Metamorphic constraints on the thermal evolution of the central Himalayan Orogen

1988 ◽  
Vol 326 (1589) ◽  
pp. 257-280 ◽  
Keyword(s):  
Middle Miocene ◽  
Thermal Evolution ◽  
Middle Eocene ◽  
Structural Evolution ◽  
Late Oligocene ◽  
Main Central Thrust ◽  
Early Stages ◽  
Early Oligocene ◽  
Mineral Assemblages ◽  
Early Late

Recent studies that integrate conventional thermobarometry of pelitic mineral assemblages with thermodynamic modeling of garnet zoning reveal complex Tertiary P -T paths for the Greater Himalayan metamorphic sequence in the central Himalaya. Viewed in light of our current understanding of the structural evolution of the Himalaya, these data provide insights into the relations between tectonic and thermal processes during orogenesis. In this paper, we present an interpretive model for tectonothermal evolution of the Greater Himalaya in the central part of the range. This model involves: (1) middle Eocene—early Oligocene burial to depths of more than 30 km during the early stages of collision between India and Asia; (2) early—late Oligocene uplift and cooling; (3) late Oligocene heating and renewed burial synchronous with the early stages of anatectic melting and leucogranite plutonism; (4) latest Oligocene-middle Miocene rapid uplift and continued leucogranite production associated with ramping on the structurally lower Main Central Thrust and tectonic denudation on structurally higher low-angle detachment systems; and (5) middle Miocene—Recent rapid cooling during the final stages of uplift to the surface.

scholarly journals The Cenozoic Malaguide Basin from Sierra Espuña (Murcia, S Spain): An Example of Geological Heritage

Geosciences ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Santiago Moliner-Aznar ◽  
Manuel Martín-Martín ◽  
Tomás Rodríguez-Estrella ◽  
Gregorio Romero-Sánchez
Keyword(s):  
Middle Eocene ◽  
Geological Heritage ◽  
Passive Margin ◽  
Early Miocene ◽  
Late Oligocene ◽  
Deep Basin ◽  
Sedimentary Evolution ◽  
Early Oligocene ◽  
Upper Oligocene ◽  
Very High

The Cenozoic Malaguide Basin from Sierra Espuña (Internal Betic Zone, S Spain) due to the quality of outcropping, areal representation, and continuity in the sedimentation can be considered a key-basin. In the last 30 years, a large number of studies with very different methodological approaches have been done in the area. Models indicate an evolution from passive margin to wedge-top basin from Late Cretaceous to Early Miocene. Sedimentation changes from limestone platforms with scarce terrigenous inputs, during the Paleocene to Early Oligocene, to the deep basin with huge supplies of turbidite sandstones and conglomerates during the Late Oligocene to Early Miocene. The area now appears structured as an antiformal stack with evidence of synsedimentary tectonics. The Cenozoic tectono-sedimentary basin evolution is related to three phases: (1) flexural tectonics during most of the Paleogene times to create the basin; (2) fault and fold compartmentation of the basin with the creation of structural highs and subsiding areas related to blind-fault-propagation folds, deforming the basin from south to north during Late Oligocene to Early Aquitanian times; (3) thin-skin thrusting tectonics when the basin began to be eroded during the Late Aquitanian-Burdigalian. In recent times some works on the geological heritage of the area have been performed trying to diffuse different geological aspects of the sector to the general public. A review of the studies performed and the revisiting of the area allow proposing different key-outcrops to follow the tectono-sedimentary evolution of the Cenozoic basin from this area. Eight sites of geological interest have been selected (Cretaceous-Cenozoic boundary, Paleocene Mula Fm, Lower Eocene Espuña-Valdelaparra Fms, Middle Eocene Malvariche-Cánovas Fms, Lowermost Oligocene As Fm, Upper Oligocene-Lower Aquitanian Bosque Fm, Upper Oligocene-Aquitanian Río Pliego Fm, Burdigalian El Niño Fm) and an evaluation has been performed to obtain four parameters: the scientific value, the educational and touristic potential, and the degradation risk. The firsts three parameters obtained values above 50 being considered of “high” or “very high” interest (“very high” in most of the cases). The last parameter shows always values below 50 indicating a “moderate” or “low” risk of degradation. The obtained values allow us considering the tectono-sedimentary evolution of this basin worthy of being proposed as a geological heritage.

