Eocene Research Articles

Tectonic Evolution and Sedimentary Responses of Palaeocene–Eocene Tethys Himalayan Foreland Basin in Southern Tibet

ABSTRACTThe tectonic evolution of the Palaeocene–Eocene Tethys Himalayan foreland basin plays a crucial role in reshaping the collisional orogenic process of the Yarlung–Tsangpo oceanic basin. However, studies examining the sedimentary response during the tectonic evolution of the foreland basin are lacking. In this study, through a detailed field investigation and analysis of Palaeocene–Eocene strata in the Tingri area, we clarified the evolution of the Tethys Himalayan tectonic regions and its sedimentary response. Carbon and oxygen isotopes, geochemistry and detrital zircon U–Pb dating demonstrated that the lower Palaeocene Jidula Formation and upper Palaeocene–lower Eocene Zongpu Formation were deposited in a coastal–shallow marine environment, with the detritus sourced from the northern Indian passive margin. The upper Eocene Pengqu Formation was deposited in a deltaic environment, with its detritus sourced from the Gangdese arc and the Yarlung–Tsangpo suture zone at the active continental margin. Combined with the nearshore subaqueous fan branch channel of the Jidula Formation and the slump deformation of the Zongpu Formation, the Palaeocene–Early Eocene southern Tethys Himalaya in the Tingri area was located in the forebulge of the peripheral foreland basin. The marine–continental interactive delta of the Pengqu Formation and its provenance from the Gangdese magmatic arc indicate that the Tingri area was situated in the foredeep of the peripheral foreland basin during the Late Eocene. The study provides valuable insights into the collisional orogenic processes between the Indian and Eurasian plates.

Tectono-stratigraphy, formation and emplacement ages of the Beyşehir-Hoyran Nappes in the south of the Sultan Dağları (Isparta, SW Türkiye)

The Beyşehir-Hoyran Nappes (BHN), in the south of Sultan Dağları, consist of ophiolite, mélange and nappe slices of different lithologies and ages belonging to the oceanic crust and related rocks, which originated from the northern Neotethys and were thrusted southwards over the Taurus Platform. These nappes, namely the Marmaris ophiolite nappe, the Gülbahar nappe and the Domuzdağ nappe, are represented by three tectonically related nappe-slices that extend as a narrow NW-SE trending belt to the south of the Sultan Dağları. The Marmaris ophiolite nappe (Upper Cretaceous) is formed by three subunits namely the Marmaris ophiolite, the Kızılcadağ mélange and the Yenicekale metamorphics. Hornblende minerals from amphibolites of the Yenicekale metamorphic rock unit yielded a 40Ar-39Ar age of 93.9±0.34 Ma (Cenomanian-Turonian boundary). Besides, late Triassic to early Jurassic ages were obtained from the deep marine sedimentary rocks of the Gülbahar nappe based on the radiolarian assemblages. Paleontological and radiometric ages obtained from this study show that the formation of the BHN should began in the Turonian and ended in the Late Maastrichtian. The nappes, on the other hand, were emplaced over southern Sultan Dağları in the early-middle Paleocene and reached their present position as a result of late Eocene movements.

Northward drift of the Burma Terrane with India during the Cenozoic and implications for the India–Asia collision

The past location of the Burma Terrane during the convergence of the Indian and Asian tectonic plates is key to unravelling the regional geodynamic, palaeoenvironmental and palaeobiogeographical history of the eastern edge of the Himalayan orogen. Palaeomagnetic data provide the ability to constrain the location of the Burma Terrane, but it has been very difficult to find rocks with palaeomagnetic records of primary characteristic remanent magnetizations. We present here new palaeomagnetic results spanning the Paleocene to late middle Eocene within the Burma Terrane, complementing palaeolatitudes previously established from Late Cretaceous intrusive rocks and late middle Eocene sedimentary rocks. Our palaeomagnetic data indicate that the Burma Terrane remained at equatorial latitudes during the Paleocene and early Eocene, at a considerable distance from the South Asian margin. In addition, palaeomagnetic results from mid- to late Eocene sedimentary rocks yield a predominantly north–south orientation of the Burma Terrane over the past 45 Myr, showing that it was not part of the NW–SE-oriented Sundaland margin before its collision with India. Our results support collision models involving a Trans-Tethyan subduction system during the Late Cretaceous and early Paleocene. We propose that this system incorporated the Burmese volcanic arc and continental fragments of Argoland before drifting north with India towards Asia. The new palaeogeographical model considers a reduced amount of oblique subduction of the Indian plate below Burma during the Cenozoic. A possible source of sediments filling the thick Myanmar basins from the Gangdese belt during the Eocene supports the hypothesis of an India–Asia collision around ∼50 Ma. The new palaeogeography supporting the formation of the Myanmar Cretaceous amber on an isolated Trans-Tethyan Arc is also a key element in discussions of the palaeobiogeographical evolution of the numerous faunas it contains.

