Early Eocene Age Research Articles

Distribution of Thanetian-Ilerdian biozones in Lorestan Zone, West of Iran

The Taleh Zang Formation is a carbonate sequence of the late Paleocene–early Eocene age in the Lorestan zone, west of Iran. This Formation overlays siliciclastic rocks of the Amiran Formation and is overlain by red sandstone of the Kashkan Formation. A biostratigraphic scheme, based on the larger benthic foraminifera, is proposed for the Thanetian–Ilerdian deposits in Lorestan Zone. We compare our results with the available data from other parts of Tethys and the zonation of shallow-marine Paleocene–Eocene of Mediterranean Tethys is made. In total, 367 samples were collected from the six sections. From a biochronostratigraphic point of view, three biozones and one indeterminate zone are identified. The zones are shallow benthic zone 3 (early Thanetian), shallow benthic zone 4 (late Thanetian), and shallow benthic zone 6 (early Ilerdian). In the northern part of the Lorestan Zone (Kabutar Bula and Psht-e Jangal sections), the Taleh Zang Formation contains poor fauna. Due to the stratigraphic position, an early Thanetian age can be considered. Our data showed that the late Paleocene and Eocene biozones in Lorestan Zone developed parallel to the axis of the folding, in a northwest-southeast trend. They get younger from the northeast to the southwest. Keywords: biostratigraphy, Eocene, Foraminifera, Lorestan Zone, Paleocene.

Biostratigraphy and Paleoecology of the Sinjar Formation (Late Paleocene-Early Eocene) in the Dokan and Sinjar Areas, Iraq

Biostratigraphy of the Sinjar Formation is investigated in two sections (Dokan and Sinjar) from northeastern and northwestern Iraq, respectively. Two hundred samples from all the limestones and marl that form the main lithological components of the studied sections were collected. The studied limestones and marl are rich in microfossils. Through thin sections, we were able to identify thirty species of benthic foraminifera and fifteen species of other microfossils (coral, algae, mollusca, bryozoa, and echinoids) at Dokan section, and fifty-one species of benthic foraminifera and thirty species of other microfossils at Sinjar section. 3 biozones were distinguished from both sections 1-Biozone A: Kathina sp.- Lockhartia hunti Assemblage zone (SBZ 5) (Dokan section); (Kathina pemavuti - Lockhartia hunti Assemblage zone (Sinjar section), 2- Biozone B: Idalina sinjarica Total Range zone (SBZ 6-7) and 3-Biozone C: Alveolina globosa- Alveolina pasitisilata Concurrent Range Zone (SBZ8-10). These zones indicate the Late Paleocene –Early Eocene age of the Sinjar formation. The biostratigraphic correlations in the studied sections are based on benthic foraminiferal zonations. Showed the correlation comparison between the biostratigraphic zones of the commonly used benthic zonal scheme around the Late Paleocene -Early Eocene in and outside of Iraq. paleoecological studies suggest that the carbonate sedimentation of the Sinjar Formation thrived in 18-25oC, with mesophotic to oligophobic light, under an oligotrophic to mesotrophic middle ramp environment with normal marine to slightly saline and at water depths from 40 - 80 m. Stable isotopic carbon (δ13C) and oxygen (δ18O) data revealed generally hot conditions with high productivity during the deposition of the Sinjar Formation accompanied by an abrupt change in paleoenvironmental conditions across the Paleocene-Eocene contact.

Investigation of Source and Reservoir Rock Petroleum Generative Potential of Early Eocene and Paleocene Sequences of the Punjab Platform Basin, Pakistan: A Geochemical and Petrophysical Approach

