Sediment routing systems of the Eocene Tremp-Jaca basin: Stratigraphic analysis and numerical models

[eng] The Eocene South-Pyrenean foreland basin provides a continuum of outcrops representing a Source to Sink sediment routing system from subaerial canyons to deep marine environments. On this context, the specific objective of this study is: (a) to contribute to the knowledge of the chronostratigraphy and the basin infill of the study area; (b) to analyze the evolution of the sedimentation rates on the Tremp-Jaca basin; and (c) to generate numerical models to (i) assess the sediment routing and sediment balance and, (ii) to evaluate the basin response to the propagation of climatic and tectonic signals. Two new magnetostratigraphic sections are built on the Tremp-Jaca basin; the Olsón (Ainsa basin) and the Yebra de Basa sections (Jaca basin). The Olsón section provides a late Lutetian to early Priabonian age for the Escanilla formation in the Ainsa basin, and the same age range is provided on the Yebra de Basa section for the strata encompassed between the Sabiñánigo sandstone and the Santa Orosia formation. The age constrains provided by these new sections and the data sorted from a systematic review of the literature have been used for an analysis of the sedimentation rates in the Tremp-Jaca basin. The studied sections were decompacted by backstripping to correct the differential burial compactions between the sections. This study shows that sedimentation rates may not show the expected variations related to depozone distribution. This lack of correlation between the depozones and the sedimentation rates are consequence of the lagged response to deformation front shifts and the complexity in the structure of the wedge-top. This complexity result in a widespread subsidence related to the emplacement of basement units in the hinterland. Also underfilled forelands may develop high sedimentation rates in the initial stages of wedge-top as basin gradients are a continuation to those developed in the previous foredeep phase. Sedimentation rates in overfilled areas are controlled by accommodation. In underfilled areas, the main control is clastic supply. During graded shelf regressive stages, maximum sedimentation rates are in foreset areas. In the transgressive stages, maximum sedimentation rates are at the topset. In out-of-grade periods, high sedimentation rates are in deep marine areas. The results obtained above have been used to feed forward stratigraphic models, using Dionisos software, to test and understand the different parameters affecting the sedimentary infill of the basin. A first model on the sediment routing systems of the Tremp-Jaca basin, based on the data from the sedimentation rates analysis, succeeds on reproducing the sedimentary routes that can be deduced from the paleocurrent patterns on the Tremp-Jaca basin, validating the inputted data. A second forward stratigraphic model, based on architectural and cyclostratigraphic analysis from previous works, determines that the high-frequency Milankovitch cyclicity of the Belsué-Atarés delta (Sierras Exteriores) is primarily forced from the sediment supply and secondary from the eustasy.[cat] A les conques Eocenes Sudpirenaiques d’avantpaís hi ha un continu d’afloraments representatius de les rutes sedimentàries del sistema Source to Sink, des de canons subaeris fins a ambients marins profunds. En aquest context, aquest estudi té com a objectiu (a) contribuir al coneixement de la cronoestratigrafia i el reompliment de les conques de l'àrea d'estudi; (b) analitzar l’evolució de les taxes de sedimentació a la conca de Tremp-Jaca; i (c) generar models numèrics per (i) avaluar les rutes sedimentàries i el balanç sedimentari i (ii) avaluar la resposta de la conca a la propagació de senyals climàtics i tectònics. S’han construït dues noves seccions magnetostratigràfiques a la conca de Tremp-Jaca; les seccions d’Olsón (conca d’Aïnsa) i de Yebra de Basa (conca de Jaca). La secció d’Olsón proporciona una edat Luteciana superior fins a Priaboniana inferior per a la part superior de la formació Escanilla a la conca d’Aïnsa. A la secció de Yebra de Basa s’obté la mateixa franja d’edat pels estrats entre el gres de Sabiñánigo i la formació de Santa Orosia . Les edats proporcionades per aquestes noves seccions i les dades obtingudes a partir d'una revisió sistemàtica de les dades publicades, s'han utilitzat per a una anàlisi de les taxes de sedimentació de la conca de Tremp-Jaca. Les seccions estudiades han estat descompactades per backstripping per corregir l’enterrament diferencial que resulta en estadis de compactació diferents entre les seccions estudiades. Aquest estudi mostra que les taxes sedimentaries poden no mostrar les variacions esperades en relació a la distribució de les depozones. Aquesta manca de correlació entre les depozones i les taxes de sedimentació són conseqüència del retard en la resposta als canvis en la posició del front de deformació al wedge-top. Aquesta complexitat resulta en l’expansió de la subsidència relacionada amb l’emplaçament d’unitats basals al hinterland. Aquesta complexitat resulta en una major subsidència relacionada amb l’apilament d’unitats basalts al hinterland. També les conques d'avantpaís underfilled poden desenvolupar altes taxes de sedimentació en els estadis inicials del wedge-top, ja que els gradients sedimentaris són la continuació dels desenvolupats a la fase de foredeep anterior. Les taxes de sedimentació a les àrees overfilled estan controlades per l’acomodació. A les àrees underfilled, el control principal és l’aport de sediments. Durant els episodis regressius de les plataformes gradades, les taxes de sedimentació màximes es donen al topset. En els períodes no-gradats, les taxes de sedimentació més elevades es troben a les àrees marines profundes. Els resultats obtinguts s’han utilitzat per alimentar dos forward stratigraphic models, utilitzant el software Dionisos, per provar i entendre els diferents paràmetres que defineixen el reompliment de la conca. Un primer model en els sistemes de rutes sedimentàries de la conca de Tremp-Jaca, basat en les dades provinents de l’anàlisi de les taxes de sedimentació, té èxit en reproduir les rutes sedimentàries que es poden deduir dels paleocorrents de la conca de Tremp-Jaca, validant les dades introduïdes. Un segon model, a partir de dades arquitecturals i cicloestratigràfiques de treballs previs, determina que les ciclicitats de Milankovitch d’alta freqüència del delta de Belsué-Atarés (Sierras Exteriores) són primàriament forçats per l’aport sedimentari i secundàriament per l’eustàcia

