Miocene to present turnover of molluscan assemblages: insights into coastal-marine ecosystem evolution along the Peruvian Margin

Sedimentary and structural evolution of the Eastern South Korea Plateau (ESKP), East Sea (Japan Sea)

The classical Late Miocene Maragheh fauna has been collected and studied sporadically for nearly 150 years. This study gives a comprehensive account of the entire mammalian fauna recovered at Maragheh to date and its biostratigraphic, biogeographic and geochronologic contexts. The sequence is divided into Lower, Middle and Upper biostratigraphic intervals, ranging fRom ca. 9.5 my to 7 my in age, based on the first appearance of a potential evolutionary series of hipparionine horses: "Hip-parion" gettyi, Hipparion prostylum, and Hipparion campbelli. Stratigraphical ranges of individual mammalian species are given, and biostratigraphic intervals are characterized. A comprehensive zoogeographic analysis of the entire Maragheh mammalian fauna shows its relationships with late Miocene–early Pliocene "savanna-mosaic" assemblages of Eurasia and Africa. It has been found that the Maragheh genera which have the broadest geographic distribution were part of a late early Miocene pan-Eurasian and African dispersal event. Their subsequent diversification may be attributable to biogeographic vicariance with both tectonic and paleoenvironmental factors playing contributing roles.

Miocene-Pliocene foraminifera recovered from three subsurface sections in the Yufutsu Oil and Gas Field, southern Hokkaido, are studied in detail to infer paleoceanographic and paleobathymetric implications and to clarify the history of the basin. Foraminiferal faunas indicate a progressive increase in bathymetry from a brackish shallow marine to a bathyal condition during the Middle Miocene. The basin then came under the spell of volcanism and nearly 1000 m of basalt-basaltic andesite flows accumulated until the top of the volcano emerged out of the sea. After the cessation of volcanic activity, the basin subsided and cold bathyal conditions prevailed in which diatomaceous-siliceous sediment was accumulated during the Late Miocene. The periodic episodes of subsidence are inferred to have been related to the genesis of the Japan Sea. The basin witnessed a major hiatus during the Late Miocene-Early Pliocene. During the Late Pliocene, coarse clastic sediments accumulated in the region in a cold bathyal condition of deposition. The clastic sediment is thought to have derived from the eastern upland where the Upper Cretaceous and Paleogene sedimentary rocks were exposed. It is supposed that the hiatus in the Late Miocene-Early Pliocene is a result of an upheaval of central Hokkaido, which unstabilized the sediment and changed bottom current condition.The Early to Middle Miocene microfauna of the region is similar to those of the Japan Sea region, whereas the Late Miocene fauna is different in abundance of agglutinated foraminifera. Such faunal differences between the study area and Japan Sea region of Honshu in the Late Miocene are mainly due to the variable distances from the proto-Tsugaru Strait that let carbonate-saturated Pacific seawater into the Japan Sea.

<p>We present a structural study on late Miocene-early Pliocene out-of-sequence thrusts affecting the southern Apennine chain. The analyzed structures are exposed in the Campania region (southern Italy). Here, leading thrusts bound the N-NE side of the carbonate ridges that form the regional mountain backbone. In several outcrops, the Mesozoic carbonates are superposed onto the unconformable wedge-top basin deposits of the upper Miocene Castelvetere Group, providing constraints to the age of the activity of this thrusting event. We further analyzed the tectonic windows of Giffoni and Campagna, located on the rear of the leading thrust. We reconstructed the orogenic evolution of this part of the orogen. The first was related to the in-sequence thrusting with minor thrusts and folds, widespread both in the footwall and in the hanging wall. A subsequent extension has formed normal faults crosscutting the early thrusts and folds. All structures were subsequently affected by two shortening stages, which also deformed the upper Miocene wedge top basin deposits of the Castelvetere Group. We interpreted these late structures as related to an out-of-sequence thrust system defined by a main frontal E-verging thrust and lateral ramps characterized by N and S vergences. Associated with these thrusting events, LANFs were formed in the hanging wall of the major thrusts. Such out-of-sequence thrusts are observed in the whole southern Apennines and record a thrusting event that occurred in the late Messinian-early Pliocene. We related this tectonic episode to the positive inversion of inherited normal faults located in the Paleozoic basement. These envelopments thrust upward crosscut the allochthonous wedge, including, in the western zone of the chain, the upper Miocene wedge-top basin deposits. Finally, we suggest that the two tectonic windows are the result of the formation of an E-W trending regional antiform, associated with a late S-verging back-thrust, that has been eroded and crosscut by Early Pleistocene normal faults.</p>