Abstract ––Investigating Early Eocene and Paleocene deposits within the Punjab Platform, Pakistan, involved comprehensive analysis using advanced geochemical and petrophysical techniques. This study evaluates the source potential of three formations: Nammal and Sakesar of Early Eocene age and Dungan and Ranikot of Palaeocene age. The Sakesar Formation, a reservoir rock, was evaluated through interpretation of wireline logs to estimate key petrophysical properties—porosity, water saturation, and hydrocarbon saturation. Geochemical investigations focused on total organic carbon content and Rock-Eval pyrolysis of twenty-one cutting samples from a well. These samples displayed TOC values ranging from 0.21 to 2.04 wt.% and S2 values ranging from 0.09 to 2.14 mg HC/g rock. Analysis positioned all samples within the immature window zone with Type II/III and Type III kerogen, suggesting limited generative potential. Findings suggest limited hydrocarbon generation from these formations. Petrophysical analysis indicated average porosity of 11.2%, water saturation of 32.58%, and hydrocarbon saturation of 67.42% for the Sakesar Formation, categorizing it as average to good reservoir potential. This study highlights complex geochemical and petrophysical characteristics of these formations. While Sakesar shows promising reservoir qualities, significant hydrocarbon generation potential from Nammal, Dungan, and Ranikot formations is constrained. Informed decision-making is crucial when considering these formations as hydrocarbon sources.

Kahi mélange complex in Kurram and Waziristan, NW Pakistan: An integrated approach for tectonic implications to India–Afghan suturing

The Kahi mélange complex in the Waziristan and Kurram sector (N–W Pakistan) is one of the several Neotethyan ophiolite–mélange complexes exposed along the westernmost margin of the Indian plate, preserving significant information on pre, syn and post–collision tectono–stratigraphic evolution of collision tectonics between the Indian plate and the Afghan block. It consists of highly dismembered ophiolitic and sedimentary units. Petrographic and field observations of mafic and ultramafic rocks within the ophiolitic unit, reveal a complete, but dismembered ophiolite suite similar to the Waziristan Ophiolite (WO) to its southwest. The sedimentary units consist of syn–orogenic deposits, turbidites and slope sediments of Campanian age as constrained by the Late Cretaceous radiolarians (Stichomitra communis Squinabol) and planktonic foraminifera (Rodotruncana Calcarata). From the structural point of view, the dismembered ophiolitic units represents the highest tectonic edifice. It’s overthrusting onto the Campanian sedimentary unit constraints the onset of the collision between the Indian plate and Afghan block to the Late Cretaceous. The subsequent obduction of combined ophiolite–sedimentary units over the brecciated Late Paleocene Lockhart Formation of Indian plate margin constraints the time of the end of the collisional stage. The unconfirmable deposition of the marine Patala Formation, Late Paleocene–Early Eocene in age, above the Kahi mélange complex documents the closure of Neotethys in the Early Eocene. In conclusion, our findings document that the Kahi mélange complex represents a typical polygenetic mélange formed by the superposition of two different dismembered units (the ophiolitic and the sedimentary units) coupled as a result of at least two tectonic events in a subduction–accretion setting related to the collision between the Indian plate and the Afghan block.

Late Paleocene to Middle Eocene Calcareous Nannofossil Assemblages from Península Mitre, Southeastern Austral Basin, Argentina

On the Fueguian Atlantic coast and in the southern Andean fold and thrust belt, the Paleogene is partially represented by numerous turbiditic systems. Between Río Bueno and Cabo Leticia on Península Mitre, the Paleocene-Eocene is represented by the Río Claro Group (Cabo Leticia, La Barca, Punta Noguera and Cerro Ruperto formations) and the Río Bueno Formation; which together constitute a ~1050 m thickness succession. Here, calcareous nannofossil assemblages recovered from 96 samples were analyzed to determine their relative ages. The Cabo Leticia Formation was barren in nannofossils. The upper LB2 Member of La Barca Formation, contained Rhomboaster cuspis and Fasciculithus richardii, frequent in the Paleocene/Eocene boundary (Subzones NP9a/NP9b). Nannofossils recovered from Punta Noguera Formation indicate an early Eocene age (biozones NP9b-NP10), with Fascilulithus tympaniformis, Rhomboaster cuspis and abundant Toweius spp. The Cerro Ruperto Formation provided one productive sample, with specimens of Reticulofenestra spp. and Toweius spp., which indicates an early Eocene age for the formation (biozones NP12-NP13). The Río Bueno Formation yield calcareous nannofossil assemblages characterized by Chiasmolithus eograndis, Chiasmolithus expansus, Toweius spp. and Reticulofenestra spp. which indicates a late early Eocene to middle Eocene age (biozones NP14-NP16). Although the calcareous nannofossil record is discontinuous due to sedimentary facies of the Río Claro Group, our data allow a better age constraint for the investigated formations and to correlate these units with others outcropping and subsurface units in the Austral Basin.