scholarly journals Late oligocene–early miocene shortening in the Thrace Basin, northern Aegean

2021 ◽  
Author(s):  
Ümitcan Erbil ◽  
Aral I. Okay ◽  
Aynur Hakyemez
Keyword(s):  
Large Scale ◽  
Middle Eocene ◽  
Early Miocene ◽  
Fold Axis ◽  
Late Oligocene ◽  
The Balkans ◽  
Sedimentary Sequences ◽  
The North ◽  
Early Oligocene ◽  
Thrace Basin

AbstractLate Cenozoic was a period of large-scale extension in the Aegean. The extension is mainly recorded in the metamorphic core complexes with little data from the sedimentary sequences. The exception is the Thrace Basin in the northern Aegean, which has a continuous record of Middle Eocene to Oligocene marine sedimentation. In the Thrace Basin, the Late Oligocene–Early Miocene was characterized by north-northwest (N25°W) shortening leading to the termination of sedimentation and formation of large-scale folds. We studied the stratigraphy and structure of one of these folds, the Korudağ anticline. The Korudağ anticline has formed in the uppermost Eocene–Lower Oligocene siliciclastic turbidites with Early Oligocene (31.6 Ma zircon U–Pb age) acidic tuff beds. The turbidites are underlain by a thin sequence of Upper Eocene pelagic limestone. The Korudağ anticline is an east-northeast (N65°E) trending fault-propagation fold, 9 km wide and 22 km long and with a subhorizontal fold axis. It is asymmetric with shallowly-dipping northern and steeply-dipping southern limbs. Its geometry indicates about 1 km of shortening in a N25°W direction. The folded strata are unconformably overlain by Middle Miocene continental sandstones, which constrain the age of folding. The Korudağ anticline and other large folds in the Thrace Basin predate the inception of the North Anatolian Fault (NAF) by at least 12 myr. The Late Oligocene–Early Miocene (28–17 Ma) shortening in the Thrace Basin and elsewhere in the Balkans forms an interlude between two extensional periods, and is probably linked to changes in the subduction dynamics along the Hellenic trench.

scholarly journals Reworked nannofossils from the Lower Miocene deposits in the Magura Nappe (Outer Western Carpathians, Poland)

2012 ◽  
Vol 63 (5) ◽  
pp. 407-424 ◽  
Author(s):  
Marta Oszczypko-Clowes
Keyword(s):  
Middle Eocene ◽  
Late Eocene ◽  
Calcareous Nannofossils ◽  
Late Oligocene ◽  
Calcareous Nannoplankton ◽  
Lower Miocene ◽  
Early Oligocene ◽  
Quantitative Studies ◽  
Outer Western Carpathians ◽  
Quantitative Analyses

Abstract Studies, based on calcareous nannofossils, proved that the level of reworked microfossils had so far been underestimated. More recently detailed quantitative studies of calcareous nannoplankton of the Magura, Malcov, Zawada and Kremna formations from the Magura Nappe in Poland documented a degree of nannofossil recycling among those formations. In the Late Eocene-Early Oligocene pelagic Leluchów Marl Member of the Malcov Formation the level of redeposition is very low (0-3.80 %), however, in the flysch deposits of the Malcov Formation reworking increased to 31.4 %. Late Oligocene through Early Miocene “molasse” type deposits of the Zawada and Kremna formations contain 43.7-69.0 % of reworked nannofossils. Quantitative analyses of the reworked assemblages confirmed the domination of Paleogene nannofossil species over Cretaceous ones. The most abundant, reworked assemblages belong to the Early- Middle Eocene age.

