Fluvial-Tidal to Fluvial-Lacustrine Sedimentation of the Middle Miocene to Pleistocene Mapia Formation, Dogiyai, Papua (Indonesia)

A sedimentological and palynological investigation was carried out on outcropping sedimentary rocks at Dogiyai, Papua, proposed to be named as the Mapia Formation. The age range is from Middle Miocene to Pleistocene. The lower Mapia Formation was deposited at Metroxylon type to Nothofagus emarcida Zone, Middle Miocene to Early Pliocene. It is comprised of three facies associations: tidal channel, tidal point bar, and tidal flat deposits. A tidally dominated fluvially influenced depositional environment is suggested for the deposition of sediments of this unit. The upper Mapia Formation was deposited at Malvacipollis diversus Zone, Garcinia cuspidata type Zone, and Proteacidites sp. Zone, Late Pliocene to Pleistocene. It is comprised of five facies associations: delta front, slump, debrite, turbidite, and lacustrine mud deposits. A non-channelized deep-lacustrine slump and debris-flow dominated depositional environment is suggested for the deposition of sediments of this unit. The lower Mapia Formation was deposited as synorogenic clastic sediments at the beginning of Central Range orogeny event while the upper Mapia Formation was deposited in the piggyback basin at the major uplift event.

Active deformation and Plio-Pleistocene fluvial reorganization of the western Kura fold–thrust belt, Georgia: implications for the evolution of the Greater Caucasus Mountains

Since Plio-Pleistocene time, southward migration of shortening in the eastern part of the Greater Caucasus into the Kura foreland basin has progressively formed the Kura fold–thrust belt and Alazani piggyback basin, which separates the Kura fold–thrust belt from the Greater Caucasus. Previous work argued for an eastward propagation of the Kura fold–thrust belt, but this hypothesis was based on coarse geological maps and speculative ages for units within the Kura fold–thrust belt. Here we investigate the initiation of deformation within the Gombori range in the western Kura fold–thrust belt and evaluate this eastward propagation hypothesis. Sediments exposed in the Gombori range have a Greater Caucasus source, despite the modern drainage network in the NE Gombori range, which is dominated by NE-flowing rivers. Palaeocurrent analyses of the oldest and youngest syntectonic units indicate a switch happened between ~2.7 Ma and 1 Ma from dominantly SW-directed flow to palaeocurrents more similar to the modern drainage network. A single successful 26Al–10Be burial date indicates the youngest syntectonic sediments are 1.0 ± 1.0 Ma, which, while not a precise age, is consistent with original mapping suggesting these sediments are of Akchagylian–Apsheronian (2.7–0.88 Ma) age. These results, along with recent updated dating of thrust initiation in the eastern Kura fold–thrust belt, suggest that deformation within the Kura fold–thrust belt initiated synchronously or nearly synchronously along-strike. We additionally use topographic analyses to show that the Gombori range continues to be a zone of active deformation.

PALAEOGRAPHIC EVOLUTION OF PINDOS BASIN DURING PALEOGENE USING CALCAREOUS NANNOFOSSILS

A different basin evolution is suggested between the northern and southern parts of the Pindos basin, based on biostratigraphic dating results. Characteristic nannofossils showed that flysch sedimentation in the whole basin started in the Paleocene and generally finished during the Eocene, with the exception of the Konitsa and Milia areas where sedimentation lasted until Early Oligocene. Although, basin depth increased southwards, Kastaniotikos and Sperchios faults affected the geometry of Pindos basin, creating ridges and troughs within the basin. Due to this segmentation of the basin, the continuity of the sedimentation in the northern part of the study area until Oligocene is suggested. Calcareous nannofossils recovered from this northern part indicate a Paleocene NP5 to early Cligocene (NP20-21) age. On the other hand, in the southern part, sedimentation of flysch was lasted until middle Eocene. According this model, sedimentation in the southern part, stopped during the middle Eocene, was followed by subaerial exposure and the migration of clastic sedimentation to the western part of Pindos zones (Pindos foreland basin of Ionian zone). At this time, in the northern part, a small-restricted basin was continuously active as a piggyback basin from upper Eocene to lower Oligocene and shallow deposits (slope and submarine canyon deposits, delta fan deposits) accumulated.

Is pull-apart basin tectonic model feasible for the formation of Kashmir basin, NW Himalaya

Kashmir Basin in NW Himalaya is considered a Neogene-Quatermary piggyback basin that was formed as result of the continent-continent collision of Indian and Eurasian plates. This model however is recently challenged by a pull-apart basin model, which argues that a major dextral strike-slip fault that runs through the Kashmir basin is responsible for its formation. And here it is demonstrated that this tectonic model is structurally unrealistic, and poses problems with geomorphology, geology, and tectonic setting of Kashmir basin. The major flaw of the model remains its orientation, and geometry, because a major dextral fault, which form a pull-apart basin, cannot cut through the center of a basin. It is therefore shown that the recently suggested pull-apart model is structurally impossible, and thus the Central Kashmir Fault (CKF), a proposed major dextral fault of Alam et al. (2015), could not exist.

Pull-apart basin tectonic model is structurally impossible for Kashmir basin, NW Himalaya

Kashmir Basin in NW Himalaya is considered a Neogene-Quatermary piggyback basin that was formed as result of the continent-continent collision of Indian and Eurasian plates. This model however is recently challenged by a pull-apart basin model, which argues that a major dextral strike-slip fault through Kashmir basin is responsible for its formation. And here it is demonstrated that the new tectonic model is structurally problematic, and conflicts with the geomorphology, geology, and tectonic setting of Kashmir basin. It also conflicts, and contradicts with the various structural features associated with a typical dextral strike-slip fault system where it shows that such a major structure cannot pass through the middle of the basin. It is demonstrated that such a structure is structurally, and kinematically impossible, and could not exist.