<p>The late Miocene-early Pliocene geology of the Makara and Ruakokoputuna Valleys in the northern Aorangi Range, south-east Wairarapa, is described in detail. In this area, a succession of Neogene sedimentary units laps onto basement rocks of Cretaceous age, and late Miocene-early Pliocene stratigraphy varies markedly, from bathyal mudstone to high energy coastal environments, over distances of only a few kilometres. Sections were measured at four key locations, which provided reference sites for stratigraphic changes across the study area. Additional detailed field mapping was carried out around Te Ahitaitai Ridge. Depositional environments were interpreted using grain size analysis, macrofossil and foraminiferal assemblages, and palynology. Foraminiferal biostratigraphy was used to constrain the ages of samples. Data obtained by these methods were combined with previous authors’ work to produce a synthesis map, unit correlations, and geological cross-sections of the Makara and Ruakokoputuna Valleys. Late Miocene-early Pliocene geological history is interpreted, and a depositional model is proposed to explain the presence of giant cross-beds in the Clay Creek Limestone. Despite major differences in lithology, the Clay Creek Limestone and Bells Creek Mudstone are shown to be partially laterally equivalent, while the overlying Makara Greensand is shown to be a diachronous unit which ranges from late Miocene (Kapitean) to early Pliocene (Opoitian) in age. This revised stratigraphy raises questions about the current classification of the Palliser and Onoke Groups, and provides new insights into regional geological history. The late Miocene-early Pliocene stratigraphy records a history of regional subsidence, punctuated by episodes of deformation which caused localised uplift and erosion. Previous seismic imaging studies identified one such episode of accelerated crustal shortening and deformation in the Wairarapa region near the Miocene-Pliocene boundary. The Clay Creek Limestone has proven to be a useful marker horizon for constraining the timing and style of deformation, which is interpreted to have occurred prior to 7.2 Ma. Major differences in stratigraphy between the upthrown and downthrown sides of the Mangaopari Fault indicate that the fault was active during this deformational episode. Lithostratigraphic units from the study area have been correlated with units in other parts of the Wairarapa, and these correlations suggest that late Miocene deformation in the region may have propagated from south to north.</p>

<p>The late Miocene-early Pliocene geology of the Makara and Ruakokoputuna Valleys in the northern Aorangi Range, south-east Wairarapa, is described in detail. In this area, a succession of Neogene sedimentary units laps onto basement rocks of Cretaceous age, and late Miocene-early Pliocene stratigraphy varies markedly, from bathyal mudstone to high energy coastal environments, over distances of only a few kilometres. Sections were measured at four key locations, which provided reference sites for stratigraphic changes across the study area. Additional detailed field mapping was carried out around Te Ahitaitai Ridge. Depositional environments were interpreted using grain size analysis, macrofossil and foraminiferal assemblages, and palynology. Foraminiferal biostratigraphy was used to constrain the ages of samples. Data obtained by these methods were combined with previous authors’ work to produce a synthesis map, unit correlations, and geological cross-sections of the Makara and Ruakokoputuna Valleys. Late Miocene-early Pliocene geological history is interpreted, and a depositional model is proposed to explain the presence of giant cross-beds in the Clay Creek Limestone. Despite major differences in lithology, the Clay Creek Limestone and Bells Creek Mudstone are shown to be partially laterally equivalent, while the overlying Makara Greensand is shown to be a diachronous unit which ranges from late Miocene (Kapitean) to early Pliocene (Opoitian) in age. This revised stratigraphy raises questions about the current classification of the Palliser and Onoke Groups, and provides new insights into regional geological history. The late Miocene-early Pliocene stratigraphy records a history of regional subsidence, punctuated by episodes of deformation which caused localised uplift and erosion. Previous seismic imaging studies identified one such episode of accelerated crustal shortening and deformation in the Wairarapa region near the Miocene-Pliocene boundary. The Clay Creek Limestone has proven to be a useful marker horizon for constraining the timing and style of deformation, which is interpreted to have occurred prior to 7.2 Ma. Major differences in stratigraphy between the upthrown and downthrown sides of the Mangaopari Fault indicate that the fault was active during this deformational episode. Lithostratigraphic units from the study area have been correlated with units in other parts of the Wairarapa, and these correlations suggest that late Miocene deformation in the region may have propagated from south to north.</p>