10 Myr evolution of sedimentation rates in a deep marine to non-marine foreland basin system: tectonic and sedimentary controls (Eocene, Tremp-Jaca basin, Southern Pyrenees, NE Spain)

The propagation of the deformation front in foreland systems is typically accompanied by the incorporation of parts of the basin into wedge-top piggy-back basins, this process is likely producing considerable changes to sedimentation rates (SR). Here we investigate the spatialtemporal evolution of SR for the Tremp-Jaca Basin in the Southern Pyrenees during its evolution from a wedge-top, foreredeep, forebulge configuration to a wedge-top stage. SR were controlled by a series of tectonic structures that influenced subsidence distribution and modified the sediment dispersal patterns. We compare the decompacted SR calculated from 12 magnetostratigraphic sections located throughout the Tremp-Jaca Basin represent the full range of depositional environment and times. While the derived long-term SR range between 9.0 and 84.5 cm/kyr, compiled data at the scale of magnetozones (0.1 to 2.5 Myr) yield SR that range from 3.0 to 170 cm/kyr. From this analysis three main types of depocenter are recognized: a regional depocenter in the foredeep depozone; depocenters related to both regional subsidence and salt tectonics in the wedge-top depozone; and a depocenter related to clastic shelf building showing transgressive and regressive trends with graded and non-graded episodes. From the evolution of SR we distinguish two stages. The Lutetian Stage (from 49.1 to 41.2 Ma) portrays a compartmentalized basin characterized by variable SR in dominantly underfilled accommodation areas. The markedly different advance of the deformation front between the Central and Western Pyrenees resulted in a complex distribution of the foreland depozones during this stage. The Bartonian-Priabonian Stage (41.2 to 36.9 Ma) represents the integration of the whole basin into the wedge-top, showing a generalized reduction of SR in a mostly overfilled relatively uniform basin. The stacking of basement units in the hinterland during the whole period produced unusually high SR in the wedge-top depozone

Fluvio-deltaic record of increased sediment transport during the Middle Eocene Climatic Optimum (MECO), Southern Pyrenees, Spain

