Tectonics and Sedimentation in Foreland Basins: Results from the Integrated Basin Studies Project

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Tectonics and sedimentation in foreland basins: results from the Integrated Basin Studies project

ALAIN MASCLE 1 & CAI PUIGDEFABREGAS 2,3 IIFP School, 228-232 avenue Napoldon Bonaparte, 92852 Rueil-Malmaison Cedex, France (e-mail: [email protected]) 2Norsk Hydro Research Centre, Bergen, Norway. 3Institut de Ciences de la Terra, (?SIC, Barcelona, Spain.

Why foreland basins? to a better understanding of some basic interact- ing tectonic, sedimentary and hydrologic pro- Over the last ten years or so, since the Fribourg cesses (More & Vrolijk 1992; Touret & van meeting in 1985 (Homewood et al. 1986), the Hinte 1992). Additional data have also been attention given by sedimentologists and struc- obtained through the development of analogue tural geologists to the geology of foreland basins and numerical models (Larroque et al. 1992; has been growing continuously, parallel to the Zoetemeijer 1993). The physical parameters increase of co-operative links between scientists controlling the forward propagation of d6colle- from the two disciplines. A number of reasons ments and thrusts (fluid pressure, roughness, lie behind this development. Attempting to sediment thickness, etc.) have been determined understand the growth of an orogen without and tested. The relationships between rapidly paying due attention to the stratigraphic record subsiding piggyback basins and growing ramp of the derived sediments would be unrealistic. It anticlines have also been imaged, although the would, moreover, be equally unrealistic to con- lack of deep-sea well control still prevents accu- struct restored sections across the chain without rate sedimentological studies. More significant considering the constraints imposed by the has been the progress in our understanding of basin-fill architecture, or to describe the basin- the role of fluids and pore pressure in the fill evolution disregarding the development of development of thrust belts. When the fluids the thrust sequence. As in other sedimentary escape from the mineral matrix of sediments basins, tectonics and sedimentation dynamically during sedimentary and tectonic burial, the interact in foreland basins. Additionally, as fore- resulting fluid flow can either be diffused land basins are incorporated in the growth through the sedimentary column if the average process of the orogen, they are more likely than permeability is high enough, or be channelled extensional basins to be subject to uplift and, along pathways such as d6collements and active therefore, more accessible to direct field obser- faults when the overall permeability is low. They vation. Foreland basins observed on the field may also remain trapped within the mineral may help in the understanding of non- matrix if such pathways are not available. With observable subsurface analogues. This is essen- increasing burial the pore pressure dramatically tially why foreland basins have always been increases, eventually approaching the vertical traditional field areas for sedimentological minimum stress, and catastrophic events such as research and training, and also why they have mud volcanoes may occur (e.g. Barbados Ridge, recently been considered as ideal field labora- Fig. 2). Migrating fluids will not only exert a tories, best suited to the study and understand- fundamental control on tectonic processes, but ing of the interplay between tectonics and will also contribute to the transfer of mineral sedimentation (Fig. 1). solutions, heat and hydrocarbons from the inner Further interest in foreland basins has also part of the thrust belt to the surface along verti- been triggered off by some spectacular results cal or more tortuous lateral pathways. from investigations of offshore accretionary Foreland basins are also important from the prisms. As a matter of fact, such prisms are con- point of view of hydrocarbon exploration. sidered to be very similar in many aspects to Source rocks are commonly provided by pre- onshore thrust belts. Extensive seismic and high- compressional rift basin sequences, whereas resolution bathymetric surveying of a few properly structured rock formations within the selected active margins (Barbados, Cascadian, foreland basin may eventually provide adequate Nanka'/, Middle America), calibrated with both reservoirs. Classical examples from the Urals, deep-sea drilling and deep-sea diving, have lead Caucasus and Carpathians together with those

MASCLE, A. & PUIGDEFABREGAS,C. 1998. Tectonics and sedimentation in foreland basins: results from the Integrated Basin Studies project. In: MASCLE,A., PUIGDEF,M3REGAS,C., LUTERBACHER,H. P. & FERNANDEZ,M. (eds) Cenozoic Foreland Basins of Western Europe. Geological Society Special Publications, 134, 1-28. Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

2 A. MASCLE & C. PUIGDEFA.BREGAS

Fig. L Location map of the study areas. of the Canadian Rockies, have been recently Atlantic continental margins. Apart from the overtaken by the discovery of giant fields in still very speculative potential of non-con- Venezuela and Colombia, with estimated ventional gas production (coal-bed methane), reserves of well over the billion barrels of oil the next (and possibly the last) frontier will equivalent mark (Duval et al. 1995). It is obvious undoubtfully be the deep gas potential of Ceno- that in such a context, good knowledge of basin zoic thrust belts: there have already been some evolution and fluid flow in relation to thrust recent attempts to define prospective plays in sequence propagation will be required. Every the Pyrenees (Le Votet al. 1996) and Northern step in the progress of knowledge acquisition Alps (Greber et al. 1996). It is there where the might be, directly or indirectly, of prime rele- Foreland Basin Module of the IBS project hopes vance. Concerning the future of hydrocarbon to be of most use. exploration in Western Europe, while the classi- Additional interest in foreland basin geology cal plays are today at a stage of extensive explor- also stems from the fact that they are often ation, the present frontier areas are HP-HT associated with alluvial plains such as the Po prospects in deep stratigraphic intervals plain in Italy, the Parana river in Argentina and (5-8 km) of well-known basins such as the North the Ganges in India, to mention only three, Sea, and deep-water prospects in areas like the which support a high human population. Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 3

Alluvial plains in foreland basins are very sensi- It has long been recognized that in most cases, tive systems in relation to both predictable and orogens have adjacent elongated foreland basins less predictable changes in climate and land use. which are filled with the erosion products of the This is, perhaps, an issue of marginal interest to mountain chain. This observation defines the our project, but of much greater importance to crustal-scale approach. It is also widely accepted society. We believe that all the newly acquired (Riba 1964) that foreland basins are asymmetric knowledge, which is of relevance to hydro- in transverse section and that their depocentre carbon exploration, is sooner or later bound to axes migrate outwards through time as the have additional socio-economic applications. thrust sequence propagates - the earlier basin- fill sequences being thus incorporated into the Objectives and research premises thrust system (Puigdef~bregas et al. 1986). This constitutes the next scale of approach. Surpris- The Foreland Basin Module of the IBS project ingly enough, this evolution of the basin-fill has been planned to study the interplay, at geometry through time, which is the main dis- different scales, between tectonics and sedimen- tinctive feature, is not always taken into account tation during the construction of an orogen, and in the definition of the foreland basin (DeCelles also to study how control is exerted on the archi- & Giles 1996). It is also recognized that, on a tecture of the basin-fill down to the scale of the third and smaller scale, the propagation of a par- depositional sequence. ticular thrust interferes with sedimentation in Three main areas of work have been selected: the adjacent basin at sequence scale. In addition, the Guadalquivir basin related to the Betic as topography is created in the orogen, a orogen, the Ebro basin related to the Pyrenees, complex chain of geomorphic and climatic con- and the German Molasse related to the Alps. In trols is exerted through weathering, erosion and each of these areas, a number of research activi- sediment-transport processes, which are not ties have been planned to provide an insight to only relevant in predicting the nature of the sedi- some of the maj or problems such as the following. ments finally deposited in foreland basins, but ~ Is the tectonic load sufficient to account for also in the further propagation of the orogenic the observed lithospheric flexure? wedge itself. ~ Can we quantify amounts and rates of With these premises in mind, the objectives of erosion and topographic growth and incor- the Foreland Basin Module within the Inte- porate them in our time-step models? grated Basin Studies (IBS) project are to con- ~ Can we relate major sedimentary cycles and tribute to the understanding of how these thrust events? interactions work, which processes are involved, ~ Would modelling of growth structures help and at what rates they operate. to understand and predict growth strata geometry? Structure and composition of the project 9 Is it possible to discriminate between tec- group tonically controlled supply sequences and eustatic sequences, or is there any purpose In order to cope both with the different scales of even to try? approach and work areas, a large team was initi- To address these and other related problems, ally set up. Whenever possible and needed, the three scales (crustal, basin-fill and sequence team spontaneously developed interconnected unit) have been adopted in each of the three links. As the project progressed, some of the areas, in the belief that operating processes are team members felt the need to enlarge the group linked from one scale to the next. The last two and extend collaborative links with new research scales (basin-fill and sequence unit) are mostly groups, thus shaping an informal network of relevant, and currently considered, in studies of research on sedimentary basins within the objec- basin evaluation and reservoir characterization, tives of the IBS project. whereas the crustal scale is seldom taken into In the final stages of the project, 45 account. In many cases, however, crustal-scale researchers belonging to 11 research institutions modelling is the only way to approach some actively contributed to the IBS Module on Fore- basic parameters such as palaeothermicity or land Basins: timing and amplitude of erosional events. The Servei GeolOgic de Catalunya: X. Ber~istegui, M. three scales should be only considered as mere Losantos, J. Cir6s, C. Puig, E. Pi, P. Arbu6s, J. research strategies. They do not really have a Corregidor, A. Mart/nez. physical entity as rocks themselves do, and it Institut de CiOncies de la Terra 'Jaume Almera' would be misleading to introduce from the start (CSIC): M. Fernandez, D. Garcia-Castellanos, any attempt of order and classification. C. Taberner, M. Torn6. Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

4 A. MASCLE & C. PUIGDEF.~BREGAS

Fig. 2. Ramp anticline and related piggyback basin in the southern Barbados Ridge (Lesser Antilles active margin). The Orinoco deep-sea fan is presently incorporated to the accretionary complex. Consequently, the distributory channels have to find their way through an highly active seabottom morphology. Relative lows, such as the piggyback basins are filled with channel-supplied fine-grained turbidites. Relative highs such as anticlinal crests and mud volcanoes are deeply eroded (locally down to 300 m) by V-shaped segments of the same channels. The turbidite flow ultimately reach the Atlantic Abyssal Plain and form an elongate fan at the foot of the Barbados Ridge deformation front. The subsequent stage will be their incorporation to the accretionary complex when the deformation front will propagate. The numerous mud volcanoes in this area probably originate from undercompacted deep marine clays of early Miocene age. These mud volcanoes and the emerging ramps are the locus of active cold seeps with deep faunal assemblages and ferruginous crust formation (Mascle et al. 1990; Jolivet et al. 1990; Faug~res et al. 1993).

