resemble the features characteristic majer Pugaczewska, p. 63, pl. 3, fig.8. of Buchia. & O 1981 cf. Propeamussium (Parvamussium) personalum (Zieten) - Wierzbowskiet al., p. 220, pl. 7, fig. 10. Material and occurrence. - Incomplete internal molds of two leftval ves. Phosphorite pebble of Plagiostoma cf. subcardiiformis the Brentskardhaugen Bed at Ioc. 8. (Grepp in 1870) Remarks. - Cox (in Moore 1969) included the Plate 2, Fig. 5 genus Va riamussium Sacco (1897) within Propea O 1853 cf. Lima cardiiformis Morris Lycett, p. 27, pl. 3, mussium (Parvamussium), and this classification & fig. 2. is followed in the present paper. Pecten persona O 1853 cf. Lima semicardiiformis Morris Lycett, p. 29, & tus described by Goldfuss (1840) is omamented pl. 3, fig. 3. with 12-14 radial ribs, while specimens referred O 1870 cf. Lima subcardiiformisGrep pin, p. 50. 44, to the same species by Birkenmajer Puga O 1961 cf. Lima (Plagiosloma) subcardiiformis Greppin - & Ronchetti Sestini, p. 125, pl. 10, fig. 13. czewska (1975) have seven ribs. Our specimens & are omamented with 9 to poorly visible ribs. Material and occurrence. - Three internal \O They show no 2nd and 3rd order radial ribs molds. Phosphorite pebbles of the Brentskard which make their specific deterrnination some haugen Bed at Ioc. 9. what uncertain. Remarks. - The Spitsbergen specimens mostly Stratigraphical range.. - Upper Lias to Bajocian resemble Ronchetti Sestini's (1961) specimens & (Birkenmajer Pugaczewska op. cit.). referred to Lima (Plagiostoma) subcardiiformis & due to their shape, size and omamentation. Cox Hertlein (in Moore 1969) regarded Plagiosto & ma as an own genus, and this classification is followed here. Stratigraphical range. - Bajocian to Bathonian (Ronchetti Sestini 1961). Chlamys (Chlamys) sp. & Plate 2, Fig. 3 Material and occurrence. - Extemal mold of one Gryhaea ? sp. specimen with attached shell fragments. Phos Plate 2, Fig. 4 phorite pebble of the Brentskardhaugen Bed at Ioc. 18. Material and occurrence. - incomplete shell. An Phosphorite pebble from the upperrnost part of Remarks.- Shape, omamentation and fragment the Wilhelmøya Forrnation at Ioc. 20. of an auricle together with stratigraphical oc currence indicate that the specimen belongs to Remarks.- A large, almost circular muscle scar the Chlamys group, and most probably to the is situated in the central part of the shell, which subgenus C. (Chlamys). is almost flat. These features are found in the 32 families Gryphaeidae and Ostreidae. Shape of Luciniola cf. pumila (Goldfuss 1840) the shell and stratigraphical occurrence indicate Plate 3, Fig. 7 that the speeimen most probably belongs to the genus Gryphaea. o 1840 cf. Venus pumila Goldfuss, p. 243, pl. 150, fig. 7. O 1975 Luciniola cf. pumila (Goldfuss) - Birkenmajer & Pugaczewska, p. 68, pl. 5, fig. 4. O 1981 Luciniola cf. pumila (Goldfuss) - Wierzbowski et al., p. 222, pl. 9, fig. 3. Liotrigonia lingonensis (Dumortier 1869) Material and occurrence. - One extemal mold Plate 3, figs. 1-4 with attached shell fragments. Phosphorite pebble of the Brentskardhaugen Bed at loe. 7. o 1869 Trigonia Lingonensis Dumortier, p. 275, pl. 32, figs. 6-8. Remarks. - The speeimen mostly resembles Lu o 1952 Liotrigonia lingonensis (Dumortier) - Cox, p. 53, ciniola cf. pumila described by Birkenmajer & pl. 4, fig.2. Pugaczewska (1975) and Wierzbowski et al. Material and occurrence. - Four more or less (1981). compl ete internalmolds. Phosphorite pebbles of Stratigraphical range. - Upper Lias (Birken the Brentskardhaugen Bed at loe. 9. majer Pugaczewska, op. cit.). & Remarks. - The speeimens are similar to Du mortier's (1869) Trigonia lingonensis which has a distinet ridge-Iike structure in its posterior part. In the present material this structure is best de Mactromya globosa Agassiz 1845 veloped on the smallest speeimen. Plate 3, Figs. 8-9 Stratigraphical range. - According to Dumortier (1869) the speeies occurs in the Pecten equivalvis O 1845 Mactromyaglobosa Agassiz, p. 200, pl. 9, figs.9- 14. Zone which corresponds to the Upper Pliens Material and occurrence. - Two internal mol ds bachian - Lower Toarcian interval, as shown with attached shell fragments. Phosphorite peb below. The oldest ammonite described by Du bles from the upper part of the Wilhelmøya For mortier from this zone was Ammonites margari mation at loe. 20. tatus (margaritatusZone, Upper Pliensbachian). Remarks.- The speeimens describedby Agassiz The oldest ammonite described by the same (1845) show some variation in convexity. The author from the overlying zone was Ammonites speeimen illustrated by him in Figs. 12-14 is exaratus (exaraturn Subzone, lower part of fal most similar to the Spitsbergen speeimens. ciferumZone, Lower Toareian). Stratigraphical range. - According to Agassiz (1845) the stratigraphical occurrence of M. globo sa is confined to the Middle Jurassic, while the Trigonia sp, time range of the genus Mactromya is Bathonian Plate 3, Figs. 5-6 - Portlandian. Consequently, the range of M. globosa must be within the Bathonian - Callo Material and occurrence. - Two incomplete in vian interval. temal molds. Phosphorite pebbles from the upper part of the Wilhelmøya Forrnation at loe. 22. Astarte (A starte) elegans Sowerby 1816 Remarks. - A ridge-like structure runs from Plate 3, Figs. 10-11 umbo towards the posterioventral portion of the shell. This, together with the general shape indi O 1816 Astarte elegans Sowerby, pI. 137, fig. 3. cate that the speeimens belong to the genus Tri O 1840 Astarte elegans Sowerby - Goldfuss, p. 191, pl. 134, gonia. fig. 12. 