Oligocene Time Research Articles

A new primate community from the earliest Oligocene of the Atlantic margin of Northwest Africa: Systematic, paleobiogeographic, and paleoenvironmental implications

We report a new Paleogene primate community discovered in the uppermost part of the Samlat Formation outcropping on the continental shore of the Rio de Oro, east of the Dakhla peninsula (in the south of Morocco, near the northern border of Mauritania). Fossils consist of isolated teeth, which were extracted by wet screening of estuarine sediments (DAK C2) dating from the earliest Oligocene (ca. 33.5 Ma). These dental remains testify to the presence of at least eight primate species, documenting distinct families, four of which are among the Anthropoidea (Oligopithecidae [Catopithecus aff. browni], Propliopithecidae [?Propliopithecus sp.], Parapithecidae [Abuqatrania cf. basiodontos], and Afrotarsiidae [Afrotarsius sp.]) and four in the Strepsirrhini (a Djebelemuridae [cf. ‘Anchomomys’ milleri], a Galagidae [Wadilemur cf. elegans], a possible lorisiform [Orogalago saintexuperyi gen. et sp. nov.], and a strepsirrhine of indeterminate affinities [Orolemur mermozi gen. et sp. nov.]). This record of various primates at Dakhla represents the first Oligocene primate community from Northwest Africa, especially from the Atlantic margin of that landmass. Considering primates plus rodents (especially hystricognaths), the taxonomic proximity at the generic (even specific) level between DAK C2 (Dakhla) and the famous Egyptian fossil-bearing localities of the Jebel Qatrani Formation (Fayum Depression), either dating from the latest Eocene (L-41) or from the early Oligocene, suggests the existence of an east–west ‘trans-North African’ environmental continuum during the latest Eocene–earliest Oligocene time interval. The particularly diverse mammal fauna from DAK C2, recorded within the time window of global climate deterioration characterizing the Eocene/Oligocene transition, suggests that this tropical region of northwest Africa was seemingly less affected, if at all, by the cooling and associated paleoenvironmental and biotic changes documented at that time or at least that the effects were delayed. The expected densely forested paleoenvironment bordering the western margin of North Africa at the beginning of the early Oligocene probably offered better tropical refugia than higher latitudes or more inland areas during the cooling episode.

Evolución de las cuencas Tumaco, Atrato y San Juan sobre una plataforma continua a lo largo del margen pacífico colombiano

Several authors have interpreted the Colombian Pacific margin as a succession of oceanic terrane accretions, with generation of forearc basins under a compressive-transpressive tectonic regime during the Late Cretaceous-Miocene. New data acquired in the last decade, consisting of reprocessed seismic lines, geological cross-sections, stratigraphic data from wells, and new stratigraphic columns, are analyzed in this study. We suggest that the proposed models of successive terrane accretions are not supported by the new data; rather, the onshore basins were likely controlled by a marine platform from the Late Cretaceous to the Middle-Late Eocene, with reef growth to the end of this period. In the Late Cretaceous, contemporary to the sedimentation stage, effusive magmatism, mainly basaltic, also occurred. Since Oligocene time, the basins were affected by three different tectonic processes. First, during the Oligocene-Early Miocene, an extensional-transtensional event occurred in the Tumaco Basin and San Juan Sub-basin, which produced horst and graben structures and domino faults, along with the emplacement of igneous bodies in the eastern flank of the basins. The Atrato Sub-basin was affected by local reverse faulting towards its eastern edge. Second, during the Mid-Late Miocene, the western side of the Tumaco Basin was uplifted, and transpressive deformation occurred in the San Juan Sub-basin as evidenced by the San Juan and Garrapatas fault systems. Finally, in the Atrato Sub-basin, a transpressional regime is evidenced by the Baudó anticline. Our results suggest there is no evidence of oceanic terrane accretions in the abovementioned basins during the Late Cretaceous-Middle Eocene. Furthermore, we do not see evidence of a subduction system during that period. We conclude that subduction in western Colombia could have begun during the Early Oligocene instead.

