Pyrenean Foreland Basin Research Articles

Deciphering Paleocene‐Eocene Thermal Maximum Climatic Dynamics: Insights From Oxygen and Hydrogen Isotopes in Clay Minerals of Paleosols From the Southern Pyrenees

AbstractThis study focuses on the Paleocene‐Eocene Thermal Maximum (PETM), a hyperthermal event characterized by a rapid increase in global temperature (5–8°C) over 20 ka, in the Southern Pyrenean Foreland Basin. Although there is evidence of increased flood discharge and erosion in the Southern Pyrenees, how paleoclimatic conditions and weathering evolved remains to be assessed. This study focuses on the catchment scale climatological changes recorded in the clay minerals of floodplain paleosols, giving insights into how rainfall affected the weathering regime during and after the hyperthermal event. The oxygen (δ18O) and hydrogen (δD) isotope compositions were analyzed in two clay fractions in paleosols of the Esplugafreda continental section. The clay minerals comprise a dominant smectite‐rich assemblage, which indicates a predominantly seasonal, semi‐arid climate throughout the section. Two positive excursions in the δ18O record during the Pre‐Onset Excursion (POE) and the Syn‐PETM support an increase in air near‐surface temperature. Using the δD and δ18O smectite fractionation factors, we estimate a Mean Annual Air Temperature (MAAT) of 24.2 ± 1.0°C for the POE and 27.0 ± 0.8°C for the Syn‐PETM. The δD values show a relatively stable composition during the climatic disturbance, which suggests that this mid‐latitude catchment was overall characterized by low yearly rainfall, with a peak in extreme events during the body of the PETM and a trend toward aridification during the recovery phase of the PETM, supported by the paleosol morphotype. These climatic conditions suggest a kinetically controlled weathering regime, where physical transport of the sediments played a primary role as a denudation mechanism.

Chronostratigraphy and tectono‐sedimentary history of the Eastern South Pyrenean foreland basin (Ripoll Syncline, North‐East Spain)

AbstractThis paper contributes to an understanding of the tectono‐sedimentary evolution of the South Pyrenean foreland system by reviewing the chronostratigraphic framework of the basin infill in its eastern sector. Six sections are analysed and cross‐correlated to build a 6.5 km thick composite magnetostratigraphy that represents the complete record of the Cadí Nappe in the Ripoll Syncline. New and previous magnetostratigraphic sections are integrated with available biostratigraphy to provide a new age calibration of the sedimentary succession of the Cadí Nappe, encompassing from Palaeocene to Middle Lutetian age. The proposed correlation with the Geomagnetic Polarity Time Scale aims at best reconcile magnetostratigraphic data with the regional biochronology built on the marine Shallow Benthic Zonation (SBZ biozones), the continental mammalian biochronology (MP levels) and the newly collected charophyte data. A subsidence analysis was performed on the calibrated composite succession, resulting in two well‐defined intervals bounded by a hiatus. A Palaeocene to Early Eocene interval with low (11–21 cm/kyr) total subsidence rates, and an Early to Middle Eocene interval, characterised by high (70–75 cm/kyr) total subsidence rates. The detailed trends in both subsidence and sedimentation mark the development and evolution of the foreland depozones, from distal foreland depozones to foredeep and wedge‐top depozones, relative to the emplacement of the Pedraforca Nappe and Cadí Thrust Nappe. The most pronounced sedimentary shift in the Cadí Nappe occurred at 49 Ma, with the rapid drowning of the carbonate platforms and its transition into talus and deep basinal environments. Carbonate platforms collapsed and resedimented on the talus of the elongated trough, newly formed parallel to the orogenic front. This marked the onset of tectonic subsidence triggered by the submarine emplacement of the Lower Pedraforca Nappe. The emersion of the orogenic wedge drove the entry of siliciclastics, lagged by 1 Myr, into the Ripoll Trough. The foredeep filled rapidly (5.5 km thickness in less than 7 Myr) compared to other South Pyrenean regions, favoured by its semi‐enclosed palaeogeography. The emplacement of the Vallfogona Thrust as early as the Middle Lutetian (43 Ma) brought the Cadi Nappe into a wedge‐top setting. However, the Ripoll growth syncline continued acting as a temporary sink for alluvial sedimentation while a foredeep developed further south in the autochthonous Ebro Basin. The flexural response of the Iberian plate to the tectonic thickening of the Axial Zone counterbalanced for a period the local uplift of the Cadi Nappe, providing accommodation space for the top sediments filling the Ripoll Syncline.

