Eocene Sequence Research Articles

Petroleum system analysis of Fujairah basin, eastern offshore of the United Arab Emirates

The Fujairah basin, located on the eastern margin of the United Arab Emirates, forms part of the hinterland basin of the Oman-UAE mountains. Despite its geological significance, the hydrocarbon potential of this basin remains unexplored. This study aims to address this knowledge gap by using 2D seismic reflection data, three exploration wells, geochemical data from one well, a 2D velocity section, and two pseudo-wells. The study began with the interpretation of the seismic profiles and then proceeded to create depth maps for the most significant units. We used Rock-Eval pyrolysis plots to identify the primary source rocks and to classify their kerogen types. The seismic interpretation formed a basis for the 1D and 2D basin modeling techniques that are used to determine the petroleum system of the basin. Our results identify the Pliocene, Miocene, and Eocene sequences as potential source rocks in the basin with TOC values less than 1 wt% and low expulsion efficiencies. The Pliocene and Miocene source rocks are mainly type-II kerogen, whereas most Eocene samples are characterized as type-III kerogen. The Pliocene and Miocene source rocks are immature in the basin. The Eocene is mature depending on the burial within the sub-basins. The Eocene started expelling hydrocarbons during the Burdigalian, which was linked to the collision of the Arabian and Central Iran plates along the Zagros suture zone. Structural and stratigraphic traps may have entrapped the generated hydrocarbons. The three drilled wells in the basin lack good reservoir rocks. However, low-velocity anomalies and bright spots indicate possible hydrocarbon accumulations in the basin.

Source rock characterization for hydrocarbon generative potential and thermal maturity of Paleocene–Eocene sequences, Jaisalmer Basin, Rajasthan, India

Source rock characterization for hydrocarbon generative potential and thermal maturity of Paleocene–Eocene sequences, Jaisalmer Basin, Rajasthan, India

Long-term carbon sequestration in the Eocene of the Levant Basin through transport of organic carbon from nearshore to deep marine environments

This study addresses a specific component associated with mass transport complexes in marine systems: the role of hyperpycnal flows, dense shelf water cascading, submarine canyons, distributary channels, and other transport mechanisms in transferring organic matter from continental and shallow marine settings into deep-marine environments. We speculate that during the Eocene, allowing for only 0.1‰ of shelf carbon to be preserved through transport mechanisms would account for up to 13.7% of all organic carbon burial. As such, the potential to mobilize through this mechanism large quantities of organic carbon is significant.Our case study focuses on a 150 m Eocene sequence composed of organic-rich chalks interleaved with displaced neritic limestones. TOC values range between 1.5 and 14%, averaging 4.5%. Displaced limestones are composed of a variety of poorly cemented mud- and wackestones, with low-diversity assemblages of large benthic foraminifera associated with planktonic foraminifera, suggesting deposition under low-energy conditions within the oligophotic zone on the outer ramp. Transport overprints include soft-sediment deformation, partially lithified rip-ups, folds, small diapirs, bed-scale imbrication, brecciation and syn-sedimentary shear. These features indicate detachment, movement and emplacement following initial sedimentation, in some cases more than once. Emplacement occurs into a chalk facies that can vary in appearance from darker (higher TOC) and lighter (lower TOC) lithofacies.Combination between the sedimentological, petrophysical, and elemental analyses indicates shifts between autochthonous and allochthonous sedimentation, whereas the organic geochemical analysis reveals a correlation between modes of sedimentation and preservation/composition of organic matter. Organic richness seems to increase within intervals of allochthonous sedimentation, with lower TOC values within intervals of autochthonous sedimentation. Organic matter preservation is enhanced due to poor oxygenation of the sea floor, further depleted by rapid burial beneath mass-transport deposits, increasing sedimentation rates and thus organic matter preservation. Horizons rich in organic matter may be derived from three different sources: organic matter with a fingerprint of terrestrial sources (e.g., enhanced contribution of plant leaf waxes) transported from nearshore environments; an allochthonous marine fingerprint with sulfurized hopanoids, which seem to be reworked from pre-existing Cretaceous organic-rich carbonates entrained within fined-grained micro-turbidites in the para-autochthonous facies; and productivity-derived organic matter deposited on the seafloor of the deep marine environment.This study demonstrates how transport mechanisms allow for the long-term burial of organic carbon in marine systems. When taking into consideration similar processes reported to occur in the world oceans today, it is clear that sediment transport and long-term burial of organic carbon is a fundamental part of the global carbon cycle.

