Geochemistry of the Mamil Choique granitoids at Rio Chico, Río Negro, Argentina: Late Paleozoic crustal melting in the North Patagonian Massif

2008 ◽  
Vol 25 (4) ◽  
pp. 526-546 ◽  
Author(s):  
Mónica G. López de Luchi ◽  
María Elena Cerredo
Keyword(s):  
Late Paleozoic ◽  
Crustal Melting ◽  
The North ◽  
Rio Negro

Subsurface stratigraphy and basin-fill architecture of the late Paleozoic eastern Taos trough, northern New Mexico, U.S.A.

2020 ◽  
Vol 57 (3) ◽  
pp. 149-176
Author(s):  
Nur Uddin Md Khaled Chowdhury ◽  
Dustin E. Sweet
Keyword(s):  
New Mexico ◽  
Sediment Accumulation ◽  
Late Paleozoic ◽  
North Central ◽  
The North ◽  
Basement Rocks ◽  
Basin Geometry ◽  
Deformation Event ◽  
Thrust System ◽  
Basin Fill

The greater Taos trough located in north-central New Mexico represents one of numerous late Paleozoic basins that formed during the Ancestral Rocky Mountains deformation event. The late Paleozoic stratigraphy and basin geometry of the eastern portion of the greater Taos trough, also called the Rainsville trough, is little known because the strata are all in the subsurface. Numerous wells drilled through the late Paleozoic strata provide a scope for investigating subsurface stratigraphy and basin-fill architecture of the Rainsville trough. Lithologic data obtained predominantly from petrophysical well logs combined with available biostratigraphic data from the greater Taos trough allows construction of a chronostratigraphic framework of the basin fill. Isopach- and structure-maps indicate that the sediment depocenter was just east of the El Oro-Rincon uplift and a westerly thickening wedge-shaped basin-fill geometry existed during the Pennsylvanian. These relationships imply that the thrust system on the east side of the Precambrian-cored El Oro-Rincon uplift was active during the Pennsylvanian and segmented the greater Taos trough into the eastern Rainsville trough and the western Taos trough. During the Permian, sediment depocenter(s) shifted more southerly and easterly and strata onlap Precambrian basement rocks of the Sierra Grande uplift to the east and Cimarron arch to the north of the Rainsville trough. Permian strata appear to demonstrate minimal influence by faults that were active during the Pennsylvanian and sediment accumulation occurred both in the basinal area as well as on previous positive-relief highlands. A general Permian decrease in eustatic sea level and cessation of local-fault-controlled subsidence indicates that regional subsidence must have affected the region in the early Permian.

Gold deposits of the northern margin of the North China Craton: multiple late Paleozoic–Mesozoic mineralizing events

2002 ◽  
Vol 37 (3) ◽  
pp. 326-351 ◽  
Author(s):  
Craig J. Hart ◽  
Richard J. Goldfarb ◽  
Yumin Qiu ◽  
Lawrence Snee ◽  
Lance D. Miller ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Gold Deposits ◽  
Late Paleozoic ◽  
Northern Margin ◽  
The North

scholarly journals The effects of geographic range size and abundance on extinction during a time of “sluggish”’ evolution

Paleobiology ◽  
2020 ◽  
pp. 1-14
Author(s):  
Michelle M. Casey ◽  
Erin E. Saupe ◽  
Bruce S. Lieberman
Keyword(s):  
North American ◽  
Fossil Record ◽  
Extinction Risk ◽  
Geographic Range ◽  
Range Size ◽  
Late Paleozoic ◽  
The North ◽  
Geographic Range Size ◽  
The Relationship ◽  
Habitat Tracking

Abstract Geographic range size and abundance are important determinants of extinction risk in fossil and extant taxa. However, the relationship between these variables and extinction risk has not been tested extensively during evolutionarily “quiescent” times of low extinction and speciation in the fossil record. Here we examine the influence of geographic range size and abundance on extinction risk during the late Paleozoic (Mississippian–Permian), a time of “sluggish” evolution when global rates of origination and extinction were roughly half those of other Paleozoic intervals. Analyses used spatiotemporal occurrences for 164 brachiopod species from the North American midcontinent. We found abundance to be a better predictor of extinction risk than measures of geographic range size. Moreover, species exhibited reductions in abundance before their extinction but did not display contractions in geographic range size. The weak relationship between geographic range size and extinction in this time and place may reflect the relative preponderance of larger-ranged taxa combined with the physiographic conditions of the region that allowed for easy habitat tracking that dampened both extinction and speciation. These conditions led to a prolonged period (19–25 Myr) during which standard macroevolutionary rules did not apply.

