Eocene Formations Research Articles

Seismic reflection data interpretation and petrophysical evaluation of the Meyal area, the Potwar Basin, Pakistan

Despite extensive exploration efforts in the Potwar Basin, a thorough understanding of the structural framework and reservoir characteristics within the Meyal Field remains critical for pinpointing potential hydrocarbon zones. This study aims to integrate geology and geophysics to emphasize the structural and stratigraphic interpretation of the Meyal Field, including reservoir characterization using seismic and well-log data. The seismic interpretation of six seismic lines focuses on four key reflectors: the Kamlial, Chorgali, Sakesar, and Salt Range Formations. The Eocene Chorgali and Sakesar Formations are of primary importance for exploration and production. Structural analysis revealed that the Meyal anticline is a plunging structure bounded by a back thrust to the north and a fore thrust to the south, suggesting a favorable location for hydrocarbon accumulation. Time-depth contour maps derived from seismic data further delineate potential sites for future investigations. The well correlation indicated an uplift toward the Meyal-2 compared with Meyal-5, signifying a shallowing trend attributed to thrust tectonics. This tectonic regime has rendered the area highly prospective for hydrocarbon exploration, with thrusting and oblique-slip faulting enhancing the reservoir qualities of Eocene Formations. The petrophysical evaluation revealed favorable reservoir characteristics, including an average porosity ranging from 0% to 12% with an effective porosity of approximately 7.5%, water saturation up to 42%, and hydrocarbon saturation reaching 58% within the pay zone of the reservoir. These findings suggest that the Sakesar and Chorgali Formations within the Meyal oil field hold promise as productive hydrocarbon reservoirs. The integrated study provides valuable insights into the structural framework and reservoir characterization, highlighting the potential of the Eocene Formations as productive hydrocarbon reservoirs supported by favorable structural configurations and petrophysical properties.

Serravallian–Tortonian (Miocene) folding in the Amakusa region, northern Ryukyu arc: Possible subduction resumption of the Philippine Sea Plate

AbstractEocene to Lower Miocene coal‐bearing formations in northern and western Kyushu, northern Ryukyu arc, are folded, and the horizontal compression has been attributed to the opening of the Japan Sea or to the significant movement along the Median Tectonic Line and its southwestern extension. However, the timing and implication of the folding are not well understood. To deal with these issues, we studied the Amakusa region where the folded Eocene strata with a total thickness of a few kilometers. Paleomagnetic directions of Middle Miocene intrusions and of Late Miocene lavas were measured in this study to apply the fold test to judge the relative timing of the folding and magmatism. As a result, the concentration of the directions was improved by the tilt‐correction, indicating the folding younger than the magmatism. Our detailed geological mapping revealed that the folding is older than a horizontally‐lying basaltic lava which yielded a K–Ar age of 6.8 Ma, because folded Eocene formations were truncated and unconformably blanketed by the lava. In addition, we found that some of the normal faults trending perpendicular to the folds were reactivated as transfer faults after the normal faulting which also postdated the magmatism. This reactivation is concordant with the above‐mentioned relative timing. Synthesizing geological data from surrounding regions, we conclude that the folding was probably contemporaneous with the Taiwan‐Shinji fold belt which grew in the Ryukyu and southwest Japan backarcs. Since the simultaneous compression affected not only these regions but also northeast Japan, the compression possibly resulted from the resumed subduction of the Philippine Sea Plate in the Serravallian–Tortonian time.