Petrology of the 31.6 Ma Central Rhodope Perelik monotonous intermediate ignimbrite eruption

Volcanism during the Priabonian–Oligocene times (35–27 Ma) in the Rhodope Massif produced large volume of shoshonitic and calcalkaline lavas and three large volume silicic ignimbrites and fallout deposits. The youngest of these ignimbrites, named here as Perelik ignimbrite (PI), consists of three areas, previously described as three separate ignimbrite units, namely Bratsigovo-Dospat, Perelik and Kotili-Vitina. The ~300 m thick ignimbrites cover an area of 700 km2, 220 km2 and 350 km2, respectively. Our study demonstrates that these ignimbrites have identical ages of ~31.6 Ma and mineral and chemical compositions and are parts of a single large eruption. Based on these data, we suggest that the original areal coverage was much larger, possibly 3000 km2, with magma volume of ~1000 km3. These results classify the Perelik eruption as one of the largest European Oligocene supereruptions These ignimbrites have notably high phenocrystal content (40–50%) and are a relatively homogeneous chemical composition, which are characteristics features of the ‘monotonous intermediate’ ignimbrites. Here, we provide petrographic observations, and chemical and isotopic (Sr, Nd) analyses to explain the P-T conditions of crystallization of these ignimbrites.

Paleomagnetic Rotations in the Northeastern Caribbean Region Reveal Major Intraplate Deformation Since the Eocene

AbstractRelative Caribbean‐North American plate motion is partitioned over the trench and intra‐Caribbean plate faults that bound large scale tectonic blocks. Quantifying the kinematic evolution of this tectonic corridor is challenging because much of the region is submarine. We present an extensive regional paleomagnetic data set (1,330 cores from 136 sampling locations) from Eocene and younger rocks of the northern Lesser Antilles, the Virgin Islands, and Puerto Rico, and use a statistical bootstrapping approach to quantify vertical axis block rotations. Our results show that the Puerto Rico–Virgin Island (PRVI) block and the Northern Lesser Antilles (NoLA) block formed two coherently rotating domains that both underwent at least 45° counterclockwise rotation since the Eocene. The first ∼20° occurred in tandem in late Eocene and Oligocene time, after which the blocks were separated in the Miocene by the opening of the Anegada Passage. The last 25° of rotation of the PRVI block ended in the middle Miocene, whereas the NoLA block rotated slower, until the latest Miocene. The boundary between the NoLA block and a non‐rotated Southern Lesser Antilles was likely the Monserrat‐Harvers fault zone. These results require hundreds of kilometers of intra‐Caribbean motions with oroclinal bending of the trench or forearc sliver motion along the curved plate boundary as endmembers. These data invite a critical re‐evaluation of the kinematic reconstruction of Caribbean‐North American plate motion. The consequent changes in paleogeography may provide a new view on the enigmatic eastern Caribbean paleo‐biogeography and the Paleogene dispersal of South American mammals toward the Greater Antilles.

Impact of mechanical stratigraphy on deformation style and distribution of seismicity in the central External Dinarides: a 2D forward kinematic modelling study

The External Dinarides fold-thrust belt formed during Mid-Eocene–Oligocene times by SW-propagating thrusting from the Internal Dinarides towards the Adriatic foreland. Although previously considered as structurally quite uniform, recent work reported along-strike contrasting deformation styles in two structural domains within this fold-thrust belt. The two areas with very contrasting deformation styles are separated by the N–S-striking dextral Split-Karlovac Fault, a 250 km long, transpressive transfer fault. The southeastern domain is characterized by a thin-skinned SW-vergent nappe stack in contrast to the northwestern domain, where a set of blind, thick-skinned top-SW thrust duplexes prevail underneath the passive NE-vergent backthrusts. To better understand why the External Dinarides underwent such contrasting along-strike deformation, we reconsidered a temporal and spatial along- and across-strike distribution of Paleo-Mesozoic lithofacies to both sides of the Split-Karlovac Fault and estimated the role of mechanical stratigraphy on deformation styles in this part of the fold-thrust belt. Therefore, we constructed a new 2D kinematic forward model in the western backthrust-dominated domain. Our best-fit forward-modelled balanced cross section across the central Velebit Mtn. portrays a 75 km wide triangle zone. This zone took up at least 47 km of shortening during Eo-Oligocene times. It comprises a set of thin-skinned NE-vergent backthrusts detached in the upper Paleozoic atop a SW-vergent thick-skinned antiformal stack detached in the lower Paleozoic Adriatic basement. The NE-vergent backthrusts likely nucleated at lateral facies boundaries related to extensional half grabens that locally formed during Middle Triassic and Late Jurassic passive margin extension. During the Eo-Oligocene folding and thrusting, the selective inversion of inherited Mesozoic half grabens boundary faults into the NE-vergent backthrusts in the northwestern domain led to the observed along-strike changes in the deformation style of the External Dinarides. A seismotectonic analysis of instrumentally recorded earthquakes suggests contrasting seismic behaviour along the central and southern Velebit transects within the northwestern structural domain. The central Velebit Mtn. triangle structure appears to currently accommodate dominantly strike-slip motion, with reverse faulting being confined to east of the Split-Karlovac Fault. In contrast, seismicity along the southern Velebit cross section appears to be confined to the structurally lowermost parts of the triangle zone and the foreland, while it´s structurally higher parts are less seismically active. Also, a predominance of reverse faulting along this transect suggests ongoing accommodation of shortening in this part. Our results indicate that both the variations in the mechanical stratigraphy and the pre-orogenic structural inheritance obtained during rifting and passive margin stages exert control on contractional structures within the External Dinarides, including the distribution of present-day seismicity.