Phosphatization of rocks and organic remains of the basal horizon of the Lower Eocene of the Middle Dnipro area


 
 
 The purpose of the work is to determine the mechanism of phosphorus deposition during the formation of deposits of Kanivska suite (Р2kn) within the region of the Middle Dnipro by researching the components of phosphorite contractions. The studied conglomerate-like formations were cemented with phosphate substance, selected from the basal horizon of the Kanivska suite for the purpose of their petrographic and paleontological study. Phosphorites of the basal horizon are formed in different shapes, colors and sizes. The phosphate substance that cements them (according to our data) varies in ages. Pebble inclusions in conglomerates that are the phosphatized remains of ichnofauna belong to the washed phosphates of the Cenomanian age of the Late Cretaceous, which entered the basal horizon of the Eocene as a result of washing, condensation, and new phosphatization during the Early Eocene transgression. The phosphate substance of these inclusions is represented by the mineral kurskite (Carbonate Rich Apatite) of three modifications: amorphous, microcrystalline, and radial-radiant which reflect different generations and diagenetic stages of phosphorite formation (Bushinsky, 1954). Phosphate of first-generation exists in the form of globules of amorphous kurskite and is a pore-filling material between sediment grains. The second type is the microcrystalline kurskite, which forms layers of film around sediment grains, with the thickness of 0.01–0.02 mm, has concentric microstructure and barely noticeable anisotropy. Aggregates of needle-like radiating anisotropic kurskite have a sheaf-like, parallel-fibrous structure oriented perpendicular to the surface of the fragments. They are the result of the further recrystallization of kurskite. Phosphate amorphous cementing substance had formed, in our opinion, in an early Eocene age. It contains numerous remnants of opal and partially phosphatized flora and fauna – diatoms, radiolarians, and spicules of sponges, as well as fragments of Phyto organics. These organisms were the source of additional phosphorus in the sediment. Centers of phosphate formations emerged in places of concentration of dead marine biota, where the processes of bacterial decomposition rapidly began, high concentrations of carbonate and phosphate ions were created, there was a replacement of organic residues with calcium phosphate. The most common in nature are the shells of diatoms and their fragments, which were studied in thin sections. With the most certainty in its attribute outline and shape, preserved fragments of marginal zones, as well as by the type of areola, determined samples of Paralia, Stephanopyxis families, and triangular valves of Trinacria sp. There are also elements of the valves, similar in contours to the family Hemiaulaceae. Phosphate substance and rapid burial contributed to the conservation of thin skeletal elements of microfossils. The determined genitive composition of diatoms from the sections of the basal horizon of the Kanivska suite does not deny their early Eocene age. Diatoms of the early Eocene age have not been known in Ukraine so far, and diatoms of the Middle Dniproarea are being studied for the first time.
 
 

Early Eocene Diatoms and Silicoflagellates of the Cis-Donets Monocline (Russian Plate): Biostratigraphical and Paleogeographical Approaches

The diatom assemblage of the Veshenskaya Formation studied in the borehole P-321 of the Cis-Donets monocline (southern part of the Russian Plate) is assigned to the lower Ypresian Moisseevia uralensis Zone. According to the available data, this zone corresponds to the Deflandrea oebisfeldensis and Dracodinium (=Wetzeliella) astra dinocyst zones and, accordingly, to the nanoplankton NP10 Zone. The presence of the zonal silicoflagellate species Naviculopsis foliacea confirms the Early Eocene age of the Veshenskaya Formation. The taxonomic similarity of diatoms and silicoflagellates of the region under consideration with silicofossil assemblages of Northern Europe suggests a stable link between these paleobasins at the beginning of the Early Eocene.