Eocene extensional tectonics in the Amakusa region, northern Ryukyu arc

AbstractPaleogene surface tectonics in Japan is not well understood because of the paucity of onshore Paleogene stratigraphic records except for those from accretionary complexes. Paralic Paleogene formations remaining in SW Japan are usually so thin that it is difficult to decipher the tectonics from them. However, the Eocene paralic sedimentary package with a thickness of kilometers indicates syn‐depositional tectonic subsidence by a few kilometers in the Amakusa archipelago, west of Kyushu Island. Thus, we made a detailed geological map of the Eocene formations in an area of ~50 square kilometers in the northwestern part of the archipelago. We identified NE‐SW and NW‐SE trending normal faults, most of which were recognized by previous researchers, and also discovered low‐angle faults. NW‐SE trending ones are known to be of the Miocene. NE‐SW trending and low‐angle normal faults are the oldest map‐scale structures in the Eocene ones. It is not obvious within the above‐mentioned area whether those normal faults are accompanied by growth strata. However, the significant southeastward thickening of the Eocene formations across the Amakusa archipelago suggests that they filled a large half graben with the basin margin fault along the eastern side of the archipelago. This basin model is consistent with the N‐S to NW‐SE transport directions of the low‐angle and NE‐SW trending normal faults. Since many NE‐SW to EW trending Eocene grabens were formed in the offshore regions west of Kyushu Island and in the East China Sea, the Amakusa region was probably a northeastern branch of the rift system. The geologic structures and depositional ages of the Eocene formations indicate that the Eocene extensional tectonics removed the overlying strata to some extent for the high‐P/T Takahama Metamorphic Rocks which crops out to the south of our study area.

Strain and stress gradients through the backarc regions of Miocene western Japan: A new type of arc-parallel extension

The overriding lithosphere is occasionally stretched parallel to the consuming plate boundary. Such arc-parallel extension manifests itself mostly in forearc regions. Here, we report unique arc-parallel extension, which affected only the backarc regions with arc-parallel strain and stress gradients. The extension took place in the backarc regions of the northern Ryukyu and western SW Japan arcs in the Middle Miocene. The extension was evidenced by NW-SE trending normal faults in the extensional zone and paleostresses that were determined from dike orientations. To determine the age of and spatial extent of this zone, we analyzed fault-slip data from the Amakusa region, northern Ryukyu arc, where early middle Miocene intrusions allowed us to judge the magmatism to be older than the faults that affected Cretaceous and Eocene formations. The slip senses of the faults have been controversial in Amakusa. As a result, the region was found to have belonged to the extensional zone. The extensional zone is 300–400 km long and ∼100 km wide. We also found that the arc-parallel extension resulted in crustal strain with a southwestward increasing trend along the zone. The strain magnitudes showed a negative correlation with distance from the Okinawa Trough. This correlation is explained by the increasing stress magnitude toward the trough. We suggest that the stalled rift propagation of the northern Okinawa Trough caused the unique arc-parallel extension in the Middle Miocene.

Geological evolution of the Hampshire Basin (southern England) during a global climate transition from ‘hothouse’ to ‘coolhouse’ in the Palaeogene

Palaeogene sediments of the Hampshire Basin were a sensitive recorder of fluctuations in climate and eustatic sea level as Earth's climate transitioned from the global early Eocene ‘hothouse’ to the early Oligocene ‘coolhouse’, accompanied by the first permanent continent‐scale glaciation of Antarctica at the Eocene/Oligocene boundary. A study of the Palaeogene sediments of the Hampshire Basin is not only interesting from a palaeoclimate perspective, but the marine middle Eocene formations are renowned for containing some of the most abundant and diverse Palaeogene fossil assemblages in the world. In this article, I take you on a tour of the geological evolution of the Hampshire Basin from the end of the Paleocene through to the Pleistocene. I highlight some of the best exposures where sediments can be studied at outcrop and representative fossil assemblages can be collected, along with the economic and archaeological significance of these Palaeogene sediments.

Reservoir Characterization of Eocene Carbonates of Central Indus Basin, Pakistan

The present study is based on petrophysical analysis of the Eocene Sui Main Limestone (SML) penetrated in wells of Qadirpur Gas Field, Central Indus Basin, Pakistan. The analyzed petrophysical property of SML includes shale volume, total porosity, effective porosity, water saturation, hydrocarbon saturation and net pay thickness. The result from the study shows that the Sui Main Limestone reservoir is capable of yielding appreciable hydrocarbon. The petrophysical interpretation revealed that the studied SML has productive reservoir characteristics with average (total and effective) porosity is in K-1, 15% in K-2 15% and 17% in K-3, average saturated hydrocarbon in SML is (70-100%) indicating that zones in wells are purely saturated with hydrocarbon, and average volume of shale in the zone of K-1, 23% in K2, 27% and in K-3, 25% respectively delineating clean formation. Facies modeling revealed that the studied Eocene formation consist of clean limestone, shaly limestone and shals. The isopach thickness map and stratigraphic correlation helps to understand the thickness of Sui Main Limestone in the field.