Differences between the central Andean and Himalayan orogenic wedges: A matter of climate

The Central Andean and Himalayan orogenic belts provide an ideal natural experiment to test the potential role of climate in controlling orogeny. Approximately equal in age and along-strike length, both orogenic wedges are forming in plate-marginal convergent tectonic settings: The Andes in a retroarc setting and the Himalaya in a collisional setting against the Tibetan backstop. The Central Andes orogenic wedge is volumetrically and aerially nearly two times larger than the Himalayan orogenic wedge, despite the Himalaya having accommodated two to three times more tectonic shortening. The Himalaya exports at least four times more sediment owing to much greater erosion rates as signified by widespread Cenozoic metamorphic rocks and very young (<10 Ma) low-temperature thermochronologic ages. The Central Andes are thermochronologically old (mostly >20 Ma), have no exposures of Cenozoic metamorphic rocks, and are mantled by volcanic and sedimentary rocks, attesting to shallow, slow erosion. We conclude that greater intensity of the Indian Monsoon relative to the South American Monsoon since Oligocene time accounts for the differences in orogen size and characteristics. When viewed as an orogenic wedge that has developed largely after formation of the Tibetan orogenic collage, the Himalaya is neither the largest nor hottest among Earth's orogens.

Cenozoic slip along the southern Sierra Nevada normal fault, California (USA): A long-lived stable western boundary of the Basin and Range

AbstractThe uplift history of the Sierra Nevada, California, is a topic of long-standing disagreement with much of it centered on the timing and nature of slip along the range-bounding normal fault along the east flank of the southern Sierra Nevada. The history of normal fault slip is important for characterizing the uplift history of the Sierra Nevada, as well as for characterizing the geologic and geodynamic factors that drove, and continue to drive, normal faulting. To address these issues, we completed new structural studies and extensive apatite (U-Th)/He (AHe) thermochronometry on samples collected from three vertical transects in the footwall to the east-dipping southern Sierra Nevada normal fault (SNNF). Our structural studies on bedrock fault planes show that the SNNF is a steeply (~70°) east-dipping normal fault. The new AHe data reveal two elevation-invariant AHe age arrays, indicative of two distinct periods of cooling and exhumation, which we interpret as initiation of normal faulting along the SNNF at ca. 28–27 Ma with a second phase of normal faulting at ca. 17–13 Ma. We argue that beginning in the late Oligocene, the SNNF marked the now long-standing stable western limit, or breakaway zone, of the Basin and Range. Slip along SNNF, and the associated unloading of the footwall, likely resulted in two periods of uplift of Sierra Nevada during the late Cenozoic. Trench retreat, driven by westward motion of the North American plate, along the Farallon–North American subduction zone boundary, as well as the gravitationally unstable northern and southern Basin and Range pushing on the cold Sierra Nevada, likely drove the late Oligoceneaged normal slip along the SNNF and the similar-aged but generally local and minor extension within the Basin and Range. We posit that the thick proto–Basin and Range lithosphere was primed for late Oligocene extension by replacement of the steepening Farallon slab with hot and buoyant asthenosphere. While steepening of the Farallon slab had not yet reached the southern Sierra Nevada by late Oligocene time, we speculate that late Oligocene slip along the SNNF reactivated a late Cretaceous dextral shear zone as the Sierra Nevada block was pulled and pushed westward in response to trench retreat and gravitational potential energy. The dominant middle Miocene normal faultslip history along the SNNF is contemporaneous with high-magnitude slip recorded along range-bounding normal faults across the Basin and Range, including the east-adjacent Inyo and White mountains, indicating that this period of extension was a major regional tectonic event. We infer that a combination of slabdriven trench retreat along the Juan de Fuca–North America subduction zone boundary and clockwise rotation of the southern ancestral Cascade Range superimposed on continental lithosphere preconditioned for extension drove this episode of middle Miocene normal slip along the SNNF and extension to the east across the Basin and Range. Transtensional plate motion along the Pacific–North America plate boundary, and likely a growing slab window, continued to drive extension along the SNNF and the western Basin and Range, but not until ca. 11 Ma when the Mendocino triple junction reached the latitude of our northernmost (U-Th)/He transect.