Universitat de Barcelona: M. Marzo, J.A. undertaken by such a large group is a difficult Mufioz, J. Verg6s, J. Poblet, J. Gim6nez, J. task. The present volume 'Cenozoic Foreland Dinar6s, M. L6pez Blanco, J. Pifia, T. Santaeu- Basins of Western Europe' constitutes a compi- laria, J. Serra-Kiel, J. Tosquella, A. Trav6. lation of most of the relevant papers (some of Norsk-Hydro Research Center (Bergen): T. them are already published) from the IBS Dreyer, J. Gjelberg. project, enriched with other valuable contri- Rijks Universiteit Utrecht: W. Nijman. butions from recent research in the same, or Vrij Universiteit Amsterdam: S. Cloetingh, R. related areas. The project would be considered Zoetemeijer, T. Den Bezemer. even more successful if IBS related papers still ETH-Z, Ziirich: M. Ford, A. Artoni, E.A. continue to be published. Our presentation here Williams. builds on the work of all, which means that all University of Tiibingen: H.P. Luterbacher, T. members of the group should be considered as Aigner, J. Jin, J. Zweigel. contributing authors. Royal Holloway University of London: C. Banks, K. McClay, D. Waltham, S. Hardy, F. Sorti. Orogenic growth and basin configuration University of Bergen: R. Steel, H. Rasmussen. Because of the existence of the ECORS-Pyre- University of Zaragoza: H. Mill~in. nees deep-reflection seismic cross-section To synthesize the results of the research obtained in 1985 (ECORS-Pyrenees Team Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 5

1988), the Pyrenees possibly constitute the area (d) Rates of shortening vary through time best suited to study the link between crustal and from a low rate (less than 0.5 mm a -I) for late surface geodynamic processes responsible for Cretaceous and Palaeocene times, to higher the orogenic growth which leads to the origin rates (up to 4.5 mm a -1) during Early and Mid- and configuration of foreland basins. The main Eocene times, and again a lower rate (2 mm a -1) results of the ECORS-Pyrenees Team have been during late Eocene and Oligocene times. published by Mufioz (1992), who gives an (e) Two stages of orogenic growth are identi- interpretation of the Pyrenean orogen on the fied: a first stage (up to Mid-Lutetian time) basis of the ECORS data, by Ber~istegui et al. characterized by submarine emplacement of the (1993) with a detailed description of the thrust sheet fronts and widespread marine sedi- ECORS-Pyrenees geological section on a full- mentation (underfilled stage), and a second colour poster format, and by Puigdefhbregas et stage (from Mid-Lutetian time onwards) where al. (1992) where a number of stages in the evol- shortening rates decrease as subaerial relief ution of the foreland basin are distinguished in increases and non-marine clastic sedimentation relation to the propagation of the orogenic becomes predominant (overfilled stage). wedge. Although modelling and quantification (f) The approximate estimate of the mean of rates was not attempted, the ECORS-Pyre- erosion rate is 0.5 mm a -1. Moreover, in the nees section constitutes a valuable reference for Eastern Pyrenees, during the overfilled stage, a new balanced and totally restored crustal-scale the rate of erosion was almost three times more cross-section constructed about 55 km eastward than the rates of sedimentation in the foreland within the framework of the IBS project (Verg6s basin. This obviously implies that the products et al. 1995; Mill~in et al. 1995). of erosion must have been deflected westwards The deep structure of this Eastern Pyrenees along the basin axis, as it is also indicated by the balanced cross-section (Verg6s et al. 1995) has well documented patterns of sediment dispersal. been constrained with the available geophysical (g) According to the calculated deflection in data, combined with projections from the the Lutetian restored cross section, the hydro- ECORS section. Since the area has been carbon source rocks of the Lower Armancies recently and extensively studied and mapped by Formation (Lower Eocene) have been subjected various authors (see Verg6s et al. 1995 for refer- to a minimum burial depth of 3 km. Hence, they ences), there has been little need for further field have been buried deep enough to be associated observations to produce a good picture of the to the upper part of the oil window (Permanyer stratigraphic frame, shallow thrust structure, et al. 1988; Clavell 1992; Verg6s et al. 1995). and timing of successive thrusting. The section The Betics, which are more complex and com- (Fig. 3) has been also partially restored at an paratively less studied than the Pyrenees and intermediate (Lutetian) stage. without a deep seismic section of reference Both the present-day and the Mid-Lutetian across the chain, are less suited to attempt suc- restorations have been flexurally modelled cessfully a time-step reconstruction of the (Mill~in et al. 1995) in order to evaluate the rela- relationship between the orogenic growth and tive contribution of topographic and subduction the basin configuration, except perhaps for the loads to the lithospheric deflection, and to Guadalquivir basin, the latest of its evolutionary obtain additional constraints on the estimation stages. Fernandez et al. (this volume) give an of the topographic load. extensive account of the present-day knowledge Relevant results from this study can be sum- of the area and incorporates the new geological marized as follows (Verg6s et al. 1995; Milhln et and geophysical data obtained within the frame- al. 1995). work of the IBS project, with special emphasis (a) Although the topographic load plays the on the constraints on the evolution of the predominant role in the external and inter- Guadaquivir basin. A set of maps including the mediate parts of the foreland basin, the subsi- Bouguer anomalies (10 mGal isoline), the geoid dence of the internal part is the result of the heights (1 m isolines), the depth of the Moho (1 combined effect of both subduction and topo- km isolines), and the surface heat flow and base- graphic loads. ment depth, is presented in the same paper, (b) Palaeotopographic elevations between 1 together with thermometric logs from water and 2 km appear to be the most plausible values wells, and hydrocarbon exploration well logs. for the Mid-Lutetian restored cross-section. The compiled data set introduces important con- (c) The total shortening obtained in the straints on the possible models of a basin for- Eastern Pyrenees cross-section is 125 km (22 km mation. However, the early stages of the less than in the ECORS section situated 55 km development of the Gudalquivir basin and its to the west). relation to the history of the orogen still remains Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

6 A. MASCLE & C. PUIGDEF.~BREGAS

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INTRODUCTION 7 obscure. Unresolved issues include: how late determined by Benistegui et ah (this volume) Cretaceaous to Langhian foreland basin and Fernandez et aL (this volume), have been sequences were incorporated in the northward- related to the tectonics of the external zone and propagating thrust wedge, or even if they existed to the emplacement of a hidden load of unde- at all. termined origin but of quantified magnitude. The stacked tectonic sheets of the inner part An additional example of orogenic growth is of the Betics were later submitted to severe provided by the 'Digne Nappe', an external stretching leading to lithospheric thinning and segment of the Western Alps well exposed in SE ultimately to the opening of the Alboran sea in France (Lickorish & Ford this volume). Miocene times. This part of the history, related Although seismic and well data are not available to extensional processes within the Alpine to constrain the proposed deep section, excel- orogen, will be developed in a second volume lent field exposures and an accurate set of geo- prepared by the IBS group, to be published by logical maps provided by the French Geological the Geological Society. Survey (BRGM) have been used to construct a Numerical models for the deflection of the 100 km long regional section through the thrust lithosphere under time-dependent loads in 2D belt. Of particular interest, time-step restored and 3D are currently being made by D. Garcia- sections show the variability of tectonic pro- Castellanos (Institute of Earth Sciences, CSIC). cesses operating through time along this single The models consider the effects of erosion, sedi- section, thin-skinned tectonics prevailing during mentation and lateral variations of the elastic late Eocene and Oligocene times, and linked thickness corresponding to a layered litho- thick- (at the rear) and thin-skinned (at the spheric rheology, and allow a closer interaction front) tectonics in Neogene times. An inter- between tectonic processes, sedimentary basin- vening event of normal faulting in Priabonian fill and large-scale lithospheric deformation times would reflect the flexuration of the eastern (Garcia-Castellanos et al. in press). The 2D and segment of the foreland, as a result of tectonic 3D numerical models have been applied to the overloading in the inner part of the Alps farther Betic foreland basin in order to obtain a detailed East (Vially 1994). This polyphase history of view of the regional isostasy in the area (Fig. 4). thrust belts should be properly taken into The basement and sediment geometries account for the hydrocabon assessment of such

Fig. 4. Processes involved in foreland basin formation which are considered in the numerical modelling by D. Garcia-Castellanos, M. Fernandez and M. Torn6: Thrust loading, regional isostasy (flexure) with various lithospheric rheologies, and surface processes (denudation and deposition), UC: upper crust; LC: lowe crust; LM: lithospheric Mantle. (From Garcia-Castellanos et al. in press, reprinted by kind permission of Elsevier Science-NL). Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

