Miocene Stratigraphy Research Articles

Lower miocene stratigraphy of the Eastern Paratethys: Problems and state of the art

The Lower Miocene regional stages of the Eastern Paratethys, the Caucasian, Sakaraulian, and Kozakhurian, have been recognized in different structural facies zones of the basin and have no reliable universal stratigraphic basis for defining their boundaries and volume. Mollusks, benthic and planktonic foraminifers, calcareous nannoplankton, and dinocysts have been studied in a number of Lower Miocene sections in stratotype areas of the Central Ciscaucasia and Kartli Depression in Georgia. The fossil biota groups of the Caucasian, Sakaraulian, and Kozakhurian sediments are briefly characterized. The available new data on the phytoplankton of these regional stratigraphic units as well as the records of the benthos composition in the marginal facies of the Ciscaucasian Basin allow a comparison between the stratotype regions and show possibilities for a more detailed correlation among them.

Characteristics of Stratigraphy and sedimentation of the Phu Khanh Basin and adjacent area

The Phu Khanh Sedimentary Basin is situated in the deep-water offshore area, east of the continental shelf of Central Vietnam. This area is said to have quite good oil and gas potential, but very few geological and petroleum research projects have been carried out in the past. In this article, the authors update new research results based on new seismic interpretation and well data conducted in recent years. The obtained results show that: Stratigraphy of the Phu Khanh Basin was subdivided into 5 large sequences, including: a. Eocene(?)/Oligocene unit is mainly clastic sediments of fluvial/lacustrine, delta plain and marine environments, b. Lower Miocene stratigraphy: Includes deltaic clastic sediments and shelfal carbonates; c. Middle Miocene stratigraphy: includes delta-plain, shallow marine terrigenous sediments and shelfal carbonate, d. Upper Miocene and Pliocene - Quaternary units include continental shelf and deep-sea terrigenous sediments. Each unit of stratigraphy and corresponding sedimentary environment is related to each stage of the geological and tectonic evolution of the basin. In general, the trend changes from the fluvial/lacustrine environment to the deltaic, shelfal and deep marine environments upward. Establishing the names of the formations and the presence of the Eocene sedimentary rocks in the Phu Khanh Basin is still an open issue. More detailed data, especially well data, are needed to obtain a more convincing interpretation.

Miocene Stratigraphy of Abu-Jir Fault Zone, Al-Baghdadi Sub-Basin, Western Iraq.

Stratigraphy of Late Oligocene to Middle Miocene age, suggested the carbonates evaporate succession in the area between Heet and Haditha cities within Abu-Jir fault zone has distinguished as “Al-Baghdadi sub-basin” after Al-Baghdadi city. It has NW–SE trending align the western bank of the Euphrates. Al-Baghdadi sub-basin is a local basin, which forms a part of the western marginal of the large foreland Tertiary basin (Zagros Basin) that was created on the Arabian shelf as a result of the collide of Arabian and Eurasian plates. The impact of the Abu-Jir fault on the formations on both regions of the Euphrates has been determined by observing the changes in thickness and lithofacies of the Euphrates, Jeribe and Fat’ha formations. On the western side, the Euphrates and Fat’ha formations were deposited with a relatively a little thickness, with absence of the Jeribe Formation between them and the top of the Euphrates Formation is above sea level. On the eastern side of the Euphrates River, the three formations were deposited with large thickness as compared to the western side, and the top of the Euphrates Formation is below sea level. This is enough to indicate that the western side was uplifting locally due to the activity of the Abu-Jir Fault as a positive flower structure during Miocene, while the eastern side was subsiding. Abu-Jir fault zone behaves as the basin bounding fault that acted like a growth fault. There are also variations in lithofacies between outcrops within Al-Baghdadi sub-basin as revealed from lateral missing or thinning of some layers.