The early Cenozoic marine sedimentary record is punctuated by several brief episodes (&lt;200 kyr) of abrupt global warming, called hyperthermals, that have disturbed ocean life and water physicochemistry. Moreover, recent studies of fluvial–deltaic systems, for instance at the Palaeocene–Eocene Thermal Maximum, revealed that these hyperthermals also impacted the hydrologic cycle, triggering an increase in erosion and sediment transport at the Earth's surface. Contrary to the early Cenozoic hyperthermals, the Middle Eocene Climatic Optimum (MECO), lasting from 40.5 to 40.0 Ma, constitutes an event of gradual warming that left a highly variable carbon isotope signature and for which little data exist about its impact on Earth surface systems. In the South Pyrenean foreland basin (SPFB), an episode of prominent deltaic progradation (Belsué–Atarés and Escanilla formations) in the middle Bartonian has been usually associated with increased Pyrenean tectonic activity, but recent magnetostratigraphic data suggest a possible coincidence between the progradation and the MECO warming period. To test this hypothesis, we measured the stable-isotope composition of carbonates (δ13Ccarb and δ18Ocarb) and organic matter (δ13Corg) of 257 samples in two sections of SPFB fluvial–deltaic successions covering the different phases of the MECO and already dated with magnetostratigraphy. We find a negative shift in δ18Ocarb and an unclear signal in δ13Ccarb around the transition from magnetic chron C18r to chron C17r (middle Bartonian). These results allow, by correlation with reference sections in the Atlantic and Tethys, the MECO to be identified and its coincident relationship with the Belsué–Atarès fluvial–deltaic progradation to be documented. Despite its long duration and a more gradual temperature rise, the MECO in the South Pyrenean foreland basin may have led, like lower Cenozoic hyperthermals, to an increase in erosion and sediment transport that is manifested in the sedimentary record. The new data support the hypothesis of a more important hydrological response to the MECO than previously thought in mid-latitude environments, including those around the Tethys.</p

Paleogeographic and Sedimentary evolution of the South-Pyrenean Foreland basin

During the Paleogene and Neogene the NE Iberian plate underwent significant paleogeographic changes driven by the Iberian and European plate collision and the resulting formation of the Pyrenean orogen and its corresponding foreland basin. Shortening resulted in the advance of the orogenic wedge, emplacement of allochthonous units, and progressive basin partitioning. Sediment transfer systems reacted to the evolving paleogeographic scenario, shifting from forebulge to foredeep and wedge-top settings. Critical reorganizations included successive shifts from open to close drainage conditions, which had an strong impact on accommodation, and the stratigraphic architecture of the basin infill, overfill and later erosion. The aim of this work is to synthesize the paleogeographic and sedimentary evolution of the south-pyrenean foreland, with emphasis on the reconstruction of sediment routing, the evaluation of sedimentation rate trends, the timing of sedimentary shifts and the analysis of their causes. Stratigraphic data are compiled in a comprehensive magnetostratigraphy-based chronostratigraphic framework. Besides, sedimentary and structural data are put together to produce a series of palinspastically restored paleogeographic maps, which reflect five key stages in the evolution of the region. These stages include: 1) the Late Cretaceous tectonic inversion of the extended Iberian margin; 2) the Early Eocene formation of the southern Pyrenean foredeep; 3) the Middle Eocene widening and overfilling; 4) the late Eocene shift into an internal drainage; and 5) the Late Miocene drainage opening and erosion. In the light of these results, the variable role of tectonics, climate and eustacy at different time scales are discussed

Origin and propagation of sedimentary sequences throughout the Escanilla fluvial routing system (South Pyrenean foreland basin)