scholarly journals Quaternary Marine Mollusk Associations of the Last Interglacials in North Patagonia (Argentina): Paleoecology and Paleoclimates

2021 ◽  
Author(s):  
M.P. Charó
Keyword(s):  
Habitat Heterogeneity ◽  
Buenos Aires ◽  
Global Changes ◽  
Buenos Aires Province ◽  
The North ◽  
Rio Negro ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Crassostrea Rhizophorae ◽  
Mis 5E

Deposits of different Quaternary marine transgressions are largely exposed in the Argentine north Patagonian littoral (39°15′S–41°02′S), south of the Buenos Aires and north of Río Negro provinces. The malacological associations of 84 sites were studied. Among them, 31 belong to Pleistocene deposits of the interglacials ≥ MIS 9, MIS 7, MIS 5e, 29 to Holocene deposits of the interglacial MIS 1, and 24 sites of modern beaches. These sites yielded 7385 fossils among valves and shells, of 78 species (42 bivalves and 36 gastropods), including 11 micromolluskan species. The record of the bivalves Crassostrea rhizophorae in the south of the Buenos Aires Province, and Anomalocardia brasiliana (both currently inhabiting lower latitudes), and very likely the gastropod Tegula atra (inhabiting today the Pacific Ocean) in the north of Río Negro Province, suggests that interglacials MIS 7, MIS 5e and MIS 1 were warmer than today. However, the associations determined for the studied interglacials have not changed in their composition, but in abundance of species, except for the latitudinal shifts of the three mentioned species, and the presence of cold to temperate water taxa since the MIS 1 in the ecotonal area of the north of Río Negro Province. Changes in the associations of northern Patagonia during the Quaternary derived from global changes (sea surface temperature, salinity, etc.), and the existence of habitat heterogeneity in each of the areas, that enabled the co-existence of different bivalve and gastropod species of the local benthic marine malacofauna.

Eclogitic rocks in the St. Cyr klippe, Yukon, and their tectonic significance

1992 ◽  
Vol 29 (6) ◽  
pp. 1296-1304 ◽  
Author(s):  
Philippe Erdmer
Keyword(s):  
High Pressure ◽  
Oceanic Crust ◽  
North American ◽  
Suture Zone ◽  
Late Paleozoic ◽  
The North ◽  
Tectonic Significance ◽  
Subducted Oceanic Crust ◽  
Ophiolitic Rocks ◽  
Subducting Slab

Until recently, the Nisutlin allochthonous assemblage, a part of the Yukon–Tanana composite terrane interpreted as trench mélange from a late Paleozoic – Mesozoic arc system, was the only tectonic assemblage known to include subducted material in the northern Cordillera. The discovery of eclogitic rocks in two parts of a klippe of the Anvil allochthonous assemblage, which comprises mafic ophiolitic rocks, above the Cassiar terrane west of the Tintina fault confirms other evidence that subducted oceanic crust was also returned to the surface. The eclogitic rocks have been largely retrograded by postsubduction metamorphism. Their existence is interpreted as additional evidence of the link between nappes above the Cassiar terrane and their inferred root, the Teslin suture zone. The Nisutlin and Anvil allochthonous assemblages can now be interpreted, not simply as crustally metamorphosed assemblages with minor, structurally interleaved high-pressure components, but as deeply metamorphosed and intensely strained slices of continental and oceanic crust switched from subducting slab to overriding plate and returned to the surface during collision of the arc with the North American margin.

Late Paleozoic tectonism of the Bogda region in  Chinese North Tianshan: Insights from sedimentary provenance analysis

2021 ◽  
Author(s):  
Qian Wang ◽  
Guochun Zhao ◽  
Yigui Han ◽  
Jinlong Yao
Keyword(s):  
Detrital Zircon ◽  
Detrital Zircons ◽  
Late Paleozoic ◽  
Provenance Analysis ◽  
The North ◽  
Tectonic Transition ◽  
Isotopic Analyses ◽  
Zircon Morphology ◽  
Detrital Zircon Ages ◽  
T Values