The paleomagnetic stratigraphy, biostratigraphy, and paleoclimatology have been studied in two marine sections of late Miocene to early Pliocene age in New Zealand. A total of over 850 separately oriented cores were collected from 270 sites. The Blind River section (41°43′ S.) is now adjacent to the southernmost subtropical (temperate) water mass, but planktonic foraminifera indicate that the area was covered by subantarctic water during much of late Miocene and early Pliocene time. The Mangapoike River section (38°55′ S.) records temperature oscillations mainly within the subtropical water mass during late Miocene–early Pliocene age, with perhaps one subantarctic interval during latest Miocene time. The Miocene-Pliocene boundary in New Zealand has consistently been placed at the first evolutionary appearance of Globorotalia puncticulata at the boundary between the late Miocene Kapitean Stage and the early Pliocene Opoitian Stage. This boundary lies within sediments deposited during the Gilbert Reversed Epoch between the Nunivak Event (base at 4.14 m.y. B.P.) and the Gilbert C Event (top at 4.33 m.y. B.P.) in both sections. Thus, the Miocene-Pliocene boundary, as recognized in New Zealand, is dated as 4.3 ± 0.1 m.y., which appears to be slightly younger than the type (International) Miocene-Pliocene boundary in Italy (4.9 to 5.1 m.y.). Biostratigraphic ranges of planktonic foraminifera between New Zealand and the Mediterranean differ in detail, perhaps due to different paleo-oceanographic histories. A major cooling episode during the early Gilbert Reversed Epoch is recorded at Blind River and Mangapoike River. This cooling is more pronounced in the southern section examined, where it is represented by the occurrence of a central subantarctic planktonic foraminiferal assemblage. In the northern section, cooling was also pronounced, although of shorter duration, represented by a probably northern subantarctic assemblage. The Miocene-Pliocene boundary in Europe has still only been dated indirectly by means of non-Mediterranean sections. Interpretation of late Cenozoic paleomagnetic data from Mediterranean deep-sea cores collected from Glomar Challenger is rejected.

Palaeoclimatic and palaeoenvironmental interpretations of the Late Oligocene, Late Miocene–Early Pliocene in the Çankırı-Çorum Basin

Oceanographic significance of Pacific late miocene calcareous nannoplankton

Tidal freshwater wetlands are complex, species-rich ecosystems located at the interface between tidal estuaries and nontidal rivers. This study conducted on the Patuxent River estuary in Maryland was designed to assess vegetation dynamics over several decades to determine if there were directional changes in the dominant communities. Aerial photographs (1970, 1989, and 2007) documented broad-scale spatial changes in major plant communities. The coverage of areas dominated by Nuphar lutea and Phragmites australis expanded; mixed vegetation and scrub–shrub habitats were essentially unchanged; and Typha and Zizania aquatica communities fluctuated in coverage. Data collected between 1988 and 2010 from permanent plots and transects were used to examine fine-scale changes. Shifts in the importance of some species through time were observed, but there were no directional changes in community species composition. The lack of directional change as measured at a fine scale is characteristic of tidal freshwater wetlands in which variations in the abundance of individual species, especially annuals, are responsible for most short-term change in species composition. Changes in the composition of plant communities are interpreted as responses to variations in vertical accretion, stability of habitat types, invasive plant species, and herbivores. In the future, vegetation changes are likely to occur as a result of the intrusion of brackish water and increased flooding associated with global climate change and sea level rise. This long-term study establishes a baseline from which potential future changes to tidal freshwater wetlands can be better understood.