Unraveling the sediment routing systems evolution of the south Pyrenean foreland basin during the lower to middle Paleogene period

Orogenesis plays a crucial role in creating, modifying, and disrupting sediment routing fairways. Reconstructing past source to sink systems is a critical step to unravel the geological history, mandatory to disentangle tectonic and climatic forcings, and to understand the perturbations that affected the overall system. The Paleocene-Eocene period is a debated early stage of the early Pyrenean orogeny, characterized by the piggy-back style tectonic partitioning of sub-basins as the deformation front propagates towards the southern foreland. An important issue is to understand how sedimentary systems reacted and reorganized in response to this dynamic scenario. and whether the stratigraphic and sediment provenance results align with the envisioned scenario.In this paper we aim at contributing to the paleogeographic, sedimentologic and tectono-sedimentary evolution of the South-Pyrenean foreland basin by reviewing the chronostratigraphic framework of the basin infill in its south-central sector (the Ager sub-basin in the Serres Marginals thrust sheet). We built five new magnetostratigraphic sections, which together encompass most of the Paleogene record, aimed to best reconcile magnetostratigraphic data with the defined biostratigraphic framework of the region including marine Shallow Benthic Zones (SBZ biozones) and continental mammalian localities (MP levels). Detailed trends in subsidence show the development and evolution of the foreland depozones, from forebulge to foredeep and wedge-top setting, relative to the successive emplacement of the Montsec and Serres Marginals thrust sheets.A correlation with the eastern portion of the foreland basin (Lower-Middle Pedraforca and Cadí Thrust Sheets) and adjacent northern Graus-Tremp basin (Montsec Thrust Sheet) was feasible and seeks to contribute to the tectono-sedimentary evolution of the South-Pyrenean foreland in the light of a source to sink approach. Our proposal includes a new paleogeographic evolution of the area in a series of paleogeographic maps from Late Thanetian to Late Cuisian times.

Interplay of Multiple Sediment Routing Systems Revealed by Combined Sandstone Petrography and Heavy Mineral Analysis (HMA) in the South Pyrenean Foreland Basin

Combined sandstone petrography and heavy mineral analysis allow to decipher different sediment routing systems that could not be resolved by one method alone in the South Pyrenean foreland basin. We apply this approach to deltaic and alluvial deposits of the southern part of the Jaca basin, and in the time equivalent systems of the nearby Ainsa and Ebro basins, in order to unravel the evolution of source areas and the fluvial drainage from the Eocene to the Miocene. Our study allows the identification of four petrofacies and five heavy-mineral suites, which evidence the interplay of distinct routing systems, controlled by the emergence of tectonic structures. Two distinct axially-fed systems from the east coexisted in the fluvial Campodarbe Formation of the southern Jaca basin that were progressively replaced from east to west by transverse-fed systems sourced from northern source areas. In the late stages of evolution, the Ebro autochthonous basin and the Jaca piggy-back basin received detritus from source areas directly north of the basin from the Axial Zone and from the Basque Pyrenees. Coupling sandstone petrography with heavy mineral provenance analysis allows challenging the existing model of the South Pyrenean sediment dispersal, highlighting the relevance of this approach in source-to-sink studies.

Hybrid compactive faults formed during burial in micritic limestone (Montpellier area, France)

Detailed fieldwork, analyses including SEM and EBSD investigations, and dynamic inversion method are used to describe and propose a conceptual model for the formation of compactive faults related to burial in micritic lacustrine-palustrine limestones (Eocene, Pyrenean foreland basin, South of France). These faults are characterized by sinuous shape, no calcite precipitation and no macroscopic fault core evidencing their development in poorly consolidated sediments. The fault pattern is composed of two sub-synchronous systems of conjugate meter-scale faults (a normal-sense system and a strike-slip system), each one with high dihedral angle (130°) and sometimes showing continuity between faults of both sets. Their pervasive distribution, angle relative to the maximum principal stress direction, incipient shear-offset, porosity reduction, their crystallographic preferred orientation, and the “ridge and groove” morphology of their slickenside, all argue for a hybrid compactive and shear deformation process combining disaggregation, comminution, and pressure-solution-recrystallization processes. A conceptual model using estimated stress path and theoretical yield envelope is proposed to explain their formation along the end cap part during early burial and compaction of the limestone beds. The slope to the South associated to the syn-sedimentary basin flexure is proposed to trigger their specific pattern.