The earliest <i>Ancistrolepis</i> (Gastropoda: Buccinidae) and its geologic implications

The buccinid gastropod Ancistrolepis carolineae Squires, 1984 is the earliest known and shallowestmarine species belonging to the extant genus Ancistrolepis Dall, 1895, which is endemic to the NorthPacific region. This species is of late early Eocene (Ypresian Stage) age and is about 7 million years older than the previously oldest known record (late Eocene) of the genus. This rare species occursat several localities in a 1-m thick bed (“Stewart bed”) of fossiliferous shallow-marine sandstone within the Llajas Formation, on the north side of Simi Valley, Ventura County, southern California.The “Stewart bed” contains a rich fauna of subtropical mollusks and other invertebrates, which lived just below effective wave base, at the distal edge of a braid delta, immediately adjacent to an upper bathyal prodelta/slope environment, where a rich microfauna of calcareous nannofossils and benthic foraminifers lived. Dispersal of A. carolineae would have been either via drifting of buoyant “pouches” containing its non-planktonic eggs or by rafting of its adults in buoyant plant material debris. The dispersal of A. carolineae northward coincided with the cooling of the NorthPacific waters during the late Eocene, thereby providing the opportunity for Ancistrolepis to adapt to living in bathyal waters and also to living in association, in some cases, with chemosynthetic (methane) cold seeps.

Geochemical indications for the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2) hyperthermals in terrestrial sediments of the Canadian Arctic

Abstract During the late Paleocene to early Eocene, clastic fluvial sediments and coals were deposited in northern high latitudes as part of the Margaret Formation at Stenkul Fiord (Ellesmere Island, Nunavut, Canada). Syn-sedimentary tectonic movements of the Eurekan deformation continuously affected these terrestrial sediments. Different volcanic ash layers occur, and unconformities subdivide the deposits into four sedimentary units. Rare vertebrate fossils indicate an early Eocene (Graybullian) age for the upper part of the Stenkul Fiord outcrop. Here, we present carbon isotope data of bulk coal, related organic-rich mud and siltstones, a plant leaf wax-derived alkane, and additional plant remains. These data provide a complete carbon isotope record of one stratigraphic section with defined unconformity positions and in relation to other Eurekan deformation features. A previously dated ash layer MA-1 provided a U-Pb zircon age of 53.7 Ma and is used as a stratigraphic tie point, together with a discrete negative carbon isotope excursion found above MA-1 in a closely sampled coal seam. The excursion is identified as the likely expression of the I-1 hyperthermal event. Based on our isotope data that reflect the early Eocene dynamics of the carbon cycle, this tie point, and previous paleontological constraints from vertebrate fossils, the locations of the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2) hyperthermals and their extent along the complete section are herein identified. Within the intervals of the PETM and ETM-2 hyperthermal events, increasing amounts of clastic sediments reached the site toward the respective end of the event. This is interpreted as a response of the fluvial depositional system to an intensified hydrological system during the hyperthermal events. Our study establishes an enhanced stratigraphic framework allowing for the calculation of average sedimentation rates of different intervals and considerations on the completeness of the stratigraphic record. As one of the few high-latitude outcrops of early Eocene terrestrial sediments, the Stenkul Fiord location offers further possibilities to study the effects of extreme warming events in the Paleogene.

New data on the age of the Emine Formation (East Balkan, Bulgaria)

The study represents new data about chronostratigraphic range of the Emine flysch Formation in its type section at the Black Sea coast near the “Irakli” touristic resort. In the highest stratigraphic levels, calcareous nannofossils of NP 10 Rhomboaster bramlettei zone have been documented, supporting early Eocene age for the formation. These new finds will shed light on the timing of cessation of the turbiditic sedimentation in East Balkan, as well as on the specific expression of the global event – the Paleocene–Eocene Thermal Maximum (PETM) in deep-water environment.