33 o 1853 Astarte elegans Sowerby - Morris Lycet!, pl. 14, Ph oladomya (Pholadomya) cf. hemicardia & fig. 14. Roemer 1836. 1905 Astarte elegans Sowerby - Benecke, p. 214, pl. 16, O Plate 4, Fig. 5 figs. 1-3. Material and occurrence. - Two internal molds O 1836 cf. Pholadomya hemicardia Roerner,p. 131, pl. 9, with attached shell fragments. Phosphorite peb fig. 18. bles from the uppermost part of the Wilhelmøya O 1840 cf. Ph oladomya hemicardia Roerner- Goldfuss, p. 269, pl. 156, fig.8. Formation at Ioc. 20. O 1945 cf. Pholadomya cf. hemicardia Roerner- Irnlay, Remarks. - Shavan (in Moore 1969) divided the p. 268, pl. 40, figs. 22, 23, 25, 28, 29. O 1975 cf. Pholadomya cf. hemicardia Roerner - Birken genus Astarte into different subgenera. Shape rnajer Pugaczewska, p. 74, pl. 6, fig. 3. and stratigraphical occurrence attribute the pre & sent speeimens to A. (A starte). Material and occurrence. - Extemal mold of one right valve. Phosphorite pebble of the Brent Stratigraphical range. - Erzformation, accord skardhaugen Bed at Ioc. 5. ing to Benecke (1905). This unit contains in its lowem10st part Dumortiera levesquei (represent Remarks. - Cox (in Moore 1969) divided the ing the uppermost zone of the Toareian), while genus Pholadomya into three subgenera. Among in its upper part Ludwigia murehisonae oceurs these the present speeies is dosest re1ated mor (representing the middle part of the Aalenian). phologically to P. (Pholadomya). Shape and dimensions show great similarity to Pholadomya cf. hemicardia recorded in the papers listed above. Stratigraphical range. - Callovian to Oxfordian Ta ncredia (Tancredia) donaciformis (Birkenmajer Pugaczewska 1975). Lycett 1850. & Plate 3, Fig. 12, Plate Figs. 1-4 4, O 1850 Ta ncredia donaci/o rmis Lycett, p. 407, pl. Il, fig. 8. O 1905 Ta ncredia donaci/o rmis Lycett - Benecke, p. 245, Ph oladomya (Pholadomya) kingi pl. 20, figs.9- 12. Meek 1873. 1969 Ta ncredia (Tancredia) donaciformis Lycett - Cox, O in Plate Figs. 7 Moore, p. 640, pl. E 123, fig. 4. 4, 6- O 1981 Ta ncredia (Tancredia) cf. donacifo rmis Lycett - Wierzbowskiet al., p. 225, pl. 12, fig. 6. O 1873 Ph oladomya Kingii Meek, p. 473. O 1899 Pholadomya kingi Meek - Stanton, p. 624, pl. 74, Material and occurrence. - Severai more or less figs. 1-3. complete internaland extemal molds, oftenwith O 1964 Pholadomya kingi Meek - Irnlay, p. 36,pl. 4, fig.36. attached shell fragments. Phosphorite pebbles of O 1967 Ph oladomya kingi Meek -- Irnlay, p. 86, pl. 5, figs.36-38, 42. the Brentskardhaugen Bed at loe. 3, 5, 6, 7 and 9; uppermost part of the Wilhelmøya Formation Material and occurrence. - One incomplete in at loe. 20. temal mold. Phosphorite pebble from the Wil helmøya Formation at loe. 19. Remarks. - The present speeimens are generally consistent with those referred to Ta ncredia dona Remarks. - P. (Pholadomya) kingi differs from ciformis by Benecke (1905). The posterior part P. (Pholadomya) cf. hemicardia recorded above of the palial line is in Benecke's speeimens in by its distinet radial ribbing. P. (Pholadomya) cf. dined somewhat more anteriorly than on the fidicula figured by Wierzbowski et al. (1981, pl. speeimens illustrated in the present paper. 5, fig. 9) is morphologically dose to the present speeimen except for its shorter anterior part and Stratigraphical range. - Erzformation (Benecke a longer posterior portion. 1905), corresponding in age to the Upper Toar cian - Middle Aalenian interval (diseussed Stratigraphical range. - Bajocian to Lower Cal under Astarte (A starte) elegans). lovian (Imlay 1964, 1967). 34 Ph oladomya sp. Stratigraphical range. - Lycett (1863) reported Plate 4, Fig. 8 the speeies from the Combrash and Inferior Oolite in England, whieh corresponds to the Material and occurrence. - Incomplete extemal Aalenian - Lower Callovian (Brinkmann 1959). mold of a left valve. Phosphorite pebble of the Brentskardhaugen Bed at loe. 9. Pleuromya elongata (Goldfuss 1836) Remarks. - Shape and omamentation of the Plate 5, Figs. 7-9 present speeimen fit with the main features of Pholadomya. With its large height the speeimen o 1836 Lutraria elongata Goldfuss, p. 258, pl. 153, fig4. shows some similarity to the subgenus P. (Bucar o 1845 Pleuromya elongata (Goldfuss) - Agassiz, p. 244, diomya) definedby Cox (in Moore 1969). pl. 26, figs. 1,2, pl. 27, figs. 3-8. o 1905 Pleuromya elongata (Goldfuss) - Benecke, p. 279, pl. 24, fig.2. o 1955 Pleuromya elongata (Goldfuss) - Ksiazkiewicz, p. 181,pI. 17, fig. 1O. Goniomya literata (Sowerby 1819) o 1961 Pleuromya e/ongata (Goldfuss) - Sibiriakova, p. 