Long-lived sedimentation in the Western Tethys oceanic basin: revisiting the metasediments of Bagliacone-Riventosa Formation (Corsica, France)

ABSTRACT In the Alpine Corsica, the Schistes Lustrés Complex consists of a stack of high-pressure metamorphic oceanic and continental units originated during the Late Cretaceous-Middle Eocene closure of the Western Tethys oceanic basin. This complex also includes the Bagliacone-Riventosa Fm. i.e. a thick succession of metaturbidites, whose interpretation is still matter of debate. In this paper, we provide the stratigraphic, metamorphic, and structural evidence that the Bagliacone-Riventosa Fm. belongs to the sedimentary cover of the Middle to Late Jurassic metaophiolites of the Inzecca Unit. The reconstructed succession of the Inzecca Unit thus comprises metaophiolites topped by metacherts and by the Erbajolo, Pietraggiolo and Bagliacone-Riventosa Fms. The former two formations derived from hemipelagic deposits whereas the latter two include both siliciclastic and carbonate turbidites. This succession is affected by a polyphase deformation history that is recognized as the same in all the metasedimentary formations, as testified by their structural field relationships. In addition, these formations experienced the same pressure-temperature metamorphic path, indicating their involvement in a subduction zone. This picture provides new evidence for the mechanism of underplating and exhumation of the oceanic slices within the frame of the subduction zone that developed since Late Cretaceous in the Western Tethys oceanic basin.

Architecture of the post-obductional Sunub Structure, northeastern Sultanate of Oman: Based on mapping, 3D gravity inversion and shale migration

We examined the structural evolution of the poorly understood Sunub Structure, which is associated with the northern margin of the Saih Hatat Dome and the extensional Frontal Range Fault (northeastern Oman). The Sunub Structure is located at a dextral transtensional segment and on the hanging wall of the NNE-striking Frontal Range Fault. The fault was active during the Campanian(?)/Maastrichtian to early Eocene (Interval I) and mid-/late Eocene to early Miocene (Interval II). Gravitational inversion using 175 stations and mapping shows: (1) The Sunub Structure is possibly >1200–1350 m deep and filled mostly with the >900-m-thick Campanian(?)/Maastrichtian siliciclastic Al-Khod Formation, including shale, and some overlying Paleogene limestones. (2) The bottom of the basin cannot be depicted. (3) The lower part of the structure is a basin (Sunub Sedimentary Basin), bounded by sub-vertical to steep contacts. (4) The upper part of the Sunub Structure is a basin fold displaying a bowl-shape down to ∼300 m below the surface, referred to as the Sunub Bowl. (5) The bowl is cut by radial faults and five ∼E/W-striking transverse faults. The Sunub Structure formed during Interval I as a deep transtensional, syn-depositional basin. Gentle post-depositional tectonics during Interval II and visco-plastic shale movements produced the present-day bowl-shape that is visible at the surface. Gravitational inversion depict possible evidence for shale migration within the Al-Khod Formation. Although no hydrocarbons are present, the Sunub Structure can serve as an analogue for hydrocarbon migration and storage in similar structures.

New species and new record of embiids (Insecta: Embiodea) from upper Eocene of Europa

The second species of the genus Electroembia, E. olmii sp. n., is described from Baltic amber (Priabonian). The new species have fully developed fore and hind wings contrary to wingless E. antiqua, the type and previously single known species of the genus Electroembia. The first embiid from Rovno amber (Priabonian of Ukraine) is described. The only specimen is a female or a last instar female larva, making precise identification impossible. However, the described species is clearly not conspecific to the described webspinners from Baltic amber.