3D Seismic reflection evidence for lower crustal intrusions beneath the Faroe–Shetland Basin, NE Atlantic Margin

Lower crustal intrusion is considered to be a common process along volcanic or magma-rich passive margins, including the NE Atlantic Margin, where it is thought to have occurred during phases of Paleogene magmatism, both prior to and during continental break-up between NW Europe and Greenland. Evidence of Paleogene magmatism is prevalent throughout the sub-basins of the Faroe–Shetland Basin as extensive lava flows and pervasive suites of igneous intrusions. However, in contrast with other areas located along the NE Atlantic Margin, no lower crustal reflectivity indicative of lower crustal intrusion has been documented beneath the Faroe–Shetland Basin. The nearest documentation of lower crustal reflectivity and interpretation of lower crustal intrusion to the Faroe–Shetland Basin is NW of the Fugloy Ridge, beneath the Norwegian Basin of the Faroese sector. Despite this, the addition of magma within the lower crust and/or at the Mohorovičić discontinuity is thought to have played a part in Paleogene uplift and the subsequent deposition of Paleocene–Eocene sequences. Advances in sub-basalt seismic acquisition and processing have made significant improvements in facilitating the imaging of deep crustal structures along the NE Atlantic Margin. This study used broadband 3D seismic reflection data to map a series of deep ( c. 14–20 km depth) high-amplitude reflections that may represent igneous intrusions within the lower crust beneath the central-northern Corona Ridge. We estimate that the cumulative thicknesses of the reflections may be >5 km in places, which is consistent with published values of magmatic underplating within the region based on geochemical and petrological data. We also estimate that the total volume of lower crustal high-amplitude reflections within the 3D dataset may be >2000 km 3 . 2D gravity modelling of a seismic line located along the central-northern Corona Ridge supports the interpretation of lower crustal intrusions beneath this area. This study provides evidence of a potential mechanism for Paleogene uplift within the region. If uplift occurred as a result of lower crustal intrusions emplaced within the crust during the Paleogene, then we estimate that c. 300 m of uplift may have been generated within the Corona Ridge area.

Genesis of the Kuh-Panj porphyry copper deposit, Kerman, Iran: Constraints from mineralization, geochemistry, fluid inclusion, and zircon U[sbnd]Pb isotope systematics

The Miocene Kuh-Panj porphyry copper deposit, with reserve estimated at about 100 Mt. at 0.21 % Cu, is located 120 km SW of Kerman in the southern part of the Urumieh-Dokhtar magmatic arc. The Eocene host rocks consist of tuff, lithic tuff, breccia tuff, and lava flows, ranging in composition from rhyodacite to andesite. A late Miocene granodiorite porphyry stock (8.57 ± 0.49 Ma, U/Pb zircon) intruded into the Eocene sequence. Subvolcanic dykes cut the Eocene rocks and porphyry stock. The Kuh-Panj porphyry system has an extensive and typical hydrothermal alteration zoning pattern, which is comprised of potassic, phyllic, argillic, and propylitic alteration types from inner proximal to outer distal zones. Copper mineralization occurs in potassic and to some extent in phyllic zones. Mineralization is mostly observed as disseminated, stockwork, and vein-veinlets forms in the porphyry stock. Vein paragenesis includes barren quartz, M-type (magnetite+biotite), A1-type (quartz+magnetite+chalcopyrite±chlorite±biotite), A2-type (quartz+chalcopyrite±pyrite), D-type (quartz+pyrite±chalcopyrite), and L-type (galena+sphalerite±chalcopyrite±pyrite) veins. The I-type granitoids with calc-alkaline affinity have enrichments of LILE (Pb, K, U, Sr, and Cs), depletion of HFSE (P, Nb, Ta, Zr, and Ti), and enrichment in LREE displaying geochemical similarity to arc-related magmatic rocks. The high SiO2 (ave. 68.9 wt%), high Al2O3 (ave. 14.5 wt%), low MgO (ave. 1.3 wt%), low P2O5 (< 0.2 wt%), high Sr (ave. 365 ppm), high Sr/Y (ave. 45), relatively high LaN/YbN (ave. 28), relatively high Th (ave. 8 ppm), low Y (ave. 8 ppm), and low Yb (0.5 ppm) contents are similar to those of fertile porphyries and lower crust-derived adakites. The most dominant type of fluid inclusions in quartz from mineralized veins are liquid-vapor-halite-solid (LVHS), liquid-vapor-halite (LVH), liquid-vapor (LV), and vapor-liquid (VL) fluids. Homogenization temperatures of LVHS, LVH, LV, and VL fluids range from 306 to 574 °C, 141–566 °C, 215–422°, and 349–571 °C, respectively. Salinities of LVHS, LVH, LV, and VL fluid inclusions range from 30 to 69, 29.0–65.5, 0.35–22.0, and 0.7–13.0 wt% NaCl eq., respectively. The extreme variations in salinities of fluid inclusions represent the combined effects of varying salinity of the magmatic fluid, aqueous fluid-phase immiscibility (boiling), and mixing with lower salinity meteoric water later in the cooling history of the porphyry system. Normal cooling, water-rock interaction, surface fluid dilution, and boiling are dominant factors that control both the distribution and abundance of mineralization. Zircon from the Kuh-Panj system has high Th/U (0.53 to 0.83), low Dy/Yb (<0.3) ratios, positive Eu/Eu* (1.28–1.85), strong positive Ce/Ce* (1.36 to 197) reflecting high Ce4+/Ce3+ ratios, and enrichment in HREEs relative to LREEs, which indicate the magmatic origin of zircon, oxidized, and hydrous conditions of the primary magma. This magma with adakitic affinities is favorable for producing fertile porphyry systems. Based on these multidisciplinary studies, the Kuh-Panj deposit is classified as a continental arc-related porphyry copper system hosted predominantly at the transition zone between potassic and phyllic alteration zones due to decreasing temperature, boiling, and fluid-rock reaction that all enhance CuFe sulfide saturation.