157, Plate 5, Figs. 1-2 pl. 28, figs.3, 4. Material and occurrence. - Severai more or less o 1819 Mya ?literata Sowerby, p. 45, pl. 224, fig. 1. complete internalmolds. Phosphorite pebbles of o 1975 Goniomya literata (Sowerby) - Birkenmajer & Pu· gaczewska, p. 76, pl. Il, fig.2. the Brentskardhaugen Bed at loe. 17, and from the uppermost part of the Wilhelmøya Forma Material and occurrence. - One internal mold. tion at loe. 20. Phosphorite pebble from the uppermost part of the Wilhelmøya Formation at Ioc. 20. Stratigraphical range. - Bajocian (Ksiazkiewiez 1955). Remarks. - Morphology of the present speei men fully corresponds to the description given by Birkenmajer Pugaczewska (1975). & ? Pleuromya marginata (Agassiz 1845) Stratigraphical range. - Bathonian to Kimme Plate 5, Figs. 10-13 ridgian (Birkenmajer Pugaczewska, op. cit.). & o 1845 My opsis marginata Agassiz, p. 257, p1. 30, figs. 1,2. ? o 1899 Pleuromya marginata (Agassiz) - Greppin, p. 60, ? Homomya gibbosa (Sowerby 1813) pl. 7, fig.5. o 1961 Pleuromya marginata (Agassiz) - Sibiriakova, ? Plate 5, Figs. 3-6 p. 155, pl. 27, fig.7. o 1813 Mactra gibbosa Sowerby, p. 91, fig. 42. Material and occurrence. - Severai more or less o 1843 Homomya gibbosa (Sowerby) - Agassiz, p. 160, compl ete internal molds, often with attached pl. 18, figs. 1-5. shell fragments. Phosphorite pebbles of the Homomya gibbosa o 1863 (Sowerby) - Lycett, p. 88, pl. 43, Brentskardhaugen Bed at Ioc. 8 and 17, and from fig. 2. o 1969 Homomya gibbosa (Sowerby) - Cox (in Moore), the uppermost part of the Wilhe1møya Forma p. 832, pl. F13, fig.3. tion at loe. 20. Materialand occurrence. - One incomplete in Remarks. - Length of the anteriorpar t is vari temal mold. Phosphorite pebble of the Brent able but less prominent than in Pleuromya elon skardhaugen Bed at loe. 7. gata. Shape and size of the speeimens show some similarity to Pleuromya marginata, but because Remarks. - The present speeimen differs from of variable length of the anterior part and a Pholadomya (Pholadomya) cf. nodosa figuredby somewhat too prominent umbo, both the generie Wierzbowski et al. (1981, pl. lO, fig.2) by a more and specifieass ignments are uncertain. anteriorly situated umbo, coneave posterio dorsal margin and absenee ofwell definedradial Stratigraphical range. - Bathonian (Sibiriakova ribs. 1961). 35 Fig . 24. Whorl sections and suture line of Dactvlioceras and Porpoceras. a-bo Dactylioceras toxo phorum (Buckman). Whorl sections (�: l) of twa specimens : a \ of A39453, b of A39454. c-do Porpoceras polare (Frebold). Whorl sec tions (x0.8) of twa specimens: c of A39456, d of A39455. ! d e. Porpoceras polare a. b c (Frebold). External suture ( x 4) of A39455 at a whorl height of Il mm. f. Porpoceras spinatum (Frebold). Whorl sec ti on ( x 0.8) of A39457. e f Pleuromya subcompressa (Meek 1873) 8.5. Ammonoidea Plate 6, Fig. I Dactylioceras toxophorum (Buckman 1928) Plate 6, Figs. 4, 5, Text-fig.24a -b D 1873 My acites (Pleuromya) subcompressa Meek, p. 472. D 1899 Pleuromya suhcompressa (Meek) - Stanton, p. 626, pL 74, figs. 8- ll. D 1928 Toxodactylites IOxophorus Buckman, pL 776. 1964 Pleuromya suhcompressa (Meek) - Imlay, p. 35. D Material and occurrence. - Internaland external D 1967 Pleuromya subcompressa (Meek) - Imlay, p. 85, p1.5, figs.16- 21. molds with attached shell fragments. Phospho rite pebbles of the Brentskardhaugen Bed at Ioc. Material and occurrence. - One internal mold 18. and one external mold of a right valve with at tached shell fragments. Phosphorite pebbles of Remarks. - The ribs of Dactylioceras toxopho the Brentskardhaugen Bed at Ioc. 9. rum are somewhat less cIosely spaced than in Dactylioceras anguiforme (Buckman 1928), but Stratigraphical range. - Bajocian to Callovian denseT spaced than in Dactylioceras commune (lmlay 1964, 1967). (Sowerby 1815). The flanks of D. toxophorum seem to be slightly more flatten ed than in the two related species mentioned above. Pleuromya sp. Plate 6, Figs. 2, 3 Stratigraphical range. - Falciferum Zone (fal ciferum Subzone), Toarcian. Material and occurrence. - One incomplete in ternal mold. Phosphorite pcoble from the upper part of the Wilhelmøya Formation at Ioc. 22. Porpoceraspolare (Frebold 1929) Plate 6, Figs. 6-9, Text-fig.24 c-e Remarks.- The speeimen resembles Pleuromya by its shape and ornamentation, but seems to be D 1929b eoelocems polare Frebold, p. 258,pL 2(34), more inflated than is lIsual within this genus. figs. II-l3. 