A plastron fragment reveals a previously unrecorded turtle species in the Eocene of Messel Pit, Germany

Depending on taxonomic opinion, between four and five turtle species are well attested for the Middle Eocene Messel Pit formation of Germany. Here, we describe specimen SMF ME-3495 from the Messel collection of the Senckenberg Museum in Frankfurt, which unambiguously corresponds to an additional turtle species. The specimen consists of a partial anterior plastral lobe that can be distinguished from other Messel turtle taxa on the basis of the presence of gular tubercles, an extensive epiplastral lip, narrow gulars that lap onto the entoplastron, and a sinuous gulo-humeral sulcus. The fragment is not sufficient to diagnose another contemporary European turtle taxon, but its epiplastral lip morphology is reminiscent of “ptychogasterid” geoemydids (Cryptodira). We also remark on bone corrosion consistent with “shell disease” and distinctive coloration.

Development of arcuate faults and controls on hydrocarbon accumulation in the Tiantai slope, Xihu Depression, East China Sea basin

The strike-slip movement of NW-trending transfer zone in the Tiantai slope of the Xihu Depression governed the development of the Cenozoic arcuate faults. These faults significantly influenced trap formation, sand-bodies distribution, and hydrocarbon migration. Based on seismic, drilling data and fault activity analysis methods, this paper describes the origin and evolution of the arcuate faults and their impact on hydrocarbon accumulation. These arcuate faults exhibit a change from NE to NW strike orientation in plan view, and are distributed in the hanging wall of the NW-trending basement faults. The main arcuate faults penetrate the bottom of the Cenozoic strata and extend upward through the top of the lower member of the Huagang Formation, markedly affecting the depositional dynamics of the Pinghu Formation. The segments of the arcuate faults began to grow during the Middle Eocene, and experienced hard linkages in the Late Eocene. The activity of these arcuate faults diminished significantly and gradually stopped during the Middle and Late Oligocene. The segmentation and linkage growth processes of the arcuate faults controlled the formation and evolution of traps. Additionally, the activities of these faults influenced the distribution of sandbodies, with the segmentation points of the arcuate faults serving as important conduits for sediment input. Moreover, the arcuate faults served as effective pathways for vertical hydrocarbon migration. The area with the arcuate faults present favorable conditions for hydrocarbon accumulation in the Tiantai slope of the Xihu Depression.

Variscan basement tectonics and Alpine shear zones in the external Balkanides: Structural data from the Vezhen Massif, Central Stara Planina Mts., Bulgaria

The Alpine Balkanides in Bulgaria are developed over Variscan orogenic fragments, which are variously affected by late-stage thick-skinned thrust tectonics. Often, these fragments hold both Variscan and Alpine structural records. А key area to shed light on important aspects of the tectonic evolution of the external parts of the Alpine Balkanide orogen is the Vezhen Massif in the Central Stara Planina Mountains. Although it is built exclusively of Paleozoic crystalline rocks, its structure was long considered as an example of intense mid Eocene to early Oligocene (Late Alpine) shortening. Detailed fieldwork in the area shows a more complicated tectonic framework and provides evidence of a polyphase structural evolution, involving an important stage of Variscan metamorphism and deformation and two stages of north-vergent Alpine shortening. The Stargel-Boluvanya Tectonic Zone that affects the western Vezhen Massif is one of the most important Variscan structures in the Balkan fold-and-thrust belt. Structural data indicate that the metamorphic basement records initial top-to-north thrusting, followed by further shortening, which led to folding and localized strike-slip deformation. The Variscan syn-metamorphic fabric is cross-cut by several post-kinematic igneous bodies of late Carboniferous to Permian ages. The tectonic history continues with a development of a network of greenschist facies north-vergent mylonitic zones for which an Early Alpine (post-late Permian but pre-Late Cretaceous) age is assumed. Late Alpine north-vergent thrusting is evident only on the eastern and northern flanks of the Vezhen Massif. In a broad structural context, the documented record in the basement rocks of the Vezhen Massif is comparable with those of the external massifs of the Alps and Iberia.