Accumulation of radiocarbon in ancient landscapes: A small but significant input of unknown origin

The persistence of organic carbon (C) in soil is most often considered at timescales ranging from tens to thousands of years, but the study of organic C in paleosols (i.e., ancient, buried soils) suggests that paleosols may have the capacity to preserve organic compounds for tens of millions of years. However, a quantitative assessment of C sources and sinks from these ancient terrestrial landscapes is complicated by additions of geologically modern (~ 10 Ka) C, primarily due to the infiltration of dissolved organic carbon. In this study, we quantified total organic C and radiocarbon activity in samples collected from 28- to 33-million-year-old paleosols that are naturally exposed as unvegetated badlands near eastern Oregon’s “Painted Hills”. We also used thermal and evolved gas analysis to examine the thermodynamic stability of different pools of C in bulk samples. The study site is part of a ~ 400-m-thick sequence of Eocene–Oligocene (45–28 Ma) paleosols, and thus we expected to find radiocarbon-free samples preserved in deep layers of the lithified, brick-like exposed outcrops. Total organic C, measured in three individual profiles spanning depth transects from the outcrop surface to a 1-m depth, ranged from 0.01 to 0.2 wt% with no clear C-concentration or age-depth profile. Ten radiocarbon dates from the same profiles reveal radiocarbon ages of ~ 11,000–30,000 years BP that unexpectedly indicate additions of potentially modern organic C. A two-endmember mixing model for radiocarbon activity suggests that modern C may compose ~ 0.5–2.4% of the total organic C pool. Thermal and evolved gas analysis showed the presence of two distinct pools of organic C, but there was no direct evidence that C compounds were associated with clay minerals. These results challenge the assumption that ancient badland landscapes are inert and “frozen in time” and instead suggest they readily interact with the modern C cycle.

Neo-Tethyan subduction triggered Eocene–Oligocene magmatism in eastern Iran

AbstractEocene–Oligocene magmatic rocks are well exposed in the region south of Birjand, eastern Iran. The ages, geochemistry and petrogenesis of these rocks are important to understand eastern Iran’s magmatic and geodynamic history during the Cenozoic. Detailed field investigations show that numerous intrusive, intermediate to felsic units are intruded into a thick sequence of Eocene–Oligocene lava flows and their accompanying pyroclastic rocks. The volcanic rocks are mainly basaltic andesitic to rhyolitic, whereas intrusive rocks are characterized by dioritic to granitic composition. Previously compiled U–Pb geochronological data indicate that Eocene–Oligocene magmatism in eastern Iran formed continuously from ∼46 Ma to ∼25 Ma. Our new zircon U–Pb data reveal crystallization ages of 43.6 ± 0.4 Ma to 39.5 ± 0.6 Ma, consistent with the upper end of this age range. Geochemically, the igneous rocks have high-K calc-alkaline to shoshonitic signatures. Rare-earth and trace element patterns show enrichment in LREEs, K, Rb, Cs, Pb, Th and U and depletion in HFSEs such as Nb, Zr and Ti, typical of a subduction-related environment.87Sr/86Sr(i)and ϵNd(i)values range from 0.7051 to 0.7064 and −0.1 to +0.2, respectively. We postulate that the Cretaceous northeastward subduction of the Neo-Tethyan oceanic lithosphere underneath the Iranian Plateau caused sub-continental lithospheric mantle (SCLM) metasomatism by slab-derived fluid components. Subsequently, slab roll-back of the Neo-Tethyan oceanic lithosphere associated with asthenospheric upwelling led to lithospheric thinning and melting of the metasomatized SCLM. The resulting parental magmas probably interacted with upper continental crust during magma ascent to form Eocene–Oligocene magmatism in eastern Iran.

