Testing Models of Cenozoic Exhumation in the Western Greater Caucasus
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Abstract The Greater Caucasus form the northernmost deformation front of the Arabia‐Eurasia collision zone. Earlier thermochronometric studies on the crystalline core of the western Greater Caucasus highlighted an abrupt along‐strike increase in cooling ages to the west of Mt. Elbrus. Twenty‐eight thermochronometric analyses conducted as part of this study confirm this pattern. Overall Cenozoic exhumation was restricted to less than 5–7 km, with slow to moderate punctuated Oligo‐Miocene cooling. Cooling rates increased during the Late Miocene to Pliocene. These are most rapid east of Mt. Elbrus, where they probably increased later than farther west (at c. 5 Ma rather than 10–8 Ma). Differential cooling rates do not appear to be driven by lateral variations in tectonic shortening. The region undergoing rapid young cooling does coincide, however, with an area of mantle‐sourced Late Miocene and younger magmatism. Thermal relaxation or overprinting is ruled out because geomorphic and modern sediment flux data mirror the thermochronometric trends. The buoyancy effects of demonstrable mantle upwelling are capable of causing the magnitude of exhumation‐related cooling recorded in this study, but typically act over wavelengths of several 100 km. We suggest that lithospheric heterogeneities are responsible for modulating the shorter wavelength differences in exhumation rate documented here. These heterogeneities may include the continuation of the same structures responsible for the eastern margin of the Stavropol High to the north of the Caucasus, although further work is required. Similar abrupt variations in mantle‐supported uplift and exhumation modulated by crustal structure may occur in other mountain belts worldwide.Keywords:
Neogene
Overprinting
Three main stages have been distinguished in the Neogene-Quaternary morphotectonic evolution in the East Marmara region. They are Early-middle Miocene, Late Miocene-Pliocene and Latest Pliocene-Present. Three different sedimentary sequences, each overlies the other with an angular uncomformity, have been formed in these stages. Early-middle Miocene sedimentary sequence is characterised by continental detritics whereas the Late Miocene-Pliocene rocks are represented by continental to marine transitional sediments. Terrestrial-marine sediments have been deposited since the latest Pliocene till Present. The region was transformed to denudational area by the closure of the Intra-Pontid Ocean in the end of the Oligocene and it was under the effect of paleotectonic events during the early-middle Miocene. In the end of this erosional period which lasted until the end of middle Miocene, a peneplain morphology covering large area was formed and terrestrial sediments were deposited. Neotectonics which has affected actual geology in the region, initiated in the beginning of late Miocene and occurred in two stages which differ tectonic styles. In the late Miocene-Pliocene time, the region was affected by N-S directed compressional regime and it was uplifted by NE-SW and NW-SE trending strike-slip faults with E-W lying folds as a result of this compression. During this stage, a Late Miocene-Pliocene sedimentary sequence which starts with fluvial sediments at the bottom and passes into lacustrine to marine at the top, was deposited. In the end of the period, depressions in which late Miocene- Pliocene sediments were deposited, were spread out and the region was formed as a denudational area in the late Pliocene. The second stage of the neotectonic period covers a time interval from the Latest Pliocene to Present and it begun with the occurrence of the North Anatolian Fault. Actual morphology and active tectonic frame of the Eastern Marmara region were developed in this time interval which is known with the transform character of the North Anatolian Fault. However, structural evolution of actual Marmara sea region which is related to North Anatolian Fault, initiated in Latest Pliocene.
Neogene
Middle Miocene disruption
Neotectonics
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Neogene
Pinaceae
Cupressaceae
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Abstract Despite the rich fossil record of Neogene chondrichthyans (chimaeras, sharks, rays, and skates) from Europe, little is known about the macroevolutionary processes that generated their current diversity and geographical distribution. We compiled 4368 Neogene occurrences comprising 102 genera, 41 families, and 12 orders from four European regions (Atlantic, Mediterranean, North Sea, and Paratethys) and evaluated their diversification trajectories and paleobiogeographic patterns. In all regions analyzed, we found that generic richness increased during the early Miocene, then decreased sharply during the middle Miocene in the Paratethys, and moderately during the late Miocene and Pliocene in the Mediterranean and North Seas. Origination rates display the most significant pulses in the early Miocene in all regions. Extinction rate pulses varied across regions, with the Paratethys displaying the most significant pulses during the late Miocene and the Mediterranean and North Seas during the late Miocene and early Pliocene. Overall, up to 27% and 56% of the European Neogene genera are now globally and regionally extinct, respectively. The observed pulses of origination and extinction in the different regions coincide with warming and cooling events that occurred during the Neogene globally and regionally. Our study reveals complex diversity dynamics of Neogene chondrichthyans from Europe and their distinct biogeographic composition despite the multiple marine passages that connected the different marine regions during this time.