8 A. MASCLE & C. PUIGDEFABREGAS areas, especially when migration paths or early seismic stratigraphy concept formulated later by generation of hydrocarbons and dismigrations Vail & Mitchum (1977); the need was obviously are considered. there for new concepts on stratigraphy and, in fact, genetic sedimentary units have long since been in mind of Pyrenean geologists, mainly Thrust sequences and basin-fill because of the ubiquitous presence of unconfor- architecture mities associated with observable syntectonic sedimentary wedges. As we have seen above, in the case illustrated by The generalization of the sequence stratigra- the Pyrenean orogen, plate convergence, oro- phy concept, as essentially controlled by eustasy, genic growth and formation of the adjacent resulted in a number of important papers, foreland basin are intimately related. We can ranging from those that, although recognizing also infer that a continuum exists between the some tectonic control on the sequence upbuild- triggering process of plate convergence down to ing, have eustasy as the main influence on the the final thrust sequence propagation. Because genesis of sequence boundaries (Fonnesu 1984; of the presence of syntectonic deposits and Crumeyrolle 1987; Mutti et al. 1988; Deramond good age constraints, it becomes even possible et al. 1993), to those believing that tectonics pre- to estimate the rates of thrust displacement dominate in the control of the changes in beteween 2 and 4.5 mm/ a -1. Identical values accommodation needed to generate sequences have been obtained for present-day rates of (Mellere 1993; Mutti et al. 1994; Puigdeb~bregas thrust displacement along the front of the off- & Souquet 1986). shore Barbados accretionary prism. Compared The acquisition of the ECORS deep seismic with the duration of the basin-fill sequences, profile between Toulouse and Balaguer pro- these figures leave little doubt that thrusting has vided the required ground for the next step in played a significant role in shaping the sequence the research. A closer link was established architecture of the basin-fill. We will now between distinct stages in the basin-fill and analyse, in each of the different work areas, the stages in the structural evolution (Mufioz 1992; characteristics and details of these relation- Puigdefhbregas et al. 1992) at the same time that ships. emphasis was given to quantification of rates of processes (Vergts 1993). Apart from the natural disagreement con- The Pyrenees cerning the number of sequences or cycles, their The existence of a close relationship between names and controlling factors, most of the thrusting and sedimentation is an old obser- authors will agree that unconformity-bounded vation that goes back to the 1960s. Riba (1964, sediment packages with a characteristic genetic 1976) recognized the general asymmetry of the signature may be distinguished in the southern Ebro basin, the outward migration of depocen- foreland basin of the Pyrenees. The asymmetric tres, and the progressive unconformities with transverse section, the outward migration of their related syntectonic sedimentary wedges. depocentres, the presence of stratal growth pat- These observations constituted the starting terns and thrust-related bounding unconformi- point of a fruitful line of research. Reille (1971) ties, and the axially deflected dispersal patterns provided a well-documented field description of are the classical features of these stratigraphic the syntectonic wedges along the northern units. They can be distinguished at several scales margin of the basin. Soler & Puigdefhbregas according to their specific relation to tectonics. (1970) related phases of thrusting and sedi- A first-order sequence would correspond to the mentary packages defined by isochronous and basin itself, considered as a sediment unit basinwide extended changes in palaeogeogra- related, as we have seen, to the growth of the phy and dispersal patterns. It was, however, orogen. Large-scale changes in the style of Garrido-Megias (1973) who first formulated the thrust-sequence propagation determine the concept of a tectonosedimentary unit (TSU): 'A piggy-back basin configuration within the fore- tectonosedimentary unit is a stratigraphic unit land basin, and define basin-fill sediment pack- made up of strata deposited during a given geo- ages that roughly correspond to the classical logical time-span, under sedimentary and tec- lithostratigraphic groups, falling within the tonic conditions characterized by a specific range of the second-order sequences in con- tendency. The TSU boundaries are basin wide ventional sequence stratigraphy. sedimentary discontinuities or their correlative Third-order sequences are genetic sediment conformities'. It is worth noting that this defi- packages essentially controlled by changes in nition has many common elements with the sediment supply (as a response to changes in Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 9 uplift rates, thrust-related changes of gradient, Basin axis shift in the Tremp-Graus basin is and efficiency of the fluvial drainage in the hin- described to follow a zigzag pattern (see Nijman terland), and changes in the accommodation this volume, Figs 15 and 16) with a net outward space (as a response to changes in local tectonic migration. The zigzag pattern would result from subsidence, thrust-related changes of gradient, the interplay between three main modes of and changes of base level or eustatic sea level). thrust translation: The Tremp-Graus basin, extensively studied (1) general uplift due to active floor thrust and by the University of Utrecht since the 1960s, and major outward displacement of the entire now incorporated in the IBS project (see thrust wedge; Nijman this volume), constitutes a classical (2) one-sided uplift due to the active growth of example that illustrates the basin architecture at the antiformal stack in the rear; that scale of observation. Most of the character- (3) active roof thrust displacement. istic features and detailed facies analysis can be found in previously published literature. It can The distinguished megasequences correlate with be described as a nappe-top syncline basin the described zigzag pattern of basin axis shift, (piggy-back basin) with an asymmetrical trans- but show a poor correlation with the eustatic verse section and a typical axially deflected dis- curve (see Nijman this volume, Fig. 13). persal pattern. The antiformal stacking of In the Ainsa basin, farther to the west, an area tectonic units constitutes the northern margin of of slope environment connects the alluvial and the basin, while the northern dip slope of the deltaic deposits with basinal turbidites farther Montsec thrust hanging wall constitutes the west (Mutti et al. 1972, 1984; Nijman & Nio southern margin. The basin is about 20 km wide 1975). A clear relation can be observed there and, over a distance of 50 km grades from between thrusting and the generation of large alluvial to shallow and deeper marine facies submarine erosion surfaces (Fig. 5), eventually whose turbidite components extend westwards canyons, produced by frequent sediment col- for another 100 km. A number of sequences lapse. Three main collapse surfaces migrate build up the Tremp-Graus basin-fill (see outward with respect to each other in relation to megasequence and cycle subdivision by Nijman thrust propagation (Fig. 6 and Mufioz et al. this volume). 1994). Submarine erosion surfaces take their The sequence elements in the eastern area, time to form as the collapse front climbs dominated by alluvial to delta plain deposits, upslope, and often connect to the base of the include (Nijman, this volume, Figs 13 and 16): next transgressive event. It is, therefore, in most of the cases impossible to physically connect sur- (1) a distinct event of degradation and channel faces of fluvial incision to surfaces of submarine incision immediately followed by multi- erosion. episodic channel filling, which results in a Sequence-bounding surfaces are, therefore, wider and thicker multi-story fluvial sand- segmented (Dreyer et al. 1994) as the result of stone body; different processes operating along the deposi- (2) a marine onlap on top of the former fluvial tional profile, from the subaerial hinterland and sandstone, recognized as a thin dark oyster all the way down to the deeper submarine slope, rich mudstone, as soil profiles reflecting the in response to the same triggering effect of gra- rise of the water table, or even by the pres- dient steepening. ence of tidal structures within the channel It is also important to note that successive sandstone bodies; piggy-back basins, located on also successive (3) a thicker aggradational finer-grained alluvial thrust sheets, are not sharply separated in time. sequence, which, towards the margin, corre- One basin may start to be actively filled while lates with major alluvial fan upbuilding. the other is still receiving sediments. Conse- These three elements are the result of a three- quently, syntectonic sequences may be present fold process which includes: in neighbouring basins, as in the case of Ager, Tremp-Graus and Ainsa, and the corresponding (1) a rejuvenation phase due to thrust induced dispersal systems may be obliged to follow a gradient steepening, rather complicated pattern between rising highs. (e) a subsequent increase of local subsidence; This is also illustrated in present-day deep (3) an increase (and then decrease) of fluvial marine accretionary prisms where several piggy- efficiency of the subaerial drainage network back basins can be contemporaneously filled, in the hinterland, in response to relief reju- within an overall outward younging of the base venation, accounting for the common thick- of the syntectonic infill. ening-up trend of alluvial-fan sequences. In the eastern Pyrenees, Verges et al. (this Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

10 A. MASCLE & C. PUIGDEFABREGAS

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93 .... ~"--- Atlart thrust ~ Alluvial fanglomerates (Campenu6 conglomerates). Delta plain, red and grey mtKIstones, sandCwnes and conglomerat,m (Capalla Fro. and pert of Perarn,,a Frn.) ~ Fan delta and delta front sandstones and conglomerates (Perarrua Fro., Caatilgaleu Fro, and Castiuent Fro. equivalents) I I Delta slope mudstones (San Vicente Fm.) Slumpized mudstones attached to submarine erosion surfaces (San Vicente Fnt) Intre-slope turbidite channel and canyon fills. Pebbly mudstones, conglomerates and sandstones.San Vicente Fro.

Fig. 5. Stratigraphic section across the transition area between the Tremp-Graus and Ainsa basins. The section illustrates the stratigraphic position of the Charo-Lascorz submarine erosion surface (Ch-Lsz), and the relations to the Atiart thrust. (From P. Arburs, unpublished.) volume), building on previous work (Puigde- outward migration of the depocentres corre- f~bregas et al. 1986; Gim6nez 1993), distinguish sponding to the successive sequences that build four third-order transgressive-regressive cycles. up the architecture of the basin-fill. The analysis is based on the time-step restored cross-section previously discussed (Vergrs et al. The German Molasse 1995; Mill~in et al. 1995), on available well and seismic data, field sections and magnetostrati- The Molasse basin, studied for at least a couple graphic dating (Vergrs & Burbank 1996). The of centuries, is a classic example of a foreland main results (Vergrs et al. this volume fig. 8) basin. It is there where the main geometric and show that tectonic subsidence started earlier basin-fill characteristics have been first (55.9 Ma) in the Ripoll piggy-back syncline basin, described and shown to be applicable to most of with subsidence rates from 0.13 to 0.38 mm a -1. In the basins related to the growth of mountain the Ebro basin south of the Vallfogona thrust a chains. Within the IBS project, the work group similar N-S trend is observed, where the of the University of Ttibingen has selected a key maximum of subsidence up to 0.30 mm a -1 is area east of Mtinich between the rivers Inn and shown to start at 41.5 Ma in the Montserrat Isar. Because of its situation between a western section, connected with the structure of the shallower and an eastern deeper sector, the area coastal ranges, allowing to accommodation of the should be suited to study the sequential upbuild- large amounts of fan delta deposits in the area. ing, and address questions such as the relative These results, further presented and discussed in role of thrust loading, subsidence, sediment the paper by Vergrs et al. (this volume), provide supply and eustasy in the basin-fill architecture. a quantification to the generally observed The study, based on about 25 seismic sections Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 11

ue!=..no

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o3 Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