The Evolutionary History and Diversity of Australian Mammals

1999 ◽  
Vol 21 (1) ◽  
pp. 1
Author(s):  
M. Archer ◽  
R. Arena ◽  
M. Bassarova ◽  
K. Black ◽  
J. Brammall ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Late Triassic ◽  
Early Eocene ◽  
Late Oligocene ◽  
Mammal Evolution ◽  
Initial Description ◽  
Fossil Records ◽  
First Time

Palaeodiversity and relationships of all groups of Australian mammals are reviewed. The fossil record spanning this time is of variable quality. 'Dark Ages' about which nothing is known in terms of Australian mammal evolution include the late Triassic to late Jurassic, late Cretaceous to late Paleocene and middle Eocene to middle Oligocene. Very little is known about the early Cretaceous and late Miocene. The late Oligocene to middle Miocene record documents the highest levels of biodiversity known for the continent, comparable to that which characterises the lowland rainforests of Borneo and Brazil. Order Monotremata spans at least the last 110 million years and includes four families. The enigmatic Ausktribosphenos from 115 million-year-old sediments in Victoria may represent an archaic monotreme, specialised peramurid or previously undocumented order of mammals but is unlikely to represent a placental as suggested in the initial description. Order Microbiotheria is represented in the early Eocene (~55 mya) by two genera similar in morphology to early Eocene taxa from Argentina. Order Peramelemorphia spans the early Eocene to Holocene and includes at least five families. Order Dasyuromorphia spans at least the late Oligocene to Holocene and includes at least three families. Other dasyuromorphian-like marsupials are indeterminate in terms of family-level affinities. Order Notoryctemorphia spans the early Miocene to Holocene with one family. Order Yalkaparidontia spans the late Oligocene to middle Miocene with one genus. Order Diprotodontia spans the late Oligocene to Holocene, represented throughout by three major groups: Phalangerida (eight families), Vombatomorphia (seven families) and Macropodoidea (at least three families). A possible placental condylarth (Tingamarra) has been recorded from the early Eocene. An archaeonycteridid bat (Australonycteris) is known from the early Eocene. Among bats, the late Oligocene to middle Miocene is dominated by rhinolophoids, many of which have European, Asian and African affinities. Mystacinids, megadermatids, hipposiderids and molossids are well-represented in the Oligocene to Miocene deposits. Vespertilionids are uncommon in the Oligocene to Miocene but become more diverse in the Pliocene to Holocene. Emballonurids and rhinolophids appear for the first time in the Plio-Pleistocene. Pteropodids are unknown prior to the Holocene. Murids span the early Pliocene to Holocene. In the oldest assemblage at Riversleigh, one undescribed lineage resembles archaic forms otherwise only known from the fossil records of Africa and Eurasia.

Palaeogene and Neogene brachyurans of the Amazon basin: a revised first appearance date for primary freshwater crabs (Brachyura, Trichodactylidae)

Crustaceana ◽  
2017 ◽  
Vol 90 (7-10) ◽  
pp. 953-967 ◽  
Author(s):  
Sebastian Klaus ◽  
Célio Magalhães ◽  
Rodolfo Salas-Gismondi ◽  
Martin Gross ◽  
Pierre-Olivier Antoine
Keyword(s):  
Late Miocene ◽  
Amazon Basin ◽  
Middle Eocene ◽  
Freshwater Crabs ◽  
Early Oligocene ◽  
The Family ◽  
Continuous Presence ◽  
Early Late ◽  
Amazonian Lowlands

We describe claw fragments of fossil primary freshwater crabs from three areas in the Amazon basin, Tarapoto (Early Oligocene) and Contamana (Middle Eocene to early Late Miocene) in Peru, and Eirunepé (Late Miocene) in Brazil. All these fragments most likely belong to the family Trichodactylidae. We show a continuous presence of primary freshwater crabs in proto-Amazonian lowlands from the Middle Eocene to the Late Miocene and can thus shift the earliest appearance date of freshwater-adapted brachyurans into the Eocene, at least in the Neotropics.