Controls on Early Miocene carbonate and siliciclastic deposition in eastern Java and south Makassar Straits, Indonesia

The Early Miocene stratigraphy of NE Java and the southern Makassar Straits is examined in the context of siliciclastic sediment supply and subsidence (creation of accommodation space), as indicated by biohermal carbonate growth. Stratigraphic variation is examined geographically and assessed quantitatively, using geohistory analysis. During the Oligocene through to basal Miocene times, basin development had been dominated by extension with local transtension. This changed within the Early Miocene to regional compression, increasing in magnitude with time. Three tectonic events, at about 24 Ma (base of section studied), at 21 Ma, and roughly 16 Ma are described in terms of the influence they had on stratigraphy. Most significant was the concentration of siliciclastics on the proximal side of the Oligo-Miocene axis of subsidence, which caused isostatic loading and nearby pinnacle reefs to achieve high relief, but ultimately an acceleration in siliciclastic input at about 16 Ma caused simultaneous reef extinction. Carbonates of Early Miocene age are important hydrocarbon reservoirs, and the siliciclastics are a geographically variable part of the overburden and seal, as well as causing the thermal maturation of hydrocarbon source rocks. The stratigraphic framework described here will have implications for facies and exploration risk prediction into under-explored regions around the study area. The tectono-stratigraphic framework is carefully constrained for age and facies inputs, and the resulting palaeogeographic history indicates a new model of basin development. This dynamic framework correlates to coeval tectonic processes over a large region and has important implications for Sundaland plate tectonics.

Tectonic control on the palaeogeographical evolution of the Miocene Seaway along the Western Alpine foreland basin

Abstract The Miocene of the Western Alpine foreland basin were deposited in a north–south seaway along the active alpine orogenic front. In the subalpine massifs and the southern Jura mountains, the revised Miocene stratigraphy documents a detailed chronology of thrust propagation at the western alpine front, where tectonic activity had a primary influence on seaway palaeogeographical evolution. Here we propose nine palaeogeographical maps during the Miocene, the first of which depicts the initial Miocene transgression at c. 21.0 Ma. Between c. 18.05 and c. 12.0 Ma, a westward retreat of the Miocene Sea occurred in response to activation of the basal thrust of the Belledonne massif, which in turn triggered successive fault zones from east to west. At c. 10.0 Ma, a major uplift phase intervened and induced a rapid southward retreat of the Miocene Sea. The reconstructed palaeogeographical maps outline the main controls on the foreland basin seaway evolution: (1) the timing of the main thrusts; (2) the inherited palaeotopography; and (3) eustatic sea-level changes during the Miocene. These reconstructions are integrated at the basin scale, highlighting the southward- to westward-directed seaway migration in response to the Belledonne thrust activity that deeply shaped the palaeogeographical evolution during the early to middle Miocene.

The Miocene stratigraphy of the Laberinto area (Río Ica Valley) and its bearing on the geological history of the East Pisco Basin (south-central Peru)

Global sea-level changes and substantial vertical displacement along the Monte Grande Fault (MGF) in the lower Río Ica Valley of south-central Peru influenced the accumulation of bioclast-bearing and diatom-bearing Miocene siliciclastic sediments in an area of the East Pisco forearc basin (EPB) colloquially known as Laberinto. Two depositional hiatuses in the Laberinto area (~17–14 Ma, ~12.5–10 Ma) manifest as sediment-filled erosional depressions a few kilometers in breadth. Erosion of the older depression was preceded by an ~18-Ma massive debris flow, possibly triggered by motion on the MGF causing lower Miocene lithoclastic olistoliths of up to two hundred meters length to spill off the footwall block. Sediment shed from the same footwall block may have formed previously recognized early Miocene deltas. From 14 to 13 Ma, the older depression filled with sediments herein assigned to the provisionally named Laberinto, Pampa, and Naranja members of the Pisco Formation, the latter member being characterized by marine delta foreset beds. The three members are at least partly correlative with the Pisco-0 sequence of the Pisco Formation. The younger depression was overrun at 10 Ma by debris flows of lithoclastic and granitic cobbles and boulders, then filled with diatomaceous silty sand with 5-m-sized lithoclastic olistoliths. The two lithologies constitute the provisionally named Mature Formation. Radiometric and newly revised biochronological data from throughout the EPB coupled with new diatom data from the Laberinto area have provided new insights into the correlation of sequences within the Chilcatay and Pisco formations and the interaction of local and basin-wide tectonism and global eustatic sea-level events across the basin.