12 A. MASCLE & C. PUIGDEFABREGAS and over 30 wells, combines three techniques: propagation, the IBS work group on the seismic stratigraphy, subsidence analysis and Guadalquivir basin has focused the research on stratigraphic modelling. Jin et al. (1995), and the sequence architecture of the Miocene fill of Zweigel et al. (this volume), give a detailed and the basin and its relation to the thrust front. precise account of the basin-fill architecture and Ber~istegui et al. (this volume) present the discuss the results. The sequence stratigraphy results of this research. Based on the seismic analysis has led to an improved reconstruction stratigraphic interpretation of more than 1400 of the depositional history, and the parameters km of seismic lines and the study of about 35 obtained have been used in stratigraphic model- exploration wells, the Neogene fill of the ling. A new back-stripping algorithm has been Guadalquivir basin is divided into six deposi- developed, allowing a two-dimensional subsi- tional sequences which correspond to the third- dence analysis along regional sections. Forward order sequences in the TB2 and TB3 supercycles stratigraphic modelling has been calibrated with in Haq et al. (1987). (Ber~stegui et al. this real data to test and refine the modelling pack- volume, fig. 8). In the southern active margin of ages, and to quantify and constrain the subsur- the basin, an allochthonous body is described face interpretations. The PHIL stratigraphic that occupies most of the basin and extends modelling package has been used in longitudinal laterally all along the Betic front. Because of its sections parallel to the basin axis in order to chaotic appearance, which mostly consists of improve the understanding of the interplay Triassic evaporites and mudstones including between subsidence, sediment supply and large extraformational blocks, the allochthon- eustasy. ous body has, until now, been interpreted as a The paper by Zweigel et al. (this volume), dis- large olistostrome fallen into the basin. In order tinguishes five depositional sequences on the to establish the relationship between the basin- basis of seismic stratigraphy analysis in longitu- fill sequences and the Betic front, a closer analy- dinal sections parallel to the basin axis, and to sis of the body was obviously needed. A number the general shoreline progradation. On the of inconsistencies have been observed, namely other hand, the subsidence analysis shows two its extraordinary size, almost as large as the distinct flexural events corresponding to the basin itself, and, most important, the fact that all classic transgressive-regressive cycles. Figure 2 the rock fragments and blocks included in the of Zweigel et al. (this volume) illustrates the cor- Triassic matrix are younger than the matrix respondence between cycles and sequences and itself, immediately ruling out the olistostrome includes the timing of thrust events. interpretation. Based on three structural tran- The authors conclude that shoreline shifts sects, the structural analysis of the allochthon- responsible for the definition of the sequence ous body itself, and supported by analogue and elements may be seen better in longitudinal numerical modelling, Ber~istegui et al. (this west-east sections through the basin, whereas volume, fig. 13), provide us with a new interpre- transverse sections show better the thrust tation as a submarine-emplaced lateral diapir of related changes of subsidence. In other words, Triassic material displaced from the Inter- there is a longitudinal sequential partitioning mediate Units, in front of an advancing thrust controlled by eustasy, and a transverse parti- sheet. As to the timing of the emplacement, tioning related to the northward propagation of sequences 1, 2 and 3 are pre-thrusting, 4 and 5 the thrust belt. The argument is supported by the are deposited during the emplacement of the good fit between the sea-level curve derived lateral diapir, and sequence 6 is post-emplace- from the seismic stratigraphic analysis and the ment. sea-level curve of Haq et al. (1987). On the The lateral-diapiric thrust front characterizes whole this is an interesting conclusion, which the external structure of the Betics. This Betic- although needs testing on other basins, will cer- type thrust belt front, not often described in tainly stimulate further research. literature, might constitute a good model for other foreland basins and should be taken into account in hydrocarbon exploration. Concern- The Guadalquivir basin ing the sequence partitioning it should be noted As previously discussed, the Guadalquivir basin that the recognized sequences show a good cor- constitutes the latest of the evolutionary stages relation with the eustatic curve of Haq et al. of the Betic foreland basin. The present know- (1987), but unlike the German molasse example, ledge of the Betic orogen does not allow the they also correspond to well-defined extensional time-step reconstruction of the previous stages. or thrusting events (see Ber~istegui et aL this As it is possible to observe the basin-fill archi- volume, fig. 8). tecture and its relation to the thrust sequence In comparing the three main basins studied, it Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 13 appears that sequence partitioning based on regimes will develop respectively. The term thin- seismic stratigraphy analysis (Guadalquivir and skinned tectonics is usually used to describe German Molasse basins) shows a good corre- structures which develop over d6collements lation with the global eustatic chart of Haq et al. within sedimentary layers. But such layers can (1987), whereas the same correlation is very be at depths in excess of 10 km, as for instance in poor in basins studied from field observation. southeast France (Philippe et al. this volume). There may be a number of explanations for this: The resulting style of superficial deformation will then be very similar to the deformation (1) sequence boundaries, because of their seg- related to thick-skinned tectonics, a term better mented character, are more distinct in used when the basement is involved. Thick- seismic sections than in detailed field obser- skinned and thin-skinned tectonics are both vations; present in the western Alps thrust belts and fore- (2) not enough effort has been made in the lands, and both can be linked and synchronous Pyrenean foreland basin toward the defi- (see Lickorish & Ford this volume). From a nition of sequence boundaries; petroleum exploration point of view, the localiz- (3) foreland basins studied at their outer areas, ation of d6collements within the sedimentary where tectonically induced changes on package is important as quite distinct structural supply and changes on subsidence are traps will develop above (synchronous ramp weaker, reveal a stronger eustatic effects in anticlines), or will be preserved below (early the sequential upbuitding. tilted blocks for instance). Active flats and This last explanation emphasizes the role of ramps will also act as potential pathways for sediment supply and tectonic subsidence in the fluids and hydrocarbons (as demonstrated in sequence definition in foreland basins. modern accretionary prisms, Moore & Vrolijk 1992). On the other hand, thick-skinned tectonic will induce the complete uplift of large parts of Thrust propagation and fluid flow sedimentary basins, thus immediately freezing Intraplate stresses are generally generated along oil or gas kitchens, or even leading to the escape divergent or convergent plate margins. In colli- of any early accumulation of hydrocarbons (to sion zones, the upper fragile crustal domain is the surface or to another trap). the locus of intense strain which is expressed by The French segment of the Western Alps does shearing, extrusion and the development of not show the development of any significant localized shear zones and thrusts where impor- Neogene foreland basin (or alternatively, the tant parts of the horizontal shortening take related deposits have been subsequently place. Such shear zones develop first at deep eroded). As a result, sedimentary layers of the crustal levels, following the initial trajectories of pre-orogenic stage (Mesozoic) are well exposed the sudducting slabs (oceanic or thinned conti- and the geometry of Neogene structures is rela- nental lithospheres). When collision of conti- tively well constrained from field data. Several nents becomes the dominant geodynamic deep wells and a few regional seismic profils are process (in late Cretaceaous times for the also available. Well-balanced sections in these Western Alps), shear zones develop between the areas are proposed in this volume by Philippe et two colliding continental crusts. These shear al.; Beck et al,; Lickorish & Ford and Burkhard zones will rapidely propagate upward and & Sommaruga (including the neighbouring forward, but some backward thrusting may also Swiss Molasse Basin). This large amount of data be initiated, resulting in the classic dual vergence allows the study of lateral variations in the tec- of the Alpine thrust belts (Verg6s et aL and tonic style of thin-skinned deformation of the Burkhard & Sommaruga; this volume). When western Alps foothills. Over a distance of about propagating to the surface, these major thrusts 30 km, the broad ramp anticlines of the Vercors follow complicated paths, often showing a 3D Plateau progressively narrow to the North to geometry with 'fiats and ramps'. The more-or- form an imbricated vertical stack of thin tectonic less horizontal fiat segments (d6collements or sheets in the Chartreuse Massif (Philippe et al. detachments) can either be localized in ductile this volume). This tectonic wedge then widens layers of the continental basement or be hosted again in the Jura Massif, with the front of defor- in sedimentary horizons with a strength lower mations being translated to about 100 km than the surrounding rocks (salt, undercom- towards the west. As a result, a large piggy-back pacted clays, marls, etc.). According to whether basin, the French and Swiss Molasse Basin, once the frontal or lateral ramps (segments with part of the northwestern Alps foredeep (in higher dips) initiate from great or shallow depth, Eocene-Oligocene times), has developped in so-called thick-skinned or thin-skinned tectonic Neogene times (Beck et al.; Burkhard & Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

14 A. MASCLE & C. PUIGDEFABREGAS

Sommaruga this volume). Can we explain this belts, fluid circulations along fault zones is lateral evolution of the thrust belt? A convincing shown by the presence of veins, usually calcite, hypothesis is that these synchronous tectonic but other mineral assemblages can be found styles are primarily controlled by two para- (Roberts 1990). A combined structural and geo- maters: chemical study of such shear veins has been undertaken in the South Pyrenean Foreland (1) the thickness of the sediment package Basin by Tray6 et al. (this volume). Channelized involved in the deformation, flows along active thrust faults are recorded by (2) the efficiency of the major decollement calcite shear veins formed by a crack-seal propagating in the foreland basin (here mechanism, suggesting an epidsodic nature of hosted in the upper Triassic interval). fault slip and related fluid migration. These A thick sedimentary package and an efficient fluids seem to be a mixture of local formation (low-friction) d6collement will favour the rapid water mixed with saline fluids from the inner and forward propagation of the tectonic wedge. A deeper parts of the belt. Meteoric waters have thin sedimentary column and higher frictions also locally contributed to the flow of water within the d6collement will lead to a more verti- through the forward-propagating thrust belt. cally imbricated stack and a slower rate of Additional studies of this type will certainly be forward propagation. Because of these con- necessary in the future for a better understand- strasting tectonic style, the timing of hydro- ing of interactions of fluids, fluid flows, and fluid carbon generation and expulsion will be quite pressures with the micro- and macro-tectonic different in these different places (Mascle et al. processes occurring in an active tectonic wedge. 1996; Sassi & Deville in press), and consequently the petroleum plays will be different. A late generation of hydrocarbon is possible: Growth folds and related sediment wedges (1) in the Chartreuse and inner Jura Massifs As previously discussed, numerous examples of due to the burial of Stephanian, Autunian synsedimentary growth of folds and thrusts are and Liasic source rocks within or below the found in the Pyrenees, especially along the verticaly imbricated tectonic stacks; northern margin of the Ebro Basin. Earlier (2) below the Molasse Basin following the descriptions come from Riba (1964), Ten Haaf burial of the same source rocks below the (1966), Reille (1971) and Garrido-Meg/as thick tertiary sedimentation of the foredeep (1973). Some of them have continuously led to and piggy-back basin stages. On the other further research and more detailed descriptions hand only localized tectonic or sedimentary have been produced. This is the case of the Sant burial of these source rocks have occured in Corneli anticline and its related B6ixols thrust Tertiary times in the Vercors and outer Jura that affected the sedimentation of the Areny Massifs; as a result, most of the oil gener- Group (Nagtegaal et al. 1983; Sim6 1985; Fonde- ation and expulsion was achieved in early cave-Wallez et al. 1988; Mutti et al. 1994), the Tertiary times. Oliana anticline described by Verg6s (1993), the Turbon anticline (Pappon 1969; Deramond et al. During burial and compaction, sediments expel 1993) and the N-S anticlines at the External formation water (and source rock hydro- Sierras (Mill~n et al. 1995). Within the IBS carbons). The behaviour of faults and decolle- project, three examples have been selected: the ment as seals or pathways during the migration Vallfogona thrust, discussed by Mart/nez-Rius et of such fluids is an important and still strongly al. (1996) and by Ford et al. (1996), the B6ixols debated problem. The nature of the rocks and of thrust discussed by Arbu6s et al. (1996) and the the damaged zone surrounding the faults must Mediano anticline, described and modelled by also be taken into account. If most of the sedi- Poblet et al. (in press). ments are permeable, the nature of the faults has probably little importance as the fluids will be able to circulate to the surface quite easily. With Syntectonic conglomerates associated to the the exception of very sandy accretionary prisms Vallfogona thrust or onshore foredeeps, this is not often the case, and either a fracture network within the sedi- According to Martinez-Rius et al. (1996), the ments, or a few single faults are then preferential emergence of the Vallfogona thrust, together pathways. This has been demonstrated in the with the emplacement of the lower units in the case of some accretionary prisms such as the northern sector, resulted in deformation of the Barbados Ridge, where fluids migrations are previously emplaced lower Pedraforca thrust presently active (Fig. 7). In now inactive thrust sheet (Fig. 8), and produced an imbricated Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 15