SEDIMENTOLOGY OF EOCENE SANDSTONES AT OGBUNIKE AREA, SOUTHERN NIGERIA: INSIGHTS FROM PETROGRAPHIC AND GRANULOMETRIC ANALYSES

The sedimentary facies exposed at Ogbunike Area belong to the Eocene Formation that made up the Anambra Basin. This research estimates the lithology, thickness, sedimentary succession, paleo-environment, reservoir quality and source area tectonics using geological mapping, petrography, grain size distribution and statistical analysis. Geological mapping shows that the section is approximately 27m thick and consists of sandstone, shale, siltstone and ironstone lithofacies. Granulometric analysis performed on selected samples shows that the sandstones are fine to medium grained (1.15 to 2.17 ϕ), moderately sorted (average 0.96 ϕ), fine skewed (average 0.16 ϕ) and leptokurtic (average 1.17 ϕ). Bivariate plot of skeweness against sorting and mean against sorting pinpoint a fluvial origin for the sandstones. The results from rose plot point to a bimodal-bipolar paleocurrent pattern while the bi-directional paleo-flow is in the northeastern-southwestern directions, which is an indication of tidal influence suggesting shore environment of deposition. Average permeability values derived from an empirical formula indicate good potential for reservoir rock. Deductions from field observations and petrographic analysis suggests that the sandstones are submature, with angular to sub-rounded quartz. The high percentage of goethite (average 30.4%) in the ferrugenized sandstones samples suggests an environment of low oxidation. Provenance and tectonic assessment reveal metamorphic source, humid climate, high relief, recycled orogeny, and derived primarily from Cameroon Basement Complex rocks.

Chemical and Isotopic Tracers for Characterization of the Groundwater in the Heterogeneous System: Case from Chichaoua-Imin’tanout (Morocco)

The geological and hydrogeological approach of the structure of the basin OuladBouSbaâ led to the definition of the geometry of the main aquifers. In general, the profiles show the complexity of the geological configuration. The filling of the depression of OuladBouSbaâ is from the Eo-Cretacian. At this level, the aquifer is recharged by direct water infiltration. The quaternary, Eocene, and Cenomanian-Turonian formations constitute the main aquifers. Horizontal as well as vertical heterogeneity lead to a higher diversification of aquifer characteristics. To define the origins and understand the groundwater flows in this complex zone, we used a multi-tracer approach with the analysis of major elements and the isotopes of δ2H and δ18O. The chemical composition is mainly governed by the interaction with the rock with low electrical conductivity except in areas around domestic landfills. Geochemical results analyzing groundwater in the Piper diagram show two distinct chemical facies: the sulfated calcium and magnesium, and the hyper-chloride calcium. The levels of δ18O range from −7.60 to −4.25 while those of δ2H vary between −53.07 and −27.03. Analyses of signature isotopes differentiate two groups. The first contains high levels of heavy isotopes (highest levels of δ2H and δ18O) having therefore been submitted to evaporation. The second with lower levels of δ2H and δ18O did not undergo evaporation. The first one belongs to the unconfined free aquifer while the second corresponds to the captive aquifer.

Detrital zircon U‐Pb geochronology of the Jianchuan Basin, southeastern Tibetan Plateau, and its implications for tectonic and paleodrainage evolution

AbstractThe Jianchuan Basin is a key region for determining the spatial‐temporal evolution of paleodrainage and tectonic at the southeastern Tibetan Plateau. New detrital zircon U‐Pb geochronology and paleocurrent data from Eocene formations in this basin suggest that the sediment sources switched from the remote sources (including Hoh‐Xil, Songpan‐Ganzi, North Qiangtang, Yidun and western Yangtze terranes) to local lithologies (adjacent Triassic and Eocene igneous rocks and western Yangtze block) from the early‐middle Eocene Baoxiangsi to the late Eocene Shuanghe and Jianchuan Formations. Such provenance changes support that large‐scale drainage reorganization occurred in the late Eocene (prior to ~36 Ma). This significant late Eocene provenance and drainage changes occurred as one of the responses to coeval topographic uplift in the southeastern Tibetan Plateau.

Was there an exchange of detritus between the northern and southern Black Sea terranes in the Mesozoic-early Cenozoic?