Geochemistry and low-temperature thermochronology of Kunyang phosphate deposit in the Yangtze block and its regional uplift history

The Kunyang phosphate deposit, located on the southwestern margin of the Yangtze Block in southern China, is hosted by the Lower Cambrian Meishucun Formation. The distribution of the deposit is restricted, and the outcrops of its phosphate layer are intermittent, probably owing to subsequent regional uplift and erosion. Therefore, investigating the denudation and uplift history of the deposit can clarify the preservation and distribution of the ore body after its formation, providing insights into the geological evolution of the mining area. Petrographic analysis indicates that collophane is the main ore mineral in the phosphorite, accompanied by dolomite, quartz, and limonite. The bulk-rock geochemical analyses suggest that the formation of phosphorite took place in a marine environment characterized by relative oxidation and high salinity, possibly involving hydrothermal activity during a drier mineralization stage. Apatite fission-track thermochronology, zircon-apatite (U-Th)/He dating, and thermal history modeling demonstrate that the Kunyang phosphate deposit underwent rapid uplift process during the Late Triassic (c. 225–211 Ma) and Eocene (c. 55–30 Ma), respectively. The average cooling rates were 1.05 °C/Myr and 0.93 °C/Myr, respectively, corresponding to average denudation rates of 42 m/Ma and 37 m/Ma. These two episodes of rapid uplift are corresponding to tectonic events on the southwestern margin of the Yangtze Plate during the Indosinian Orogeny, and the collision between the Eurasian and Indian Plates during the Himalayan Orogeny.

Paleobotanical Evidence for Mediterranean Climates in the Western Canadian Paleoarctic During the Late Middle Eocene

AbstractPaleogene age deposits east of the Fifteenmile River, northwest of Dawson City, Yukon, Canada preserve a diverse high‐latitude fossil flora. Here, we provide new data on the age of the fossil site based on laser ablation–inductively coupled plasma–mass spectrometry (LA‐ICP‐MS) U‐Pb dating of tephra zircons, paleobotanical paleoclimate reconstructions, and growing season length estimates based on photoperiod. These new data indicate an age of the Fifteenmile River fossil locality as late middle Eocene and likely within the Middle Eocene Climatic Optimum episode. The paleoflora‐based paleoclimate reconstruction indicates the region was relatively wet and warm with non‐freezing winters, but also experienced seasonal dryness, with an approximate 7 months long growing season as suggested by photoperiod. We interpret this paleoclimate as summer dry and winter wet—a climate analogous to modern day warm Mediterranean climates in the Köppen‐Geiger climate classification system. These findings provide a new perspective on the past climate and environment of high‐latitude ecosystems during warm greenhouse intervals and contribute to our understanding of the Earth's climate history and its potential future changes.

Inhomogeneous strain partitioning in the Cenozoic Bohai Bay Basin controlled by pre-existing crustal fabrics and oblique subduction: insights from the Jizhong and Huanghua subbasins

The tectonic features and geodynamics of the Bohai Bay Basin (BBB) have been extensively studied over several decades. It is generally accepted that the Cenozoic BBB was subjected to a superimposed extensional and strike-slip stress field. However, the specific basin-forming mechanism remains ambiguous. Basin-scale studies with high spatial and temporal resolution reveal how strain migrates and localizes during multiphase rifting. Understanding these strain-related processes is crucial for deciphering the formation mechanisms and controlling factors of rift basins. This study investigates the rift-related evolution and strain partitioning in the Jizhong and Huanghua subbasins, the western half of the BBB. Using high-resolution 3D and 2D seismic datasets and well data, we present detailed geological sections, residual thickness maps, and fault systems, showing two distinct patterns of strain partitioning in the Cenozoic. In the Jizhong Subbasin, strain migrated inwards from the NE-trending boundary faults and finally became localized along the NE-trending rift axis; in the Huanghua Subbasin, strain migrated northeastwards from the southern part and then was largely localized along the near E–W-trending faults in the northeastern part. By integrating our results with previous studies of other subbasins, we identify two separate extensional domains within the Cenozoic BBB. The suborthogonal extensional domain in the Jizhong Subbasin is dominated by relatively stable NW–SE extension. In contrast, the extended areas to the east (i.e., the Huanghua, Bozhong, and Liaohe-Liaodongwan subbasins) comprise the oblique extensional domain, characterized by asymmetric transtensional pull-apart deformation and subjected to a clockwise-rotated extensional stress field from NW–SE to NNW–SSE. We suggest that the spatially inhomogeneous strain partitioning in the BBB has developed since the middle Eocene, and was controlled by the interaction of pre-existing crustal fabrics (e.g., the Tan-Lu Fault Zone) and the oblique subduction of the Pacific Plate. The boundary between the two domains may represent a transition zone where the margin-parallel residual velocity component of the oblique convergence decreased considerably landwards. Our study highlights the Cenozoic strain evolution and the associated geodynamics in the BBB, emphasizing the strain complexity within the back-arc rift basin under the oblique subduction background.