I km

671 541

675 542 676 ~6.5 ! I ...... 1111 .i iiii_iii

...... > ~~~r.,,'~",~'<-,,,,,~v~~ '... .~Y,:~,,.;#c,;'.'.~ ;t:.,,;c'~-,~A~,' .~-,#-.,e.'.:,~':r '~ ~,, --;.~ .. _~._, _,,...~" ~,~:_,~_' ~tt~.g.'L~ ~.~ii',.~,:~.;e~,.:~. " ~..~, I) ', ,. .... ~:,~;,,,;~ ....~',:~.~*,~,;~,,,~._"~%'='~,'~' ,',, ,,~, ~p,~, ~,',; .~,':'~,,D~'~,~,g',",::,{,'~,~,~,,,,~. >' u i'~.; ,,~' '~UI~ ,..'. -' ".li,','" ..... '; ...... ", :,. ;'~" ..1~,.,~ ~jT,~;;-~.d;D',,"~, ,,,~:'-~".*',~,~';':~,X.~. ;,r ./,~.~,~,~'.,:~;'.'.,~,.~"-7 "~:,:' ,. li~,;;~/~:. 2",:~:~'~,\~;:,~:!~::'.,,'; ;~~,,~ ,iv ., ~,;,.;~ .., ~,..~- ~" .., ,.~.,~.~,. 4 ,,,.,~;,,:;~.~,...,.,.,,,-,;{~14. . e~g~..~ - ,,,..~,,-_~:...

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90133 1 Sec.

Fig. 7. Barbados Rige, deformation front. 541-542: DSDP leg 75-A; 671 to 676: ODP leg 110; 7 other holes (DSDP leg 75-A and ODP legs 110 and 156) are located a few kilometres to the West and East respectively: A, Miocene to Recent; B, Campanian to Oligocene (the strong reflectors around B represent Eocene sandy turbidites); C, top of the Atlantic oceanic crust. Note that earlier normal faults in the underthrust sequences (B) are preserved below the main decollement (D), while presently active thrust characterized the accreted complex (A). The very low gradient of the sea bottom slope (taking into account a vertical exageration of 3.3 for the water and 2.5 for sediments) is a typical feature of d6collements with a low rugosity and high pore fluid pressure. Packer tests in nearby holes 948 and 949 (ODP leg 156) suggest that pore pressures in the d6collement exceed hydrostatic pressure. The large set of data now available in this area allows us to constrain the present migration paths of fluids expelled from both the accreted and subducted low permeability sediments: pore water geochemistry, distribution of mineral veins and temperature measurements indicate that the main conduits for a lateral migration are:the Eocene sandy turbidites, the d6collement and the presently active thrust faults in the accreted complex. For instance at site 676, pore fluids show anomalous contents in methane (here expressed in micromoles per litre) closely related with the location of thrust faults (Behrmann et al., 1988; Gieskes et al. 1989; Vrolijk & Sheppard 1991; Labaume et al. 1995). system of hanging-wall thrust slices that propa- fault propagation fold pair. The growth axial gated out of sequence. Increased relief together planes form an enechelon pattern on the anti- with out-of-sequence thrust propagation cline, and an upward converging pattern on the resulted in the deposition of four conglomerate syncline, together defining the growth triangle wedges unconformably related to each of the (Fig. 9). Sedimentological and structural data are thrust slices. These relations are comparable to combined with magnetostratigraphy in order to those described by Martinez-Rius et al. (1996), model the structure and to describe the details of Verg6s (1993) and Mellere (1993) in other local- erosional and sedimentary responses to the fold ities of comparable structural setting. growth, where gradient steepening plays a sig- The last of the conglomerate units is time nificant role, even at the smallest scale of obser- equivalent (Upper Eocene-Oligocene) to the vation (Williams et aL this volume). spectacular conglomerate wedge of Sant Llorenq de Morunys (Riba 1976) which developed at the Relations between the BOixols thrust and footwall of the Vallfogona thrust. Ford et al. the Areny Group (1996) give an outstanding description of that growth structure, based on the construction of The Maastrichtian Areny Group is perhaps one three profiles. The geometry is interpreted as a of the more studied sedimentary units in the Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

16 A. MASCLE & C. PUIGDEFIkBREGAS Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 17 (b)

Fig. 8. Cross-section displaying the general structure of the eastern Pyrenees in the Pedraforca area (a). The footwall thrust sequence of the lower Pedraforca and Cadi units ends up with a hanging-wall overstep sequence within the Lower Pedraforca thrust sheet. This is shown by the relationships between the syntectonic sediments and related thrust (b). The oldest syntectonic sediments are the A conglomerates (Coubet Fm, late Early Lutetian), which overlay the floor thrust of the lower Pedraforca (unconformity 1). The sediments B, C, D and E unconformably overlie the thrust slices (unconformities 2, 3 and 4) which are progressively younger towards the hinterland. (From Martfnez-Rius et al. 1996, reprinted with permission).

Pyrenees. The IBS project specifically focused Synsedimentary growth of the Mediano on the relations between the growth of the anticline B6ixols anticline and the Maastrichtian sedimentation. Two parallel structural sections have The Mediano anticline is the easternmost anti- been constructed (Fig. 10), and four sequences cline within succession of N-S-trending folds have been characterized within the Areny that characterize the western segement of the Group (Arbu6s et al. 1996). From the facies and Central Pyrenees. It constitutes the eastern flank thickness analysis within each of the sequences of the Ainsa syncline basin. The synsedimentary (Fig. 11), it can be concluded that the generated growth of the Mediano anticline has long been differential subsidence mostly controlled the recognized (Garrido-Megfas 1973; Nijman & distribution of thickness and facies, but did not Nio 1975). In a comprehensive paper, Poblet et exert a direct control on sequence partitioning, al. (in press) describe and model its geometry, more likely connected to less local changes in and quantify the rates of growth. Figure 12 accomodation and gradient steepening. If such shows the geometry of the structure and associ- sequence bounding surfaces are in relation to ated sedimentary wedges, and Figure 13 shows local tectonics, and are at the same time of basin the evolution of the structure on a section per- wide extent, then a link between basin wide pendicular to the fold axis. Two main unconfor- flexure and local thrusting must be assumed. mities are observed: a lower unconformity Otherwise, the generation of sequence-bound- between pre-growth and growth strata, and an ing surfaces is more likely under eustatic control, upper unconformity separating the growth with differential subsidence and sediment strata onlapping the anticline limbs, from those supply under tectonic control. which overlap the fold crest. It is interesting to Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

18 A. MASCLE & C. PUIGDEFABREGAS

Fig. 9. Section (a), and line drawing (b) through Tossal de Vall-Llonga showing hinge points in the growth syncline. Note that in the anticline the axial planes at various levels form a discontinuous, en-echelon pattern jumping progressively down to the south. The synclinal and anticlinal growth axial planes converge upward to describe a growth triangle. (From Ford et al. 1996, fig. 9, reprinted with kind permission of Elsevier Science- NL.) note that a typical carbonate platform facies, this survey is that palaeomagnetic data show including Nummulites beds and coral and algal that the whole Ainsa basin has been rotated by reefs, seems to, by preference, develop at the 30 ~ clockwise during sedimentation. base of the second unconformity around the The results of growth-fold modelling are not anticline top. only relevant to the understanding of the role of Reverse modelling (Poblet et al. in press) pro- tectonics in basin sequence architecture, but also vides estimation of rates of thrust slip (max. 0.58 provide a useful tool to predict suitable facies mm a-l), uplift (up to 0.70 mm a-l), limb rotation and traps in hydrocarbon exploration. and lengthening. The average erosion of the anticline crest is estimated in 0.51 mm a -x. The growth strata were deposited from 47.90 to Sedimentation and tectonics at sequence 43.73 Ma, and from that age onwards, the sedi- scale ments overlap the anticline crest. It must also be noted that the growth strata Two field areas have been selected to illustrate wedges form in response to the relief generation the relations between tectonics and sedimen- and not directly to changes in compression rates tation at smaller sequence scale. The Sant (Hardy & Poblet 1994). An additional result of Lloren~ del Munt fan delta, in relation to the Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 19 SSW-NNE Sant Comeli 2000- anticline Tremp syncline I