Geophysical architecture of tectonized volcanic bodies near flysch thrust fronts (Outer Western Carpathians)

Teschenite association rocks (TAR) represent a specific type of mostly alkaline igneous rocks which form an almost 100 km long belt of discontinuous rock bodies within the Outer Western Carpathians (OWC) in the territory of Czechia and Poland. At present, a detailed mineralogical, geochemical, and stratigraphic analysis or dating of the volcanic formations is available, but basic structural and spatial relations characterizing TAR bodies and their origin are missing due to the poor exposure of TAR and lack of borehole data. A drill-hole- and outcrop-data-calibrated geophysical survey has proven to be a powerful tool for the interpretation of spatial extent and subsurface structure of TAR. At two type localities of TAR in Czechia (sites Staré Město and Bruzovice), a geophysical investigation combining ground conductivity mapping (CM) with profile measurement of electrical resistivity tomography (ERT), gravity survey, and magnetic survey was performed. A joint interpretation of the geophysical data served to determine the spatial extent (up to 500 m long and 40 m deep), geometry, and structural features (often fault-bounded with highly anisotropic heterogeneous structure of mélange character) of the studied TAR bodies. The interpreted magmatism of the study area included a stage of intrusion and extrusion of magmatic bodies in the Early Cretaceous, followed by a phase of fold-thrust deformation during the tectonic shortening of the area from the Late Cretaceous to Oligocene times. The resulting highly anisotropic rock mass consisting of TAR and its country rocks structurally controls the subsequent post-tectonic gravity-driven deformation.

Saint Anthony Cave: Morphology, genesis, and age of one of the oldest religious shrines, Southern Galala Plateau, Eastern Desert, Egypt

Saint Anthony Cave is an important cultural, religious, and historic site; it was home of Saint Anthony, one of the earliest Christian monks (ca. 251–356 AD). The cave is located in a tectonically-complex karst area developed in partially dolomitic, sandy limestones of latest Paleocene age. Saint Anthony Cave had been described as a phreatic cave in previous research, but the cave lacked a detailed map and its speleogenesis was unclear. New data show the cave is a multi-phased uplifted cave formed primarily under phreatic conditions, with later modification by rising water levels. Deep sources of dissolutionally aggressive solutions likely have been involved. Speleogenesis likely began in Oligocene time associated with the Gulf of Suez Rift evolution and has been erosionally dissected. New, detailed mapping using ArcGIS shows the cave has an area of 22.13 m2 with a length and depth of 17.10 m and 5.33 m, respectively. The cave consists of a northwest–southeast oriented, steeply inclined, fracture controlled, upper-level entrance passage connected to an east–west oriented, fracture controlled, lower-level room with a vertical drop of 2.46 m. Dissolution pockets, cupola-like features, ceiling bell holes, notches, and corrosion tables are present in the cave. Subaerial and subaqueous speleothems moderately decorated the cave with likely Egyptian calcite alabaster. Based on field investigation, regional volcanic and tectonic history, paleoclimates, and other background information, we identify four distinct speleogenetic phases: First, during the late Oligocene, volcanic and extensional tectonic activities fractured the rocks, generated deep-seated acids, and enhanced the rising deep thermal water. Dissolution by other mechanisms such as carbonic/sulfuric acid and mixing dissolution were prevalent. In the early Miocene (Burdigalian), the cave was uplifted. Second, in the late Miocene (about 7.5 Ma), subaerial speleothems were being deposited in the cave under humid climate conditions. Third, post-Miocene, the cave enlarged and modified at and above the water level by likely warm, sulfuric water. Fourth, water levels dropped and speleothems were deposited again during later humid climate conditions.

Ghosts of the Holobiont: Borings on a Miocene Turtle Carapace from the Pisco Formation (Peru) as Witnesses of Ancient Symbiosis

In spite of the widespread occurrence of epibiotic turtle barnacles (Coronuloidea: Chelonibiidae and Platylepadidae) on extant marine turtles (Chelonioidea: Cheloniidae and Dermochelyidae), and although the association between these cirripedes and their chelonian hosts has existed for more than 30 million years, only a few studies have investigated the deep past of this iconic symbiotic relationship on palaeontological grounds. We describe probable platylepadid attachment scars in the form of hemispherical/hemiellipsoidal borings on an Upper Miocene (Tortonian) fragmentary turtle carapace, identified herein as belonging to Cheloniidae, from the Pisco Lagerstätte (East Pisco Basin, southern Peru). When coupled with the available molecular data, this and other similar ichnofossils allow for hypothesising that platylepadid symbionts were hosted by sea turtles as early as in early Oligocene times and became relatively widespread during the subsequent Miocene epoch. Chelonian fossils that preserve evidence of colonisation by platylepadid epibionts in the form of pits on the turtle shell should be regarded as fossil holobionts, i.e., palaeontological witnesses of discrete communal ecological units formed by a basibiont and the associated symbionts (including the epibiota). A greater attention to the bone modifications that may be detected on fossil turtle bones is expected to contribute significantly to the emerging field of palaeosymbiology.

