scholarly journals A Middle to Late Miocene Trans-Andean Portal: Geologic Record in the Tatacoa Desert

2021 ◽  
Vol 8 ◽  
Author(s):  
C. Montes ◽  
C. A. Silva ◽  
G. A. Bayona ◽  
R. Villamil ◽  
E. Stiles ◽  
...  
Keyword(s):  
Late Miocene ◽  
Amazon Basin ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Structural Data ◽  
Coverage Area ◽  
Geologic Record ◽  
Mapping Models ◽  
Central Cordillera ◽  
Lines Of Evidence

Integration of several geologic lines of evidence reveals the prevalence of a lowland trans-Andean portal communicating western Amazonia and the westernmost Andes from at least middle Miocene until Pliocene times. Volcanism and crustal shortening built up relief in the southernmost Central and Eastern Cordilleras of Colombia, closing this lowland gap. Independent lines of evidence consist first, of field mapping in the Tatacoa Desert with a coverage area of ∼381 km2, 1,165 km of geological contact traces, 164 structural data points, and 3D aerial digital mapping models. This map documents the beginning of southward propagation of the southernmost tip of the Eastern Cordillera’s west-verging, fold-and-thrust belt between ∼12.2 and 13.7 Ma. Second, a compilation of new and published detrital zircon geochronology in middle Miocene strata of the Tatacoa Desert shows three distinctive age populations: middle Miocene, middle Eocene, and Jurassic; the first two sourced west of the Central Cordillera, the latter in the Magdalena Valley. Similar populations with the three distinctive peaks have now been recovered in western Amazonian middle Miocene strata. These observations, along with published molecular and fossil fish data, suggest that by Serravallian times (∼13 Ma), the Northern Andes were separated from the Central Andes at ∼3°N by a fluvial system that flowed into the Amazon Basin through the Tatacoa Desert. This paleogeographic configuration would be similar to a Western Andean, or Marañon Portal. Late Miocene flattening of the subducting Nazca slab caused the eastward migration of the Miocene volcanic arc, so that starting at ∼4 Ma, large composite volcanoes were built up along the axis of today's Central Cordillera, closing this lowland Andean portal and altering the drainage patterns to resemble a modern configuration.

The Inachoididae spider crabs (Crustacea, Brachyura) from the Neogene of the tropical Americas

2021 ◽  
pp. 1-21
Author(s):  
Daniel Lima ◽  
Orangel Aguilera ◽  
Marcos Tavares
Keyword(s):  
Late Miocene ◽  
Amazon Basin ◽  
Middle Miocene ◽  
Distribution Patterns ◽  
Late Eocene ◽  
Central American ◽  
Sea Level Changes ◽  
Fossil Species ◽  
North Brazil ◽  
Tropical America

Abstract The spider crabs Willinachoides santanai n. gen. n. sp. from the early-middle Miocene of north Brazil and Paradasygyius rodriguezi n. sp. from the late Miocene of Venezuela are described and illustrated. Additionally, Eoinachoides senni Van Straelen, 1933, from the late Oligocene–early Miocene of Venezuela, is redescribed based on photographs of the holotype, and the diagnosis of Eoinachoides latispinosus Carriol, Muizon, and Secretan, 1987, from the late Miocene of Peru, is emended also on the basis of photographs of the holotype. The past distribution points to a Tethyan background for the current amphi-American Inachoididae, with the oldest fossil species known from the early Eocene Tethyan regions (Pakistan and Italy), and from the late Eocene–late Pliocene of the Americas. The high number of monotypic genera in Inachoididae could be the result of rapid dispersion followed by diversification during the Neogene of the tropical America, facilitated by global and regional events (e.g., eustatic sea level changes, the Mi-1 Oligocene-Miocene boundary global cooling, the global warming period of the Middle Miocene Climate maximum, closure of the Panama Isthmus, and marine incursions into the Amazon Basin). The shoaling and final closure of the Central American Seaway are thought to have critically affected the evolution of the inachoidids and shaped their current distribution patterns. UUID: http://zoobank.org/6275fdc4-4bfa-4873-9320-3143d4915172.

The continental Middle Miocene Climatic Transition in Southern Europe as derived from clumped isotope analyses

2020 ◽  
Author(s):  
Niklas Löffler ◽  
Andreas Mulch ◽  
Wout Krijgsman ◽  
Emilija Krsnik ◽  
Jens Fiebig
Keyword(s):  
Late Miocene ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Time Interval ◽  
Suitable Model ◽  
Southern Europe ◽  
Carbonate Formation ◽  
Carbon And Oxygen Isotope ◽  
Clumped Isotope ◽  
Isotope Analyses