<p>The Chinese North Tianshan (CNTS) extends E-W along the southern part of the Central Asian Orogenic Belt and has undergone complicated accretion-collision processes in the Paleozoic. This study attempts to clarify the late Paleozoic tectonism in the region by investigating the provenance of the Late Paleozoic sedimentary successions from the Bogda Mountain in the eastern CNTS by U-Pb dating and Lu-Hf isotopic analyses of detrital zircons. Detrital zircon U-Pb ages (N=519) from seven samples range from 261 ± 4 Ma to 2827 ± 32 Ma, with the most prominent age peak at 313 Ma. There are Precambrian detrital zircon ages (~7%) ranged from 694 to 1024 Ma. The youngest age components in each sample yielded weighted mean ages ranging from 272 ± 9 Ma to 288 ± 5 Ma, representing the maximum depositional ages. These and literature data indicate that some previously-assumed “Carboniferous” strata in the Bogda area were deposited in the Early Permian, including the Qijiaojing, Julideneng, Shaleisaierke, Yangbulake, Shamaershayi, Liushugou, Qijiagou, and Aoertu formations. The low maturity of the sandstones, zircon morphology and provenance analyses indicate a proximal sedimentation probably sourced from the East ­Junggar Arc and the Harlik-Dananhu Arc in the CNTS. The minor Precambrian detrital zircons are interpreted as recycled materials from the older strata in the Harlik-Dananhu Arc. Zircon ɛ<sub>Hf</sub>(t) values have increased since ~408 Ma, probably reflecting a tectonic transition from regional compression to extension. This event might correspond to the opening of the Bogda intra-arc/back arc rift basin, possibly resulting from a slab rollback during the northward subduction of the North Tianshan Ocean. A decrease of zircon ɛ<sub>Hf</sub>(t) values at ~300 Ma was likely caused by the cessation of oceanic subduction and subsequent collision, which implies that the North Tianshan Ocean closed at the end of the Late Carboniferous. This research was financially supported by the Youth Program of Shaanxi Natural Science Foundation (2020JQ-589), the NSFC Projects (41730213, 42072264, 41902229, 41972237) and Hong Kong RGC GRF (17307918).</p>

By-catch of sharks in Patagonian coastal trawl fisheries

1998 ◽  
Vol 49 (7) ◽  
pp. 641 ◽  
Author(s):  
Silvina Van Der Molen ◽  
Guillermo Caille ◽  
Raúl González
Keyword(s):  
Central Zone ◽  
Squalus Acanthias ◽  
Coastal Fisheries ◽  
The North ◽  
Rio Negro ◽  
Palabras Clave ◽  
By Catch ◽  
Galeorhinus Galeus ◽  
Cetorhinus Maximus ◽  
Mustelus Schmitti

In coastal Patagonia, Argentina, an unknown number of species of sharks are frequently caught in bottom-trawl nets. Between 1993 and 1996, 454 trawls by Patagonian coastal fisheries (41˚–51˚S) were analysed; 264 included sharks. Of the seven species of sharks caught, the most frequent was the smoothhound Mustelus schmitti, mainly in Bahía Engaño (off Chubut). The argentine angelshark (Squatina argentina) and the tope (Galeorhinus galeus) were common in the north of Patagonia, the piked dogfish (Squalus acanthias) in the central zone, and the narrowmouthed catshark Schroederichthys bivius in the south. The broadnose sevengill shark (Notorhynchus cepedianus) was rarely caught. A single basking shark (Cetorhinus maximus) was caught in San Matías Gulf (off Río Negro). Although undesirable, the by-catch of sharks is growing as a result of the increase in the fishing activities of the region, and the sustainability of the shark populations in Patagonian coasts is a matter of concern. Resumen. En las costas de Patagonia, Argentina, un número desconocido de especies de tiburones son frecuentemente capturados en las redes de arrastre de fondo. Entre 1993 y 1996 se analizaron a bordo 454 lances de pesca en las pesquerías costeras de Patagonia, entre los 41 y 51˚S, y en 264 de ellos se registraron capturas de tiburones. De las siete especies de tiburones capturadas el mas frecuente fue el gatuzo Mustelus schmitti, principalmente en Bahía Engaño, frente a las costas de Chubut. El pez ángel Squatina argentina y el cazón vitamínico Galeorhinus galeus fueron comunes en el norte de Patagonia, el cazón espinoso Squalus acanthias en la zona central, y el tiburón pintarroja Schroederichthys bivius en el sur. El tiburón gatopardo Notorhynchus cepedianus resultó una especie rara en las capturas. En el Golfo San Matías, frente a las costas de Río Negro, se capturó un ejemplar de tiburón peregrino Cetorhinus maximus. Aunque no deseadas, las capturas de tiburones están aumentando debido al incremento de las actividades pesqueras en la región, y la sustentabilidad de las poblaciones de tiburones en Patagonia es motivo de creciente preocupación. Palabras clave: tiburones, capturas, redes de arrastre, pesquerías costeras, Patagonia.

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