Resolving the time of rifting of the Black Sea basin is critical to reconstructing the tectonic evolution of the Pontides arc in northern Turkey. U–Pb geochronology of detrital zircons from Middle Jurassic, Upper Cretaceous, and lower Eocene formations in the Eastern Pontides (NE Turkey), as well as published data from circum-Black Sea terranes, reveals that sediments preserved along with the northern (East European Craton-Scythian Platform) and southern (Eastern and Central Pontides-southern flank of the Greater Caucasus-Transcaucasus) margins of the Eastern Black Sea basin display distinct detrital provenances. The U–Pb detrital zircon ages of the sedimentary samples from the Eastern Pontides have distinct populations with ages of ~650–540, ~200, ~170, ~80, and ~50 Ma. In contrast, the ages of the sedimentary samples from the northern Black Sea terranes are characterized by age peaks of ~1400 and ~1100 Ma compared to those of the Eastern Pontides. Only a few detrital zircons in the range of ~650–540 Ma and <200 Ma are identified in the sedimentary samples from the northern Black Sea terranes. This contrast in detrital zircon ages, together with modal analysis of the samples and published paleocurrent data, suggests that Middle Jurassic–lower Eocene sedimentary samples in the Eastern Pontides were locally sourced from Gondwana affinity crustal basement rocks and associated Mesozoic–Cenozoic igneous rocks. Furthermore, there was no exchange of detritus across the Eastern Black Sea basin during the Middle Jurassic–early Eocene. These inferences require the Eastern Black Sea basin to have rifted in a back-arc setting behind the Eastern Pontides arc by the Middle Jurassic or survived as a relict basin of the Paleotethys.

Geological structure and paleogeographic zoning of the Khadum formation in Pre‑Caucasus

Unconventional oil and gas resource development and exploration is the one of the most prospective concept in petroleum geology. High carbon Khadum facies are investigated as unconventional resources in the Precaucas basin and contain gas, gas condensate and oil accumulations. Oligocene and Lower Miocene structure, prospectivity and fields distribution are the one of the most relevant subjects nowadays. This study is focused on the main stages Late Eocene and Early Oligocene deposits formation and the paleogeography of the Khadum formation in the Precaucas oil and gas basin. The new prospective zones are developed in Khadum formation based on the complex analysis of seismic, paleogeography and lithofacies analysis.

Source rock evaluation of the Central Gulf of Suez, Egypt: A 1D basin modelling and petroleum system analysis

Geochemical studies were applied to evaluate the possible source rocks of Cretaceous–Eocene formations in the October oil field, including pyrolysis analysis data such as total organic carbon (TOC %), generating source potential (S2), production index (PI), oxygen, and hydrogen indices (OI, HI) and (Tmax). Three source rocks are characterized by fair to good and very good TOC%, which are Thebes, Duwi, and Abu Qada formations with kerogen type I and type II, respectively, and some samples are in the type III region reflecting the degree of maturation and can generate oil and gas. 1D basin models were constructed for five wells to simulate the multi‐tectonic phases and multiple burial histories, migration path, and event chart in the study area. The sedimentation rates from Cretaceous to Palaeocene age are characterized by low burial rate sedimentation, low to medium in the Eocene age, and high burial rate and rapid sedimentation in the Miocene and post‐Miocene age. The petroleum system of the October oil field was studied, and two petroleum systems can be recognized, according to the integration studies between the source rock evaluation and petroleum basin modelling.

Lithological mapping and automatic lineament extraction using Aster and Gdem data in the Imini-Ounilla-Asfalou district, South High Atlas of Marrakech, Morocco

Lithological and lineament mapping using remote sensing is a fundamental step in various geological studies, as it forms the basis for the interpretation and validation of the results obtained. There were two objectives for this study, applied in the Imini-Ounilla-Asfalou district, South High Atlas of Marrakech region: first, lithological mapping by satellite image processing techniques such as ASTER L1B (hight spectral and spatial resolution), namely Principal Component Analysis (PCA), Minimum Noise Fraction (MNF), as well as the application of three types of supervised classification, namely Spectral Angle Mapper (SAM), Maximum Likelihood (ML) and Minimum Distance (MD), on the visible/near-infrared (VNIR) and short-wave infrared (SWIR) spectral bands of our ASTER image; second, an analysis of the distribution of lineaments by automatic extraction using a Global Digital Elevation Model (GDEM) and the PC1 image derived from the PCA transformation applied to the satellite image. The best results are highlighted by the delineation of new facies in relation to the existing map; after confirmation in the field, all of these facies, which include Eocene, Triassic and Jurassic formations, are represented on the new map. The results of lineaments showed that each of them systematically shows a similarity in terms of concentration and orientation, with four preferential oriented systems: NE-SW, E-W, NNE-SSW and NW-SE. The lineaments mainly follow those of the major fault zones, with high concentrations in the northeast and southwest parts of the study area.