The effect of geology and agricultural development on the groundwater, West Minia, Egypt

Fifty groundwater samples were collected from the Oligocene sand and Middle Eocene limestone aquifers and analyzed for major ions and stable isotopes. Aquifer sediment samples were examined to determine hydraulic properties, and sixty-six well logs were investigated to understand the subsurface geology. The study reveals that lithofacies, mineral composition, and geologic structures significantly influence groundwater quality and behavior. Karst features in the Middle Eocene limestone aquifer create subsurface caves, leading to challenges such as abrupt salinization and well failure. In the Oligocene aquifer, groundwater is predominantly of the sodium chloride type. In the Middle Eocene aquifer, 80 % of samples are sodium chloride, with variations of sodium bicarbonate (10 %) and sodium sulfate (10 %) types. Remote sensing from 2013 to 2021 shows significant agricultural expansion, with vegetation increasing by over 227 km². This growth, driven by large agricultural projects, has led to substantial groundwater consumption, resulting in a 5-meter decline in water levels within just one year (from 2020 to 2021). The over-extraction poses a risk to the aquifers, threatening long-term sustainability. Understanding the region's geology is crucial for mitigating these issues and ensuring sustainable groundwater management.

Early Eocene Metasequoia and Taxodium (Cupressaceae) from Lingbao, Henan Province and their implication for a perhumid climate in central China

In this study, fossil leaves of Metasequoia Hu and Cheng, along with leaves and cones of Taxodium Richard, from the lower Eocene of the Xiangcheng Group in Lingbao, Henan Province, central China, were examined. These fossils have been taxonomically assigned to Metasequoia sp. (cf. M. glyptostroboides Hu and Cheng) and Taxodium dubium (Sternberg) Heer. The closest modern relatives are Metasequoia glyptostroboides and Taxodium distichum (Linnaeus) Richard, which typically thrive in humid environments, indicating that similar conditions may have prevailed in early Eocene. Through the Species Distribution Model (SDM) experiment, it was suggested that T. distichum is significantly influenced by precipitation levels, highlighting the importance of moisture in their historical distribution. Moreover, the analysis of the survival environments of native Metasequoia and Taxodium indicates that the annual precipitation in Lingbao during the early Eocene exceeded 1000 mm, which is roughly double the current annual precipitation in the area. This precipitation level is comparable to the present-day subtropical climate zone. During the late Eocene and early Oligocene, the seasonal variation in precipitation was intensified due to the strengthening of the East Asian monsoon, which constrained the seed germination and seedling survival. This may have contributed to the decline in the populations of Metasequoia and Taxodium in East Asia during that period.

Middle - Late Eocene cold and wet climatic interval in East Asia: Evidence from lacustrine sediments of the lower Huoshaogou Formation in the Hexi Corridor, NE Tibetan Plateau

Knowledge of the climate of the Late Eocene is important for understanding the global climatic shift from a global Warmhouse to a Coolhouse. We obtained a climatic record for the interval of 38.10–36.33 Ma based on sedimentary facies analysis combined with measurements of color indices (CI) and magnetic susceptibility (MS) of the lower Huoshaogou Formation in the westernmost Hexi Corridor, Northeastern Tibetan Plateau. Our results reveal the following temporal sequence of sedimentary environments: delta plain, shore–shallow lake, deep lake, and braided river. The records of MS and CI co-vary with changes in sedimentary facies and color, respectively. The various proxy indicators indicate an overall warm and dry climate interrupted by a cold and wet interval in the middle part of the section during ~37.67–36.44 Ma, corresponding to a thick, greenish-colored lacustrine sedimentary layer with high values of lightness and low valuer of MS, frequency-dependent MS and redness. We suggest that this event was driven by the diversion of westerly winds due to the uplift of the southern Tibetan Plateau, together with the Tethys Sea retreat and the short-lived emergence or enhancement of the Asian monsoon.