~~ ~ X~ -'7""~~ Cretaceous ] Om

-2000 ~' [[ - ' -----IT~'-'~ lower Cretaceous I ,~. A A^,,A -, ~Jurassic] L_____.L~____~____~___~__~___~__~, , ,, ,,. A O A ,, ,, ,, A ,, .,..~. CD I Triassic ,. . **+.+.+.+++.+++.+;+-+++;.+.+;+ +~+~-;+~+-;~-C~-:T~+~---~ Eocene.J - .++*+++*+'.++++*+++*+§ +++*+*+*+§ Basement [

-4000 H=V

Fig. 10. Geological cross-sections through the Boixols-Sant Corneli anticline. Numbers i to 4 correspond to the successive depositional sequences in the Aren Group. la, Puimanyons olistostrome; lb, slope marls-Salas marls; 2a, bioclastic nearshore sandstones; 2b, offshore sandstones and shales; 2c, offshore shales; 2c', bioclastic nearshore sandstones; 3a, bioclastic nearshore sandstones; 3b, offshore shales; 3b': nearshore sandstones; 4a, nearshore sandstones; 4b, lagoonal shales; 4c, alluvial red shales (From Arbu6s et al. 1996, reprinted with permission.) structure of the Catalan Coastal Ranges at the Composite sequences result from stacking of southeastern margin of the Ebro basin, and the fundamental sequences. Stacking patterns, Ainsa basin-fill as an example of a growth syn- defined from shoreline trajectories (L6pez- cline in the central sector of the Southern Pyre- Blanco et aL in press, fig. 7) may be transgressive nees. or regressive. Major surfaces of maximum The Sant Llorenq del Munt fan delta offers a regression are taken as the composite sequence unique opportunity to study and discuss the boundaries. Thicknesses are in the order of one sequence definition in a supply-dominated to three hundred meters, they are traceable for environment, and in a setting where the marine a few tens of kilometres, even into the neigh- to non-marine correlation can be guaranteed. bouring fan bodies, and they take between 0.1 L6pez Bianco et al. (in press) give a synthesis of and 1.0 Ma to form. several years of study based on detailed Composite mega sequences result from stack- mapping of the area. The authors distinguish ing of composite sequences, and include the same transgressive-regressive units of three orders of elements. The Sant Llorenq del Munt fan itself magnitude: fundamental sequences, composite constitutes a composite mega sequence, which, sequences and composite megasequences. with a thickness of more than 1000 m and a dura- Fundamental sequences are 3-80 m thick and tion in the order of 3 Ma, falls in the scale of the range in duration between 10 000 and 100 000 previously discussed thrust-related sequences years. They include a basal transgressive part (Puigdefhbregas et al. 1986). In general, the pro- and an upper regressive part, and they are later- posed sequence partitioning for the Sant Llorenq ally persistent and mappable. The transgressive del Munt fan delta (L6pez-Blaneo et aL in press, surfaces are the fundamental sequence bound- fig. 17) does not fit to the global eustatic chart of aries. The transgressive-regressive couplets cor- Haq et al. (1987). This misfit, together with the respond to pulses of fan progradation in results of subsidence analysis, suggest that com- response to changes in sediment supply. posite megasequences are controlled by changes Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

20 A. MASCLE & C. PUIGDEF.~BREGAS

~rn

" I uxrmem oonl,n l' "" I domain, .~''~ . t Pie de Tolulre Els~krs I Sallent I E I _~ I I III.__:....

a 1~ 2~" 1 3~ 4~ .....

~llhnt

0 500 m

Fig. 11. Stratigraphic section concerning depositional sequence number 3 (A3), between Salient and Pla de Tolustre localities. 1, Les Vinyes olistostrome, slumps and debris flow deposits; 2, offshore marls; 3, nearshore sandstones; 4, fandeltaic Salient conglomerates; 5, unconformity; 6, surface of submarine gravity driven erosion; 7, submarine condensed section; 8, time line. (From Arburs et al. 1996, reprinted with permission.)

in sediment supply related to tectonics and, to It may be concluded, from this case study, that some extent, to climate. tectonics and climate are the main controls in It must be noted that cycles defined on proxi- supply dominated sequences, climate becoming mal fan reaches may, or may not coincide with downscale predominant (Amorosi et al. 1997). cycles defined on the coastal reaches of the sedi- A similar partitioning in three sequential ment wedge. Proximal fan sequences are more orders was obtained from a detailed study of the likely to be related to changes in slope gradients Ainsa basin fill (Fig. 14). The higher sequence in response to tectonic activity. When they do not order corresponds to the concept of uncon- fit with the sequences defined on the coastal formity bounded tectono-sedimentary unit reaches, it may be due to the fact that sediment (Garrido-Meglas 1973). They include a number supply is not equally distributed across the area of of transgressive-regressive sequences (second deposition. In other words, as previously disc- order), each of them resulting from stacking of ussed, different processes acting at different parts lower third order sequences. In all cases, of the sedimentation profile result in segmenta- sequences start with a transgressive event fol- tion of sequence boundaries (Dreyer et al. 1994). lowed by a regressive trend that includes a swift Fundamental sequences, in turn, can be progradation, which gradually becomes more generated by relative sea level changes, by aggradational and ends up with a prominent changes in sediment supply or by autocyclic pro- progradal maximum. cesses or, more likely, by all factors combined. In The distinction between sequence orders is this case it will not be possible to discriminate based on the character of the transgressive between them. events. First-order transgressions correspond to Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 21

. ,...~ O

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22 A. MASCLE& C. PUIGDEFABREGAS W-E A) Samifier unit base (46.59 + 0.1 Ma) -- , , ~.... reef ; -~-~ \ /

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~ scanillaFro. ~ Coscojuela level CretaceousUpper Bug level Entrembr~ unit t 9Cuisiart ~ La Pardina interval Samitier unit ~ Triassic Mesbn de LigOerre level __ 0 2.5 km ~ Mediano unit '- ' r----] Camporrotunointerval H =V Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

INTRODUCTION 23

Nummulites carbonate beds whose lateral conti- the Pyrenees. The technique proves to be useful nuity goes beyond the syncline-basin itself and in general to understand the flexural evolution can be found in neighbouring basins. Second- of the orogen and to estimate parameters other- order transgressions are Nummulites and patch- wise difficult to measure, such as palaeotopo- reef carbonate beds whose extent is restricted to graphic elevations, rates of shortening, the syncline basin, but whose lateral equivalents topographic growth and erosion, and to con- can be traced to overlay the upper delta plain of strain better already known concepts such as the the underlying sequence. Third-order transgres- definition of the evolutionary stages, and under- sions are limited to delta front. They may be standing of the linked hydrocarbon evolution. allocyclic, but also may be related to autocyclic processes, bounded by abandonment or minor flooding surfaces. The Betic thrust front model First-order sequences distinguished in the The understanding of the role of the salt in Ainsa basin range in thickness between 300 and thrust fronts, and the description of the Betic 800 m, have an approximate duration of 1.3 Ma thrust front model as an extruded lateral diapir (Bentham 1992) and closely compare to the com- interfering with the foreland basin fill, is an posite depositional sequences of Posamentier et important achievement of the IBS project. The al. (1988) and to the composite sequences of model can be applied in analogous thrust fronts L6pez-Blaneo et aL (in press). It should be also of other mountain chains, and may be of noted that delta-plain strata from first-order additional use in hydrocarbon exploration in sequences are often slightly tilted in relation to foreland basins. those of the overlying sequence, and that a distinct component of differential subsidence is appreciated, all suggestive of an important tec- Growth folds tonic control on the sequence organisation. Growth folds and their related growth strata As in the case of Sant Llorenq del Munt, the have been described at various localities lower the sequence order, the higher the proba- (Barr6me syncline, Sant Llorenq de Morunys, bility of introduction of new controlling factors B6ixols thrust and Mediano anticline). Model- other than tectonics, down to the lower order ling of these growth folds makes the estimation where the autocyclic control predominates. of rates of growth possible, and enhances the potential of predicting particular types of facies Discussion of results and traps in relation to the growth stratal geometries. The paper by Williams et al. (this The IBS Module on Foreland Basins is charac- volume), represents a first attempt to analyse the terized by the geographic dispersion of field relations between folding and alluvial fan sedi- areas, some of which have been studied from mentation at the level of the sedimentary outcrops and some from subsurface data. In process. addition, a diversity of results has been obtained by the different groups, each of them linked to their own research tradition. Far from an Role of tectonics in sequence stratigraphic undesired difficulty, this apparent heterogeneity partitioning constitutes an important added value to a project that, like the IBS, makes comparison Four orders of stratigraphic partitioning can be between different basins one of the main issues. distinguished. The foreland basin in itself consti- We have been through the main results of the tutes the first order of tectonostratigraphic par- various groups in the different areas, following a titioning in relation to the plate collision, down-scale sequence from the orogen to the subduction forces and growth of the orogen. The depositional sequences. Some of the more rele- successive piggy-back sub-basin stages consti- vant conclusions should, at this stage, be stressed tute the second order, related to the propagation and eventually discussed. of the thrust system. Tectono-sedimentary units and composite megasequences fall in this cat- egory. Composite sequences and fundamental Time-step restored cross-sections sequences constitute the third and fourth orders, Construction and modelling of time-step where climate and eustasy combine with all the restored cross-sections has been attempted in preceding tectonic controls in defining the

Fig. 13. 2D evolutive diagram for the Mediano anticline in a section perpendicular to the fold axis. The upper continental sediments have not been represented. (From Poblet et al. in press, fig. 18, reprinted with permission.) Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