Neogene
Origination
Extinction (optical mineralogy)
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The intent of this study was to show the Neogene mammalian faunal change of the sub-Saharan Africa and the Relationships of the late Miocene mammalian faunas of the sub-Saharan Africa and the Eurasia. I reviewed the Neogene mammalian fauna of the sub-Saharan Africa and studied the phylogenetic relationships of some taxa from the Namurungule Formation (late Miocene), Northern Kenya.The sub-Saharan mammalian fauna of Neogene and its environments change from forest type to savanna type at the late Miocene. Tetralophodon from the Namurungule Formation was the most advanced type of Gomphotheriidae (Proboscidea) of the Eurasia and Africa, the large form of Hipparionine (Equidae, Perissodactyla) was very similar to Cormohipparion perimense of the Siwaliks, Iranotherinae (Rhinocerotidae, Perissodactyla) was similar to the taxa from Spain, Iran, the Siwaliks, and China.These facts support the idea that the Namurungule mammalian fauna consists mostly of the common Eurasian taxa and the unique African taxa, and this late Miocene fauna becomes the nucleus of the Pliocene to Pleistocene mammalian fauna of the sub-Saharan Africa.
Neogene
Eutheria
Proboscidea
Biochronology
Early Pleistocene
Equidae
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Abstract The Neogene Period/System (approximately the past 24 million years) is the younger of a twofold subdivision of the Cenozoic Era which includes as its lower component the Palaeogene Period/System (65–24 Ma). It includes the Miocene, Pliocene and Pleistocene (and in some sources Holocene) Epochs/Series.
Neogene
Paleogene
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The timing of continental-scale marine flooding events in Western Amazonia during the Neogene is still an unsolved question. Despite broad proxy-based evidence of such events, the pathways and duration of late Miocene marine incursions remain controversial. We provide coupled calcareous and organic microfossil and geochemical data from six onshore cores from Neogene sequences of the Solimões Basin, Brazil. Our records support minor marine influence in the early Miocene (23.0, 21.1, 18.6, and 16.3 Ma), middle Miocene (14.9, 13.7, and 12.9 Ma) and early Pliocene (4.7, 4.2–4.1, and 3.8 Ma), and conspicuous marine incursions in the late Miocene (11.1–8.8 Ma) suggested by the consistent presence of salinity-indicative microfossils and geochemical data. Our findings challenge the view of major marine incursions in the early and middle Miocene in the studied area. We propose for the first time a new late Miocene incursion (LMI) event as the main marine flooding event in Western Amazonia during the Neogene. These onshore records are compared with three offshore cores from the Atlantic and Pacific Oceans. The similarity between microfossil assemblages of the Solimões Basin and the Caribbean Sea, and evidence of increased runoff from the Orinoco river drainage system, strongly suggest the Caribbean Sea as the primary source area of the marine incursions, supporting a Venezuelan seaway. We further show for the first time the potential linkage between Neogene marine incursions (mainly the LMI) into the Solimões Basin and major disturbances in the global carbon cycle.
Neogene
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This paper analyzes the diversification of the Neotropical mangrove flora from the Miocene to the present, using a fairly comprehensive database of 110 pollen records distributed across the whole Caribbean region. A Neogene-Quaternary diversification trend (NQDT) has been identified, characterized by an increase of 25 genera (∼78%) with respect to the 7 already existing Paleogene representatives. Only two genera appeared during the Miocene and the maximum increases were observed in the Pliocene-Quaternary transition and the modern-living record. Half of the true-mangrove genera (Rhizophora, Pelliciera, Acrostichum) were already present before the Neogene and the others appeared gradually in the Oligo-Miocene (Crenea), the Early-Middle Miocene (Avicennia) and the Mio-Pliocene (Laguncularia). None of the extant associate mangrove genera were present during the Paleogene and all appeared in the Miocene (23 genera) or the Oligo-Miocene transition (3 genera), being the main responsible for the NQDT, in absolute numbers. No regional extinctions were recorded since the Miocene in the Caribbean mangroves, at the generic level. These observations should be complemented with further high-resolution quantitative studies aimed at finding potential causal relationships with climatic, eustatic and paleogeographical shifts.
Neogene
Paleogene
Middle Miocene disruption
Avicennia marina
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