Basin inversion, drifting and hyper-extension in the Central Atlantic Ocean and Maghrebian Tethys as fluid driving mechanisms for the superimposed base metal mineralization events in the Jbel Bou Dahar carbonate-hosted Pb-Zn-Ba deposits (High Atlas, Morocco)

The Early Jurassic Jbel Bou Dahar reef-bearing carbonate platform in the eastern High Atlas, Morocco, contains numerous carbonate-hosted and fault-controlled Pb-Zn-Ba deposits, prospects, and showings. Combined field, petrographic and geochemical data, including REE + Y analyses, stable (C-O-S), radiogenic (SrPb) and noble gas (He, Ne, Ar) isotopic compositions, record two temporally distinct metallogenic events. Both events are related to post-rifting and inversion of the inherited Mesozoic Atlas paleorift. The ore deposits are thought to have been formed during large-scale episodes of transtensional basin evolution, which developed as a far-field effect of the drifting of the Central Atlantic Ocean and Maghrebian Tethys while the basin continued to invert in response to the ongoing convergence between the African and the Eurasian plates. The paragenetically earliest Zn-rich ore was generated in a transtensional setting coincident with the hyper-extension of Maghrebian Tethys and the initial stages of drifting and formation of the Central Atlantic passive margin. Crustal extension and high heat fluxes provided by the hot upwelling mantle would have triggered buoyancy-driven convection of deeply sourced fluids and maturation of organic matter dispersed within the host carbonates to produce hydrocarbons within an extensional basin setting. These relatively reduced Zn-rich ore-forming fluids acquired metals mainly through protracted interaction with the country rocks including the underlying Triassic siliciclastic series and the granitic basement rocks. Regional ENE- to E-W-trending major faults would have acted as conduits for upward fluid flow and traps for Zn-Pb-Ba mineralization. Conversely, the late Pb-rich mineralization stage II is broadly constrained to have occurred between ca. 70 Ma and 10 Ma and is thought to be related to the transition from orogenic shortening (late Eocene) to post-orogenic crustal extension and exhumation (early Miocene) following Alpine orogenic collapse. Mixing of down-ward percolating meteoric fluids and ascending rock-buffered hydrothermal brines that had previously equilibrated with the radiogenic basement rocks along with thermochemical sulfate reduction of transported sulfate and/or thermal cracking, would have been the main ore-forming processes that controlled ore deposition. Given these fluid characteristics and geodynamic settings, the Jbel Bou Dahar ore field is classified as a hybrid carbonate-hosted Pb-Zn-Ba district formed by the juxtaposition of two deposit types rather than one progressively evolving mineralizing system. From an exploration standpoint, new delineation here of the two metallogenic events provides valuable exploration tools for further targeting PbZn and barite resources in the Atlas system of North Africa and other areas where similar orogenic belts experienced post-rift subsidence and basin inversion.

Lead and Barium Strata-Bound deposits in Eocene Carbonate ramps of Iran: Implications for the Influence of Sedimentary environment characteristics on the Distribution of Ore reserves

In the case of ore deposits that are formed in marine environments, including kuroko deposits, the effect of paleo-sedimentary environment parameters and microfacies changes is very important, but it is often neglected in economic geological research. These factors determine the dispersion and concentration of ore horizons in an ore deposit area, and recognition them leads us to the localization of high concentration ore horizons.In this regard, lead and barite ore deposit area in the southeastern of Tafresh city (the border of Markazi and Qom provinces, Iran) was investigated. This ore deposit is of the kuroko type and is of the early to middle Eocene epoch (Ypresian-Lutetian ages) and was formed in a relatively deep ancient carbonate ramp. Investigating the concentration of different minerals and ore minerals in the mentioned ore deposit area using by remote sensing techniques indicates that the distribution of minerals and ore minerals is non-uniform with a noteworthy correlation unto the carbonate ramp microfacies in the southeastern of Tafresh. The scrutiny of microfacies characteristics and paleo-sedimentary environment showed that the distance from hydrothermal smokers, the action of different seawaves, sedimentological changes, structural features and initial morphology of microfacies have a remarkable impressiveness in the dispersion of ore reserves and the formation of horizons with a high concentration of ore.