24 A. MASCLE & C. PUIGDEFABREGAS

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INTRODUCTION 25 sequence architecture. The first two orders may It may be concluded that tectonics and climate be referred to as tectono-stratigraphic units, and (and therefore eustasy), interact to such a the last two as sequences. This is an advisable degree in sequence generation, so that discrimi- conservative proposal of sequence partitioning. nation between these factors becomes not only Many other and equally valid orders may be also difficult, but to some extent irrelevant. What proposed by adding intermediate subdivisions really matters, in terms of predictive potential, is and further extending the lower-scale end to the the understanding of sequence upbuilding autocyclic sequences. It is, nevertheless, our within the particular basin fill, and the inte- feeling that overclassification should be avoided. gration of this understanding as an additional It should be noted that the controls acting on piece in the geological knowledge of the area. a particular higher-sequence order are also present in all the lower orders. In other words, 'The authors wish to thank Tom Dreyer and Kjell-Owe when downscaling, the controlling factors are Hager for the review of the manuscript, and for their added, not substituted. This is contradictory to sensible and useful suggestions. Thanks are also due to P. Arbues, J. Corregidor, D. Garcia Castellanos, A. the concept that high-order sequences are exclu- Martinez, J. Poblet, J. Verges for allowing us to use sively controlled by tectonics, and low order, previously published figures, some of them not yet exclusively eustatic. published. As the aim of this paper is to give an over- It is also important to bear in mind that classi- view of the results of the IBS Project, and at the same fications of sequence orders are mere research time introduce the papers included in this volume, all strategies, only meant to help the understanding the authors and members of the Project are here of the dynamics of the basin-fill. In fact, although acknowleged.' sequence boundaries may be sharp, there is a continuum between plate collision, propagation of the orogenic wedge, and motion of a particular thrust, through a chain of unpredictable pro- References cesses of stress accumulation and release, finally AMOROSI, A., CAPORALE, L., PUIGDEFABREGAS, C. transmitted to the sedimentary record through a SEVERI, P. 1997. Correlation between drainage complex link of geomorphic processes. and Depositional Basins: Late Quaternary Drumond & Wilkinson (1996), based on a statis- Sequences From The Reno Fluvial System tical analysis of hierarchies in thickness and dura- (Northern Italy). In: ROGZRS, J. (ed.) 6th. Inter- tion of different orders of stratigraphic packages, national Conference on Fluvial Sedimentology, conclude that 'discrimination of stratigraphic University of Cape Town. Abstract volume, 7. hierarchies and their designation to cycle orders ARBUTUS,P., PI, E. & BERASTEGUI,X. 1996. Relaciones may constitute little more than the arbitrary sub- entre la evoluci6n sedimentaria del Grupo de division of an uninterrupted stratigraphic con- Areny el cabalgamiento de B6ixols. Geogaceta, 20, 446--449. tinuum'. The situation in which 'the use of a BEHRMANN J., BROWN K., MOORE J. C., MASCLE A. d: particular classification scheme tends to become TAYLOR E. 1988. Evolution of structures and a framework where in its very application serves fabrics in the Barbados Accretionary Prism. to suppress certain lines of inquiry' (Drumond & Insights from Leg 110 of the Ocean Drilling Wilkinson 1996) should be avoided. Program. Journal of Structural Geology, 10, 577-591. Segmented character of sequence BENTHAM,P.A. 1992. The tectonestratigraphic development of the western oblique ramp of the south- boundaries central Pyrenean thrust system, northern Spain. Doctoral Disertation, University of Southern From the case studies of Sant Lloren~ del Munt California, Los Angeles. and the Ainsa Basin it could be concluded that BERASTEGUI, X., LOSANTOS, M., MU~OZ, J. A. & sequence boundaries are formed by different PUIGDEF)d3REGAS, C. 1993. Tall geoldgic del processes in each of the three parts (subaerial, Pirineu Central 1/200.000. Publ. Inst. Cartogrfific shallow marine and deeper marine) of the sedi- de Catalunya. mentary profile. Sequence boundaries are there- CLAVELL,E. 1992. Geologia del petroli des les conques fore segmented, and their continuity interrupted tercigtres de Catalunya. Tesi Doctoral, Univ. at the coastline, between the alluvial plain and Barcelona. shallow marine, and at the upper slope, between CRUMEYROLLE,1 ~ 1987. Stratigraphie physique et sddi- mentogie des syst~mes de dOpOt de la Sequence de shallow and deeper basin. Santa Liestra (Eocene sud-pyrdndeen, PyrdnOes Within the sedimentary profile, considered aragonaises, Espagne). PhD Thesis, University of from the fluvial valley down to the basin floor, Bordeaux III. changes of gradient and a accomodation space DECELLES, P. G. & GILES, K. A. 1996. Foreland Basin differ from one profile segment to the next. Systems. Basin Research, 8, 105-123. Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

26 A. MASCLE & C. PUIGDEFABREGAS

DERAMOND, J., SOUQUET, P., FONDECAVE-WALLEZ,M. sistema deltaico y de plataforma carbondtica de la J. & SPETCH, M. 1993. Relationships between Formaci6n de Corones. Tesis Univ. Barcelona. thrust tectonics and sequence stratigraphy sur- GREBER, E., LEU W., BERNOUILLI, D., SCHUMACHER, faces in foredeeps: model and examples from the M. & WYSS, R. 1997. Hydrocarbon provinces in Pyrenees (Cretaceous-Eocene, France, Spain). the Swiss Southern Alps-a gas geochemistry and In: WILLIAMS, G. D. & DOBB, A. (eds) Tectonics basin modelling study. Marine and Petroleum and Seismic Stratigraphy. Geological Society, Geology, 14, 3-25. Special Publications London, 71, 193-219. HAQ, B. U., HARDENBOL,J. & VAIL,E R. 1987. Chronol- DREYER, T., WADSWORTH, J., ARBUI~S, P., PUIGDE- ogy of Fluctuating Sea Levels Since the Triassic. FABREGAS, C. & TAYLOR, A. M. 1994. Sequence Science, 235, 1156-1166. Architecture in a Tectonically Active Setting: The HARDY, S. & POBLET, J. 1994. Geometric and numeri- Sobrarbe Formation, Ainsa Basin, Spain. In: cal models of progressive limb rotation in detach- JOHNSON, S. D. (ed.) High Resolution Sequence ment folds. Geology, 22, 371-374. Stratigraphy: Innovations and Applications. HOMEWOOD, V., ALLEN, V. & WILLIAMS, G. 1986. Abstract Volume. University of Liverpool. Dynamics of the Molasse Basin of Western DRUMOND, C. N. & WILKINSON, B. H. 1996. Stratal Switzerland. In: ALLEN, P. A. & HOMEWOOD, P. Thickness Frequencies and the Prevalence of (eds), Foreland Basins. IAS Special publications, Orderedness in Stratigraphic Sequences. Journal 8, 199-219. of Geology, 104, 1-18. JIN, J.,AIGNER,T., LUTERBACHER,H. P., BACHMANG. H. DUVAL, B. C., CRAMEZ, C. & VALDt~S,G. E. 1995. Giant & MOLLER, M. 1995. Sequence stratigraphy and fields of the 80s associated with an 'A' subduction depositional history in the south-eastern German in S. America. Oil & Gas Journal, 17 July and 24 Molasse Basin. Marine and Petroleum Geology, July, 67-71 and 61-64. 12, 929-940. ECORS-PYRENEES TEAM 1988. The ECORS deep JOLIVET, D;, FAUGI~RES J. C., GRIBOULARD, R., DES- reflection seismic survey across the Pyrenees. BRUYERES,D. & BLANC,G. 1990. Composition and Nature, 331, 508-511. spatial organisation of a cold seep community on FAUGI~RES J. C., GONTHIER, E., GRIBOULARD R. & the South Barbados accretionary prism: tectonic, MASSE, L. 1993. Quaternary sandy deposits and geochemical and sedimentary context. Pro- canyons on the Venezuelan Margin and South grammes in Oceanography, 24, 24-45. Barbados accretionary prism. Marine Geology, LABAUME,P., HENRY,P., RABAUTE,A. & THE ODP LEG 110, 115-142. 156 SCIENTIFIC PARTY 1995. Circulation et sur- FONDECAVE-WALLEZ, M. J., SOUQUET, P. & GOURI- pression de l'eau interstitielle dans le prisme d'ac- NARD, Y. 1988. Synchronisme des s6quences s6di- cr6tion Nord-Barbade. Comptes Rendus de mentaires du comblement fini Cr6tac6 avec les l'Acad6mie des Sciences, Paris, 320, s6rie IIa, cycles eustatiques dans les Pyr6n6es Centro- 977-984. M6ridionales (Espagne). Comptes Rendus de LARROQUE, CH., CALASSOU, S., MALAVIEILLE, J. & l'Academiedes Sciences, Paris, 307(2), 289-293. CHANIER, E 1995. Experimental modelling in FONNESU, E 1984. Estratigrafia fisica y andlisis de facies forearc basin development during accretionary de la secuencia de Figols entre el rio Noguera Pal- wedge growth. Basin Research, 7, 255-268. laresa e Iscles (Provs. de Ldrida y Huesca). PhD LE VOT, M., BITEAU, J. J. & MASSET, J. M. 1996. The Thesis of the Universitat Aut6noma de Barcelona. Aquitaine Basin: oil and gas production in the FORD, M., WILLIAMS, E. A., ARTONI, A., VERGI~S, J. & foreland of the Pyrenean fold-and-thrust belt. HARDY, S. 1996. Progressive evolution of a fault- New exploration perpectives. In: ZIEGLER, E & related fold pair from growth strata geometries, HORVATH, E (eds) Structure and Prospects of the Sant Llorenq de Morunys, SE Pyrenees. Journal Alpine Basin and Forelands. Edition du Mus6um, of Structural Geology, 19, 413--441. Paris, 15%172. GARCIA-CASTELLANOS,D., FERNANDEZ, M. & TORNI~, LOPEZ BLANCO, M., MARZO, M., BURBANK, D., M. Numerical modeling of foreland basin for- VERGES, J., ROCA, E., ANADON, P. & PINA, J. In mation: a program relating thrusting. Flexure, press. Tectonic and climatic control on the sediment geometry and lithosphere rheology. development of large foreland fan deltas: Paper accepted in Computers & Geoscience, in Montserrat and Sant Llorenq del Munt systems press. (middle Eocene, Ebro basin, NE Spain). GARRIDO-MEG~AS, A. 1973. Estudio geoldgico y In: MARZO, M. & STEEL, R. (eds) Sedimentology relacidn entre tect6nica y sedimentacidn del Secun- and Sequence Stratigraphy of the Sant Llorenf del dario y el Terciarion de la vertiente meridional Munt clastic wedges (SE Ebro Basin, NE Spain). Pirenaica en su zona central. PhD Thesis of the Sedimentary Geology special issue. University of Granada. MART~,!EZ, A., VERGI~S, J. & Mur~oz, J. m. 1988. GIESKES, J. M., BLANC, G.,VROLIJK AND THE ODP LEG Secuencias de propagaci6n del sistema de cabal- 110 Scientific Party 1989. Hydrogeochemistry in gamientos de la terminacidn oriental del manto the Barbados Accretionary Complex: Leg 110 del Pedraforca y relaci6n con los conglomerados ODP. Palaeogeography, Palaeoclimatology, sinorog6nicos. Acta Geologica Hispania, 23, Palaeoecology, 71, 83-96. 119-128. GIMI~NEZ, J. 1993. Andlisis de cuenca del Eoceno MARTINEZ RIGS, A., BERASTEGUI,X. & LOSANTOS,M. inferior de la Unidad Cadi (Pirineo oriental): el 1996. 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INTRODUCTION 27