36 o 1930 Coe/oceras polare Frebold - Frebold, p. 61, pl. 22, Stratigraphical range. � Bifrons Zone (fibula fig. 4. turn Subzone) � thouarsense Zone (striatulum O 1975 Cataeoe/oceras polare (Frebold) - Birkenmajer & Subzone), Toareian ; as diseussed under Porpoce Pugaczewska, p. 81, pl. 10, fi gs. 2, 3. ras polare. O 1975 Peronoceras pa/are (Frebold) - Frebold, p. 14, pl. 5, fig. 2. O 1981 Porpoceraspolare (Frebold) - Wierzbowskiet al., p. 208, pl. I, figs.5, 6. Porpocerascf. sp inatum (Frebold 1958) Material and occurrence. � Two incomplete in Plate 6, Figs. 12, 13 ternal molds and one complete speeimen. Phos phorite pebbles from the Brentskardhaugen Bed For synonyms, see under Porpocerasspi natum. at Ioc. 7, and from a sandstone bench 4 metres Material and occurrence. � Two incomplete ex below the Brentskardhaugen Bed at Ioc. 12 (A ternal molds. Phosphorite pebbles of the Brent 39477). skardhaugen Bed at Ioc. 14. The age of the Porpoceras � Pseudolioceras Remarks. � The general shape of the shell and fa una. � The widespread arctic Porpoceras � its ribbing pattern with high and thin ribs, show Pseudolioceras fauna contains Porpoceraspolare. a dose similarity to P. spinatum. P. spinatum. Pseudolioceras compactile and other representatives of Pseudolioceras. It is known from the Canadian Arctic, East Greenland, Ps eudolioceras compactile (Simpson 1855) northem Sibiria and from the Brentskardhaugen Plate 7, Fig, 3 Bed in Svalbard. The age of the fauna is discus sed by severai authors and diverging opinions are O 1855 Ammonites compactilis Simpson, p. 75. propounded, e.g. thouarsense Zone, striatulum O 1889 Pseudolioceras compactile (Simpson) - Buckman, Subzone (Frebold 1975); bifrons Zone, fibula p. 85. O 1904 Pseudolioceras compaetile (Simpson) - Buckman, turn Subzone (Howarth 1978); fibulaturn Sub p. 159 suppl. zone to variabilis Zone (Wierzbowskiet al. 1981). O 191 1 P5eudolioceras eompactile (Simpson) - Buckman, Condusive evidence for a more precise zonal p. 41b, pl. 41a, b. assignment is, however, not presented. We prefer O 1929a Ps eudolioceras cf. compacti/e (Simpson) - Frebold, p. 9, pl. l,fig. 3. therefore to place the Porpoceras � Pseudolio O 1929b Ps eudolioceras cf. eompactile (Simpson) - Frebold, ceras fauna of the Brentskardhaugen remanie p. 261, pl. 2(34), figs. 1-4. bed provisionally within the total time interval O 1955a P5eudolioceras aff. eompactile (Simpson) - Frebold, suggested above, without doser age specifica p. 5, pl. 3, figs. 3 -6. tion. O 1968 Pseudolioceras compactile compacti/e (Simpson) - Kopik, p. 46, pl. 2, fig. 3, 4. Material and occurrence. � Incomplete internal and external molds. Phosphorite pebbles of the Brentskardhaugen Bed at Ioc. 8, 13, IS and 16. Porpocerassp inatum (Frebold 1958) Stratigraphical range. � Bifrons Zone (fibula Plate 6, Figs. 10, Il, Text-fig.24f turn Subzone) � thouarsense Zone (striatulum Subzone), Toareian ; as diseussed under Porpoce 1956 Coe/oceras n. sp. Frebold (in Tozer), p. 21. O ras polare. O 1955a Coe/oceras spinatum Frebold, p.3. pl. 2,fi gs. 1 -4. O 1975 Peronoceras spinatum (Frebold) - Frebold, p. 13, pl. 5, fig. l. Material and occurrence. � One external mold. Ps eudolioceras gradatum Buclanan 1904 Phosphorite pebble of the Brentskardhaugen Plate 7, Fig. 4, Text-fig.25c�e Bed at loe. 17. O 1889 Ps eudolioceras compactile Buckman, p. 85, pl. 20, Remarks. � Thisspeeies can be separated from figs. 3-4. Porpoceraspolare by its thinner and higher ribs. D 1904 Pseudo/ioceras gradatum Buckman, p. 158 suppl. 37 Fig. Whorl sections and suture25. lines of Brasilia and Pseudolioceras. a-bo Brasilia aff. bradfo r dense (Buckman): a. whori section ( x 0.8); b. external suture ( x 3) of A39460. b c-e. Pseudolioceras gra a datum (Buckman) c. external suture (x 3) of A39462 at a whori height of 22 mm; d. whorl section ( x 0.8); of A39462; e. exter nal suture (x 2.4) of A39478 at a whorl height of 29 mm. d o 1929b Pseudolioceras cf. compactile Buckman - Frebold, tigraphical occurrence, i.e. bifrons Zone (fibula p. 261, pl. 2(34), figs. 1-4. turn Subzone) - thouarsense Zone (striatulum o 1968 Pseudolioceras compactile gradatum Buckman - Subzone), Toareian. Kopik, p. 43, pl. 2, fig. 2. Material and occurrence. - Three more or less Pseudolioceras cf.gradatum Buckman 1904 complete intemal molds. Phosphorite pebbles of Plate 7, Fig. 5, Text-fig.27c the Brentskardhaugen Bed at Ioc. 5, 7 and Il. For synonyms, see under Ps eudolioceras grada Remarks. - This speeies can be separated from tum. Pseudolioceras pumilum by a somewhat broader umbilicus and a more dominating keel. Kopik Material and occurrence. - incomplete mold, An (1968) dassified his speeimen as a sub-species of an extemal mold, and cross section of an intemal Pseudolioceras compactile. The material treated mold belonging to three different speeimens. in the present paper show, however, marked dif Phosphorite pebbles of the Brentskardhaugen ferences between the two fonns indicating that Bed at Ioc. 8, 13 and 18. the dassification of Buckman (1904) should be Remarks.- Shape of urnbilieus, rib pattem and preferred. cross seetion of the intemal mold show dose Stratigraphical range. - Close morphological similarity to Pseudolioceras gradatum. Rib pat relation between Ps eudolioceras compactile and tem and a rather high keel of the extemal mold Pseudolioceras gradatum suggests a similar stra- also resemble that speeies. 38 Fig . 26. Suture lines and who ri sections of Ps eudo lioceras. a-c. Pseudolioceras pumi lum (Buckman): a. extemal suture ( x 2.2) of A39465 at a whorl height of 14 mm; b. who ri section ( x 0.8) of A39465; c. whorl section x 0.8) Vi:? ( of A39464. f"II1, d-e. Ps eudolioceras mae f lintocki (Haughton): .. d. external suture ,,� ' :'.': . ··C·\·; ( x 5.3) of A39466 at I� a whorl height of 14 ;;.