Reservoir heterogeneity of an Eocene mixed siliciclastic-carbonate succession, northern Pannonian Basin

The quality of any reservoir is strongly controlled by diagenetic processes, especially of those that are comprised of mixed siliciclastic-carbonate sequences. An Eocene mixed siliciclastic-carbonate sequence forms reservoirs with diverse reservoir quality in the Hungarian Palaeogene Basin, which is found within the Pannonian Basin. Late Eocene transgression established extensive shallow-marine depositional environments strongly controlling the early diagenetic processes. Drill cores and cuttings were selected from several boreholes, representing a wide range of lithofacies to reveal the cause for reservoir heterogeneity. Petrographic, stable isotope and fluid inclusion analyses were performed to identify the diagenetic processes that controlled the porosity evolution of the reservoir, The early diagenetic calcite neomorphism caused lateral homogeneity, whereas the early meteoric water incursion enhanced reservoir properties via the development of dissolution pores, which in turn resulted in vertical reservoir heterogeneity. The deterioration of porosity started in the eogenetic realm by kaolinite formation and continued during mesodiagenesis as burial calcite, quartz, dolomite and minor illite cement precipitated in remaining pore spaces. Petrographic evidence, such as kaolinite transformation into dickite and fluid inclusion homogenisation temperatures highlight the role of temperature increase with burial, the effect of changing fluid chemistry during the evolution of the basin is documented by the chemical zonation of dolomite, the variation in salinities of the fluids enclosed fluid inclusions, as well as recurrent and prolonged periods of cementation with calcite, quartz and dolomite. Mesogenetic processes were accompanied by hydrocarbon emplacement and the formation of late-stage pyrite. The propagation and cementation of faults first contributed to increase and later to reduce fluid flow, respectively. These steps collectively resulted in a heterogeneous reservoir, characteristic of the Eocene sequence in the Hungarian Palaeogene Basin.

Sequence stratigraphic control on the variations of organic matter in Eocene lacustrine shales within the Dongying Depression, Eastern China

• A third-order sequence is identified in Eocene shales in the Dongying Depression. • The abundance, type and preservation of organic matter (OM) are intimately related to the sequence development. • Sequence development affects OM accumulation, resulting in differential OM distribution within the Eocene sequence stratigraphic framework. Eocene organic-rich shales in the Dongying Depression, Eastern China, are well preserved and ideal for examining stratigraphic controls on the variations of organic matter (OM). This study concerns the Eocene sedimentary succession in the Dongying Depression and recognizes a third-order sequence based on the stacking patterns of lithofacies, mineralogical changes, and geochemical proxies. The total organic carbon content, Rock-Eval parameters S1 and S2 values, and the chloroform bitumen “A” content are low in the lowstand systems tracts, reaching their maxima within the transgressive systems tracts and gradually decreasing within the highstand systems tracts. The paleoclimate index and ratios of quartz/feldspar, Sr/Ca, TiO 2 /Al 2 O 3 , Cr/Al, Ni/V, Th/U, Zn/Al, and Ni/Al indicate that OM accumulation was influenced by primary productivity, sedimentation rate (SR), and redox conditions, which are intimately related to the sequence development under the influence of tectonics, climate, sediment supply, and relative lake-level fluctuations. The OM distribution is related to the sequence stratigraphy in three ways: (1) climate and relative lake-level fluctuations affected the primary productivity and OM production via algae blooms and terrestrial OM input; (2) relative lake-level fluctuations and sediment supply were influenced by tectonics and climate, causing a change in SR and OM deposition; and (3) relative lake-level fluctuations under different climatic conditions affected the development of anoxic bottom-water favoring OM preservation.

Calcareous nannofossil biostratigraphy and paleoenvironmental study along the Upper Maastrichtian- Eocene sequence at Eastern and Western Deserts, Egypt