emplazamiento en una secuencia de bloque 1983. Syntectonic Coastal offlap and Concurrent superior de las l~iminas cabalgantes que forman el Turbidite Deposition: the Upper Cretaceous manto inferior del Pedraforca. Geogaceta, 20, Aren sandstone in the South-Central Pyrenees, 450--453. Spain. Sedimentary Geology, 34, 185-218. MASCLE A., ENDIGNOUX L. & CHENNOUF T. 1990. NIJMAN, W. & NIO, S. D. 1975. The Eocene Montahana Frontal accretion and piggyback basin develop- Delta (Tremp-Graus Basin, Prov. Lerida and ment at the southern edge of the Barbados Ridge Huesca, Southern Pyrenees, N. Spain). IAS 9th accretionary complex. In: Proceedings of ODP International Sedimentology Congress, Nice, Leg 110 Scientific Results. College Station,TX, Excursion Guidebook, 19, part B. 17-29. PAPPON, J. P. 1969. Etude de la zone sud-Pyr~ndenne --, VIALLY, R., DEVILLE, E., BIJU-DUVAL, B. & RoY, dans le Massif de Turb6n (Prov. de Huesca - J. R 1996. The petroleum evaluation of a tectoni- Espagne). These 3e cycle. Univ. Toulouse. cally complex area: the western margin of the PERMANYER, A., VALLES, D. & DORRONSORO, C. 1988. Southeast Basin (France). Marine and Petroleum Source rock potential of an Eocene carbonate slope: Geology, 13, 941-961. the Arm~ncies Formation of the Southern Pyrenean MELLERE, D. 1993. Thrust-generated, back-fill stack- Basin, Northeast Spain. American Association of ing of alluvial fan sequences, South Central Pyre- Petroleum Geologists Bulletin, 72,1019. nees, Spain (La Pobla de Segur Conglomerates). POBLET, J., Mulqoz, J. A., TRAVE, A. & SERRA-KIEL, J. In: FROSTICK, L. & STEEL, R. (eds) Tectonic Quantifying the kinematics of detachment folds Control and Signatures in Sedimentary Succes- using the 3D geometry: application to the sions. Special Publications of the International Mediano anticline (Pyrenees, Spain). Geological Association of Sedimentologists. 20, 259-276. Society of America Bulletin, in press. MILLAN, H., DEN BEZEMER,Z. VERGt~S, J., MARZO, M., POSAMENTIER, H. W., JERVEY, M. T. & VAIL, P. R. 1988. MuIqoz, J. A., ROCA, E., CIRI~S, J., ZOETEMEIJER, Eustatic controls on clastic deposition I - concep- R., CLOETING, S. & PUIGDEF.~BREGAS, C. 1995. tual framework. In: WILGUS, C. K. & HASTINGS,B. Palaeoelevation and effective elastic thickness S. (eds) Sea level changes: an integrated approach. evolution at mountain ranges: inferences from SEPM. Special Publications, 42, 109-124. flexural modeling in the Eastern Pyrenees and PUIGDEF~.BREGAS, C. & SOUQUET, P. 1986. Tectono- Ebro Basin. Marine and Petroleum Geology, 12, sedimentary Cycles and Depositional Sequences 917-928. of the Mesozoic and Tertiary from the Pyrenees. MOORE, J. C. & VROLIJK, P. 1992. Fluids in accretionary Tectonophysics, 129, 172-203. prisms. Reviews of Geophysics, 30, 113-135. , MuIqoz, J. A. & MARZO, M. 1986. Thrust belt Mutqoz, J.A. 1992. Evolution of a continental collision development in the Eastern Pyrenees and related belt: ECORS-Pyrenees crustal balanced cross- depositional sequences in the southern forelan section. In: MCCLAY, K. (ed.) Thrust Tectonics. basin. In: ALLEN, P. A. & HOMEWOOD, P. (eds) Chapman & Hall, London, 235-246. Foreland Basins. Special Publications, 8, 229-245. --, MCCLAY, K. & POBLET, J. 1994. Synchronous -- & VERGI~S, J. 1992. Thrusting and foreland extension and contraction in frontal thrust sheet basin evolution in the southern Pyrenees. In: of the Spanish Pyrenees. Geology, 22, 921-924. MCCLAY, K. (ed.) Thrust Tectonics, Chapman & MUTI'I, E., DATTILO, P., SGAVETTI, M., TEBALDI, E., Hall, London, 247-254. BUSATTA, C. & MORA, S. 1994. Sequence strati- REILLE, J. L. 1971. Les relations entre tectogdnOse et graphic response to thrust propagation in the sOdimentation sur le versant sud des Pyrdndes Cen- upper cretaceous Aren Group, south-central trales. Th6se, Univ. Montpellier. Pyrenees. In: Mufti, E., DAVOLI, G., MORA, S. & RIBA, O. 1964. Estructura sedimentaria del Terciario SGAVETTI, M. (eds) Second high-resolution continental de la Depresi6n del Ebro en su parte sequence stratigraphy conference, June 1994, riojana y navarra. Aportaci6n Esp. al XX Congr Tremp. Spain. Part III, 25-36. Geogr. Int. 1964, 127-138.

, LUTERBACHER, H. P., FERRER, J. & ROSELL, J. -- 1976. Syntectonic unconformities of the Alto 1972. Schema stratigrafico e lineamenti di facies Cardener, Spanish Pyrenees: a genetic interpre- del paleogeno marino della zona centrale sud- tation. Sedimentary Geology, 15, 213-233. pirenaica tra Tremp (Catalogna) e Pamplona ROBERTS, G. 1990. Structural control on fluid migration (Navarra). Memorie della Societd Geologica Ital- through the Rencurel thrust zone, Vercors, French iana, 11, 391-416. Sub-Alpine chain. In: ENGLAND, R. & FLEET, A. J. --, SEGURET, M. & SGAVETTI, M. 1988. Sedimen- (eds) Petroleum Migration, Geological Society, tation and deformation in the Tertiary sequences of London, Special Publications, 59, 245-262. the southern Pyrenees. AAPG Mediterranean SASSI, W. & DEVILLE, E. Maturity modelling in thrust Basins Conference, Nice, Field Guide 7. Special belts, methodology and cases histories. AAPG Publication of the Institute of Geology, Uni- Bulletin, in press. versity of Parma, Italy. SIM0, A. 1985. Secuencias deposicionales del Cretdcico --, SGAVETrI, M. & REMACHA,E. 1984. Le relazioni superior de la Unidad del Montsec (Pirineo tra piataforme deltizie a sistemi torbiditici nel Central). Tesi doctoral. Univ. de Barcelona. Bacino Eocenico Sudpirenaico di Tremp-Pam- SOLER, M. & PUIGDEFABREGAS,C. 1970. Lfneas gen- plona. Giornale di Geologia Ser. 3, 46(2), 3-32. erales de la geologia del Alto Arag6n Occidental. NAGTEGAAL, P. J. C., VAN VLIET, A. & BROUWER, J. Pirineos, 96, 5-20. Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021

28 A. MASCLE & C. PUIGDEFABREGAS

TEN HAAF, E. 1966. Le Flysch sud-Pyr6n6en le long du CIRr J., DEN BEZEMER, T., ZOETEMEIJER, R. & rio Ara (Huesca). Pirineos, 81-82, 143-150. CLOETINGH, S. 1995. Eastern Pyrenees and related TOURET, J. & VAN HINTE, J. (eds) 1992. Le role des foreland basins: pre-, syn- and post-collisional fluides dans les zones de subduction. Koninklijke crustal-scale cross-sections. Marine and Petroleum Nederlandse Akademie van Wetenschappen Pro- Geology, 12, 893-915. ceedings, 95, 293-403. VIALLY,R. 1994. The southern French Alps Paleogene VAIL, P. R. • MITCHUM, R. M. 1977. Seismic stratigra- basin: subsidence modelling and geodynamics phy and global changes of sea level, Part 1: implications. In: MASCLE, A. (ed.) Hydrocarbons Overview. AAPG Memoirs, 26, 51-52. and Petroleum Geology of France, Springer- VERGt~S, J. 1993. Estudi geologic del vessant sud del Veflag, 281-294. Pirineu oriental i central. Evoluci6 cinemdttica en VROLHK, P. ~r SHEPPART, S. 1991. Syntectonic carbon- 3D. Tesi Doctoral. Univ. Barcelona. ate veins from the Barbados accretionary prism & BURBANK, D. W. 1996. Eocene-Oligocene (ODP Leg 110): record of paleohydrology. Sedi- thrusting and basin configuration in the eastern mentology, 38, 671-690. and central Pyrenees (Spain). In: FRIEND, P. E & ZOETEMEIJER, R. 1993. Tectonic modeling of foreland DABRIO, C. J. (eds) Tertiary Basins of Spain. Cam- basins: thin skinned thrusting, syntectonic sedi- bridge University Press, 120-133. mentation and lithospheric flexure. PhD Thesis, , MILLAN,H., ROCA, E., MU~OZ, J. A., MARZO, M., Vrije Universiteit, Amsterdam.