Origin of geothermal waters from the Upper Cretaceous to Lower Eocene strata of the Jiangling Basin, South China: Constraints by multi-isotopic tracers and water-rock interactions

Fluids in geothermal reservoirs can be affected by the interaction with host rocks. To determine solute sources and water-rock interaction processes, this study collected water samples from the Upper Cretaceous to Lower Eocene strata of the Jiangling Basin, South China. Their chemical and isotopic (hydrogen, oxygen, strontium, boron) characteristics and the mineralogy of corresponding reservoir rocks were investigated. Five high-salinity water samples (343–359 g/L) were collected from deep boreholes tapping Paleocene to Eocene formations in the central basin. Seven water samples (four oilfield and three saline waters) were collected from boreholes tapping Upper Cretaceous formations in the northwestern part of the basin and had salinities of 23.1–81.4 g/L. These water samples showed depletion of Mg and SO4 and enrichment of K, Na, Ca and Cl, compared with the ion trajectories of evaporated seawater. The observed Cl/Br mass ratios (709–1390), Na/Cl molar ratios (0.79–1.01), Ca excess and Na deficit imply contributions of halite dissolution and multiple diagenetic processes of albitization, dolomitization, and calcite and anhydride cementation, which are consistent with the reservoir rock mineralogy. Chemical geothermometers of these geothermal fluids estimated temperatures of around 200 ± 20 °C and 125 ± 10 °C for hot brines and saline waters, respectively. Compared with the chemical compositions of Upper Cretaceous saline waters, the hot brines are enriched in K, Li, B, Sr, Rb, Cs, Br, Ba and transition metals such as Co, Ni, Cu, Zn, V, Ti and Mn. Correlations of δ18O–Li, δ18O–Rb, δ18O–Cs and δ18O–K values indicate that equilibrium with rocks caused enrichments in K, Li, Rb and Cs. Variations in 87Sr/86Sr ratios (0.706954–0.711249) and δ11B values (+8.7‰–+23.1‰) were used to find many discrepancies due to water-rock interactions involving basalt and clastic rocks. The integration of chemical and isotope data suggests that the geothermal waters in the Jianging Basin are derived from water-rock interactions and recharge of meteoric waters. In addition, the boron isotope data are consistent with traditional hydrogen, oxygen and strontium isotopes in terms of explaining water-rock interaction processes. Multi-isotopic characterization of Upper Cretaceous to Lower Eocene geothermal waters indicates that the isotopic compositions of water from the Jiangling Basin are consistent with a fluid signature of interactions involving basalt and clastic rocks with water derived from primary brine diluted by meteoric waters. The combined water chemistry and multi-isotope approach shows that high-temperature water-rock interaction is a major influence on the mineralization of hot brines in the Jiangling geothermal system.

Consumed tectonic plates in Southeast Asia: Markers from the Mesozoic to early Cenozoic stratigraphic units in the northern and central Philippines