Biostratigraphy and paleoenvironment of seventy surface samples were studied based on calcareous nannofossils along the Upper Maastrichtian – Eocene sequence at Gebel Duwi and Gebel Ghanima sections, Egypt. This succession includes three rock units, arranged from base to top as follow: Dakhla, Tarawan and Esna formations. Seven calcareous nannofossil biozones have been recorded, arranged as follow: CC 25c, CC 26, NP 2/3, NP 4, NP 5, NP 6 and NP 9b, discussed and compared with their counterpart in and outside Egypt. Four present stage boundaries have been discussed; the Cretaceous/Paleogene boundary, it seems to be incomplete in the Gebel Duwi section due to the absence of the biozone NP 1. The Danian/Selandian boundary, it can be determined in the Gebel Ghanima section based on the FO of Fasciclithus tympaniformis. The Selandian/Thanetian boundary, it was difficult to trace in the Gebel Ghanima section, where the topmost part of Zone NP 6 was missed. The Paleocene/Eocene boundary, it cannot be accurately determined in the Gebel Ghanima section, owing to the presence of a small hiatus represented by the absence of the Subzone NP 9a. There is predominance in assemblages’ taxa and were relatively warm-water temperature during the Late Danian in the Gebel Duwi section and highly warm-water temperature around the Paleocene-Eocene boundary in the Gebel Ghanima section. There are two ecozones have been recognized in our study. In the Gebel Duwi, the sediments of ecozone (A) are deposited in cool-water, and transitional states between eutrophic and oligotrophic environments, while that of ecozone (B) are deposited in warm-water and also transitional states between eutrophic and oligotrophic environments. The sediments of ecozone (B) in the Gebel Ghanima are deposited in warm-water and mainly oligotrophic environments.

Middle Eocene benthic foraminifera from Qattamiya area, Cairo\u2013Suez district, Egypt: biostratigraphy, paleoecology, and their relation to the Southern and Western Tethyan Provinces

This study deals mainly with the biostratigraphy, paleoecology and paleobiogeogrphy of the Middle Eocene benthic foraminifera from an outcrop exposed at Qattamiya area, Cairo–Suez district, Egypt. This district is covered by relatively thick Eocene sequences composed of limestone intercalated with shales and marl. Stratigraphically, the oldest rock unit exposed in the study area is the Observatory Formation which is followed by the Qurn Formation. The examination of the collected samples led to the recognition of 27 species belonging to 17 genera and 10 families. Three benthic foraminiferal biozones are recognized Elphidium trompi-Quinqueloculina carinata Assemblage Zone, Bulimina jacksonensis Zone, and Quinqueloculina ludwigi Zone. These local biozones are correlated with their equivalents inside Egypt. Therefore, the age is assigned to the Middle Eocene. To detect the paleoecology of the recorded foraminiferal community, some parameters (Foraminiferal abundance, richness, and the percentages of epifaunal and infaunal species) are calculated. Three local paleoecologic ecozones are proposed signifying a hyper-to hyposaline inner neritic environment for the lower part of the Observatory, the middle shelf with low oxygen conditions for the upper part of the Observatory Formation, and hypersaline inner neritic environment for the Qurn Formation. Recently, multivariate analyses are considered as a valuable tool in establishing the paleoecology and paleobiogeographical provinces of the Paleogene microfossils. In this study, a matrix composed of 18 species from six countries (Tunisia, Egypt, Libya, France, Spain and Italy) is suggested for multivariate analyses. This matrix is subjected to the principal component analysis (PCA) and the Q-mode cluster analysis to detect the possible provinces. Consequently, two significant provinces are detected, the Southern Tethyan Province (Tunisia, Libya and Egypt) and the Western Tethyan Province (Spain, Italy, and France). Based on the similarity index, there is a strong similarity between the two provinces, which proposes a marine connection between them during Eocene.

The Regional Extents of Local Thrust Systems in Jabbari and Rupper Town, South East of Hazara Pakistan

Geological traverse between the town of Jabbri and Rupper, southeast Hazara delineates the stratigraphic and structural element of the area presented by high resolution geological map and cross section of the area. Oldest rocks in this section is Precambrian Hazara formation which is disconformably overlain by a Jurassic to Eocene sequence including Samana Suk, Chichali, Lumshiwal, Kawagarh, Hangu, Lockhart, Patala, Margalla-hill-limestone, Chorgali and Kuldana formations. Located in Lesser Himalayas, under the influence of main boundary thrust (MBT), this area developed several thrust systems from north to south including Hazara thrust, Haro thrust, Sangoda thrust, Rupper thrust. The main regional Hazara thrust has Precambrian rock in its hanging wall thrusted over the Jurassic Samna Suk formation. In lower detachment, there are several local thrust systems within Jurassic-Eocene strata.These thrusts trends in NE-SW direction indicating NW-SE compressional regime with the hanging wall Drag folds showing southward vergence. The stereographic plot of mesoscopic scale folds shows at least three folding events and varying plunging directions between the range of 240° and 290°. Most of the folds are plunging towards west and this is yet another indicator of east-west compressional forces. These folds orientations suggest transpressional deformation rather than pure compression. The balanced restore section shows that there is about 2.5 km shortening along 15 km restored section which makes about 16% shortening along the section.&#x0D; &#x0D;