The myth of the Messinian Dardanelles: Late Miocene stratigraphy and palaeogeography of the ancient Aegean-Black Sea gateway

The Dardanelles region has formed a key gateway connecting the Eastern Paratethys and the Aegean/Mediterranean since the late Miocene. Its sedimentary sequences contain crucial information about connectivity and tectonics but so far lack unambiguous age constraints. Only a few Miocene marine episodes have been documented and fossil assemblages are predominantly composed of Paratethyan fauna (mollusks and ostracods). Here, we apply an integrated stratigraphic approach and use the recently established chronostratigraphy for the Eastern Paratethys to re-evaluate the faunal assemblages and palaeoenvironments of the Seddülbahir and İntepe sections that allegedly played a crucial role in the geodynamic evolution of the Dardanelles during the Messinian-Zanclean. The Paratethyan ostracods and mollusks, however, clearly indicate that these sections correspond to the middle Tortonian (~9 Ma; Bessarabian–Khersonian in Eastern Paratethys terminology). Nannofossil assemblages are dominated by a mixing of reworked taxa from the late Eocene and Oligocene and no age-diagnostic taxa have been observed. Dinoflagellate analyses are also hampered by reworking and mainly reveal non-marine (fresh to oligohaline) aquatic conditions. Fossil mammal remains in the Seddülbahir section and other localities in the region confirm the late Miocene age. Strontium (87Sr/86Sr) isotope ratios of the anomalohaline (brackish) ostracods are significantly below open ocean values and similar to values obtained from Khersonian ostracods of Bulgaria. Fresh water assemblages reveal much higher 87Sr/86Sr values, which are interpreted to reflect the composition of local rivers. We conclude that in late Miocene times the Dardanelles region was a fresh to anomalohaline embayment, ephemerally connected to the Eastern Paratethys. We found no evidence for a major Messinian erosional surface nor for marine Mediterranean fossils indicative of the early Zanclean. Our results furthermore indicate that the proposed Messinian age for the propagation of the North Anatolian Fault into the Dardanelles region must be revised.

From Khersonian drying to Pontian “flooding”: late Miocene stratigraphy and palaeoenvironmental evolution of the Dacian Basin (Eastern Paratethys)

In the late Miocene, a large inland sea known as the Eastern Paratethys stretched out across the present-day Black Sea – Caspian Sea region. The basin was mostly endorheic and its water budget thus strongly dependent on regional climate. The basin was therefore prone to high-amplitude water-level fluctuations and associated turnovers in water chemistry and fauna. Profound palaeoenvironmental changes happened in the Eastern Paratethys during this time period. This article documents the evolution of the Dacian Basin of Romania, the westernmost branch of the Eastern Paratethys, during the time interval between 7.7 and 6.0 Ma. Our integrated study of sedimentary facies, micro- and macro fauna along the Slănicul de Buzău Section was constrained with a timeframe based on magnetostratigraphy. The remarkable 1.3 km-thick sedimentary record, high depositional rate (0.65–1.26 m/kyr) and abundance of fossils along this section provide a unique opportunity to study sedimentary and biotic turnovers in high detail. Our analyses reveal several marked water-level and salinity changes: A predominance of freshwater coastal plain environments, only occasionally flooded, indicates a low water-level in the Khersonian (~7.7–7.63 Ma). The coastal plain deposits are overlain by offshore muds revealing a low mesohaline early Maeotian transgression, which was followed by the installation of littoral/nearshore environments with freshwater molluscs in shallow settings and oligohaline ostracods in slightly deeper settings. Subsequent delta progradation and a prevalence of freshwater fauna in both marginal and more distal environments characterize the late Maeotian. This was followed by a remarkable freshwater transgression that started at 6.3 Ma and led to predominantly offshore deposition. The late Maeotian fossil record suggests brackish water pulses from Lake Pannon (Central Paratethys), followed by mass occurrences of Coelogonia novorossica. At 6.1 Ma, a short influx of meso- to polyhaline microfauna including benthic and planktonic foraminifera defines the “Pontian Salinity Incursion”. Molluscs, including Eupatorina littoralis, that biostratigraphically mark the onset of the Pontian arrived with a negligible delay of ~5 kyr after the microfauna influx. The onset of the Pontian at Slănicul de Buzau at 6.1 Ma (± 5 kyr), is thus synchronous with the onset in other Paratethys basins. Our integrated approach, placing the preserved fossil fauna in its respective sedimentary environment, allows for a detailed insight into the salinity of coeval marginal as well as basinal environments and could be more widely applied in the Paratethys realm and other semi-isolated basins with a deviant salinity.