<p>Reconstructing Cenozoic terrestrial paleoclimate is frequently limited by temporal resolution and suitable quantitative tools to reliably assess changes in temperature and aridity. The dynamics of ocean temperatures<sup>1</sup> and chemistry<sup>2</sup>, varying <em>p</em>CO<sub>2</sub><sup>3</sup>, and faunal assemblages are known to a certain extent, however, terrestrial data on temperatures, which are mostly indirectly derived from fossil assemblages and palynologycal data<sup>4</sup> are rare. This study contributes to the understanding of the dynamics and variability of terrestrial temperatures during one of the most extreme Neogene climate changes, the Middle Miocene Climate Transition (MCT). The comparison of <em>p</em>CO<sub>2</sub> forecasts for the coming century and reconstructed Mid-Miocene <em>p</em>CO<sub>2</sub> levels suggest that the Mid-Miocene is an important time interval for ascertaining suitable model projections of the future anthropogenic impact on climate. In order to establish an appropriate understanding and modeling of the natural variability of the European/Mediterranean climate system, quantitative climate information of the European continental Mid-Miocene is mandatory. This would facilitate the identification of main drivers of climate evolution in an area which is exposed to the present climate change and its subsequent natural hazards.</p><p> </p><p>This study presents a profound and well-dated terrestrial clumped isotope (Δ<sub>47</sub>) paleosoil carbonate dataset from Spain that ranges from 13.0 to 15.1 Ma (100 kyr resolution) and hence covers an interval that was previously classified as the MCT. The Δ<sub>47 </sub>data is supported by stable carbon and oxygen isotope analyses that are in agreement with previously published continental and oceanic records. A distinct decline in apparent Δ<sub>47</sub>-based temperatures between 13.7 and 14.1 Ma reveals a substantial drop in continental temperatures and indicates changes in seasonality of pedogenic carbonate formation. The major cooling thereby coincides with a change in Milanković periodicities and can be linked to oceanic isotope records<sup>5</sup>. While the transition into the MCT shows a high temperature variability indicating varying environmental conditions, calculated oxygen isotopic values of the soil water point to a rather stable moisture source across the MCT in Southern Europe.</p><p> </p><p>1: Super, J. R., Thomas, E., Pagani, M., et al. (2018) North Atlantic temperature and pCO<sub>2</sub> coupling in the early-middle Miocene. Geology, 46(6), 519-522.</p><p>2: Pearson, P. N., and Palmer, M. R. (1999) Middle Eocene seawater pH and atmospheric carbon dioxide concentrations. Science, 284(5421), 1824-1826.</p><p>3: Pagani, M., Freeman, K. H., and Arthur, M. A. (1999) Late Miocene atmospheric CO<sub>2</sub> concentrations and the expansion of C4 grasses. Science, 285(5429), 876-879.</p><p>4: Lewis, A. R., Marchant, D. R., Ashworth, A. C., et al. (2008) Mid-Miocene cooling and the extinction of tundra in continental Antarctica. Proceedings of the National academy of Sciences.</p><p>5: Holbourn, A., Kuhnt, W., Clemens, S., et al. (2013) Middle to late Miocene stepwise climate cooling: Evidence from a high resolution deep water isotope curve spanning 8 million years. Paleoceanography, 28(4), 688-699.</p>

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.

Middle Miocene (∼14 Ma) and Late Miocene (∼6 Ma) Paleogeographic Boundary Conditions

2021 ◽  
Author(s):  
Zhilin He ◽  
Zhongshi Zhang ◽  
Zhengtang Guo ◽  
Christopher R. Scotese ◽  
Chenglong Deng
Keyword(s):  
Boundary Conditions ◽  
Late Miocene ◽  
Middle Miocene

A new argyrolagoid (Mammalia: Marsupialia) from the middle Miocene of Bolivia

1988 ◽  
Vol 62 (3) ◽  
pp. 463-467 ◽  
Author(s):  
Villarroel A. Carlos ◽  
Larry G. Marshall
Keyword(s):  
South America ◽  
Late Miocene ◽  
Adaptive Radiation ◽  
Middle Miocene ◽  
Northwest Argentina ◽  
The Family ◽  
Size And Structure

A new argyrolagoid marsupial, Hondalagus altiplanensis n. gen., n. sp., from the middle Miocene (Santacrucian–Friasian) age locality of Quebrada Honda in southernmost Bolivia represents the smallest and most specialized member of the family Argyrolagidae known. The lower molars are hypselodont and lack vertical grooves labially and lingually, and M4 is greatly reduced relative to M3. In overall size and structure, H. altiplanensis compares best with Microtragulus catamarcensis (Kraglievich, 1931) from rocks of late Miocene (Huayquerian) age in northwest Argentina. Hondalagus altiplanensis demonstrates that the adaptive radiation of argyrolagoids was much greater than previously envisioned, and that generic differentiation of known taxa occurred no later than early–middle Miocene time in South America.

scholarly journals Structural setting and tectonic evolution of the Bahariya Depression, Western Desert, Egypt

GeoArabia ◽  
2003 ◽  
Vol 8 (1) ◽  
pp. 91-124 ◽  
Author(s):  
Adel R Moustafa ◽  
Ati Saoudi ◽  
Alaa Moubasher ◽  
Ibrahim M Ibrahim ◽  
Hesham Molokhia ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Tectonic Evolution ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Western Desert ◽  
Normal Faults ◽  
Surface Mapping ◽  
Early Mesozoic ◽  
Hydrocarbon Fields ◽  
Stable Area