Assessment of the thermal maturation, organofacies, and petroleum generation history of Sirte Shale Formation in Sirt Basin, Libya

The current study is conducted to investigate the upper Cretaceous (Campanian) Sirte shale Formation to better understand the regional abundance of the organofacies, thermal maturation levels, and the petroleum generation and expulsion histories during the geological time in one of the most important petroliferous basins in North Africa (Sirt Basin). Rock-Eval pyrolysis analysis of 988 samples in 56 wells that penetrated the Cretaceous section in the Sirt Basin was used to screen and study the geological and geochemical characteristics of the Sirte shale Formation. Multi-dimensional basin modeling, including 1D burial histories and 2D modeling approaches, was calibrated with %VRo and pyrolysis Tmax data to establish refined regional maturity of the Sirte shale Formation. By using the Rock-Eval data, the type, occurrence, and distribution of organofacies in time and space were investigated using analytical assessment procedures and present-day mapping, such as total organic carbon (%TOCp), hydrogen index (HIp), and kerogen transformation ratio (TRp) to define the lateral and vertical special variation. Key biological marker (biomarkers) data is used to determine their special types, abundance, and host sedimentary environments. We used integrated geochemistry with basin modeling to define the Sirte shale petroleum generation and expulsion history, petroleum phase-type and quantity, and expulsion efficiency. Results indicate that the current maturation levels in the general range of 0.4–1.35 %VRo (equivalent to 405 °C–460 °C pyrolysis Tmax) that found to allow Sirte shale Formation to enter transformation levels ranging from 20% to 91%, which is equivalent to 1,615 m–3,627 m burial depth. Sirte shale Formation is dominated by two types of organofacies (B and D/E), which are characterized by %TOC up to 5% and hydrogen index from 400 to 700 mg HC/g TOC with sudden lateral and vertical variation due to the influence of the marine and transitional – terrestrial sedimentary environments. Similar indications from the biomarker data were Pr/Py ratio shows a significant existence of anoxic and dysoxic environments (generally, 0.4–2.4). Alga marine (dominant), mixed, and minor terrestrial organic matter was defined to dominate the Sirte shale Formation as indicated by Pr/nc-17 and Py-nc18 data. The petroleum generation history of the Sirte shale Formation occurred in the Oligocene time (∼30 Ma). The higher expulsion efficiency for the oil phase, up to 84% detected in the deeper parts of the basin, and lower gas expulsion efficiency with its maximum up to 63%. During the geological time, two primary petroleum phases were generated and expelled (oil and gas) from the Sirte shale. The bulk fluid properties generated from Sirte Shale Formation indicate that range of GOR from 400 to 2000 scf/bbl and API in the range of 30–60.

CLIMATE RECONSTRUCTION OF SOUTHERN UKRAINE IN THE OLIGOCENE ON THE BASIS OF SPORE-POLLEN STUDY DATA BY THE COEXISTENCE APPROACH METHOD

Based on the data of spore-pollen studies of the Oligocene sediments of Southern Ukraine, a reconstruction of the Oligocene climate of this region was carried out using the latest method of coexistence approach. For each of the intervals of Oligocene time (early Borysphenian, late Borysphenian, Molochanian, Sirogozian, Askanian, and Hornostaivian) the values of the following climatic parameters were calculated: mean annual temperature, coldest month temperature (January), warmest month temperature (July), mean annual precipitation, highest month precipitation, lowest month precipitation, warmest month precipitation. It was established that the paleoclimate was warm, close to subtropical, with dry hot summers. It is classified as Csa type according to Köppen. A trend of gradual cooling and aridization of the climate within Southern Ukraine during the Oligocene was revealed. In the middle of the Oligocene (Molochanian — Sirogozian) an episode of noticeable warming and drying: an increase of continentality of the climate was recorded (an increase of mean annual temperature and a decrease of precipitation in the wettest month, a decrease of precipitation in the driest month and a decrease of precipitation in the warmest month), which corresponds to the period of the least development of the sea basin within the Southern Ukraine in the Oligocene.