The age and paleoenvironment of a late Miocene floodplain alongside Lake Pannon: Rodent and mollusk biostratigraphy coupled with authigenic 10Be/9Be dating in the northern Danube Basin of Slovakia

We present new age constraints for the late Miocene Volkovce Formation of Slovakia, alluvial facies that accumulated adjacent to Lake Pannon. Facies analysis and authigenic 10Be/9Be dating was undertaken at the Bernolákovo and Triblavina localities while the latter outcrop also yielded additional small mammal and mollusk assemblages as well as remains of flora. The results of seven radiometric dating ages yielded a weighted mean age of 9.65 ± 0.61 Ma for the Triblavina outcrop and 8.85 ± 0.32 Ma for the Bernolákovo outcrop. The small mammal assemblage at the Triblavina outcrop is indicative of the lowermost MN11 zone, which in the Western European standard definition suggests an age of <8.9 Ma. The ~0.1 Ma inconsistency between absolute dating and biostratigraphic dating at the Triblavina outcrop might be explained either by the variation of initial 10Be/9Be ratio in the depositional environment or/and by diachronous development of the mammal faunas across the Europe. The mollusk assemblage at this outcrop indicates the paleoenvironment of freshwater lakes affected by rivers with evidence for a nearby riparian forests; it may be roughly correlated with Papp's lithostratigraphic units G and H defined for the Pannonian stage in the Vienna Basin. Our results provide a detailed insight to the late Miocene stratigraphy and terrestrial environments alongside the Lake Pannon shoreline.

Stratigraphic Revision of the Miocene Trealla Limestone (cape Range, Western Australia): Implications For Australasian Foraminiferal Biostratigraphy

AbstractOutcrops of Miocene coral-rich limestones mapped as Trealla Limestone are widespread along the coast of north-west Western Australia. Despite their central importance in Australian Miocene stratigraphy, the age of these outcrops is poorly constrained as they were only dated in their type area, and as the age assignation was based only on off-centred sections of sparse planktonic foraminifera and a broad correlation based on larger benthic foraminiferal species.This study aims to refine the dating of the Trealla Limestone in its type area, and to provide the first dating of outcrops located elsewhere in the Cape Range Anticline. Results are based on microscopic observations made on large acetate peels, which allowed the observation of numerous planktonic foraminifera, and also of serial sections of species.The coral-rich deposits mapped as “Trealla Limestone” can be divided into three age-based units in the Cape Range Anticline: (1) upper Burdigalian, (2) Langhian to lower Serravallian, and (3) Serravallian. This revised stratigraphic framework provides a standard for future correlations with sections located elsewhere in Australia. The Trealla Limestone at its type section on Mt Lefroy contains mainly upper Burdigalian strata of the mid-neritic zone, with the top of the formation marked by an erosion surface. It may in part be equivalent to the Tulki Limestone mapped elsewhere in the anticline. Further north in the anticline, the Trealla Limestone ranges stratigraphically higher into the Langhian and Serravallian in shallower water facies. An influx of quartz sand in the Cape Range Anticline, probably indicative of a wetter environment in the hinterland to the east, started during or after the Serravallian.This study also brings new insight into the environmental and stratigraphic ranges of larger benthic foraminifera from north-west Western Australia. Austrotrillina asmariensis was recorded above levels with Orbulina universa. This suggests that the species has a more extended stratigraphic range in this area than in Asia. A re-examination of the soritids reveals that Marginopora, previously recorded here, is not present in the deposits. Borelis is replaced by Flosculinella after the end of the Te Letter Stage, a zone based on larger benthic foraminifera recognized throughout the Indo-West Pacific region. The morphology of Flosculinella may be environmentally controlled, with the most globular specimens more abundant in protected and shallow environments. Finally, Cycloclypeus from the Cape Range Anticline had a similar bathymetric range to its modern analogue found in the lower part of the photic zone, as indicated by its co-occurrence with minute planktonic foraminifera.