EGU2020: Sharing Geoscience Online, 4-8 may 2020During middle Eocene, the Escanilla fluvial system transported and deposited material from East to West in the southern Pyrenees foreland basin. The paleogeography and sedimentology of the source to sink system is well established. The temporal framework is made of scattered low resolution magnetostratigraphies, and a robust temporal framework in the most distal (Olson) and most proximal (Sis) parts of the system. We built a new high resolution magnetostratigraphy from the middle part of the system, the Lascuarre section. The correlation of Lascuarre with the high resolution magnetostratigraphies and the integration of these data with other available chronological constraints results into a robust complete temporal framework from source to sink. Sedimentological analyses of the Lascuarre section allow recognizing a set of sedimentary sequences throughout the record. Here we present the result of the analyses, and discuss the relative weight of the different forcing. Particularly, we elucidate the role of tectonics in relation to subsidence distribution patterns, and also the distinct expression of climate. Eventually, we identify and explore the signal propagation mechanisms of climate aberrations and of quasi-regular orbital variations along the routing system

10 Myr evolution of sedimentation rates in a deep marine to non-marine foreland basin system: Tectonic and sedimentary controls (Eocene, Tremp–Jaca Basin, Southern Pyrenees, NE Spain)

The propagation of the deformation front in foreland systems is typically accompanied by the incorporation of parts of the basin into wedge-top piggy-back basins, this process is likely producing considerable changes to sedimentation rates (SR). Here we investigate the spatial-temporal evolution of SR for the Tremp–Jaca Basin in the Southern Pyrenees during its evolution from a wedge-top, foreredeep, forebulge configuration to a wedge-top stage. SR were controlled by a series of tectonic structures that influenced subsidence distribution and modified the sediment dispersal patterns. We compare the decompacted SR calculated from 12 magnetostratigraphic sections located throughout the Tremp–Jaca Basin represent the full range of depositional environment and times. While the derived long-term SR range between 9.0 and 84.5 cm/kyr, compiled data at the scale of magnetozones (0.1–2.5 Myr) yield SR that range from 3.0 to 170 cm/kyr. From this analysis, three main types of depocenter are recognized: a regional depocenter in the foredeep depozone; depocenters related to both regional subsidence and salt tectonics in the wedge-top depozone; and a depocenter related to clastic shelf building showing transgressive and regressive trends with graded and non-graded episodes. From the evolution of SR we distinguish two stages. The Lutetian Stage (from 49.1–41.2 Ma) portrays a compartmentalized basin characterized by variable SR in dominantly underfilled accommodation areas. The markedly different advance of the deformation front between the Central and Western Pyrenees resulted in a complex distribution of the foreland depozones during this stage. The Bartonian–Priabonian Stage (41.2–36.9 Ma) represents the integration of the whole basin into the wedge-top, showing a generalized reduction of SR in a mostly overfilled relatively uniform basin. The stacking of basement units in the hinterland during the whole period produced unusually high SR in the wedge-top depozoneAgència de Gestió d'Ajuts Universitaris i de Recerca, Grant/Award Number: 2017SGR596; Secretaría de Estado de Investigación, Desarrollo e Innovación, Grant/Award Number: BES-2015-073302 and CGL2014-55900-P; Swiss National Science Foundation, Grant/Award Number: 200020_18201

Orbital forcing in transgressive/regressive high-frequency sequences (Belsué Syncline, Eocene, South-Pyrenean foreland Basin, Spain).

34th IAS Meeting of Sedimentology (10-13 Sep 2019, Rome, Italy)The Belsué syncline crops out in an area of ca. 14 km2 in the southern margin of the Jaca basin (South-Central Pyrenees) which records the transition from marine to non-marine sedimentation over a period of 5.7 Myr during the Eocene (Bartonian-Priabonian). The studied strata are up to 900 m thick and represent a westwards-prograding delta complex, including prodelta (Margas de Arguis formation), delta front (Belsué-Atarés formation) and fluvial beds (Campodarbe formation). These strata were deposited in between two growing anticlines trending perpendicular to the direction of progradation: the Pico del Águila and Gabardiella anticlines. Throughout the syncline a number of transgressive-regressive cycles are governed by Milankovitch eccentricity cycles (Kodama et al., 2010; Garcés et al, 2014). In this work we aim at assessing the mechanisms driving sedimentary cycles by using forward stratigraphic modeling. To build the model we have used the DIONISOS OpenFlow (Granjeon & Joseph, 1999) to build a reference model of the Belsué syncline, on which different experiments using the available orbital solutions were tested. We explore the nature of changes in the sedimentary record in response to variations in eustacy, sediment supply, and water discharge. These parameters were modulated at different intensities, and tested independently and in different combinations using a Monte-Carlo approach. The results have been compared with the Belsué outcrops to find the best match with the transgressive-regressive cycles previously defined. In particular, our work is focused on the analysis of the geometry of the different delta front regressive units. In order to evaluate the solutions, a numerical comparison between a representative sedimentary log in the syncline and a virtual log at the same position in the model was carried out, and also a visual comparison of the outcropping section with the virtual equivalent section