(\� '�.). mm; e. whori section \r � ( x 0.8) of A39466. b a c .. ,' tt ... .= .. / ": \.:'.' . : , . " .... . 1...... ::\. }, } uO . d e The cross section of the internalmold shows a area (Text-fig. 26b, c) which may be due to rather wide umbilicus with perpendicularly bent different growth stages. The present species can walls, and a distinct peripheral keel, all features be separated from Pseudolioceras compactile by characteristic for Pseudolioceras gradatum. The its less distinct ribs which are narrower in the whorIs, however, seem somewhat more inflated ventrai area. One of the ammonites referred to P. than in the illustrations published by Buckman compactile by Wierzbowski et al. (1981, pl. 2, fig. (1904). 3) is here induded in P. pumilum because it shows a dose similarity to the present speeimens by its rib pattem and umbilical area. Pseudolioceras pumilum Buckman 1902 Stratigraphical range. - Close morphological Plate 7, Figs. 6-9, Text-fig.26a -c relation between Pseudolioceras compactile and Pseudolioceras pumilum suggests a similar stra D 1889 Pseudolioceras compactile (Simpson) - Buckman, tigraphical occurrence, i.e. bifrons Zone (fibula p. 85, pl. 20, figs.5, 6. turn Subzone) - thouarsense Zone (striatulum D 1902 Ps eudolioceras pumilum Buckman, p. 159, suppl. D 1930 P�eudolioceras pumilum Buckman - Frebo1d, p. 28, Subzone), Toarcian. pl. 6, fig. l. D 1981 P�eudolioceras compactile (Simpson) - Wierzbowski et al., pl. 2, fig.3 only. Ps eudolioceras cf. pumilum Buckman 1902 Material and occurrence. - Two almost com For synonyms, see under Pseudolioceras pumi plete specimens. Phosphorite pebbles of the lum. Brentskardhaugen Bed at Ioc. 6. Material and occurrence. - One incomplete in Remarks. - The two specimens show minor temal mold. Phosphorite pebble of the Brent differences in the development of the ventrai skardhaugen Bed at Ioc. 15. 39 Fig. 27. Suture lines and whorl sections of Pseudo lioceras. a-bo Pseudolioceras ro- senkrantzi (Dagis): a. extemal suture ()( 8) of A39467at at whorl height of 10 mm; b. whorl section ( x 0.8) of A39467. b a C. Pseudolioceras cf. gradatum (Buck man). Whorl sectilon ( x 0.8) of A39476. d-e. Pseudolioceras spp. Extemal sutures ( x 3) of twa speei mens: d. of A39474, e. ofA39475. d c Remarks. - This speeimen is similar to Ps eudo Material and occurrence. - Two more or less lioceras pumilum with regard to cross section, com plete internalmolds. Phosphorite pebbles of ventrai margin and urnbilicus. It differs in having the Brentskardhaugen Bed at loe. 7 and 14. somewhat high er ribs. Stratigraphical range. - Opalinum Zone, Lower Aalenian (Frebold 1958a). Ps eudoliocerasma clintocki (Haughton 1858) Plate 7, Fig. 10, Text-fig.26d-e Ps eudolioceras rosenkrantzi Dagis 1965 Plate 7, Fig. Il, Text-fig.27a, b o 1858 Ammonites m"clintocki Haughton, p. 244, pl. 9, figs. 2-4. o 1929 Pseudolioceras cf. wuerttenbergeri (Denekmann) - o 1885 Hatpocerasm 'c/intocki (Haughton) - Neumayr, Frebold, p. 262, pl. 2, fig. 5. p. 85, figs. 5-8. o 1965 Ps eudolioceras rosenkrantzi A.A. Dagis (in Dagis & o 1958a Ludwigia m 'c/intocki (Haughton) Frebold, p. 7, Dagis), p. 23, pl. I, figs. 1-3. pl. 5, figs.3, 4. O 1974 Ps eudolioceras rosenkrantzi Dagis - Dagis, p. 52, o 1960 P5eudolioceras m'dintocki (Haughton) - Frebold, pl. 18, figs.2-7, Text-fig. 18, pl. 14, fig.4. ? p. 20, pl. 8, figs. 1-9, pl. 9, figs. 1-4, pl. 10, fig. I, O 1981 Ps eudolioceras rosenkrantzi Dagis - Wierzbowskiet pl. II,figs. I-3, pl. 12, fig. !. al., p. 213, pl. 2, fig.6, pl. 3, figs. 1,2. 40 Material and occurrence. - One incomplete in Ps eudogrammoceras fa llaciosum temal mold with attached shell fragments. Phos (Bayle 1878) phorite pebble of the Brentskardhaugen Bed at Plate 8, Fig. I Ioc. 17. o 1878 Grammocerasfallaciosum Bayle, pl. 78, figs. 1.2. Remarks.- The Spitsbergen specimen is similar Material and occurrence. - One incomplete in to Pseudolioceras wuerttenbergeri (Denckmann temal mold. Phosphorite pebble of the Brent 1887) in its general appearance. It differs, how skardhaugen Bed at Ioc. 13. ever, from that species in having slightly back ward bent ribs instead of the fa lcoid or almost Stratigraphical range. - Thouarsense Zone (fal straight ribs seen on the illustrations given by laciosum Subzone), Toarcian. Denckmann. Another distinguishing feature of Pseudolioceras rosenkrantzi is its comparatively inflatedwhor l section. Brasilia aff. bradfordense (Buckman 1887) Plate 7, Figs. 1,2, Text-fig.25a-b Stratigraphical range. - Pseudolioceras rosen o 1887 aff. Lioceras hradfordense Buckman. p. 22, pl. 4, krantzi indicates the rosenkrantzi Zone in ac figs.5-8 , pl. 5. cordance with Dagis (1974). This zone is correlat o 1905 aff. Harpoceras ILudwigia) hradfordense (Buckman) - Benecke, p. 423, pl. 57, figs.2, 3. ed by Russian geologists with the thouarsense and levesquei Zones which form the Upper Material and occurrence. - One almost complete Toarcian in north western Europe. Frebold