Multi‐proxy approach of the stratigraphy, geochemistry, and sedimentology of Eocene Margalla Hill Limestone: Case study from Muzaffarabad area, Sub‐Himalayas, Pakistan

To investigate the sedimentological characteristics of the Margalla Hill Limestone (MHL), a multi‐proxy approach including geochemical, mineralogical, and micropalaeontological investigations were carried out. Using detailed field observations and petrographic investigation of the studied section, five microfacies were dentified. Total organic carbon (TOC) values of the limestone are generally low (0.10–0.96%) and highly degraded, as observed from the low hydrogen index (i.e., 17–349 mg HC/g TOC). TOC is mainly Type‐III and Type‐IV organic matter that reflects a continental source or highly weathered marine organic matter (OM) with minor Type‐II which corresponds to algal or bacterial OM. The values of Tmax range from 419 to 512°C for most of the samples, which lies within the mature stage. Major element abundances do not vary significantly in the studied unit and are mainly linked to variations in clay contents. Trace elements (V, Cr, Mn, Zn, Ni, Cu, Th, Rb, U, and Zr) of the MHL depict a mainly detrital origin for shales, and overall decrease in trace element's concentration suggests a change from physical to chemical weathering. The rate of sedimentation as determined by the Th/U ratio indicates a regular to irregular low rate of sedimentation, from base to top of the studied section. The redox conditions, as reflected in the variation of Cr (V/Cr), using the V/Cr ratio with Ni + V indicate that the MHL was deposited under oxic‐dysoxic conditions. Chemical Index of Alteration, Chemical Index of Weathering, Plagioclase Index of Alteration, and Weathering Index of Parker showed that the source region was subjected to intense chemical weathering likely under tropical palaeoclimatic conditions with abundant rainfall. The limestone consists mainly of calcite followed by minor quartz and dolomite. Clay mineralogy revealed that the clay fraction is dominated by kaolinite, smectite, mica, and chlorite. The microfossils of various genera of benthic foraminifera have been identified. Based on benthic foraminifera, an Early Eocene (SBZ‐8; Middle Ilrdian 2) age has been assigned to the MHL.

Lithostratigraphy, age and distribution of Eocene volcanic sequences on eastern King George Island, South Shetland Islands, Antarctica

AbstractNew mapping and dating of volcanic outcrops on the east coast of Admiralty Bay, King George Island, has demonstrated that Eocene volcanic sequences are dominant and also crop out extensively elsewhere, particularly on the eastern part of the island. The sequences can be divided into at least three formations (Hennequin, Cape Vauréal and Carruthers Cliff) together with Eocene strata at Warkocz and near Lions Rump that are currently unassigned stratigraphically. New and recently published40Ar/39Ar ages indicate that all of the formations are Early Eocene in age, mainly Ypresian, extending to Lutetian and possibly even Priabonian time in more easterly outcrops. Compositional contrasts exist between the groups (calc-alkalinevstholeiitic). The formations are mainly composed of lavas, and many show evidence for contemporary inundation by water. They are interbedded with sedimentary rocks deposited mainly during flooding events as debris flows, debris avalanches, hyperconcentrated flows, from traction currents and in lakes. The common presence of juvenile volcanic detritus suggests that the sediments were probably linked to explosive hydrovolcanic eruptions, some of which were possibly rooted in summit ice caps. Other evidence is also permissive, but the presence of Eocene ice on King George Island is not well established at present.

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.

Deposition History and Paleo‐Current Activity on the Southeastern Lomonosov Ridge and its Eurasian Flank Based on Seismic Data