Astronomical calibration of late middle Eocene radiolarian bioevents from ODP Site 1260 (equatorial Atlantic, Leg 207) and refinement of the global tropical radiolarian biozonation

Abstract. The middle Eocene sedimentary sequence drilled at Ocean Drilling Program Site 1260 (Leg 207), Demerara Rise, western equatorial Atlantic, yielded a rich and diverse radiolarian fauna. The exceptionally expanded and complete sedimentary record of this site, as well as the existence of an orbital chronological framework, allowed us to study a number of radiolarian bioevents with a very fine temporal resolution. We compiled a well-resolved succession of 71 radiolarian bioevents (first occurrences, last occurrences, and evolutionary transitions) and provided calibrations to the geomagnetic polarity timescale and astronomical timescale. Comparison of the radiolarian successions at ODP Site 1260A with the northwestern Atlantic IODP Site U1403 and the IODP Sites U1331, U1332, and 1333, situated in eastern equatorial Pacific, allowed the demonstration of the synchroneity of primary radiolarian bioevents that underpin the middle Eocene zonal scheme. Several secondary bioevents were also found to be synchronous between the two oceans and were therefore used to define seven new subzones for the low-latitudinal middle Eocene sequences: Siphocampe ? amygdala interval subzone (RP13a), Coccolarnacium periphaenoides interval subzone (RP13b), Artostrobus quadriporus interval subzone (RP14a), Sethochytris triconiscus interval subzone (RP14b), Podocyrtis (Podocyrtopsis) apeza interval subzone (RP14c), Artobotrys biaurita interval subzone (RP15a), and Thyrsocyrtis (Pentalocorys) krooni interval subzone (RP15b). This refined radiolarian biozonation has significantly improved stratigraphic resolution and age control for the late middle Eocene interval (an average of two subzones per 1.5 million years). A substantial diachronism was also found in 20 secondary radiolarian bioevents between the two oceans. The majority of radiolarian species appear to have evolved first in the equatorial Atlantic Ocean and subsequently in the equatorial Pacific. However, the reasons for this pattern of diachroneity currently remain uncertain and would require a greater sampling coverage to be elucidated.

Calcareous nannofossil biostratigraphy of Nag El Quda, South of Dababiya, Eastern side of the Nile Valley, Egypt.

The biostratigraphy of calcareous nannofossils of the upper Paleocene-lower Eocene sequence in Nag El Quda area (South of Dababiya, Eastern Side of the Nile Valley, Egypt carried out in detail. This study of the P-E transition, allow us to recognize some of the prominent and abrupt events that characterize the P/E boundary, and to relocate this boundary with respect to the recent redefinition of the Paleocene/Eocene boundary. The present stratigraphic study of the P/E interval based on close sampling. This study has provided a high resolution litho- and biostratigraphic data based on calcareous nannofossils. The study interval includes from the base to top; El Hanadi, Dababiya, and El Mahmiya members. The P/E boundary is situated at the NP9a/NP9b boundary, which lies at El Hanadi/Dababiya contact. We identify the first occurrence (FO) of excursion taxa (Discoaster anartios, D. araneus, Rhomboaster spp.) at the base of the Eocene. These taxa are adapted to warm climatic conditions that prevailed at this boundary. An abrupt and sharp decrease in the diversity, abundance of the genus Fasciculithus occurs at the NP9a/NP9b (Paleocene/Eocene boundary), and disappeared completely shortly afterwards. The lowermost Eocene sediments studied here only yield F. tympaniformis and F. involutus.

Sequence stratigraphy of the Andaman Basin, northern Indian Ocean

Andaman Basin, a poly history basin in the northeastern Indian Ocean, preserves the sedimentary record from Late Cretaceous to Recent with several stratigraphic breaks. Studies from outcropping sedimentary succession, integrated with subsurface data from drilled wells in the offshore, have enables to work out a sequence stratigraphic framework of the sedimentary succession in the basin.The succession comprises of three first-order sequences viz., Late Cretaceous – Eocene, Oligocene and Neogene. These have been related to basin forming tectonic events related to accretionary prism formation and subduction in Paleogene, Oligocene uplift and renewed subduction in Neogene, respectively. Excellent bio-stratigraphic control and field evidence have enabled identification of unconformities of various magnitudes, which in turn has enabled mapping second-order sequence. The 3 second-order sequences within first-order Late Cretaceous–Eocene sequence are: Late Cretaceous-Early Paleocene, Late Paleocene-Middle Eocene and Late Eocene sequence. The Oligocene first-order sequence related to the major uplift and emergence of the main Andaman Island chain, contributed >2000m of flysch sediments. Three second-order sequences within the first-order Neogene sequence are Early Miocene - early Middle Miocene, Middle Miocene - Middle Pliocene and Late Pliocene - Pleistocene sequences separated by unconformities of various magnitude. Each sequence is discussed with respect to its extent, nature of sequence boundaries, sedimentary fill and sequence stratigraphic surfaces to understand the sequence stratigraphic architecture of the basin.