Diachronous initiation of Arabia–Eurasia collision from eastern Anatolia to the southeastern Zagros Mountains since middle Eocene time

ABSTRACT The persistent debate over the timing of initial Arabia–Eurasia collision has eluded consensus for decades, with most estimates ranging widely from ~50 to 10 Ma along both the Anatolian and Zagros segments of the orogen. Here, we independently evaluate the timing and location of initial collision using a quantitative plate tectonic reconstruction that is the first to include the entire Arabian microcontinent and regions to the north in eastern Anatolia, northwestern Iran, and the Caucasus. The reconstruction combines new kinematic constraints from recent global plate models with a synthesis of available constraints on crustal shortening and continental and back-arc subduction to restore the pre-collisional geometries of the Arabian and Eurasian continental margins and to track their interaction through time. Our preferred model suggests that initial continental underthrusting, or soft collision, of the relatively thin Arabian passive margin with Eurasia occurred by ca. 42 Ma along the eastern Bitlis suture zone and began transmitting strain across central and eastern Anatolia, the Caucasus, and northwestern Iran. Collision inception then propagated westward into central Anatolia and southeastward into the northwestern Zagros Mountains by late Eocene time (ca. 40–35 Ma), the central Zagros by latest Eocene to early Oligocene time, (ca. 35–25 Ma), and finally the southeastern Zagros by latest Oligocene to middle Miocene time (ca. 25–15 Ma). The diachroneity of Arabia collision led to widespread upper-plate (Eurasian) contraction and a similarly time-transgressive magmatic lull that lagged behind the onset of collision by ~2–12 Myr. By incorporating the entire Arabian microcontinent and regions to the north, this new tectonic reconstruction highlights the diachronous nature of Arabia–Eurasia collision that occurred first along the Bitlis suture zone in eastern Anatolia during late middle Eocene time and became progressively younger to the southeast along strike of the Zagros suture zone.

The dire straits of Paratethys: gateways to the anoxic giant of Eurasia

Abstract A complex interplay of palaeoclimatic, eustatic and tectonic processes led to fragmentation and dissipation of the vast Tethys Ocean in Eocene–Oligocene times. The resulting Paratethys Sea occupied the northern Tethys region on Eurasia, grouping water masses of various sub-basins, separated from each other and from the open ocean through narrow and shallow gateways and land bridges. Changes in marine gateway configuration and internal connectivity affected regional hydrology, shifting most Paratethyan basins to extreme carbon-sink anoxic environments, anomalohaline evaporitic or brackish conditions, or even endorheic lakes. Paratethys gateway restriction triggered the onset of a long-lasting ( c. 20 myr) giant anoxic sea, characterized by stratified water masses and anoxic bottom-water conditions, resulting in thick hydrocarbon source rocks. Here, we review the geological evolution of the ‘dire straits’ of Paratethys that played a crucial role in the Eocene–Oligocene connectivity history of the Central Eurasian seas and we show that the main anoxic phases (Kuma and Maikop) correspond to restricted connectivity with the global ocean and a period of CO 2 depletion in the atmosphere. Paratethys represents one of the largest carbon sinks in Earth's history and may thus have played a prominent role in global climate change.

Levels of changes in the genus Pinus Linné in the composition of Mesozoic and Cenozoic flora and vegetation as an additional criterion for the division of sediments by the Mesozoic and Cenozoic of Ukraine

&#x0D; &#x0D; &#x0D; &#x0D; The article presents an analysis of a large array of results of palynological studies of Mesozoic and Cenozoic sediments of Ukraine and adjacent regions of Belarus and Russia. Numerous literature data on the palynological characteristics of Meso-Cenozoic sediments and the materials of the authors are summarized according to the results of spore-pollen analysis of Mesozoic and Cenozoic sediments within the main tectonic structures of Ukraine. It has been established that the genus Pinus (Pinaceae) is an integral part of the Meso-Cenozoic flora of Ukraine. Although, the participation in the flora and vegetation of the genus Pinus and its species diversity in different periods of geological time were different. Despite the long history and significant achievements of palynological research of Meso-Cenozoic sediments of Ukraine, no attention has been paid to the historical aspect of Pinus development in the Meso-Cenozoic flora. This work is presented as the first stem to fill this gap. The genus Pinus has a large stratigraphic range, but its species diversity and quantitative changes in the composition of Mesozoic and Cenozoic flora of different ages are markedly different. The analysis of these changes made it possible to trace the emergence and main levels at which the species composition was renewed and the role of Pinus in flora increased during the Mesozoic and Cenozoic. According to the results of the research, 5 levels of increasing the participation of the genus Pinus and changes in its species affiliation in the Mesozoic flora were established: Aalenian period of the Middle Jurassic (appearance of the first representatives of Pinus); Oxfordian time of the Late Jurassic; Valanginian – Early Barremian times of the Early Cretaceous; Albian time of the Early Cretaceous; Late Campanian time of the Late Cretaceous. 5 levels of increasing the role of Pinus and its species diversity for the flora and vegetation of the Cenozoic were also established: Oligocene time of the Paleogene, Konkian-early Sarmatian time of the Middle Miocene; early Pontian (Ivankov) time of the Late Miocene; early Kimmerian time (early Sevastopol) of the Early Pliocene and Martonosha time of the Early Neopleistocene. Certain levels have been traced for the similar age of Cenozoic flora of Belarus and Russia.&#x0D; &#x0D; &#x0D; &#x0D;