Thermal record of the building of an orogen in the retro‐foreland basin: Insight from basement and detrital thermochronology in the eastern Pyrenees and the north Pyrenean basin (France)

AbstractAn understanding of the evolution of foreland basins improves our knowledge of how mountain belts have grown and helps us to decipher events which may not be preserved in the orogen. The infilling of the north Pyrenean retro‐foreland basin (Aquitaine Basin, France) during the main exhumation of the Pyrenees and its corresponding thermal history have not been fully investigated. We applied apatite fission track (AFT) and (U‐Th‐Sm)/He (AHe) methods coupled with inverse thermal modelling on both the detrital Eocene (47 to 33 Ma) syn‐orogenic Palassou conglomerates of the eastern part of the Aquitaine Basin and basement samples from the North Pyrenean Zone and the Axial Zone of the Pyrenees. Apatite crystals were separated from granitic cobbles found in the conglomerates. AFT ages for detrital samples range from 27 ± 2 to 43 ± 4 Ma, and AHe ages from 13 ± 1 to 76 ± 5 Ma. For in situ massifs AFT ages range from 35 ± 2 to 90 ± 17 Ma and AHe ages from 39 ± 2 and 80 ± 5 Ma. AFT ages for detrital samples are close to deposition ages, whereas AHe ages are older and younger than deposition ages and show a partial thermal resetting due to burial. A detailed analysis of the ages obtained and thermal histories derived from modelling shows that ages reflect (a) exhumation from 70 to 55 Ma revealed by a long stay in the partial retention zone (PRZ), (b) a Palaeocene–Eocene cooling in the Pyrenees, (c) a post‐depositional episode of moderate heating of the sediments in the basin represented by partially reset young AHe and AFT ages compared to deposition ages and (d) an early to mid‐Miocene final exhumation of the basin deposits as evidenced by young AHe ages and geological constrains. These results reflect a common event with the south Pyrenean foreland basin that is characterized by high piedmont aggradation from the late Eocene to the Miocene. The aggradation of sediments is possibly connected with well‐known high elevation low relief surfaces in the core of the Pyrenees and followed by a Miocene exhumation event that is already observed on the southern flank. However, the timing of the aggradation and exhumation events could be different between the north and the south. Erosion occurred most probably during the early to mid‐Miocene in the north and during the late Miocene–early Pliocene in the south.

A diverse crinoid fauna (Echinodermata, Crinoidea) from the Lower Eocene of the Gulf of Languedoc (Corbières, Aude, southern France)

Detailed studies of the middle Ilerdian (lower Ypresian) blue marls of the Gulf of Languedoc (Corbières, Aude, France), belonging to the north Pyrenean foreland basin, have revealed a more abundant and diverse crinoid fauna than previously documented from the Lower Eocene. Here we describe five species of stalked crinoids in the family Rhizocrinidae (Cherbonniericrinus requiensis n. sp., ?Democrinus elongatus, Globulocrinus amphoraformis n. gen., n. sp., Pseudoconocrinus doncieuxi and P. lavadensis n. sp.), one barnacle-like species in the stalkless family Holopodidae (Holopus plaziati n. sp.) and a single feather star in the family Conometridae (Amphorometra atacica). Several sites have yielded brachials and rhizoids in addition to abundant aboral cups and columnals indicating in situ fossilisation of the dissociated skeletal elements. P. lavadensis n. sp. and ?D. elongatus have been collected only from outcrops located in the upper part of the middle blue marls, while P. doncieuxi predominates, with a wide range of morphological variation, in the lower blue marls. The fossil assemblage at the locality of Réqui near Montlaur differs from the others in the smaller size of most individuals and the presence of H. plaziati n. sp., C. requiensis n. sp., G. amphoraformis n. gen., n. sp., and P. doncieuxi suboblongus n. subsp. This particular association with high juvenile mortality corresponds to an unstable environment with mixed substrates (muddy and rocky). The crinoid fauna of the Corbières appears to be the most diverse of Early Eocene age known to date. With the fauna of the London Clay, a boreal formation of the same age, it shares the presence of the genera Democrinus and Amphorometra in an open-sea environment. A comparison with extant faunas allows the depth of deposition at the Ypresian sites in the Gulf of Languedoc to be estimated between from 100 and 140 meters.