In evolutionary paleontology of terrestrial biotas, the Miocene is the most important age especially for evolution of hominids and mammalian faunas. The modern mammalian fauna appeared from the end of this age in Eurasia. In Sub-Saharan Africa, the assemblage of the late Miocene mammalian faunas was very poor, and these faunas were represented by only few faunas. Therefore, this incompleteness of the late Miocene East African faunas, it is very difficult to analyze faunal turnover of Sub-Saharan mammalian faunas and compare with Eurasian and Sub-Saharan faunas of this age.The paleontological contribution of the Japan and Kenya joint expedition to the Samburu Hills, northern Kenya covered this gap of mammalian evolution in Sub-Saharan Africa.In this work, the Miocene mammalian faunas in Sub-Saharan Africa is examined the half-life (Kurtén 1959, 1972, 1988) of each faunal assemblages (sets).Assemblage of the mammalian faunas from early Miocene was comparatively stable and had long half life in Sub-Saharan Africa on the basis of the results of this work.However, mammalian assemblage changed drastically at the middle Miocene (Astaracian) in Sub-Saharan Africa.A great number of early to middle Miocene mammalian taxa were extinct and the modern mammalian taxa appeared in this period. The half life of middle and late Miocene mammalian faunas is shortened compared with the early Miocene faunas in the East Africa. This geological event of faunal turnover occurred by the immigration and divergence of open land taxa.It is evident that the rise of open land taxa is related to the environmental change for the plateau phonolite and basalt volcanism in the middle Miocene East Africa (Pickford 1981) and the worldwide warm and arid event (savannitisation) of continental temperate zone in the middle to late Miocene (Liu 1988). In the middle Miocene (16 Ma) Pacific region, it has been proposed that the tropical event is recognized from shallow marine faunas of the Southwestern Japan (Tsuchi 1986). African and Eurasian land connection was also established before the middle Miocene (16 Ma±) (Bernor et al. 1987).The Astaracian faunal turnover in Sub-Saharan Africa is considered to be caused by immigration and diversity of open country mammalian taxa and that was related to the worldwide middle Miocene warm event and the plateau volcanism in middle Miocene East Africa. Furthermore, the Pleistocene and modern taxa and their direct ancestors of Sub-Saharan Africa appeared from the late Miocene faunas of East Africa. It has been made clear that the Namurungule Fauna is the forerunner of the modern Sub-Saharan mammalian fauna of savanna environments.As mentioned before, the Hominid Fossil was found from the Namurungule Formation (late Miocene) of northern Kenya. The savannitisation in the Sub-Saharan Africa began in middle Miocene. The origin of hominid bipedalism seems to be closely related to the environmental change from forest to open land (Foley 1984). Human evolution in East Africa is accelerated by the savannitisation of Sub-Saharan Africa which commenced earlier than that of Eurasia and continued throughout the Neogene.

Neotectonic intersection of the Aegean and Cyprus tectonic arcs: extensional and strike-slip faulting in the Isparta Angle, SW Turkey