Seismic-based lower and middle Miocene stratigraphy in the northwestern Vienna Basin (Austria)

Seismic-based lower and middle Miocene stratigraphy in the northwestern Vienna Basin (Austria)

A calcite crisis unravelling Early Miocene (Ottnangian) stratigraphy in the North Alpine–Carpathian Foreland Basin: a litho- and chemostratigraphic marker for the Rzehakia Lake System

Abstract Within the Lower Austrian part of the North Alpine Foreland Basin (NAFB), up to 1000 m of sediments were deposited throughout the Ottnangian (Early Miocene, Burdigalian). According to homogeneous compositions and sparse biostratigraphic resolution, a consistent stratigraphic concept from the basin margins into the foreland depocenter was still lacking. New investigations on several deep drill cores throughout the basin provide comprehensive sedimentological, mineralogical, chemical and micropaleontological data. A calcite poor, fossil- and pyrite-free, smectite-rich, up to 800 m thick interval was identified and correlated to the time interval of the late Ottnangian brackish Rzehakia Lake System. For this section, we introduce the term Calcite Minimum Interval (CMI). We define the onset of the CMI by a sharp decrease of calcite contents and the disappearance of autochthonous (and reworked) calcareous nannofossils. We define the termination of the CMI by the permanent increase of pyrite contents and the reappearance of calcareous nannofossils. The CMI as a litho- and chemostratigraphical marker for the Rzehakia Lake System constitutes a stratigraphic key horizon. Within the NAFB in Lower Austria, its onset corresponds to the middle/upper Ottnangian transition while its termination correlates roughly to the Ottnangian / Karpatian boundary. This allows a precise definition, identification and correlation of (upper) Ottnangian stratigraphic units of the NAFB. For the central basinal parts of the Rzehakia Lake System, we introduce the new lithostratigraphic term Wildendürnbach Formation which correlates to the marginal Traisen Formation.

LATE MIOCENE CALCAREOUS NANNOFOSSIL STRATIGRAPHY AND BIOEVENTS CORRELATION: KALIDONIA CASE SECTION (NW CRETE, GREECE)

Calcareous nannofossils are widely used for biostratigraphic correlations. Quantitative approaches enable better understanding of reliability of bioevents. In order to refine the late Miocene stratigraphy ofNW Crete, the deposits of Kalidonia basin along its type section are here investigated. It was possible to distinguish the Tortonian/Messinian boundary by NNlla &amp; NNllb, CN9a &amp; CN9b, MNNlla &amp; MNNllb biozones. Reticulofenestra pseudoumbilicus PB (Paracme Beginning) and R. rotaria FO (First Occurrence) proved to act as additional significant biohorizons improving the stratigraphie evolution of the studied paleobasin and providing a tight biochronologic framework. The Kalidonia section fully covers an undisturbed marine depositional cycle from the upper Tortonian to upper Messinian, where a predominant deep water fades (DWF) is followed by transitional sediments (TF) and the sequence closes at the top by a reefal-bioclastic fades (RF) relative to the 'Calcare di Base ' in Italy indicating the 'Messinian Salinity Crisis Event.

Taxonomy, Stratigraphy and Phylogeny of the Middle Miocene Fohsella Lineage: Geometric Morphometric Evidence

Abstract The taxonomy and phylogeny of the planktonic foraminifera Fohsella lineage has been controversial for nearly 50 years, despite its widespread application in Middle Miocene stratigraphy. We have re-examined type specimens of this lineage together with specimens from a continuous deep-sea record (Ocean Drilling Program Site 806, Ontong Java Plateau, western equatorial Pacific Ocean) with an astronomic chronology. Landmark-based geometric morphometry is employed to visualize and quantify morphologic variation within this lineage. Combined morphologic and stratigraphic data help clarify the evolutionary occurrence of diagnostic traits that characterize two problematic taxa, F. praefohsi and F. “praefohsi”, resulting in a revised taxonomy and phylogeny of the lineage. We emphasize the importance of biometric studies of populations from continuous geologic records in establishing taxonomy and phylogeny of planktonic foraminifera. In the past, over-emphasis on the importance of type specimens as reference points in delineating various evolutionary stages of the Fohsella lineage has resulted in inaccurate phylogenetic reconstructions.