Sedimentary Basin Reconstruction and Tectonic Development of Paleocene-Eocene Succession, Southern Iraq, by Geohistory Analysis

The Paleocene-Early Eocene sequence is represented by Aliji and Umm Er Radhuma formations, while the Middle-Late Eocene sequence is represented by Jaddala and Dammam formations. The Rus Formation has been described and its basin was analyzed separately because it was deposited during the regression period (Middle Eocene), which is a transitional period between these two cycles. &#x0D; This study includes analysis of the geohistory of this succession, interpretation of the changes of the accumulation, and calculation of subsidence rates. The results were compared with the space available to explain the basin development. The study site included the boreholes of Garraf-84 and 92, Halfaya-1, Nasirya-13 and 40, and Noor-5 at the Mesopotamian Block, in addition to the Ratawi-8, Tuba-15, Rumaila-217, Zubair-45, and West Qurna-60 at the Basra Block.&#x0D; The Aliji basin was characterized by the decrease in accommodation values to the northeast direction and the increase in all the other parts of the study area. A comparison of the setting of this basin with the Umm Er Radhuma basin gives a clear evidence of the tectonic impact coming from the northeast. During the Middle Eocene stage, we notice that the basin was affected by comprehensive uplifting processes. This led to the generation of a very shallow basin (Rus basin) with the exposure of the northern part of the basin during the regression stage.&#x0D; The Middle-Late Eocene basin is represented by a transgression stage with high subsidence, where the sea level had been raised and covered the northeastern and eastern parts of the studied area by deep sea deposits (Jaddala Formation). While the other parts of the study area were characterized by shallow sediments of Dammam Formation. This period ended with a clear tectonic uplift occurring in the northeastern parts and decreasing towards the southwest. This confirms the reactivation of the tectonic action from the northeast, represented by the continental collision.&#x0D; All these sources of evidence indicate that the study area is divided into a northern part and a southern part. Both of these parts are separated by a major tectonic lineament extending from the West Qurna oil field to the Nasiriya oil field, which confirms the presence of the tectonic boundary between the Mesopotamian block and the Basra block. In addition, there exists a secondary tectonic boundary that divides the Mesopotamian block into two parts, the first is to the east and the other is to the west. The results showed that the eastern side was most affected by the collision of the Iranian Plate with the Arabian Plate, which led to its uplift, while the western side was less affected by this tectonics evidence.

Reconstructing Eocene Eastern Indian Ocean Dynamics Using Ocean‐Drilling Stratigraphic Records

AbstractThe Eocene Epoch corresponds to the runup toward the Greenhouse to Icehouse Cenozoic transition. To fully appreciate this climate evolution, detailed and accurate age‐depth models are required. While much progress has been made recently in the field of Eocene astrochronology, the construction of unambiguous Eocene astronomical timescales (ATS) is hampered by lithologically undetected hiatuses, the scarcity of carbonate‐rich marine successions, and conflicting cyclostratigraphies. In this study, we present an orbital‐scale cyclostratigraphy for Ocean Drilling Program (ODP) Hole 762C, and we reconstruct Eastern Indian Ocean dynamics. This reconstruction is based on two ocean‐drilling Eocene sequences: ODP Hole 762C and International Ocean Discovery Program (IODP) Site U1514. Our eccentricity‐based cyclostratigraphy for Hole 762C is integrated with existing bio and magnetostratigraphies and constitutes the most precise available chronology for this legacy site. The Hole 762C stratigraphy is combined with the existing Site U1514 age‐depth model to obtain a high‐resolution Eocene ATS for the Eastern Indian Ocean. We apply sedimentary noise modeling to obtain new insights in benthic turbulence at both sites. Despite the significant difference in paleo‐waterdepth, noise levels at both sites carry a 1.2‐Myr obliquity amplitude imprint. We interpret the sedimentary noise at Hole 762C, on a submarine plateau, in terms of sea‐level change. The sedimentary noise at U1514, by contrary, is interpreted to be modulated by bottom current intensity as this site represents a deep‐sea basinal environment. We conclude that, despite very similar astronomical signatures, the mechanistic pathways between astronomical forcing and sedimentary response were radically different at these two sites.