The Isparta Angle and adjacent Antalya Bay areas constitute an important segment of the eastern Mediterranean region, located at the intersection of the southwardconvex Aegean and Cyprus arcs. Some recent tectonic maps show the Isparta Angle as a NW–SE compressional lineament extending eastwards into the Kyrenia Range of northern Cyprus. However, fault data from the onshore Isparta Angle, together with offshore shallow seismic reflection data, show that the present morphotectonic setting is dominated by extension. The last phase of compression to affect the area studied in the Late Miocene, was accompanied by regional nappe emplacement (Lycian Nappes). Onshore, fault planes, measured from fault zones bounding both the limbs and the core of the Isparta Angle are oriented predominantly NE–SW, NW–SE and N–S. Superimposed slickenfibres show that reverse faults were succeeded, in turn, by right-lateral faults, then by normal faults. The fault phases are dated by stratigraphical and geomorphological evidence. Reverse faults date from the Late Miocene, or earlier compressional deformation, whereas the right-lateral faults mainly developed during latest Miocene–Early Pliocene. Normal faulting dominated from the Late Pliocene–Recent. An interpretation of shallow seismic reflection data shows that Antalya Bay is characterised by a NW–SE-trending asymmetrical graben system that has continued to be active. During the Late Miocene–Early Pliocene right-lateral strike-slip resulted from shear along the eastern termination of a zone of extension and rotation that characterises the western Aegean. This shear was focused in a N–S direction by inherited zones of structural weakness in the basement (Antalya Complex). The switch to NE–SW extension in the Late Pliocene–Quaternary relates to a regional change in stress direction throughout the Aegean region and was accompanied by strong uplift of the Bey Daˇglari region of the Taurus Mountains, bordering the Isparta Angle in the west. The Isparta Angle is the link between: (a) the extensional province of western Turkey bounded to the south by the actively subducting Hellenic arc; and (b) the uplifted Anatolian plateau bounded to the south by the Cyprus subduction zone. Understanding the Miocene to Recent tectonic development helps elucidate the kinematics of the region. The new structural data presented lend no support for recent suggestions that the Isparta Angle and Antalya Bay represent parts of a regional compressional zone related to plate collision. © 1998 Elsevier Science B.V. All rights reserved. Translation permission of this article has been taken from Elsevier (CCC) on April 01 2015 date and 3600420598320 Licence number

Decades of exploration activities in the Sandakan Basin offshore eastern Sabah, Malaysia, since the 1970s have yet to yield commercial hydrocarbon discoveries. Of the nineteen wells that have been drilled in the basin up to 2015, only five are classified as discoveries, all made between 1970 and 1995. There are essentially two main proven play types: (1) Early to Middle Miocene “Segama play”, in which the reservoir targets are the Tanjong Formation equivalents within the Segama Group, which were deposited as part of the synrift sequence. (2) Middle to Late Miocene “Sebahat play” in which the reservoirs belong to the Sebahat Formation, characterised by prograding deltaic shoreface and shelf sequences, advancing eastwards and southwards from an uplifting hinterland in central and northern Sabah. The best reservoir facies are shoreface sands, which have porosities greater than 20%, particularly at depths shallower than ~2000 m. Although the generative source rocks have not been penetrated, geochemical data indicate that they are present at depths greater than 3200 m. The source rocks are characterised by predominantly Type III and Types II/III organic matter, which are typical of deltaic settings. The data indicate that hydrocarbons were generated by source rocks with a maturity range of 0.7 – 0.8% vitrinite reflectance (Ro). The Sandakan Basin was affected by several compressional deformation events which are expressed as major erosional unconformities; most significantly, the Middle Miocene (“D2 event”, 13.0 Ma) and Late Miocene (“D3 event”, 8.6 Ma). The unconformities were the result of compression and faulting which, while being responsible for trap formation, may also pose significant risk to trap integrity and preservation. Modelling results indicate that hydrocarbon generation and migration took place during Late Miocene–Early Pliocene and continues today. The basin’s prospectivity, therefore, critically depends on the delicate interplay between the timing of trap formation and hydrocarbon migration. Understanding these processes requires detailed understanding of the structural evolution and petroleum systems of the basin.

Extensional faults exposed in the Peloponnesus and mainland Greece, most of which are described here for the first time, record a transition from regional extension of the Aegean domain to the modern tectonic system. The East Peloponnesus Detachment System trends north‐northwest from the southern Peloponnesus to ∼30 km north of the Gulf of Corinth, dips gently northeast, and is late Miocene–early Pliocene in age. It has a minimum displacement of 25–30 km and appears to be the youngest of the regional‐scale extensional systems with significant displacement that formed parallel to the Hellenic arc. The partially coeval East Sterea Extensional System, which extends from the Gulf of Corinth to the Aegean Sea, contains low‐angle normal faults that both crosscut and trend parallel to older structures of the Hellenic arc. Late Miocene to early Pliocene displacement within this zone disrupted the arc‐parallel structures of the Hellenides. Upper Pliocene‐Quaternary normal faults, which trend approximately east‐west and generally dip steeply at the surface, continue the disruption of the Hellenic arc. Much of the subsidence within the Gulf of Corinth appears to be unrelated to the younger faults and is instead related to the motion on the East Peloponnesus Detachment, which crosscuts the modern graben.