Miocene-Pliocene Foraminifera from the subsurface sections in the Yufutsu Oil and Gas Field, Hokkaido

Role of climate in partial drowning of the Queensland Plateau carbonate platform (northeastern Australia)

<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>

Late Neogene paleoceanography of the eastern Caribbean, the Gulf of Mexico, and the eastern Equatorial Pacific

Morphotectonic evolution of Maviboğaz canyon and Suğla polje, SW central Anatolia, Turkey

The structure of the Philippine archipelago results from the juxtaposition, between the Late Miocene and the present, of a volcanic belt against fragments of the Eurasian margin and associated marginal basins. The southern Philippines offers the opportunity of studying the mechanics of the deformation from active contraction to a more complex post-docking setting. The docking period is characterized by a compression which began during the early Late Miocene in the central Philippines and has been recently studied in the island of Mindanao. There, deformation initiated in the Late Miocene-Early Pliocene on a NW-trending wrench zone, and continued until the Late Pliocene with thrusting on west-verging flats and ramps within the arc and east-verging thrusts within the Sangihe forearc. This deformation is still active to the south in the Molucca Sea. The post-docking period began in the Early Pleistocene in northern Mindanao and is represented by a new geodynamic framework with a paired subduction zone and strike-slip fault. However, convergence is still active in the Manila and the Negros trenches, although the Philippine fault is not offset. Large wrench faults, which reactivate the ramp faults of the collision stage, transfer strain from the Philippine fault to the Manila and Negros trenches. These observations imply active intra-arc extension and fragmentation within the Philippine mobile belt.

This study discusses paleoceanographic changes in the Japan Sea across the Miocene/Pliocene boundary based on foraminiferal distributions and geochemical evidence obtained in the Akita Prefecture of northern Japan.Q-mode cluster analysis differentiates six foraminiferal associations from a total of 55 assemblages. Their paleoceanographic implications are based on previous studies on the ecology of benthic foraminifers Spirosigmoilinella compressa and Miliammina echigoensis, microhabitat preferences of constituent species inferred from morphotypes, and other ecologic information of extant species. The stratigraphic distribution of each association reveals a history of oxygen depletion in the bottomwaters of the Japan Sea during the Late Miocene, followed by the oxic bottomwaterwith conditions of higher organic matter flux in the Early Pliocene. This interpretation is reinforced by the geochemical data of organic facies such as total organic carbon and hydrogen index fromRock-Eval analysis. It is inferred that this paleoceanographic change was a result of the rise in the eustatic sea level during the earliest Pliocene. Throughout the stratigraphic interval organic matter flux, related to primary productivity, is inferred to be higher in the northern sections than in the southern sections. This geographic variation is in agreementwith previous studies on other Japan Sea regions, and suggests that eutrophic conditions were prevalent in the northern region, where the Tsugaru Strait links the Japan Sea with the Pacific Ocean. The organic matter fluxes and oxygen depletion controlled by eustatic sea level variation are closely related to the source rock deposition of the oil and gas fields in the Japan Sea region.

<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>

Summary The distribution of the Holocene-Recent sedimentary environments of the Nile Delta is related to secular variations of the semi-arid climate and of the Nile River sediment input and flux, and to coastal subsidence and high wave energy, together with an eastward littoral drift. The delta started to form in the Late Pliocene, with its main development taking place in the Pleistocene, associated with progradation of large volumes of coarse coastal delta sands and the offshore accumulation of turbidities (Nile Cone). In the Oligocene-Early Miocene, an ancestral Nile discharged to the NW. Fluvio-deltaic deposits appeared in the present delta area in the Late Miocene, where they built a narrow prism close to an active faulted flexure, which in the subsurface now separates the South Delta Block from the deep North Delta Basin. The stratigraphy, structure and depocentre development of the region are functions of the interaction between the E-W- to WSW-ENE-trending Mediterranean margin structures, active since the end of the Cretaceous, and the NW-, NNW- and NNE-trending Red Sea-Gulf of Suez structural fabric associated with arching and rifting from the Oligocene to Pleistocene. The main phases of tectonic activity and of clastic deposition, which also correlate with lowered sea levels, were in Late Oligocene-Early Miocene, late Middle Miocene, Tortonian-Messinian, Middle Pliocene and Early-Middle Pleistocene. Petroleum exploration in the Nile Delta has produced modest results to date with a few medium-sized gas fields and minor oil discoveries.

Structural analysis of the northern part of the East Anatolian Fault System

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

Fossil remains herein described are referred to different species of Dasypodidae Gray, 1821 (Mammalia, Xenarthra, Cingulata) and come from the upper levels of the lower member (Late Miocene-Early Pliocene) of the Toro Negro Formation at Quebrada de Las Torrecillas, La Rioja Province, Argentina, where previous vertebrate records only include those of Pyramiodontherium scillatoyanei De Iuliis, Ré & Vizcaíno, 2004 (Mammalia, Xenarthra) and Opisthodactylus cf. kirchneri Noriega, Jordan, Vezzosi & Areta, 2017 (Aves, Rheidae). The remains of Dasypodidae herein presented include Vetelia ghandii Esteban & Nasif, 1996, Chasicotatus peiranoi Esteban & Nasif, 1996, Macrochorobates scalabrinii (Moreno & Mercerat, 1891), Prozaedyus sp., and Paleuphractus argentinus (Moreno & Mercerat, 1891), and constitute the first records of these species for the Toro Negro Formation, increasing the mammal diversity for this unit. The association of dasypodids here described shows strong affinities with those described for Late Miocene localities of Northwestern Argentina. Under these evidences, the Dasypodidae here reported for Quebrada de Las Torrecillas site show a characteristic association of taxa from Northwestern Argentina, suggesting a Messinian age (Late Miocene) for the bearing levels of the Toro Negro Formation. In this way, these records support the accurate ages recently proposed for the lower Member of the Toro Negro Formation (i.e., Late Miocene-Early Pliocene).

We present a structural study on late Miocene-early Pliocene out-of-sequence thrusts affecting the southern Apennine orogenic belt. The analyzed structures are exposed in the Campania region (southern Italy). Here, 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. Moreover, a 4-km-long N-S oriented electrical resistivity tomography profile, carried out along the Caserta mountains, sheds light on the structure of this thrust system in an area where it is not exposed. Further information was carried out from a tunnel excavation that allowed us to study some secondary fault splays. The kinematic analysis of out-of-sequence major and minor structures hosted both in the hanging wall (Apennine Platform carbonates) and footwall (Castelvetere Group deposits and Lagonegro-Molise Basin units) indicates the occurrence of two superposed shortening directions, about E-W and N-S, respectively. We associated these compressive structures to an out-of-sequence thrusting event defined by frontal thrusts verging to the east and lateral ramp thrusts verging to the north and south. We related the out-of-sequence thrusting episode to the positive inversion of inherited normal faults located in the Paleozoic basement. These envelopments thrust upward to crosscut the allochthonous wedge, including, in the western zone of the chain, the upper Miocene wedge-top basin deposits.

Fossil murine rodents as ancient monsoon indicators of the Indian subcontinent

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