Sediment provenance and routing evolution in the Late Cretaceous–Eocene Ager Basin, south‐central Pyrenees, Spain

AbstractThis study constrains the sediment provenance for the Late Cretaceous–Eocene strata of the Ager Basin, Spain, and reconstructs the interplay between foreland basin subsidence and sediment routing within the south‐central Pyrenean foreland basin during the early phases of crustal shortening using detrital zircon (DZ) U‐Pb‐He double dating. Here we present and interpret 837 new DZ U‐Pb ages, 113 of which are new DZ (U‐Th)/He double‐dated zircons. U‐Pb‐He double dating results allow for a clear differentiation between different foreland and hinterland sources of Variscan zircons (280–350 Ma) by leveraging the contrasting thermal histories of the Ebro Massif and Pyrenean orogen, recorded by the zircon (U‐Th)/He (ZHe) ages, despite their indistinguishable U‐Pb age signatures. Cretaceous–Paleocene sedimentary rocks, dominated by Variscan DZ U‐Pb age components with Permian–Triassic (200–300 Ma) ZHe cooling ages, were sourced from the Ebro Massif south of the Ager Basin. A provenance shift occurred at the base of the Early Eocene Baronia Formation (ca. 53 Ma) to an eastern Pyrenean source (north‐east of the Ager Basin) as evidenced by an abrupt change in paleocurrents, a change in DZ U‐Pb signatures to age distributions dominated by Cambro‐Silurian (420–520 Ma), Cadomian (520–700 Ma), and Proterozoic–Archean (>700 Ma) age components, and the prominent emergence of Cretaceous–Paleogene (<90 Ma) ZHe cooling ages. The Eocene Corçà Formation (ca. 50 Ma), characterized by the arrival of fully reset ZHe ages with very short lag times, signals the accumulation of sediment derived from the rapidly exhuming Pyrenean thrust sheets. While ZHe ages from the Corçà Formation are fully reset, zircon fission track (ZFT) ages preserve older inherited cooling ages, bracketing the exhumation level within the thrust sheets to ca. 6–8 km in the Early Eocene. These DZ ZHe ages yield exhumation rate estimates of ca. 0.03 km/Myr during the Late Cretaceous–Paleocene for the Ebro Massif and ca. 0.2–0.4 km/Myr during the Eocene for the eastern Pyrenees.

Tectonic and sediment provenance evolution of the South Eastern Pyrenean foreland basins during rift margin inversion and orogenic uplift

The Cretaceous to Oligocene detrital record in the southern Eastern Pyrenees is utilized to address the degree to which precursor basin architecture and hyper-extensional rift structures impacted subsequent sedimentary provenance and dispersal systems and foreland basin evolution. This study presents new isotopic provenance analysis of detrital zircon UPb and (UTh)/He double-dating, and detrital rutile UPb and trace element geochemistry to track sediment provenance evolution. Late Cretaceous-Paleocene sediments show zircon with dominantly Variscan UPb and Jurassic-Early Cretaceous ZHe cooling ages that are derived from southeastern Catalan Coastal Ranges and eastern Corsica-Sardinia regions, and localized structural inversion along inherited Mesozoic extensional faults and erosional recycling of syn-rift sediments. Eocene deposits have multimodal UPb ages that stratigraphically upsection change to unimodal Variscan ages, with the appearance and upsection increase in Pyrenean ZHe ages, and increase in Variscan aged detrital rutile that record a significant shift in sediment source area to northern sources recording exhumation and unroofing of the Axial Zone Paleozoic basement sources, and development of new ramp-flat style structures in the Southern Pyrenean Zone fold-thrust belt. During the Oligocene, incipient foreland basin deposits were cannibalized and recycled into the foreland basin as thrusting advanced toward the foreland. The Eastern Pyrenean foreland basin records a different provenance history from Central Pyrenean Tremp Basin, suggesting the basins were segmented throughout the Late Cretaceous to Oligocene, while the Ripoll and Ager basins appear to have shared similar source areas. The sediment provenance evolution coupled with Pyrenean fault activity and shortening rates, hinterland exhumation, foreland basin subsidence, and climate proxies presents a detailed dataset to understand these relationships within the Eastern Pyrenean orogenic system and highlight the dominant control precursor basins and structural inheritance has on the subsequent fold-thrust belts and foreland basin evolution.