scholarly journals New wombats from Riversleigh, northwestern Queensland, include pouch young

2018 ◽  
Author(s):  
Philippa Brewer
Keyword(s):  
Middle Miocene ◽  
Middle Eocene ◽  
Large Degree ◽  
Species Level ◽  
Late Oligocene ◽  
Additional Species ◽  
Variable Species ◽  
Degree Of Confidence ◽  
Qualitative Characters ◽  
Insight Into

Despite an estimated molecular divergence date of 40 million years (middle Eocene) between wombats and their closest living relative, the koala, the fossil record of wombats is poor. The two oldest described wombats, Nimbavombatus boodjamullensis and Rhizophascolonus crowcrofti, are both early Miocene in age. The former is known from maxillae, upper cheek teeth and isolated lower molars from Riversleigh in northwestern Queensland. The latter is known only from the isolated teeth from central Australia. Here we describe additional specimens of Rhizophascolonus from Riversleigh that are late Oligocene to middle Miocene in age as well as at least one additional species. Excitingly, the new specimens show an ontogenetic range from pouch young with occlusal cusp details intact to fully adult specimens with heavily worn teeth. The unworn teeth from Riversleigh are compared with those pouch young from two extant wombat taxa and the extant koala. In addition, comparisons of quantitative and qualitative characters of all known Rhizophascolonus specimens with other koala and wombat taxa reveal a large degree of variation in the sample of Rhizophascolonus teeth from Riversleigh. However, the number of species of Rhizophascolonus present is difficult to ascertain and it is not inconceivable that there is only one or two highly variable species present. Despite uncertainty at the species level, these new specimens provide an unprecedented insight into this enigmatic group, and we can now start to reconstruct intrafamilial relationships with a greater degree of confidence. Furthermore, occlusal morphology can now be used to help clarify interfamilial relationships in the suborder Vombatiformes, which in addition to wombats and koalas, includes five additional extinct families.

scholarly journals New wombats from Riversleigh, northwestern Queensland, include pouch young

2018 ◽  
Author(s):  
Philippa Brewer
Keyword(s):  
Middle Miocene ◽  
Middle Eocene ◽  
Large Degree ◽  
Species Level ◽  
Late Oligocene ◽  
Additional Species ◽  
Variable Species ◽  
Degree Of Confidence ◽  
Qualitative Characters ◽  
Insight Into

Despite an estimated molecular divergence date of 40 million years (middle Eocene) between wombats and their closest living relative, the koala, the fossil record of wombats is poor. The two oldest described wombats, Nimbavombatus boodjamullensis and Rhizophascolonus crowcrofti, are both early Miocene in age. The former is known from maxillae, upper cheek teeth and isolated lower molars from Riversleigh in northwestern Queensland. The latter is known only from the isolated teeth from central Australia. Here we describe additional specimens of Rhizophascolonus from Riversleigh that are late Oligocene to middle Miocene in age as well as at least one additional species. Excitingly, the new specimens show an ontogenetic range from pouch young with occlusal cusp details intact to fully adult specimens with heavily worn teeth. The unworn teeth from Riversleigh are compared with those pouch young from two extant wombat taxa and the extant koala. In addition, comparisons of quantitative and qualitative characters of all known Rhizophascolonus specimens with other koala and wombat taxa reveal a large degree of variation in the sample of Rhizophascolonus teeth from Riversleigh. However, the number of species of Rhizophascolonus present is difficult to ascertain and it is not inconceivable that there is only one or two highly variable species present. Despite uncertainty at the species level, these new specimens provide an unprecedented insight into this enigmatic group, and we can now start to reconstruct intrafamilial relationships with a greater degree of confidence. Furthermore, occlusal morphology can now be used to help clarify interfamilial relationships in the suborder Vombatiformes, which in addition to wombats and koalas, includes five additional extinct families.