ABSTRACT An integrated surface mapping and subsurface study of the Bahariya Depression aided the regional subsurface interpretation. It indicated that four major ENE-oriented structural belts overlie deep-seated faults in this part of the ‘tectonically stable’ area of Egypt. The rocks of the Bahariya area were deformed in the Late Cretaceous, post-Middle Eocene, and Middle Miocene-and subsurface data indicated an early Mesozoic phase of normal faulting. The Late Cretaceous and post-Middle Eocene deformations reactivated the early normal faults by oblique slip and formed a large swell in the Bahariya region. The crest was continuously eroded whereas its peripheries were onlapped by Maastrichtian and Tertiary sediments. The tectonic evolution of the Bahariya region shows great similarity to the deformation of the ‘tectonically unstable’ area of the northern Western Desert where several hydrocarbon fields have been discovered. This similarity may indicate that the same phases of deformation could extend to other basins lying in the ‘tectonically stable’ area, such as the Asyut, Dakhla, Nuqura, and El Misaha basins.

scholarly journals Peranan Kontrol Struktural dan Hidrologis dalam Perkembangan Lorong Gua Bagus-Jebrot di Malang-Indonesia

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Mohammad Ainul Labib ◽  
Agung Suprianto ◽  
Devi Prasetyo ◽  
Aan Seftian Hardianto ◽  
Alfi Sahrina ◽  
...  
Keyword(s):  
Surface Water ◽  
Groundwater Flow ◽  
Cross Section ◽  
Frequency Analysis ◽  
Late Miocene ◽  
Structural Control ◽  
Middle Miocene ◽  
Field Measurements ◽  
Underground Water ◽  
And Control

Bagus-Jebrot Cave is located in Donomulyo District, Malang Regency which is in the Wonosari Formation which was formed in the Middle Miocene and Late Miocene. The purpose of this study is related to the developmental control that affects the cave passageways. The approach used is a geomorphological approach by conducting field measurements and documentation. The analysis used is frequency analysis and cross-section of the passage. Bagus-Jebrot Cave is a type of Epigenic Cave which is formed from surface water flowing into doline/sinkhole. It can be seen from the planview map that has a curvilinear passage pattern. The existence of groundwater flow also forms a physiographic cave passage with ellipse passage formation, asymmetrical ellipse, potholes, callops, solution notches, cups, solution pockets. Besides underground water flow, the development of the Bagus-Jebrot Cave aisle is related to the process of structural lifting and control. The lifting process is marked by the formation of 4 levels of the cave passage. While the formation of the canyon, joint passage, rectangular passage and keyhole is the result of structural control

scholarly journals The two-stage Aegean extension, from localized to distributed, a result of slab rollback acceleration

2016 ◽  
Vol 53 (11) ◽  
pp. 1142-1157 ◽  
Author(s):  
Jean-Pierre Brun ◽  
Claudio Faccenna ◽  
Frédéric Gueydan ◽  
Dimitrios Sokoutis ◽  
Mélody Philippon ◽  
...  
Keyword(s):  
Middle Miocene ◽  
Middle Eocene ◽  
Sedimentary Basins ◽  
Ductile Deformation ◽  
Metamorphic Rocks ◽  
Western Anatolia ◽  
Two Stage ◽  
The North ◽  
Slab Rollback ◽  
Slab Tearing

Back-arc extension in the Aegean, which was driven by slab rollback since 45 Ma, is described here for the first time in two stages. From Middle Eocene to Middle Miocene, deformation was localized leading to (i) the exhumation of high-pressure metamorphic rocks to crustal depths, (ii) the exhumation of high-temperature metamorphic rocks in core complexes, and (iii) the deposition of sedimentary basins. Since Middle Miocene, extension distributed over the whole Aegean domain controlled the deposition of onshore and offshore Neogene sedimentary basins. We reconstructed this two-stage evolution in 3D and four steps at Aegean scale by using available ages of metamorphic and sedimentary processes, geometry, and kinematics of ductile deformation, paleomagnetic data, and available tomographic models. The restoration model shows that the rate of trench retreat was around 0.6 cm/year during the first 30 My and then accelerated up to 3.2 cm/year during the last 15 My. The sharp transition observed in the mode of extension, localized versus distributed, in Middle Miocene correlates with the acceleration of trench retreat and is likely a consequence of the Hellenic slab tearing documented by mantle tomography. The development of large dextral northeast–southwest strike-slip faults, since Middle Miocene, is illustrated by the 450 km long fault zone, offshore from Myrthes to Ikaria and onshore from Izmir to Balikeshir, in Western Anatolia. Therefore, the interaction between the Hellenic trench retreat and the westward displacement of Anatolia started in Middle Miocene, almost 10 Ma before the propagation of the North Anatolian Fault in the North Aegean.

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