Syn‐orogenic fluid flow in the Jaca basin (south Pyrenean fold and thrust belt) from fracture and vein analyses

AbstractThis study aims at understanding the origin and nature of syn‐orogenic fluid flow in the Jaca basin from the South Pyrenean fold and thrust‐belt, as recorded in calcite and quartz veins of the Sierras Interiores (Spain) and the turbiditic basin, which cover upper Cretaceous to Late Eocene syntectonic deposits. The fracture network consists of a classical pattern of transverse and longitudinal fractures related to Layer Parallel Shortening (LPS) and folding respectively. Veins filled equally about the third of fractures in the carbonate shelf and turbidites. Carbon and oxygen isotopes of calcite veins mostly indicate precipitation from isotopically buffered water, consistent with high water‐rock interaction. In the Sierras Interiores, petrographical observations and fluid inclusion microthermometry are consistent with two distinct stages of precipitation. The first stage is characterized by relatively low Th and low salinities (155–205 °C and 0.5–3.2 wt% eq. NaCl). The second stage, which was characterized both by the formation of mode‐I joints and by mode‐I reactivation of pre‐existing veins, shows higher Th and salinities (215–270 °C and 2.2–5.7 wt% eq. NaCl). Waters recorded in the second stage are interpreted to have interacted with underlying Triassic evaporites and flowed along major thrusts before vein precipitation, which are locally in thermal disequilibrium with host‐rocks. We suggest the transition from a rather closed hydrological system during the first stage of vein formation, interpreted to have occurred during Eaux‐chaudes thrusting (upper Lutetian‐Bartonian), to a more open hydrological system during the second stage, which likely occurred during Gavarnie thrusting (Priabonian‐early Rupelian). Finally, we also document the migration in space and time of hydrothermal pulses along the South Pyrenean Foreland Basin, related to the westward propagation of major thrusts during the Pyrenean orogeny.

Detrital zircon (U‐Th)/(He‐Pb) double‐dating constraints on provenance and foreland basin evolution of the Ainsa Basin, south‐central Pyrenees, Spain

AbstractSouth central Pyrenean foreland basin fill preserves the eroded remnants of the early stages of fold‐thrust belt evolution and topographic growth. Specifically, the Eocene Hecho Group in the Ainsa Basin contains a succession of turbiditic channels and levees deposited in the transition zone between the fluvial‐deltaic and deep marine depozones. Detailed isotopic provenance analyses allow for the reconstruction of sediment sources of the ancient sediment routing systems. This study presents 2332 new detrital zircon (DZ) U‐Pb ages and 246 new DZ double‐dated (U‐Th)/(He‐Pb) ages from 19 turbiditic and fluvio‐deltatic sandstones in the Ainsa Basin. These data indicate a progressive provenance shift from Cadomian/Caledonian plutonic and metamorphic rocks of the eastern Pyrenees to Variscan plutonic rocks in the central Pyrenees. Minor sediment contributions from sources located to the S and SE of the basin are seen throughout the section. New DZ (U‐Th)/He results identify four main cooling events: Pyrenean orogenesis (~56 Ma), initial basin inversion (~80 Ma), Cretaceous rifting (~100 Ma), and pre‐Mesozoic cooling ages related to earlier tectonic phases. This study imposes new constraints on the paleogeographic evolution of the Pyrenees and illustrates that high‐frequency fluctuations in sediment delivery processes and sediment routing introduce superimposed noise upon the basin‐scale long‐term provenance evolution during orogenesis.

Lithium saltworks of the Salar de Atacama: A model for MgSO4-free ancient potash deposits

Potash basins similar to those in the geological past no longer exist at present. There are only hypersaline lakes such as those in the Tibetan Plateau where carnallite [KCl·MgCl2·6H2O] precipitates. Given that the purpose of common saltworks is to obtain NaCl, the halitic stage is not exceeded. By contrast, saltworks extracting lithium by solar evaporation reach more advanced stages of brine evolution and saline precipitation. In the Salar de Atacama saltworks, with a relative humidity commonly below 30% (monthly average), salts precipitate following a sequence of halite [NaCl], sylvite [KCl], carnallite and bischofite [MgCl2·6H2O] and display a useful model of evolution similar to that which gave rise to MgSO4-free potash deposits in the past. Prismatic-acicular gypsum [CaSO4·2H2O], the main accessory mineral, is transformed into a less hydrated calcium sulfate, probably anhydrite [CaSO4], during carnallite precipitation. Mineral crystal size and annual sedimentary thickness of each paragenesis are compared with those in ancient potash deposits. The behavior of sylvite and carnallite as cements is observed at the onset of their precipitation in ponds where both minerals coexist with previous halite. Millimeter cyclicity due to day-night thermal variations is observed in these saltworks, whereas cm- and mm-cyclicities have been interpreted in ancient sites as annual (regular) and intra-annual (irregular), respectively. Conditions similar to those existing at the Salar de Atacama were necessary to preserve carnallite, which is commonly the most evolved mineral in the ancient deposits. The development of potash deposits in the South Pyrenean Foreland Basin and the Rhine Graben, near the Eocene-Oligocene boundary, is attributed to global aridity and cooling and to the basin restriction associated with a decrease in the ocean level caused by the spread of the Antarctic ice cap.