New insights into stratigraphy and paleoenvironment of the Upper Cretaceous–Eocene succession, Farafra Oasis, Western Desert, Egypt

Detailed field, litho-, bio-, sequence stratigraphy, and paleoenvironmental studies are carried out on the Aqabaat section, Farafra Oasis, Western Desert, Egypt. Lithostratigraphically, the Khoman Formation is here differentiated for the first time into three new distinctive members, which are easily detected at the field: the White Desert (at base), the Gunna (at middle), and the Aqabaat (at top). Biostratigraphically, six planktonic foraminiferal zones and subzones are here identified ranging in age from Maastrichtian to Ypresian. The foraminiferal indices, as well as the benthonic foraminiferal biofacies, indicated an outer neritic paleoenvironmental condition of the Maastrichtian rocks interrupted with shallowing of the relative sea-level at some intervals, especially at the upper parts. These shallowing settings are due to the impact of three syn-sedimentary tectonic events (I, II, and III), which are related to the Syrian Arc orogeny. The Tectonic Event I had a regional impact and led to form a positive structure in the sedimentary basin at the Cretaceous/Paleogene (K/Pg) boundary. The Tectonic Event II and III synchronized with the Danian/Selandian (D/S) and Paleocene/Eocene (P/E) boundaries, respectively. Four depositional sequences (SQ1–SQ4) are defined separated by four sequence boundaries (SB1–SB4) covering the Maastrichtian–Eocene sequence.

Middle to late Eocene chemical weathering history in the southeastern Tibetan Plateau and its response to global cooling

Continental weathering is a crucial factor to maintain the balance of the carbon cycle and thus the livability of the Earth. The Tibetan Plateau (TP), known as the Third Pole of the Earth, has undergone strong uplift since the Cenozoic, thus making it an ideal area to study continental weathering processes and associated driving factors. However, early Cenozoic weathering records are rare in this region. Here, we report high quality mineralogical and geochemical records of clay fraction (< 2 μm) of a middle to late Eocene sequence retrieved from the Qujing Basin, southeastern TP, to track the early Cenozoic chemical weathering history in this area. The results show that the main clay mineral assemblages contain illite-smectite mixed layers, illite and palygorskite. The chemical weathering intensity indicators (e.g., clay mineral assemblages and the chemical index of alteration (CIA)) collectively indicate a clear long-term modulation of global cooling on regional chemical weathering processes during middle to late Eocene, as indicated by high correlation between global temperatures and chemical weathering indicators and the similarity in their periodicity characteristics. Moreover, a sudden decrease of the chemical weathering intensity with large fluctuations was identified at 42–39.9 Ma, which may be linked to rapid transport of clay minerals caused by tectonic activity and/or an increased precipitation in the southeastern TP. This study indicates a control of global cooling on chemical weathering of the southeastern TP area during middle to late Eocene, while tectonic activity or other factors might exert catalytic influences at some certain periods.

Uplift of Anatolia

The Cenozoic history of the Anatolian Plateau is investigated using the distribution of the last Cenozoic marine strata, the ages of Neogene continental sediments and magmatic rocks, and thermochronology. In central and northern Anatolia, the youngest marine sediments are of Middle Eocene age and show that the region has been above the sea level since ca. 41 Ma. The preservation of marine Eocene sequences over large regions and widespread distribution of Neogene continental sediments point to minor erosion or subsidence, except in the Miocene core complexes, and indicate average surface uplift or subsidence rates of less than 0.05 km/Myr since 41 Ma. The Cenozoic mammal ages point to widespread continental deposition on the Anatolian Plateau from Early Miocene ca. 22 Ma to the present, and a similar pattern of semicontinuous magmatism has been observed in Anatolia since ca. 23 Ma. New thermochronological data from central Anatolia to west of Ankara have indicate a major exhumation phase during the Paleocene and Early Eocene, followed by minor uplift and/or subsidence. Miocene exhumation is restricted to the core complexes, such as the Kazdag Massif. The Anatolian Plateau has been a land area since 41 Ma and was characterized by continental sedimentation and volcanism in the last 22 Myr. In this period, subsidence and uplift were balanced so that central Anatolia was maintained above sea level. In contrast, its southern mountainous margin, the Taurides, is free of Neogene magmatism and has undergone a fast uplift above sea level since 8 Ma ca. 0.3 km/Myr . These differences indicate that the uplift of Anatolia cannot be ascribed to a single mechanism. Flat subduction, followed by mantle upwelling under Anatolia in the post-Middle Eocene period, maintained the region above the sea level, whereas the Late Miocene rupture of the subducting eastern Mediterranean oceanic slab have induced fast uplift of the Taurides.