Tectonic reconstruction models of Southeast Asia all invoke in the early Cenozoic the collision of Mesozoic oceanic plates, which have been fragmented, consumed along subduction zones or emplaced onto the overriding plate. However, with marked variations in these models, we reinvestigate the tectonic evolutionary landscape of Southeast Asia through the lens of Philippine geology. In particular, we present revisions to the more recent models by adopting the unique approach of integrating data that we have gathered for the past 17 years from the Upper Mesozoic to Lower Cenozoic stratigraphic formations in northern and central Philippines. These formations, which resulted mainly from submarine mass transport processes, evolved in response to early arc-related processes of oblique subduction, frontal wedge deformation, terrane accretion and strike slip faulting. Additional key constraints for the revisions include: (1) the timing of early Cenozoic magmatism in eastern Luzon; (2) the spatial distribution of the Upper Mesozoic to Lower Cenozoic sedimentary formations with respect to other key features (e.g. distribution of Mesozoic ophiolite fragment and continent-derived rocks) in the Philippine arc; (3) the paleolatitudinal position of Luzon and surrounding regions and; (4) the movement of the surrounding plates since the Late Mesozoic.In revising previous models, a subduction zone (proto-East Luzon Trough) separating Benham Plateau and the Philippine arc was placed to explain the spatial distribution of Eocene arc-related formational units and Mesozoic ophiolite materials comprising the accretionary complex east of Luzon at ~40 Ma period. During this time, Luzon was modeled at the southern margin of the East Asia Sea or the proto-Philippine Sea Plate. Mesozoic ophiolitic complexes that line the eastern Philippine arc as well as the ophiolitic and pelagic limestone and chert fragments included in the arc-derived, Eocene formations in Luzon could very well be traces of the now consumed East Asia Sea-proto-Philippine Sea Plate. Within the same period, we modified the Palawan Microcontinental Block (PCB), positioned at the trailing edge of the proto-South China Sea to include the whole Mindoro island and the Romblon Island Group in Central Philippines. Pieces of the consumed Izanagi Plate, the proto-South China Sea and continental-derived sediments from Asia mainland are reflected in the Mesozoic metamorphic rocks and the Eocene sedimentary formation in western Mindoro. Finally, we model Cebu, Bohol and Negros islands in Central Philippines as being at the leading oceanic edge of the Indo-Australian Plate during the early Cenozoic. With the northward movement of the Indo-Australian plate and the trench roll back of the southern margins of the Philippine Sea Plate, the accretion of the Cretaceous arc-related rocks of Cebu, Bohol and Negros onto the Philippine arc by the end of Eocene or early Oligocene becomes a possibility.

Radwany Formation: A new formation name for the Early-Middle Eocene carbonate sediments of the offshore October oil field, Gulf of Suez: Contribution to the Eocene sediments in Egypt

The Eocene sediments plays critical role in the evolution and development of the petroleum system in the Gulf of Suez region, where it is representing a self-source rock or self-reservoir or combination in some areas within the basin. Microfacies analysis and paleontological studies have not been conducted on these Eocene sediments in the area of the October oil field, which is mandatory for the formation characteristics assessment. Therefore, sidewall core and ditch-cuttings samples that was obtained from October Eocene carbonate sediments so far ascribed to the Thebes formation was studied in terms of sedimentology, paleontology and depositional environment. A total of 64 thin sections were analyzed petrographically, and three microfacies types recognized. Both Calcareous nanoplankton and Foraminifers were examined. The study of the Eocene carbonate facies in the October field revealed that the succession is composed of pelagic foraminiferal limestone of varied color, containing abundant planktonic foraminifers and minor traces of chert. Three microfacies are distinguished including wackestone of smaller planktonic foraminifera (50%), wackestone-packstone of planktonic foraminifera (40%) and packstone of planktonic foraminifera (10%). Nannoplankton and foraminifers indicate that the studied succession is of early Eocene to middle Eocene age. Microfacies and fossil assemblage of the studied section indicate a pelagic environment and deposition in deep basin at water depths of a few hundred meters. Finally, the current results were compared with data from previous publications on Eocene sediments in the region. It is revealed that the studied succession provides new data and contribution for the evolution of carbonate platform in the Ypresian-Lutetian age, and differs from the typical Thebes Formation and other Eocene Formations concerning facies, lithology, fossil content, age and depositional environment. Therefore, we suggest to abandon the term Thebes Formation for this Eocene carbonate succession in the October field, and a new lithostratigraphic unit, named Radwany Formation, is formally introduced.

Chapter 4 Late Cretaceous to Eocene cover of New Caledonia: from rifting to convergence