Lower Miocene Stratigraphy and its paleo-environments of the Ame and Nukui River Areas, northwestern part of the Kanto Mountains, central Japan

Lower Miocene Stratigraphy and its paleo-environments of the Ame and Nukui River Areas, northwestern part of the Kanto Mountains, central Japan

Dogielophis, a replacement name for Dogielina Sobolev 1950 (Nematoda)non Bogdanowicz & Woloszynova 1949 (Foraminifera).

The generic name Dogielina was proposed by Sobolev (in Skrjabin & al. 1950: 68; for Physaloptera inexpectata Dogiel & Bychowsky 1939: 93, type species by original designation) for a parasitic nematode of the fishes from the western shores of the Caspian Sea (Sara Island) of the former USSR (now Azerbaijan: Sarı adası, Nərimanabad). However, this name is already preoccupied by a fossil Foraminifera Dogielina Bogdanowicz & Woloszynova (1949: 185), published earlier in the same year (see note on publication dates below), which is in active current use in palaeontology and even served as a basis for a specific geological Dogielina sarmatica biozone in the Upper Miocene stratigraphy of Eurasia (Krézsek & Filipescu 2005). Besides this earliest generic name, a later homonym is also known in Protista: Dogielina Raabe (1959: 448) [Infusoria].

Tectonics and Topography of the Tibetan Plateau in Early Miocene

Abstract:Early Miocene stratigraphy, major structural systems, magmatic emplacement, volcanic eruption, vegetation change and paleo‐elevation were analyzed for the Tibetan Plateau after regional geological mapping at a scale of 1:250,000 and related researches, revealing much more information for tectonic evolution and topographic change of the high plateau caused by Indian‐Asian continental collision. Lacustrine deposits of dolostone, dolomite limestone, limestone, marl, sandstone and conglomerate of weak deformation formed extensively in the central Tibetan Plateau, indicating that vast lake complexes as large as 100,000–120,000 km2 existed in the central plateau during Early Miocene. Sporopollen assemblages contained in the lacustrine strata indicate the disappearance of most tropical‐subtropical broad‐leaved trees since Early Miocene and the flourishing of dark needle‐leaved trees during Early Miocene. Such vegetation changes adjusted for latitude and global climate variations demonstrate that the central Tibetan Plateau rose to ca. 4,000–4,500 m and the northeastern plateau uplifted to ca. 3,500–4,000 m before the Early Miocene. Intensive thrust and crustal thickening occurred in the areas surrounding central Tibetan Plateau in Early Miocene, formed Gangdise Thrust System (GTS) in the southern Lhasa block, Zedong‐Renbu Thrust (ZRT) in the northern Himalaya block, Main Central Thrust (MCT) and Main Boundary Thrust (MBT) in the southern Himalaya block, and regional thrust systems in the Qaidam, Qilian, West Kunlun and Songpan‐Ganzi blocks. Foreland basins formed in Early Miocene along major thrust systems, e.g. the Siwalik basin along MCT, Yalung‐Zangbu Basin along GTS and ZRT, southwestern Tarim depression along West Kunlun Thrust, and large foreland basins along major thrust systems in the northeastern margin of the plateau. Intensive volcanic eruptions formed in the Qiangtang, Hoh‐Xil and Kunlun blocks, porphyry granites and volcanic eruptions formed in the Nainqentanglha and Gangdise Mts., and leucogranites and granites formed in the Himalaya and Longmenshan Mts. in Early Miocene. The K2O weight percentages of Early Miocene magmatic rocks in the Gangdise and Himlayan Mts. are found to increase with distance from the MBT, indicating the genetic relationship between regional magmatism and subduction of Indian continental plate in Early Miocene.