The Bartonian-Priabonian marine record of the eastern South Pyrenean foreland basin (NE Spain): a new calibration of the larger foraminifers and calcareous nannofossil biozonation

This study presents a combined biostratigraphic (calcareous nannofossils, larger foraminifers) and magnetostratigraphic study of the Middle and Late Eocene marine units of the Igualada area, eastern Ebro Basin. The studied sections of Santa Maria de Miralles and La Tossa encompass the complete marine succession of the Santa Maria Group, where assemblages rich in larger foraminifers have been studied since the early 1950's. A total of 224 paleomagnetic sites and 62 biostratigraphic samples were collected along a 1350m-thick section that ranges from chron C20n to chron C16n (~43Ma to ~36Ma). The resulting magnetostratigraphy-based chronology challenges existing chronostratigraphic interpretations of these units and results in a new calibration of the biostratigraphic zonations. The base of calcareous nannofossil Zone NP19-20 is pinned down to an older age than its presently accepted attribution, whereas the time span assigned to Zone NP18 is significantly reduced. A revised calibration of larger foraminifers indicates that Zone SBZ18, formerly assigned exclusively to the late Bartonian, extends its range to the earlymost Priabonian, the Bartonian stage being almost entirely represented by Zone SBZ17. A division of Zone SBZ18 into two subzones is proposed.

An inventory of the marine and transitional Middle/Upper Eocene deposits of the Southeastern Pyrenean Foreland Basin (NE Spain)

In the southeastern Ebro Foreland Basin, the marine deposits of Lutetian and Bartonian age show excellent outcrop conditions, with a great lateral and horizontal continuity of lithostratigraphic units. In addition, the rich fossil record -mainly larger foraminifers-, provides iostratigraphic data of regional relevance for the whole Paleogene Pyrenean Basin, that can be used for the Middle Eocene biocorrelation of the western Tethys. This contribution is a sedimentary and biostratigraphic synthesis of the basic outcrops and sections of the Lutetian and Bartonian marine and transitional deposits in the southeastern sector of the Ebro Foreland Basin.

Nummulitic banks in the upper Lutetian ‘Buil level’, Ainsa Basin, South Central Pyrenean Zone: the impact of internal waves

AbstractNummulites,a particularly abundant and diverse genus of larger benthonic foraminifera, formed huge accumulations (banks) during the Eocene, which are often good hydrocarbon reservoirs, especially in North Africa. Despite their economical interest, these accumulations are not well‐understood and their origin is still under discussion. Reasons for this debate are the absence of livingNummulitesaccumulations and the high‐variability of facies, including the size, shape and extension of the banks, which reflect the array of processes controlling sediment production and accumulation. The nummulitic banks near Santa María de Buil, in the Ainsa Basin (South Pyrenean Foreland Basin) are composed of recurrent facies associations within mappable bed units bounded by physical surfaces. The depositional processes that produced theNummulites deshayesiaccumulations are interpreted considering the shape of the banks, the type of bounding surfaces, the distribution of sedimentary textures,Nummulitestest shapes and the associated skeletal components within the banks. This integrative analysis indicates that nummulitic banks accumulated from mass flows, with very poor sediment sorting. Textural and compositional differences among banks suggest that globoseNummulitesthrived in the shallower part of the mesophotic zone with abundant nummulithoclasts, whereas flat nummulitic forms thrived in deeper mesophotic, clay‐dominated settings. Interbedded with nummulitic banks, coral biostromes and coral mounds bearingOperculina,DiscocyclinaandAsterocyclina, representin situaccumulation near the base of the photic zone. Internal waves (waves that propagate along the pycnocline) are thought to be the triggering mechanism for the density flows. Internal waves and induced bottom currents are sporadic but strong enough to bring sediments into suspension. In contrast to surface waves (both fair‐weather and storm), whose impact is strongest near the sea surface and decreases with bathymetry, the impact of internal waves is usually strongest in the mid‐shelf region and weaker in shallow water. This explains the compositional character of the nummulitic banks.

