scholarly journals Holocene tephrochronology around Cochrane (~47° S), southern Chile

2015 ◽  
Vol 43 (1) ◽  
pp. 1 ◽  
Author(s):  
Charles Stern ◽  
Patricio I. Moreno ◽  
William I. Henríquez ◽  
Rodrigo Villa-Martínez ◽  
Esteban Sagredo ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Late Holocene ◽  
Thin Layers ◽  
Southern Chile ◽  
The South ◽  
Hudson Volcano ◽  
Glass Color ◽  
Tephra Layers ◽  
Glass Chemistry ◽  
Lake Cores

Two Holocene tephras encountered in outcrops, cores and trenches in bogs, and lake cores in the area around Cochrane, southern Chile, are identified (based on their age, tephra glass color and morphology, mineralogy, and both bulk and glass chemistry) as H1 derived from Hudson volcano, and MEN1 derived from Mentolat volcano. New AMS radiocarbon ages indicate systematic differences between those determined in lake cores (MEN1=7,689 and H1=8,440 cal yrs BP) and surface deposits (MEN1=7,471 and H1=7,891 cal yrs BP), with the lake cores being somewhat older. H1 tephra layers range from 8 to 18 cm thick, suggesting that both the area of the 10 cm isopach and the volume of this eruption were larger than previously suggested, but not greatly, and that the direction of maximum dispersion was more to the south. MEN1 tephra layers range from 1-4 cm in thickness, indicating that this was probably a reasonably large (>5 km3) eruption. Some of the lake cores also contain thin layers (<2 cm) of late Holocene H2 tephra and the recent H3 (1991 AD) tephra, both derived from the Hudson volcano. No tephra evidence has been observed for any late Pleistocene tephra, nor for the existence of the supposed Arenales volcano, proposed to be located west of Cochrane.

scholarly journals Topographic Thresholds and Soil Preservation along the Southern High Plains Eastern Escarpment, Northwest Texas, USA

Geosciences ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 476
Author(s):  
Travis Conley ◽  
Stance Hurst ◽  
Eileen Johnson
Keyword(s):  
Late Pleistocene ◽  
Late Holocene ◽  
High Plains ◽  
Buried Soils ◽  
Lateral Migration ◽  
South Fork ◽  
The South ◽  
Southern High Plains ◽  
Middle Holocene ◽  
Semi Arid

The eastern escarpment of the Southern High Plains (USA) is today a semi-arid erosional landscape delineated by canyon breaks and topographic relief. A series of buried soils were identified, described, and sampled at 19 soil profile localities exposed along terraces of the South Fork of the Double Mountain Fork of the Brazos River (South Fork) and two associated tributaries (Spring Creek and Macy 285 drainage). Radiocarbon dating revealed late-Pleistocene to early Holocene (~12,580–9100 14C B.P.), middle-Holocene (~6025–4600 14C B.P.), and late-Holocene (~2000–800 14C B.P.) buried soils. The late-Pleistocene to middle-Holocene soils were preserved only at higher elevations within the upper section of the South Fork and Spring Creek. A topographic position analysis was conducted using GIS to identify and examine the impacts of a soil topographic threshold on the preservation and distribution of buried soils within this geomorphic system. Above the identified ~810 m threshold, lateral migration of channels was constrained. Extensive channel migration below the threshold removed older terraces that were replaced with late-Holocene terraces and associated buried soils. Landscape topography constraints on geomorphic processes and soil formation impacted the preservation of archaeological sites in this semi-arid region.

Fossil rodents in Mylodon Cave as indicators of late Pleistocene–Holocene environmental evolution in southern Chile

2021 ◽  
pp. 1-17
Author(s):  
Ulyses F.J. Pardiñas ◽  
Luis Borrero ◽  
Fabiana M. Martin ◽  
Mauricio Massone ◽  
Fernando J. Fernández
Keyword(s):  
Late Pleistocene ◽  
Small Mammal ◽  
Late Holocene ◽  
Environmental Changes ◽  
First Record ◽  
Climatic Conditions ◽  
Southern Chile ◽  
Environmental Evolution ◽  
Local Conditions ◽  
Almost All

Abstract We conducted the first taphonomic and paleoenvironmental study based on late Pleistocene–Holocene small mammal remains recovered from the famous Mylodon Cave (Cerro Benítez area, Última Esperanza, Chile). Most of the analyzed material came from the extensive excavations made by Earl Saxon in 1976. We also studied late Holocene small mammal samples of the neighboring rock shelter Dos Herraduras 1. Analyzed remains were mostly produced by owls, probably living inside the caves. In Mylodon Cave, the higher values of girdle bones are consistent with a windblown litter. We recorded nine species of rodents, seven cricetids, and two caviomorphs; almost all the identified taxa integrate recent local communities. Late Pleistocene–Holocene assemblages are characterized by the chinchilla rat Euneomys, indicating unforested areas around the caves under cold and moist climatic conditions. Middle Holocene amelioration is reflected by incremental rodent species richness, including the first record of taxa clearly associated with forest (e.g., Abrothrix lanosa). Late Holocene assemblages are markedly stable, indicating local conditions similar to the current (historical) environment. Quaternary rodents from Cerro Benítez area do not indicate abrupt environmental changes during middle–late Holocene, but a progressive trend towards forest increase.