Organic petrographic and geochemical insights into organic matter derived from land plants and marine algae in the Lark Formation, Danish North Sea

Climatic fluctuations from the Eocene to the Miocene highlight the importance of investigating the paleoenvironment of the latest Eocene to the Middle Miocene Lark Formation in the Danish North Sea. This study investigates immature sedimentary organic matter in the Lark Formation using 54 cuttings samples and one core sample collected from seven wells in the eastern North Sea Basin. Organic petrography and molecular geochemistry analyses were performed to determine the variations in the quantity and origin of allochthonous and autochthonous organic matter. Additionally, the study assesses the impact of climate fluctuations on marine productivity in the eastern North Sea Basin and land plant vegetation at the basin margins during the latest Eocene to the Middle Miocene.The organic matter in the Lark Formation originated from mixed sources, primarily land plants, with a secondary contribution from marine algae. This is indicated by the maceral composition and the types and abundance of aliphatic and aromatic hydrocarbon biomarker compounds. Moreover, the presence of diterpenoids (gymnosperm biomarkers) and non-hopanoid triterpenoids (angiosperm biomarkers) reveals that the allochthonous organic matter originated from conifers and angiosperms.Climatic impacts on land plants and marine algae during the latest Eocene to the Middle Miocene are revealed by several parameters: the Averaged Chain Length (ACL) of land plant waxes, the proportion of coniferous contribution (C/(C + A)), and the whole rock volume percentages of huminite, inertinite (H + I, vol%) and liptinite (L, vol%). The shifts to cooler and drier climates highlighted the cold adaptation of onshore conifers and resulted in the input of higher molecular weight waxy components into the sediments. However, under these conditions, reduced precipitation and runoff resulted in lower amounts of terrigenous organic matter supplied to the basin. Additionally, the drop in water temperature and the warm-affinity of local algae assemblage led to reduced marine productivity. Together, these factors contributed to an overall decrease in organic richness. In contrast, during shifts to warmer and more humid climates, the trend reversed. The contribution of conifers to the floral assemblage diminished, but higher amounts of terrigenous organic matter were transported to the basin due to increased precipitation and runoff. This was accompanied by warmer water temperatures, boosting the productivity of organic-walled microplankton in the marine environment and contributing to greater organic richness.

The Paleogene Forebulge Carbonate Banks, Zagros Foreland Basin, Northern Iraq: their Paleogeography, Basin Evolution, and Economic Implications

The Paleogene sequence of Zagros foreland basin NE Iraq during the Late Paleocene- Middle Eocene is punctuated by linear and disconnected chains of carbonate bank-ramp associations. These carbonate units had developed over the NW-SE trending Paleogene basin forebuldge. Discussion of origin, facies type, and stratigraphic architecture of these banks and associated facies was fully covered by the first part of this research project. In this part the chronostratigraphic synthases of the sequence, the paleogeography, and basin evolution is examined as an integral part of the investigation of the evolution of the Paleogene Zagros foreland basin. Research methods include regional stratigraphic correlation, and biostratigraphic data compilation to infer the chronostratigraphic sequence of the events. The paleogeographic facies mapping and basin history are reviewed accordingly. Research data are collected from 15 master surface sections. In addition to the re-examination and re-interpretation of 40 previously studied surface and subsurface well logs, which are compiled for basin-wide study and regional paleogeographic mapping. The analysis of the compiled biostratigraphic data shows that the inferred age of the associated stratigraphic units is as follows: Sinjar Formation. (E. Thanetian – L. Ypresian), Khurmala Formation (Ypresian - E. Lutetian), Kolosh Formation (Daian -Thanetian), and Aaliji Formation (Danian - Ypresian). Based on this chronostratigraphic synthesis, the basin forebulge history during the Paleogene period is divided into 5 stages: the Pre-bank, Early Bank Development, Bank-ramp Development, Back-bank Lagoon, and Lagoonal dolomitization stage. The paleogeography and paleofacies maps of each stage is discussed in terms of the basin forebulge evolution. An alternative hydrocarbon play of the forebulge-controlled Paleogene sequence is discussed, with a case study from the Sufaiyah oil field of northwest Iraq.

Cenozoic climate change and the evolution of North American mammalian predator ecomorphology

Abstract The trend of global cooling across the Cenozoic transformed the North American landscape from closed forest to more open grasslands, resulting in dietary adaptations in herbivores in response to shifting resources. In contrast, the material properties of the predator food source (muscle, skin, and bone) have remained constant over this transition, suggesting a corresponding lack of change in predator dietary adaptations. We investigated the North American mammalian predator fossil record using a tooth-shape metric and body mass, predicting that the former would exhibit stability. Instead, we found that mean molar morphology became more blade-like, with our tooth-shape metric sharply increasing in the late Eocene and remaining high from the Oligocene onward. Subsequent tests in extant carnivorans reveal taxa with more bladelike teeth are prevalent in more open environments. Our results reveal an unexpected functional shift among North American predators in response to large-scale environmental changes across the Cenozoic.