Closing and continentalization of the South Pyrenean foreland basin (NE Spain): magnetochronological constraints

ABSTRACTThis paper presents new magnetostratigraphic results from a 1100‐m‐thick composite section across the marine to continental sediments of the central part of the SE margin of the Ebro basin (NE Spain). Integration with existing marine and continental biochronological data allows a robust correlation with the geomagnetic polarity time scale. The resulting absolute chronology ranges from 36.3 to 31.1 Ma (Priabonian to Rupelian), and yields an interpolated age of ∼36.0 Ma (within chron C16n.2n) for the youngest marine sediments of the eastern Ebro basin. This age is in concordance with a reinterpretation of earlier magnetostratigraphic data from the western South Pyrenean foreland basin, and indicates that continentalization of the basin occurred as a rapid and isochronous event. The basin continentalization, determined by the seaway closure that resulted from the uplift of the western Pyrenees, was probably coincident with a mid‐amplitude eustatic sea level low with a maximum at 36.2 Ma. The base level drop that followed the basin closure and desiccation does not appear associated to a significant sedimentary hiatus along the margins, suggesting a late Eocene shallow marine basin that rapidly refilled and raised its base level after the seaway closing. Rapid basin filling following continentalization predates the phase of rapid exhumation of the Central Pyrenean Axial Zone from 35.0 to 32.0 Ma, determined from the thermochronology data. It is possible then that sediment aggradation at the front of the fold‐and‐thrust belt could have contributed to a decrease in the taper angle, triggering growth of the inner orogenic wedge through break‐back thrusting and underplating. Contrasting sedimentation trends between the western and eastern sectors of the South Pyrenean foreland indicate that basin closing preferentially affected those areas subjected to sediment bypass towards the ocean domain. As a result, sediment ponding after basin closure is responsible for a two‐fold increase of sedimentation rates in the western sector, while changes of sedimentation rates are undetected in the more restricted scenario of the eastern Ebro basin.

Integrated calcareous nannofossil biostratigraphy and magnetostratigraphy from the uppermost marine Eocene deposits of the southeastern Pyrenean foreland basin: evidences for marine Priabonian deposition

An integrated magneto-biostratigraphic study, based on calcareous nannofossils, was carried out on the Eocene uppermost marine deposits of the southeastern Pyrenean foreland basin. The study was performed along six sections of the upper portion of Igualada Formation, cropping out in the Vic area. Common late Middle/Upper Eocene nannofossil assemblages allow recognizing, within a normal magnetozone or immediately below, the FO of Istmolithus recurvus, which identifies the base of NP19 Zone, in the Priabonian. This event occurs within C16n.2n magnetozone in several oceanic and Mediterranean sections, which allows the correlation of the normal magnetozone in the Vic area to chron C16n.2n. This challenges previous magnetostratigraphic interpretations in the Vic area that correlated the uppermost marine sediments to chron C17n. The estimated age for the FO of I. recurvus is 36 Ma and collectively with the magnetostratigraphic data indicates that the uppermost marine sediments in the basin are of Priabonian age. The new results indicate that the entire chronology of the marine strata needs reassessment. The thickness of chron C16n.2n varies from 45 m in the Collsuspina area (southern sector) to about 270-290 m in the Sant Bartomeu del Grau area (northern sector), which is indicative of a marked asymmetry in the basin deposition.

Author index

The aim of this paper is to test a new approach combining ¢eld studies and sequence stratigraphic analysis to gain insights into the in£uence of local deformation on the sequence stratigraphic architecture of syndeformational deposits.To assess the in£uence of fold growth on coeval deltaic sedimentation, we investigated the development of the Pico del Aguila anticline, a kilometre-scale compressive fold in the Jaca basin, located on the south-western border of the Pyrenean foreland basin. We analyse six stratigraphic sections located along the structure, identifying the facies associations and palaeoenvironments.This leads us to propose a new sequence stratigraphic framework, taking into account three orders of depositional cycle (genetic units, minor cycles and major cycles) and their stacking pattern.We quantify the rates of accommodation variation, sediment accumulation and relative uplift of the anticline, showing that minor cycles are driven by accommodation variations of regional scale rather than sediment supply variations.We also demonstrate that the uplift rate of the anticline axis is continuously decreasing through time.The growth of the anticline exerts four diierent types of control: (i) on the distribution of sedimentary thicknesses, (ii) on the depositional pro¢le (shallower facies are preserved on the hinge of the anticline), (iii) on the thickness ratio between the progradational and retrogradational sub- cycles (P/R ratio) of the depositional sequences (most of the thickness diierences arise during the prograding trend) and (iv) locally, on the timing of the transition from progradational to retrogradational trend between the hinge and the synclines.The growth of the anticline consistently distorts the geometry of the three scales of depositional cycles, to an extent depending upon the diierence in subsidence rate between the hinge and the synclines (i.e. the uplift rate).The distortions of the ratio between the thicknesses of progradational and retrogradational sub- cycles and the variation in the timing of the trend inversion can be explained by a simple superimposition of continuous uplift of the anticline (local deformation) and regional variations of relative sea level (eustasy and/or foreland basin subsidence).