Morphometrical and molecular evidence suggests cryptic diversity among hookworms (Nematoda: Uncinaria) that parasitize pinnipeds from the south-eastern Pacific coasts

2018 ◽  
Vol 94 ◽  
Author(s):  
M.T. González ◽  
Z. López ◽  
J.J. Nuñez ◽  
K.I. Calderón-Mayo ◽  
C. Ramírez ◽  
...  
Keyword(s):  
Large Subunit ◽  
Principal Component ◽  
Eastern Pacific ◽  
Lsu Rdna ◽  
Molecular Evidence ◽  
South American ◽  
Southern Chile ◽  
The South ◽  
South Eastern ◽  
Neophoca Cinerea

AbstractHookworms of the genus Uncinaria parasitize pinniped pups in various locations worldwide. Four species have been described, two of which parasitize pinniped pups in the southern hemisphere: Uncinaria hamiltoni parasitizes Otaria flavescens and Arctocephalus australis from the South American coast, and Uncinaria sanguinis parasitizes Neophoca cinerea from the Australian coast. However, their geographical ranges and host specificity are unknown. Uncinaria spp. are morphologically similar, but molecular analyses have allowed the recognition of new species in the genus Uncinaria. We used nuclear genetic markers (internal transcribed spacer (ITS) and large subunit (LSU) rDNA) and a mitochondrial genetic marker (cytochrome c oxidase subunit I (COI)) to evaluate the phylogenetic relationships of Uncinaria spp. parasitizing A. australis and O. flavescens from South American coasts (Atlantic and Pacific coasts). We compared our sequences with published Uncinaria sequences. A Generalized Mixed Yule Coalescent (GMYC) analysis was also used to delimit species, and principal component analysis was used to compare morphometry among Uncinaria specimens. Parasites were sampled from A. australis from Peru (12°S), southern Chile (42°S), and the Uruguayan coast, and from O. flavescens from northern Chile (24°S) and the Uruguayan coast. Morphometric differences were observed between Uncinaria specimens from both South American coasts and between Uncinaria specimens from A. australis in Peru and southern Chile. Phylogenetic and GMYC analyses suggest that south-eastern Pacific otariid species harbour U. hamiltoni and an undescribed putative species of Uncinaria. However, more samples from A. australis and O. flavescens are necessary to understand the phylogenetic patterns of Uncinaria spp. across the South Pacific.

Stratigraphy and structure of a Late Wisconsinan salt collapse in the Saskatoon Low, south of Saskatoon, Saskatchewan, Canada: an update

2001 ◽  
Vol 38 (11) ◽  
pp. 1601-1613 ◽  
Author(s):  
E A Christiansen ◽  
E Karl Sauer
Keyword(s):  
Late Pleistocene ◽  
Middle Devonian ◽  
Upper Cretaceous ◽  
Middle Pleistocene ◽  
Second Phase ◽  
The South ◽  
Glacial Erosion ◽  
Lake Formation ◽  
South Saskatchewan River ◽  
Late Wisconsinan

The Saskatoon Low is a collapse structure that formed as a result of dissolution of salt from the Middle Devonian Prairie Evaporite Formation. In this study, the collapse has affected the Upper Cretaceous Lea Park, Judith River, and Bearpaw formations of the Montana Group; the Early and Middle Pleistocene Mennon, Dundurn, and Warman formations of the Sutherland Group; and the Late Pleistocene Floral, Battleford, and Haultain formations of the Saskatoon Group. Locally, the collapse is about 180 m, which is about equal to the thickness of the salt. The first phase of collapse took place after deposition of the Ardkenneth Member of the Bearpaw Formation and before glaciation or during a pre-Illinoian glaciation. The second phase of collapse occurred during the Battleford glaciation (Late Wisconsinan). Prior to deposition of the Battleford Formation, the Saskatoon Low was glacially eroded, removing the Sutherland Group and the Floral Formation. After the glacial erosion, up to 110 m of soft till of the Battleford Formation and up to 77 m of deltaic sand, silt, and clay of the Haultain Formation were deposited in the Saskatoon Low. Lastly, the South Saskatchewan River eroded up to about 40 m into the deltaic sediment and tills before up to about 15 m of Pike Lake Formation was deposited. The Haultain and Pike Lake formations are new stratigraphic units.

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