The Nazca Drift System – palaeoceanographic significance of a giant sleeping on the SE Pacific Ocean floor

AbstractThe evolution and resulting morphology of a contourite drift system in the SE Pacific oceanic basin is investigated in detail using seismic imaging and an age-calibrated borehole section. The Nazca Drift System covers an area of 204 500 km2 and stands above the abyssal basins of Peru and Chile. The drift is spread along the Nazca Ridge in water depths between 2090 and 5330 m. The Nazca Drift System was drilled at Ocean Drilling Program Site 1237. This deep-water drift overlies faulted oceanic crust and onlaps associated volcanic highs. Its thickness ranges from 104 to 375 m. The seismic sheet facies observed are associated with bottom current processes. The main lithologies are pelagic carbonates reflecting the distal position relative to South America and water depth above the carbonate compensation depth during Oligocene time. The Nazca Drift System developed under the influence of bottom currents sourced from the Circumpolar Deep Water and Pacific Central Water, and is the largest yet identified abyssal drift system of the Pacific Ocean, ranking third in all abyssal contourite drift systems globally. Subduction since late Miocene time and the excess of sediments and water associated with the Nazca Drift System may have contributed to the Andean orogeny and associated metallogenesis. The Nazca Drift System records the evolution in interactions between deep-sea currents and the eastward motion of the Nazca Plate through erosive surfaces and sediment remobilization.

Geology, geochemistry, mineralogy and genesis of the Spetsugli high-germanium coal deposit in the Pavlovsk coalfield, Russian Far East

The geology, mineralogy, and geochemistry of the Spetsugli high-germanium coal deposit in the Pavlovsk coalfield were studied. The deposit is characterized by the complex polyelemental composition of the ores and can be evaluated as a complex rare metal-coal deposit. The metal-bearing coals of the deposit are characterized by abnormally high, tens or even hundreds of times greater than the mean contents for brown coals of the world, for Ge, Sb, Hg, W, Li, Be, Cs, and As. Somewhat less anomalous are the levels of accumulation of U, Mo, Y, Rb, medium and heavy lanthanides, Zn, and Ga. Detailed mineralogical and geochemical characteristics of the germanium mineralization and associated anomalous concentrations of W, Sb, Hg, As Li, Be, Cs, U, Mo, Y, Rb, and HREE are described in the paper. The variations in concentrations were studied in vertical profiles and laterally. Complex mineralogical-geochemical and geological-structural analysis of the composition and structural features of the Spetsugli Ge-coal deposit allow us to revise the accepted hydrothermal model of the Ge mineralization formation in coals and substantiate the previously proposed hypergenic model for deposits of this type. The new data are in good agreement with the hydrogenic hypergenic model of the formation of complex Ge coal deposits where the source of metals is the basement rocks or the coal-bearing depression margins. The formation of the Ge and associated mineralization in the Spetsugli deposit was controlled by the weathering crust formation on hydrothermally altered rare metal granites of the Voznesenk Complex, broken through by the Late Permian dikes. The isotopic ages of the granites (448.2 Ma) and dikes (263.6 Ma) were determined and also the rhyolitic tuffs (25.1 Ma) which overlie the Eocene-Oligocene coal- bearing sediments in the basin. The isotopic age of the granites (448.2 Ma), dikes (263.6 Ma), and rhyolite tuffs overlapping the carbonaceous deposits (25.1 Ma) was determined. The rare metal mineralization is related to the basement protrusion in the centre of the deposit, forming a concentric-zone halo of Ge and associated elements around it. The basement protrusion granites were hydrothermally altered to form quartz-albite-microcline metasomatites and greisen containing the W-Mo and Hg-Sb-As mineralization. The metasomatically altered granites and dikes were transformed into a kaolin weathering crust as a result of late hypergenic alterations, with destruction of primary endogenous mineralization and removal of major elements to the surrounding paleopeatlands. Both types of endogenous mineralization in granites and dikes have anomalous accumulation of W, Mo, Sb, Hg, As, Li, Rb, Cs, Be, U, Y, lanthanides, Zn and Ga in the germanium-bearing coals during the Eocene- Oligocene time.