Discussion: Basin infill architecture and evolution from magnetostratigraphic cross-basin correlations in the southeastern Pyrenean foreland basin

Research Article| February 01, 2003 Discussion: Basin infill architecture and evolution from magnetostratigraphic cross-basin correlations in the southeastern Pyrenean foreland basin J. Serra-Kiel; J. Serra-Kiel 1Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Martí Franques s/n E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar C. Ferràndez-Cañadell; C. Ferràndez-Cañadell 1Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Martí Franques s/n E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar L. Cabrera; L. Cabrera 1Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Martí Franques s/n E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar M. Marzo; M. Marzo 1Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Martí Franques s/n E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar P. Busquets; P. Busquets 1Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Martí Franques s/n E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar F. Colombo; F. Colombo 1Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Martí Franques s/n E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar S. Reguant S. Reguant 1Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Martí Franques s/n E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar GSA Bulletin (2003) 115 (2): 249–252. https://doi.org/10.1130/0016-7606(2003)115<0249:DARBIA>2.0.CO;2 Article history received: 13 Mar 2000 accepted: 12 Aug 2000 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation J. Serra-Kiel, C. Ferràndez-Cañadell, L. Cabrera, M. Marzo, P. Busquets, F. Colombo, S. Reguant; Discussion: Basin infill architecture and evolution from magnetostratigraphic cross-basin correlations in the southeastern Pyrenean foreland basin. GSA Bulletin 2003;; 115 (2): 249–252. doi: https://doi.org/10.1130/0016-7606(2003)115<0249:DARBIA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search The chronostratigraphy of the middle Eocene–upper Eocene successions of the southeastern Pyrenean foreland basin has been revised by Taberner et al. (1999). This contribution was based on the correlation of the magnetic polarity stratigraphy (MPS) for several partial stratigraphic sections recording the Paleogene marine succession throughout a north-south transect of 25 km in the Vic area (northeast Spain). The new chronostratigraphic proposal by Taberner et al. (1999) is in contradiction with earlier biostratigraphic studies of the area based on larger foraminifera, implying a shift of ∼5 m.y. (range, 4.8–6.4 m.y.) in the age of the earliest marine sediments. Furthermore,... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Marine and Transitional Middle/Upper Eocene Units of the Southeastern Pyrenean Foreland Basin (NE Spain)

The stratigraphic basis of this work has allowed the use of larger foraminifers in the biostratigraphic characterisation of the new Shallow Benthic Zones (SBZ). This part of the volume presents a description of the sedimentary cycles formed by the transgressive-regressive systems of the Lutetian and Bartonian in the southeastern sector of the Ebro Foreland Basin.Concerning the Lutetian deposits studied in the Amer-Vic and Emporda areas, four sedimentary cycles have been characterised. The first and second are found within the Tavertet/Girona Limestone Formation (Reguant,1967;Palli,1972), while the third and fourth cycles cover the Coll de Malla Marl Formation (Clavell et al.,1970), the Bracons Formation (Gich,1969,1972), the Banyoles Marl Formation (Almela and Rios,1943),and the Bellmunt Formation (Gich,1969,1972). In the Bartonian deposits studied in the Igualada area,two transgressive-regressive sedimentary cycles have been characterised in the Collbas Formation (Ferrer,1971),the Igualada Formation (Ferrer,1971),and the Tossa Formation (Ferrer,1971). The Shallow Benthic Zones (SBZs)recognised within the Lutetian are the following:SBZ 13, from the Early Lutetian, in the transgressive system of the first cycle;SBZ 14,from the Middle Lutetian, in the second cycle and the lower part of the transgressive system of the third cycle; SBZ 15,from the Middle Lutetian, in the remaining parts of the third system; SBZ 16, from the Late Lutetian,throughout the fourth cycle.The association of larger foraminifers in the first and second cycles of the Bartonian in the Igualada area has been used as the basis for the definition of SBZs 17 and 18 recognised in the Bartonian of the western Tethys.