Abstract In New Caledonia, the cover refers to the autochthonous Late Cretaceous to Paleogene sedimentary and volcanic formations unconformably overlying the basement rocks and underlying the allochthonous nappes. The first period of deposition, broadly from the Late Cretaceous to Paleocene ( c. 105–56 Ma) was controlled by extension and rifting. The second period, broadly the Eocene ( c. 56–34 Ma), was dominated by convergence and contraction. The Late Cretaceous part of the cover consists of synrift conglomerates and coal-bearing deposits with interlayered bimodal, subduction-related and intra-plate volcanic rocks. The post-rift deposits are deep water sedimentary rocks deposited under anoxic conditions with reduced terrigenous input. The Paleocene to Eocene formations, mainly carbonates, attest to profound palaeogeographical changes and a switch to a different geodynamic regime, linked to the onset of Eocene convergence. The Middle to Late Eocene formations are typically composed of turbidites and breccias. They were deposited in a typical flexural foreland basin context as an upwards-coarsening sequence topped by an olistostrome. They are associated with tectonic convergence and east-dipping subduction that led to the end-Eocene obduction of ophiolitic nappes. This two-fold evolution, extension then compression, can be integrated in the wider framework of the plate tectonic evolution of the SW Pacific.

Partitioned tectonic shortening, with emphasis on outcrop-scale folding and flattening, Pindos fold-and-thrust belt, Peloponnese, Greece

Shortening estimates for fold–thrust belts seldom take into consideration outcrop-scale folding, especially folding related to prethrusting layer-parallel shortening (LPS) and flattening. The Pindos belt of the Peloponnese contains products of Maastrichtian to Paleocene tectonic shortening amenable to assessing strain partitioning. Shortening there initiated with LPS, including outcrop-scale folding, which was superseded by thrusting and macrofolding, with both macromechanisms producing additional outcrop-scale folding and (or) form-modification of initial LPS outcrop-scale folds. Skourlis and Doutsos (2003. International Journal of Earth Sciences, 92: 891–903) concluded that total shortening in this region was 68%, the summation of ∼15% LPS, ∼6% fault-related macrofolding, and ∼47% thrust–slip translation. But even this degree of shortening may be underestimated when outcrop-scale folding is considered. Two limestone-dominated Cretaceous formations and one Cretaceous–Eocene formation of limestone and mudstone display spectacular outcrop-scale folding produced by true multilayer behavior, internal buckling, and disharmonic quasi-flexural folding. Fold forms vary from chevron buckling of multilayers to more rounded folding of true multilayers to disharmonic flattened folds in pseudo-bedded limestone. Ramsay analysis of layer thickness variations across individual disharmonic folds underscores the disharmonic fold forms and intense degree of pressure dissolution generated fold flattening. Line-length shortening for well exposed “packages” of LPS outcrop-scale folding is as high as 30%, but overlying and underlying panels may be more modestly folded and (or) flattened, suggesting that shortening transfer mechanisms may have caused some sections to be bypassed. Achieving more meaningful shortening estimates of the outcrop-scale folding within an entire progressive deformation will require understanding of the partitioning of distribution of this folding regionally.

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. • A paleogeographic evolution of the south pyrenean foreland from palinspastic reconstructions and a revised chronostratigraphy. • Tectonics controlled the long-term processes of basin partitioning and the evolution of sediment routing systeand sinks. • Climate forcing overprinted the long-term tectonic signal, pacing sedimentary sequences in the 10 5 -10 6 yr time range.

New evidence of perfect overlapping of Haploops and pockmarks field: Is it a coincidence?

In the shallow waters of the Bay of Concarneau (South Brittany, France), previous studies reported a dense settlement of the species Haploops (tube-dwelling bioengineer amphipod) that perfectly overlaps a field of pockmarks. A possible mechanistic link may therefore exist between the Haploops colonies and the shallow pockmarks. To test this hypothesis, interferometry sonar and sub-bottom profiler chirp data were acquired in two new areas located in the marine estuary of the Loire River, “La Lambarde” and “Le Croisic”. The new sites share the same sedimentary and geological characteristics as those found in the Bay of Concarneau. The three sites are similarly located in shallow and muddy environments above a faulted Middle Eocene formation that is incised by paleo-valleys. Despite different hydrodynamic conditions and estuarine influence, in the two new investigated areas, the Haploops also settle within the pockmarks field limits. To better constrain the association pockmarks/Haploops, we compared the sedimentary features, seismic signatures and total organic carbon (TOC) content of the sediment. Active pockmark chimneys displaying highly reworked profiles and slightly higher TOC contents suggest a local deeper source of organic matter, which might be an important source of nutrient for the Haploops. In Southern Brittany the pockmarks/Haploops spatial overlap is not a simple coincidence and may therefore present a general pattern for identification of settlement preferences of the specie.