internal mold. Phosphorite pebble of the Brent (1975) tentatively considers the rosenkrantzi skardhaugen Bed at Ioc. 7. Zone as an equivalent to the striatulum Subzone Remarks. - The present specimen resembles (thouarsense Zone) only. This approach is regar specimens of Lioceras bradfordense illustrated ded to be disputable by Wierzbowski et al. by Buckman (1887 pl. 4, fig. 7) and Benecke (1981), who share the opinion of Dagis (1974) (1905, pl. 57, figs.2, 3). It differs, however, from and other Russian geologists. those forms by its somewhat narrower umbilicus, and by its ribs which are pointed slightly more forwards in the ventraI area. Harpoceras kopiki Wierzbowski Kulicki described from the & Brentskardhaugen Bed (in Wierzbowski et al. Pseudolioceras spp. 1981) differs from the present specimen by its Text-fig.27d, e bisulcate venter. Lioceras radfordense is referred to Brasilia b Material and occurrence. - Two incomplete in and is chosen as the type species of that genus temal mol ds. Phosphorite pebbles of the Brent (ArkelI et al., in Moore 1957). This generic as skardhaugen Bed at Ioc. 15, and 17. signment is followed in this paper. Stratigraphical range. - Murehisonae Zone (bradfordense Subzone), Middle Aalenian. Remarks.- Rib pattem and suture lines of both specimes show diagnostic features of the genus Pseudolioceras. 8.6. Decapoda The sutures preserved in one of the specimens Hastites resemble those found in P. gradatum. The other ? sp. specimen shows more complicated sutures, re Plate 8, Fig. 4 sembling those of P. pumilum. Differences are, however, observed in both cases and more cer Material and occurrence. - One nearly complete tain specific determinations require additional rostrum. Phosphorite pebble of the Brentskard material. haugen Bed at Ioc. 9. 41 Remarks. - Without having seen the specimen Acknowledgments in cross section, attribution to the genus Hastites The authors wish to thank Tor Bjærke (Strati is somewhat doubtful. graphical Laboratory AlS, Stavern) and Hen ning Dypvik (University of Oslo) for valuable Belemnitidae genus indet. suggestions improving the manuscript, and Plate 8, Figs. 2, 3 Ragnar Knarud (Saga Petroleum AlS, Oslo) for inspiring discussions and cooperation in the Material and occurrence. - Severai incomplete field. We are indebted to Derek South (Statoil, internal molds of phragmocones, often with at Stavanger) who kindly corrected the English text. tached shell fragments. Phosphorite pebbles of Thanks are also due to TorbjørnSætre (Universi the Brentskardhaugen bed at Ioc. 3, 5, 6, 7, 9, 14, ty of Oslo) for draftingmost of the illustrations. 18 and in the uppermost part of the Wilhelmøya Appreciation is expressed to the Norwegian Formation at Ioc. 20. Research Council for Science and the Humani ties, and to the Norwegian Polar Research Insti Remarks.- These internalmol ds are considered tute for financialsupport of the fieldwork. to be indeterminable pieces of belemnite phrag mocones with no c\os,er age significance. 42 References Dagis, A.A. 1974: Toarcian ammonites (Hildocera Agassiz, L. 1842-45 : Etudes critiques sur les moll us tidae) from northern Sibiria. Tr. Inst. Geol. Sibir ques fossiles. - Monographie des Myes. Neucha otd. AN SSSR 40. (In Russian). tel. Dagis, A.A. Dagis, A.S. 1965: About zonal subdivi & Atlas, E. L. 1975: Phosphate equilibria in seawater and sion of Toarcian deposits in northeastern SSSR. interstitial waters. 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Norsk Polarin Toarcian dinoflagellates from Spitsbergen. Palyno stitutt Skrifter15 4a. logy 4. Frebold, H. 1929 a: Oberer Lias und Unteres Callovian Bjærke, T. Dypvik, H. 1977: Sedimentological and in Spitsbergen. Skrift er om Svalbard og Ishavet 20. palynological& studies of Upper Triassic - Lower 1929 b: Die Schichtenfolge des Jura und der Un Jurassic sediments in Sassenfjorden, Spitsbergen. terkreide an der Ostkuste von Siidwestspitzbergen. Norsk Polarinstitutt Arbok 1976. Abh. A. d. Gebiet d. Naturw. Verein. Hamburg. 22. Brinkmann, R. 1959: Abriss der Geologie. 2. Bd. Ferdi 1930: Verbreitung und Ausbildung des Mesozoi nand Enke Verlag. Stuttgart. kums in Spitzbergen. Skrifter om Svalbard og Isha Buckmann, S. S. 1887-1907 : A monograph of the vet 31. Ammonites of the «Inferior Oolite Series». Vol. 1956: in Tozer: Geological reconnaissance, Prince l Text & Atlas. The Palaeontographical Society. Patrick, Eglinton, and Western Melwille Islands, 1909-30: Yorkshire Typ e Ammonites. 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Nansen; Geological Sketch of Cape nian Glauconitic Mari of south-east England. Let Flora and its neighbourhood. The Norw. North haia 4. Polar Exped. 