Latest Eocene and Oligocene tectonic controls on carbonate deposition in eastern Java and the south Makassar Straits, Indonesia

This review examines the development of carbonates and their enclosing siliciclastic sediments, from the Late Eocene until the end of the Oligocene, in eastern Java and the southern Makassar Straits. Five genetic sedimentary sequences are recognised, which correlate to other studies in the area, and points to an episodic sedimentary history controlled by tectonism. An additional intra Late Miocene uplift and unconformity is also described as it illustrates the speed at which tectonic transitions occurred. These genetic sedimentary sequences are part of a regional stratigraphic framework that describes the tectonic evolution of Sundaland. Two unconformities, in mid-Oligocene and at terminal Oligocene times, correlating across the entire eastern margin of Sundaland, are highlighted as part of a new regional tectonic model. Quantitative approaches such as geohistory analysis are used to integrate stratigraphy with tectonic controls on accommodation space, and closely spaced wells are correlated to show abrupt facies shifts during tectono-stratigraphic transitions. A zone under the modern island of Java and continuing northeast through the centre of the Makassar Straits is, by far, the most tectonically active region, and also is the site of the largest hydrocarbon discoveries, yet is the least understood area. Measurement and mapping of the highly variable unconformities appears to be the key to understanding the development of this dynamic plate margin, and reaching a better understanding of carbonate reservoirs, all elements of petroleum systems, and the tectonic development of Sundaland.

Structural architecture and tectonic evolution of Haimour block, Gulf of Aqaba, Egypt: An example of multiphase deformed stepover

A unique outcrop of a dilational NNE-oriented stepover takes place between two left-stepping NE sinistral faults at the Haimour block along the western margin of the Gulf of Aqaba basin. Detailed surface geological mapping was achieved in order to unravel structural architecture and deformation style of the Haimour stepover (HSO). The HSO comprises N- to NNE- oriented transtensional and normal faults that affect all the sedimentary succession including the syn-kinematic sediments. Contrarily, the southern part includes a remarkable push-up structure that comprises NNE-to NE-oriented compressional structures affecting the Upper Cretaceous rock units. The southern end of the HSO is marked by a NNE-oriented Principal Displacement Zone (PDZ), which encloses NNE- and NE-oriented sinistral faults. Structural analysis of field data considering the previous analogue and numerical models indicates a well-developed basin side-walls and basin cross-fault zone of the HSO. Additionally, divergent-oblique slip model (30° transtension) is suggested for the HSO. The proposed tectonic model of the HSO revealed that the initiation of the pull-apart basin took place during the Oligocene times concurrently with the opening of the Red Sea rift and continued to the Post-Miocene times. The outcomes of this study provide a model for architecture and evolution of similar structural style along Gulf of Aqaba and Dead Sea Transform. Moreover, the proposed architecture of the HSO should provide an analogue for subsurface mapping and exploration at strike-slip zones.

HIGH CORAL DIVERSITY IS COUPLED WITH REEF-BUILDING CAPACITY DURING THE LATE OLIGOCENE WARMING EVENT (CASTRO LIMESTONE, SALENTO PENINSULA, S ITALY)

The Oligocene, well known as the apex of Cenozoic reef growth, is a crucial period of time to investigate the mutual relationship between coral reef construction and coral diversity and their link with palaeoclimate and palaeoenvironmental changes. Here we provide a complete characterization of the Upper Oligocene reef complex of the Castro Limestone (Salento Peninsula, S Italy), which is one of the best-preserved Oligocene coral reefs of the Mediterranean region. By combining facies analysis with the first detailed characterization of its coral fauna, we show that the Castro Limestone has both a rich scleractinian coral fauna (25 genera and 41 species) and a large reef volume, and it represents a luxuriant fringing reef formed within the euphotic zone in clear water conditions facing the open sea. The coral fauna differs both in its composition and in its proportions among reef palaeoenvironments, ranging from the shallow back reef to the fore reef slope, and its stratigraphic and palaeogeographic distribution testifies to the persistence of a cosmopolitan Tethyan fauna in Oligocene time, with the Mediterranean and Indo-Pacific provinces being more closely connected than the Mediterranean and the Caribbean. The age of the Castro Limestone is here reassigned to the middle-late Chattian, which coincides with the Late Oligocene Warming Event (LOWE) when atmospheric CO2 values declined. We suggest that the strong reef-building capacity of the Castro Limestone, coupled with high coral diversity, was not hampered by warming conditions but most probably promoted by the reduced pCO2 and a suitable local/regional physiographic setting.