An integrated pore-pressure model and its application to hydrocarbon exploration: A case study from the Mahanadi Basin, east coast of India

An integrated pore-pressure modeling approach was adopted to understand the basin architecture from a pressure perspective and its inference toward possible hydrocarbon occurrence. Kriging-based 3D pore-pressure modeling was used with offset well data and seismic velocities to establish the pressure stratigraphy of the northeast coast (NEC) field (southern part) in the Mahanadi Basin. Late Pliocene sediment is moderately pressured ([Formula: see text]), whereas early Pliocene sediment is normally pressured ([Formula: see text]) and compacted, representing a regional seal for this part of the basin. Miocene represents the onset window for major undercompaction and associated high pressures ([Formula: see text]) in conformance with the regional pressure trend. Overpressure distribution and its mechanisms in the late Miocene level across the NEC field shows distinct patterns with highly elevated pressures ([Formula: see text]) in the northern part resulting from a hybrid unloading mechanism, whereas moderate to high pressure ([Formula: see text]) toward the southern part is associated with undercompaction. Regional pressure correlation across the study area suggests a pressure dependent habitat of hydrocarbons in the Miocene and late Pliocene levels. Pressure distribution and an excess pressure pattern within the Miocene stratigraphy shows a regression trend from north to south, possibly indicating a preferred subsurface fluid flow direction, which is supported by high-quality gas reservoirs discovered in the southern part of the study area. A similar but reverse pressure regression trend is observed within the late Pliocene stratigraphy, which is also validated by the presence of gas reservoirs in the northern part of the study area. Major hydrocarbon reservoirs in the Miocene and Pliocene stratigraphy from the southern part of study area exhibit a strong correlation with effective stress distribution. High-quality gas reservoirs are mostly associated with high effective stress ([Formula: see text]), whereas a high probability for reservoirs to be water wet are observed below this threshold value.

Correlating Mediterranean shallow water deposits with global Oligocene–Miocene stratigraphy and oceanic events

Shallow-marine sediment records have the strong potential to display sensitive environmental changes in sedimentary geometries and skeletal content. However, the time resolution of most neritic carbonate records is not high enough to be compared with climatic events as recorded in the deep-sea sediment archives. In order to resolve the paleoceanographic and paleoclimatic changes during the Oligocene–Miocene transition in the Mediterranean shallow water carbonate systems with the best possible time resolution, we re-evaluated the Decontra section on the Maiella Platform (central Apennines, Italy), which acts as a reference for the correlation of Oligocene–Miocene shallow water deposits in the Mediterranean region. The 120-m-thick late Oligocene–late Miocene carbonate succession is composed of larger foraminiferal, bryozoan and corallinacean limestones interlayered with distinct planktonic foraminiferal carbonates representing a mostly outer neritic setting. Integrated multi-proxy and facies analyses indicate that CaCO3 and total organic carbon contents as well as gamma-ray display only local to regional processes on the carbonate platform and are not suited for stratigraphic correlation on a wider scale. In contrast, new biostratigraphic data correlate the Decontra stable carbon isotope record to the global deep-sea carbon isotope record. This links relative sea level fluctuations, which are reflected by facies and magnetic susceptibility changes, to third-order eustatic cycles. The new integrated bio-, chemo-, and sequence stratigraphic framework enables a more precise timing of environmental changes within the studied time interval and identifies Decontra as an important locality for correlating not only shallow and deep water sediments of the Mediterranean region but also on a global scale.

Middle-Upper Miocene stratigraphy of the Taman Peninsula, Eastern Paratethys

AbstractThe stratigraphy of the Taman Peninsula is defined using the sections at Zelensky Hill — Panagia, Popov Kamen, Taman and Zheleznyi Rog. The stratigraphy is constructed from distribution of mollusks, foraminifers, nannofossils, diatoms, and organic-walled phytoplankton, as well as incorporating paleomagnetic data. The occurrence of oceanic diatom species in the Middle-Upper Sarmatian, Maeotian and Lower Pontian makes a direct correlation possible between the sections studied, the Mediterranean basin and oceanic zonation. The new data on planktonic and benthic biotic groups suggests a pulsating connection of the Eastern Paratethys with the open marine basins, especially during transitional intervals within constant environments. Comprehensive studies of the Chokrakian-Kimmerian microbiota provide evidence for several levels of marine microbiotic associations that are related to short-term marine invasions. The biotic and paleomagnetic data of the Taman Peninsula sections give a more comprehensive, but sometimes a controversial picture on the Eastern Paratethys history and the nature of its relationship with the adjacent marine basins.