AbstractA regional seismic survey on the southeastern Lomonosov Ridge (LR) and adjacent basins provides constraints on the coupled evolution of ocean circulations, depositional regime, and tectonic processes. First, Mesozoic strata on the LR, its faulted flanks and the initial Amundsen Basin were covered with syn‐rift sediments of Paleocene to early Eocene age. Numerous vertical faults indicate differential compaction of possibly anoxic sediments deposited in the young, still isolated Eurasian Basin. The second stage, as indicated by a prominent high‐amplitude‐reflector sequence covering the ridge, was a time of widespread changes in deposition conditions, likely controlled by the ongoing subsidence of the LR and gradual opening of the Fram Strait. Episodic incursions of water masses from the North Atlantic probably were the consequences and led to the deposition of thin sedimentary layers of different lithology. The third stage is marked by continuous deposition since the early Miocene (20 Ma). At that time, the ridge no longer posed an obstacle between the Amerasia and Eurasia Basins and pelagic sedimentation was established. Drift bodies, sediment waves, and erosional structures indicate the onset of circulation. Faulting on the ridge slope has led to a series of terraces where sediment drifts have accumulated since the early Miocene. It is suggested that ongoing sagging of the ridge and currents may have shaped the steep sediment free flanks of the terraces. Lastly, a sequence of high‐amplitude reflectors marks the transition to the early Pliocene large‐scale Northern Hemisphere glaciations.

New charophyte flora from the Pine Hollow and Claron formations (southwestern Utah). Taxonomic, biostratigraphic, and paleobiogeographic implications

Paleogene non-marine deposits of the Pine Hollow and Claron formations (southwestern Utah, USA) provided a rich microfossil assemblage composed of charophytes, freshwater gastropods and ostracods. Charophytes were extracted from a ca. 450-m-thick section, especially from floodplain deposits belonging to the Claron and the Pine Hollow formations. The samples from the Pine Hollow Formation includes small and recrystallized populations of Psilochara sp., Peckichara sp. and Harrisichara sp. The occurrence of these genera suggests that this unit is Paleogene in age. The richer charophyte assemblage was recovered from the Claron Formation and is dominated by Microchara cristata, Microchara cf. punctata and Peckichara torulosa (here synonymized with the well-known Eurasian species Peckichara varians), along with Lychnothamnus sp. and Dughiella sp. Based solely upon charophyte Euroasiatic biostratigraphic ranges of M. cristata, M. punctata and P. torulosa, the basal/middle part of the Claron Formation is probably Danian in age. However, recent biostratigraphic studies based on mammals indicate that the middle part of the Claron Formation (unit 7) is early Eocene in age. The correlation of charophytes with mammals and the lack of significant unconformities in this formation suggest that these species could live longer in North America than Eurasia. The lack of North American charophyte studies, along with the long biostratigraphic ranges of the dominant taxa, M. cristata and P. torulosa, makes precise relative dating, solely on the basis of charophytes, difficult. This study also provides valuable data about Eurasian charophyte species and genera discovered for the first time in North America.

Morphology and Affinities of Ampelocissites Seeds (Vitaceae: Ampelopsis clade) from the Paleogene of Texas, USA

Abstract—The type material on which the fossil genus name Ampelocissites was established in 1929 has been reexamined with the aid of X-ray micro-computed tomography (μ-CT) scanning and compared with seeds of extant taxa to assess the relationships of these fossils within the grape family, Vitaceae. The specimens were collected from a sandstone of late Paleocene or early Eocene age. Although originally inferred by Berry to be intermediate in morphology between Ampelocissus and Vitis, the newly revealed details of seed morphology indicate that these seeds represent instead the Ampelopsis clade. Digital cross sections show that the seed coat maintains its thickness over the external surfaces, but diminishes quickly in the ventral infolds. This feature, along with the elliptical chalaza and lack of an apical groove, indicate that Ampelocissites lytlensis Berry probably represents Ampelopsis or Nekemias (rather than Ampelocissus or Vitis) and that the generic name Ampelocissites may be useful for fossil seeds with morphology consistent with the Ampelopsis clade that lack sufficient characters to specify placement within one of these extant genera.