scholarly journals The rise to dominance of lanternfishes (Teleostei: Myctophidae) in the oceanic ecosystems: a paleontological perspective

Paleobiology ◽  
2021 ◽  
pp. 1-18
Author(s):  
Werner Schwarzhans ◽  
Giorgio Carnevale
Keyword(s):  
Ocean Circulation ◽  
Evolutionary History ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Food Resource ◽  
Deep Ocean ◽  
Early Oligocene ◽  
Diatom Abundance ◽  
Deep Ocean Circulation ◽  
Upper Slope

AbstractLanternfishes currently represent one of the dominant groups of mesopelagic fishes in terms of abundance, biomass, and diversity. Their otolith record dominates pelagic sediments below 200 m in dredges, especially during the entire Neogene. Here we provide an analysis of their diversity and rise to dominance primarily based on their otolith record. The earliest unambiguous fossil myctophids are known based on otoliths from the late Paleocene and early Eocene. During their early evolutionary history, myctophids were likely not adapted to a high oceanic lifestyle but occurred over shelf and upper-slope regions, where they were locally abundant during the middle Eocene. A distinct upscaling in otolith size is observed in the early Oligocene, which also marks their earliest occurrence in bathyal sediments. We interpret this transition to be related to the change from a halothermal deep-ocean circulation to a thermohaline regime and the associated cooling of the deep ocean and rearrangement of nutrient and silica supply. The early Oligocene myctophid size acme shows a remarkable congruence with diatom abundance, the main food resource for the zooplankton and thus for myctophids and whales. The warmer late Oligocene to early middle Miocene period was characterized by an increase in disparity of myctophids but with a reduction in their otolith sizes. A second and persisting secular pulse in myctophid diversity (particularly within the genusDiaphus) and increase in size begins with the “biogenic bloom” in the late Miocene, paralleled with diatom abundance and mysticete gigantism.

scholarly journals Paleoecology of the Upper Eocene-Lower Oligocene Malcov Basin based on the calcareous nannofossils: a case study of the Leluchów section (Krynica Zone, Magura Nappe, Polish Outer Carpathians)

2012 ◽  
Vol 63 (2) ◽  
pp. 149-164 ◽  
Author(s):  
Marta Oszczypko-Clowes ◽  
Bartłomiej Żydek
Keyword(s):  
Middle Eocene ◽  
Late Eocene ◽  
Calcareous Nannofossils ◽  
Late Oligocene ◽  
Upper Eocene ◽  
Early Oligocene ◽  
Lower Oligocene ◽  
Quantitative Analyses ◽  
Outer Carpathians

Paleoecology of the Upper Eocene-Lower Oligocene Malcov Basin based on the calcareous nannofossils: a case study of the Leluchów section (Krynica Zone, Magura Nappe, Polish Outer Carpathians)During the period of ca. 20 Ma (Middle Eocene-Chattian) the Leluchów Succession of the Magura Basin passed through drastic changes of sedimentary condition and paleobathymetry from well oxygened red shales withReticulofragmium amplectens, deposited beneath CCD, redGlobigerinaoozes, to oxygen depleted organic-rich menilite-type shales and finally to flysch deposition of open marine conditions. The biostratigraphic and lithostratigraphic scheme is well established with the Leluchów Marl Member — Zones NP19-20 to NP22 (Late Eocene-Early Oligocene), Smereczek Shale Member, Zone NP23 (Early Oligocene) and the Malcov Formation s.s., Zone NP24 (Early-Late Oligocene). The aim of the paper is to present the quantitative analyses as the basis for paleoecological changes in the Magura Basin during the Late Eocene-Late Oligocene period. The changes manifest themselves through a decrease in the water temperature and progressing eutrophication. Species typical of brackish water conditions and restricted to the Paratethys region were identified from the NP23 Zone.

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