1893- 96. Scientif. Res. l. KeIT, P. F. 1959: Optical Minera/ogy. 3rd. edition. - Ravn, J. P. J. 1912: On Jurassic and Cretaceous Fossils. McGraw-Hill Book Company, New York, Toron Medde/e/ser om Grøn/and 45. to, London. Roemer, F. A. 1836: Die Versteinungen des nord Kopik, J. 1968 : Remarks on some Toarcian ammonites deutschen Oo/iten-Gebirge. Hannover. from the Hornsund area, Vestspitsbergen. Studia Ronchetti, C. R. Sestini, N.F. 1961: La fauna giuras Geologica Polonica 21. sica di Karkar& (Afghanistan). Riv. lta/. Pa/eont. 67 Ksiazkiewicz, M. 1955: The Jurassic and Cretaceous (2), ser. P, Il4. of Bachowice, Western Carpathians. Rocs. Pol. Rosenkrantz, A. 1934: The lower Jurassic rocks of East To w. Geol. (A nn. Soc. Geol. P% gne.) 24 (2/3). Greenland. Part l. Medde/e/ser om Grøn/and 1I0(l). Krakow. (In Polish). Sibiriakova, L.V. 1961 : Middle Jurassic mollusc fauna Lycett, J. 1850: Tabular view of fossil Shells from the of Bolsoi Balchan and its stratigraphical signifi middle Division of the Inferior Oolite in Glouches cance. Gosgeo/techizdat Moscow. (In russian). tershire. Ann. a. Mag. of Nat. History,2. ser., vol. 6. Siedlecka, A. 1970: investigal. tions of Permian cherts 1863: Supp/ementary monograph of the Mol!usca and associated rocks in south em Spitsbergen. fr om the Stonesfie/d. Fo rest Marb/e and Combrash. Norsk Polarinstitutt Skrifter147 . - London. Simpson, M. 1855: A monograph of the ammonites of McConnel, D. 1958: The apatite-like minerals of sedi the YorkshireLias. London. ments. Econ. Geo/., Smith, I. 1817: Stratigraphica/ System of Organised Meek, F. B. 1873 : Prelimi53. nary paleontological report Fossi/s. - London. consisting of lists and descriptions of fossils with Sowerby, J. 1812-30: The Minera/ Conch% gy of remarks on the ages of the rocks in which they were Great Britain, vol. 1-6. London. found. S. Geo/. Surv. Terr. (Hayden), 6 th. Ann. Spath, L. F. 1947 : Additional observations on the in Rept. U. vertebrates (chiefly ammonites) of the Jurassic and Moore, R. C. (editor) 1957: Treatise on lnvertebrate Cretaceous of East Greenland. Medde/elser om pa/eont% gy. - Pari L. Mol!usca 4, Cehpha/opoda. Gøm/and. 132 (3). Ammonoidea. Stanton, T. W. 1899: Mesozoic fossils of the Yellowsto 1965. op. cit. Part H. Brachiopoda (I &2). ne National Park. S. Geo/. Surv. Mon. 32, pt. 2. 1969. op. cit. Part Mollusca 6 (I &2). Biva/via. Wierzbowski, A., Kulicki,U. C. Pugaczewska, H. 1981 : N. & 1971. op. cit. Part Mol!usca 6 (3).Biva/viva. Fauna and stratigraphy of the uppermost Triassic Morris,J. Lycett, K.N. 18 53-54: A monograph of the and the Toarcian and Aalenian in the Sassenfjor & Mollusca from the Great Oolite, chieflyfrom Min den, Spitsbergen. - Acta Pa/eontologica Polonica. chinhampton and the coasts of Yorkshire, part 2, 26(3-4). Bivalves. Pa/aeontograph. Soc. London. Wright, T. 1878-86 : Monograph on the Lias Ammon Mørk, A., Knarud, R Worsley, D. 1982: Depositi ites of the British Islands. The Palaeontographical onal and diagenetic& environments of the Triassic Society. London. and Lower Jurassic succession of Svalbard. - In: Zieten, C.H. V. 1830: Die Versteinerungen Wiirttem Embry, A.F. Blackwill, H.R. (eds.): Arctic Geolo- bergs Stuttgart. & l. 44 PLATES 1-8 45 PLATE I Fig. Lingula cf. beani Phillips. Internalmold (A39420) from phosphorite pebble of the Brentskardhaugen Bed at localitlyl. 4; x 1.5. Fig.2. Lingula sp. Numerous internal molds in phosphorite pebble (A39421) of the Brentskardhaugen Bed at locality 5; x I. Fig . 3-5. Discinisca cf. reflexa (Sowerby). Internal molds (A39422-Fig. 3 and A39424-Fig. 5) and external mold (A39423-Fig. 4) in phosphorite pebbles of the Brentskardhaugen Bed at locality 7; x 1.5. Fig. 6- 7. Buchia ? sp. Internalmol ds (A39425-Fig. 6 and A39426-Fig. 7) in two phosphorite pebbles of the Wil helmøya Formation at locality 20; Fig. 6, x 1.5; Fig. 7, x I. Fig. 8. Inoceramus sp. Internalmold (A39427, right hand speeimen) from phosphorite pebble of the Brentskard haugen Bed at locality 9; x I. Fig. 9. Oxytoma (O.) inequivalvis (Sowerby). Internal mold (A39428) from phosphorite pebble of the Brentskard haugen Bed at locality 6; x 1.5. Fig. 10. Oxytoma sp. Internal mold (A39429) from phosphorite pebble of the Wilhelmøya Formation at locality 21; x l. 46 PLATE I 47 PLATE 2 Fig. Meleagrinella cf. echinata (Smith). Internalmold (A39430) with parts of the shell preserved ; in phospho l. rite pebble with numerous crinoide fragments ; from the Brentskardhaugen Bed at locality 5; x 1.5. Fig. 2. Propeamussium (Parvamussium) cf. personatum (Zieten). Internalmold (A3943 I ) from phosphorite pebble of the Brentskardhaugen Bed at locality 8; x 2. Fig. 3. Chlamys (C) sp. Internal mold (A39432) with most of the shell preserved; phosphorite pebble of the Brentskardhaugen Bed at locality 18; x I. Fig. 4. Gryphaea ? sp. Part of a shell with muscle scar (A39433); phosphorite pebble of the Wilhelmøya Formation at locality 20; x l. Fig. Plagiostoma cf. subcardiiformis (Greppin). Internalmold (A39434) from phosphorite pebble of the Brent 5. skardhaugen Bed at locality 9; x I. 48 PLATE 2 49 PLATE 3 Fig. 1 -4. Liotrigonia lingonensis (Dumortier). Internal mold (A39435-Figs. 2, 3, 4) and its latex replica (Fig. I); phosphorite pebble ofthe Brentskardhaugen Bed at locality 9; x I. Fig. 5-6. Trigonia sp. Internalmold (A39436) from phosphorite pebble of the Wilhelmøya Formation at locality 22; x l. Fig. 7. Luciniola cf. pumila (Goldfuss). Internal mold (A39437) with parts of the shell preserved ; phosphorite pebble of the Brentskardhaugen Bed at locality 7; x 1.5. Fig. 8-9. Mactromya globosa Agassiz. Internalmold (A39438) with large parts of the shell preserved ; phospho rite pebble of the Wilhelmøya Formation at locality 20; x 1.5. Fig. /0-1 Astarte (A.) elegans Sowerby. Internalmold (A39439) with parts of the shell preserved; phosphorite pebble of thel. Wilhelmøya Formation at locality 20; x 1.5. Fig. 12. Ta ncredia (T.) donaciformis Lycett. Internal mold (A39440) with the shell preserved ; phosphorite pebble of the Brentskardhaugen Bed at locality 6; x I. 50 PLATE 3 51 PLATE 4 Fig . ]-4. Ta m·redia (T.)donaci fo rmis Lyeett. One speeimen showing the inside of valves (A39441-Fig. I), internal molds (A39442-Fig. 2, A39444-Fig. 4) and latex east ofinternalmold (A39443-Fig. 3); phosphorite pebbles of the Brentskardhaugen Bed at locality 7; x l. Fig . 5. Pholadomya (P.} cf. hemicardia Roemer. Internalmold (A39445) with parts of shell preserved ; phosphorite pebble of the Brentskardhaugen Bed at locality 5; x 1. Fig . 6- 7. Pholadomya (P.} kingi Meek. Internal mold (A39446) from phosphorite pebble of the Wilhelmøya Fonnationat locality 19; x l. Fig . 8. Pholadomya sp. External mold (A39447) in phosphorite pebble of the Brentskardhaugen Bed at loeality 9; x l. 52 PLATE 4 53 PLATE S Fig . 1-2. Goniomya literata (Sowerby). Internal mold (A39437) from phosphorite pebble of the Wilhelmøya Formation at loeality 20; x 1.5. Fig. 3-6. Homomya gibbosa (Sowerby). Internal mold (A39448-Figs. 3, 4, 5) and its latex east (Fig. 6); from phosphorite pebble of the Brentskardhaugen Bed at loeality 7; x I. Fig. 7-9. Pleuromya elongata (Goldfuss). Internal mold (A39449) from phosphorite pebble of the Brentskard haugen Bed at loeality x l. 17; Fig. /0-13. ? Pleuromya marginata (Agassiz). One speeimen (A39450) represented by an internalmold (Figs. 10, 12, 13) and an extemal mold (Fig. with parts of shell preserved; phosphorite pebble of the Wilhelmøya For mation at loeality 20; x l. Il) 54 PLATE 5 55 PLATE 6 Fig . Pleuromya subcompressa (Meek). External mold (A3945 I ) from phosphorite pebble of the Brentskard haugenl. Bed at loeality 9; x I. Fig. 2-3. Pleuromya sp. Internalmold (A39452) from phosphorite pebble of the Wilhelmøya Formation at loeali ty 22; x I. Fig. 4-5. Dactyliocers toxophorum (Buekman). Two speeimens represented by internal mold (A39453-Fig. 4) and latex east of externalmol,d (A39454-Fig. 5); phosphorite pebbles of the Brentskardhaugen Bed at loeality 18; x l. Fig . 6-9. Porpoceraspolare (Frebold). Internal mold (Fig. 6) and latex east of external mold (Fig. 7) of A39455; latex casts (Figs. 8, 9) of external mold (A39456). Phosphorite pebbles of the Brentskardhaugen Bed at locality 7; Figs. 6 and 7, x 1.5; Figs. 8 and 9. x I. Fig . 10-1 Porpoceras spinatum (Frebold). Latex casts of an externalmold (A39457); phosphorite pebble of the Brentskardhaugenl. Bed at locality 17; x 1.5. Fig . 12-13. Porpoceras cf. spinatum (Frebold). Latex casts of two external mol ds (A39458-Fig. 12 and A39459- Fig. 13); phosphorite pebbles of the Brentskardhaugen Bed at loeality 14; x 1.5. 56 PLATE 6 57 PLATE 7 Fig. l �2. Brasilia aff. bradfordense Buekman. Internal mold (A39460) from phosphorite pebble of the Brent skardhaugen Bed at loeality 7; x I. Fig. 3. Pseudolioceras compactile (Simpson). Internal mold (A39461) from phosphorite pebble of the Brentskard haugen Bed at loeality 13; x l. Fig. 4. Pseudolioceras gradatum Buekman. Internalmold (A39462) in phosphorite pebble of the Brentskardhaugen Bed at loeality 5; x I. Fig . 5. Pseudolioceras cf. gradatum Buekman. Latex east of an external mold (A39463); phosphorite pebble of the Brentskardhaugen Bed at loeality 18; x I. Fig. 6�9. Pseudolioceras pumilum Buekman. Latex east oftwo natural molds (A39464-Figs. 6, 7 and A39465-Figs. 8, 9); phosphorite pebbles of the Brentskardhaugen Bed at loeality 6; Figs. 6 and 7, x 1.2, Fig. 8, x I, Fig. 9, x 0.8. Fig. 10. Pseudolioceras maclintocki (Haughton). Internalmold (A39466) with shell fragments; phosphorite pebble of the Brentskardhaugen Bed at loeality 7; x I. Fig. Il. Pseudolioceras rosenkrantzi Dagis. Partly internalmold (Iower left)and latex east (A39467); phosphorite pebble of the Brentskardhaugen Bed at loeality 17; x I. 58 PLATE 7 59 PLATE S Fig . Pseudogrammoæras fa llaciosum (Bayle). Internal mold (A3946S) from phosphorite pebble of the Brent J. skardhaugen Bed at locality 13; x 0.75. Fig . 2-3. Belemnitidae genus indet. Two internal molds of phragmocone (A39469-Fig. 2 and A39470-Fig. 3) with parts of shell preserved ; phosphorite pebble of the Brentskardhaugen Bed at locality 14 (Fig. 2) and locality 7 (Fig. 3); x l. Fig. 4. Hastites :)sp. Rostrum (A3947 I ) from phosphorite pebble of the Brentskardhaugen Bed at locality 9; x I. Fig. 5. Saurian vertebra (A39472) in phosphorite pebble of the Brentskardhaugen Bed at locality S; x I. Fig. 6. Piece of wood in phosphorite pebble (A39473) collected 25 m below the top of the Wilhelmøya Formation on Wilhelmøya ; x I. 60 PLATE 8 61