Seismic, morphologic and scale variabilities of subsurface pipes and vent complexes in a magma-rich margin

Subsurface pipes related to fluid flow are observed in seismic reflection data as vertical to sub-vertical features of low-amplitude reflections, linking chaotic reflections at the base (root zones) of volcanic constructs to their summits which can comprise craters, mounds or eye-shaped vents. To date, uncertainties remain regarding the linear correlation and scaling relationship between pipes and their overlying vent structures. Using 3D seismic reflection data from a magma-rich basin, the Vigrid Syncline in the Voring Basin (offshore Norway), this study provides a seismic, morphometric and statistical description of forty (40) pipes and their associated structures. These pipes include conical, bifurcated, fault-controlled and columnar types, which are a consequence of the intrusion of two mappable magmatic sills of Early Eocene age. The heights (av. 1098 m), widths (av. 1740 m) and slenderness ratios (i.e. the heights/widths (Ω)) of the pipes (av. 0.6) show low to moderate correlation coefficients with vent parameters such as height (av. 258 m), area (av. 2.3 km2) and ellipticity (av. 1.5). The morpho-statistical analyses provided here show that ‘pipe’ formation mechanisms are mutually exclusive and that vent geometries are not particularly systematic in nature.

LES SERIES DETRITIQUES DU BASSIN DE L'INDUS AU LADAKH: NOUVELLES DONNEES STRATIGRAPHIQUES ET STRUCTURALES

The study of the Indus detritic series in the western part of the Indus basin, between Khalsi and the Zanskar river allows us to distinguish various lithostratigraphic units. New datations have been obtained in several sedimentar y horizons. Marine deposits ceased at the end of early Eocene (Ilerdian —Cuisian) time; detritical series is mainly continental in feature and younger than early Eocene in age. The Indus formations are folded in a large dissymetric north vergent synclinorium of N 120 orientation; numerous folds and reverse faults are observed. The deformation and the epimetamorphism increase southward close to the northward thrusting of the Indus flysch nappes against the Indus detritics. Two main tectonic phases have been observed.

Eocene seismogenic reactivation of a Jurassic ductile shear zone at Cap de Creus, Pyrenees, NE Spain

The Cap de Creus peninsula in NE Spain exposes Variscan amphibolite-facies rocks, transected by greenschist-facies mylonitic shear zones accommodating displacements of up to 1 km. One of these shear zones contains pseudotachylytes with 1–4 mm thick fault veins and cm-scale high-angle injection veins and breccias. The pseudotachylyte matrix encloses mm-to μm-scale wallrock fragments and consists of ultrafine biotite and feldspar, often with a microporphyritic structure suggesting crystallization from a melt. Recent dating of the host shear zone yielded a Jurassic (170-160 Ma) age. Here we present 40Ar/39Ar dating of the pseudotachylytes yielding Early Eocene ages between 52.76 ± 1.64 Ma and 44.55 ± 0.77 Ma, indicating Alpine brittle faulting at times that Jurassic low-angle ductile shears had been tilted to their present vertical position following Alpine thrusting in the Pyrenees. The kinematics of the pseudotachylytes suggest strike-slip reactivation along the host shear zone, consistent with plate-kinematic analyses indicating coeval Iberia - Europe motion dominated by strike-slip. The dimensions of the pseudotachylyte-bearing zone and estimated brittle displacements suggest a moment magnitude of ~4.7–4.9. The average thicknesses of the fault veins indicate deformation at ≥4 km depth, an energy density of ~9.106 J/m2 and a frictional resistance of ~23 MPa.

Micropaleontology and Biostratigraphy of Zgaimat Al-Hasah Anticline, SE-Jordan

This study presents the first attempt to recognize the planktonic foraminiferal biozones and to determine the time of deposition of the carbonate deposits exposed in the Zgaimat Al-Hasah anticline, Southeastern Jordan. Five equivalent planktonic foraminiferal biozones; Zones E3 (P6a), E4 (P6b), E5 (P7), E6 (P8), and E7 or E7a were identified by analyzing twenty-eight samples from a 20 m thick section. Ten planktonic foraminiferal species belonging to seven genera and thirteen benthic foraminiferal species representing eleven genera were recorded. An Early Eocene age was assigned to the carbonate deposits exposed in Zgaimat Al-Hasah anticline based on some typical index species of calcareous planktonic foraminifera.