Reconstructing the Early Eocene Sediment Routing System of the south-eastern Pyrenees

EGU2020: Sharing Geoscience Online, 4-8 may 2020The Early Eocene was the period of most intense plate collision during the building of the Pyrenean orogen. Tectonic loading of the overriding European plate caused flexure of the subducting Iberian plate and formation of an elongated foredeep connected westward with the Atlantic Ocean. The uneven distribution of the Triassic evaporites caused the formation of a thrust salient in the central Pyrenees related to tectonic inversion of the pre-existing Mesozoic rift basins. This process ultimately resulted in the partitioning of the foreland basin and the isolation of the Ripoll Basin in the East from the Tremp-Graus and Ainsa-Jaca basins in central and western south-Pyrenees. The precise timing and the surface processes related to this reorganization of the sediment routing system remains not fully understood. Early tectono-stratigraphic reconstructions envisaged a scenario of isolation of the eastern Pyrenean Foreland basin in the early Eocene, while other recent studies on detrital zircon geochronometry suggest that the sedimentary transfer system in the Tremp-Graus basin connected upstream to the Ripoll basin until middle Lutetian times. In this contribution we discuss constraints on the early Eocene paleogeography of the south-eastern Pyrenees in the light of a revised chronostratigraphic scheme. We put forward a scenario that tries reconciling all available structural, stratigraphic, petrologic, geochronologic, and sedimentologic datasets

Interrelations among tectonic and sedimentary controls on 10 Myr sedimentation rates evolution (South-Pyrenean foreland basin)

Foreland basins are characterized by the propagation of the deformation front towards the foredeep. This is typically accompanied by the incorporation of foredeep portions to wedge-top depozones leading to piggy-back basins. The transition from foredeep to wedge-top is usually related to a reduction of the sedimentation rates (SR). The specific objective of this study is to investigate the evolution in time and space of the SR along the Tremp-Jaca basin (TJB) by integrating the published data with strategically selected new logs and relate them with the local subsidence. At Eocene the TJB was divided in two connected sub-basins, the proximal thrust-top Tremp-Graus basin and the distal foredeep Ainsa-Jaca-Pamplona basin. A dynamic tectonic setting modified the subsidence distribution, and conditioned the sediment routing system. With the objective of approaching subsidence and the sediment routing system, a comparison of SR was made from the study of 12 logs representative of different positions in the basin, all accompanied with sufficient chronostratigraphic information, particularly magnetostratigraphy data. Ten of these logs (total thickness of ... m) were taken from literature; the other two were measured for the purpose, adding 2325 m of section completed with magnetostratigraphy data. The logs were correlated into a panel and the basis to derive compaction-corrected sedimentation rates for each magnetozone. Three main types of depocenter were recognized: (a) regional tectonic dominated, associated to the foredeep depozone; (b) local tectonic dominated, related to thrusting, folding and salt tectonics on the wedge-top depozone; and (c) depositional dominated related to the underfilled to overfilled accommodation front advance, with different situations associated with transgressive or regressive events. Our results show an evolution of the SR values and their relation to the depozone migration coeval to the TJB evolution allowing us to distinguish two evolutionary stages of the TJB Eocene: The Lutetian stage with a very variable SR in a more compartmentalized basin (wedge-top, foredeep and forebuldge depozones) controlled by the Pyrenean tectonic structures, and the Bartonian-Priabonian stage, when the whole area had been incorporated into the wedge-top, with generalized reduction of the SR values in a more connected basin. However, SR distribution expected for the main depozones is not always stated since local variations related to the basin infill and tectonics of the wedge-top modify the general trends