Datierung der jungpleistozänen Vereisung Lauricocha in den Peruanischen Anden

Der Gebirgszug Raura im zentralen Peru (ungefahr 10° 25′ sudl. Breite und 76° 45′ westl. Lange) ist ein wichtiger Gletscherkernpunkt an der Kontinentalwasserscheide. An seiner NO-Seite, wo der Maranon bzw. Amazonas entspringt, lassen sich im Gebiet von Lauricocha eine Reihe alter Gletschervorstose nachweisen, die der letzten pleistozanen Vereisung der Anden zugeordnet werden (A. Cardich, 1958, 1963, 1964). Eine Radiokohlenstoffdatierung an eingelagertem organischen Material bestatigt das angenommene Alter und legt gleichzeitig ein Interstadial fest (Interstadial Aguamiro, 12 500 Jahre B.P.). Die Gletschervorstose vor diesem Zeitpunkt waren bedeutender, sowohl in ihrer Ausdehnung und der Eismachtigkeit (bis 300 m) als auch in ihrer Dauer. Die spateren Vorstose waren kleinraumiger und kurzlebiger, wie aus dem geringeren Volumen der glazialen Ablagerungen hervorgeht. Ein Vergleich mit anderen untersuchten Gebieten unterstutzt bei Berucksichtigung der 14C-Datierung grostenteils die fruher aufgestellte Systematik.The mountain chain Raura ix the central region of Peru (about 10° 25' southern latitude, and 76° 45' western longitude) is an important center of glaciers at the continental drainage divide. At its NE-side, from where the river Marafion and Amazonas, respectively, originates, in the region of Lanricocha it is possible to identify a series of old advances of glaciers, which are attributed to the last great glaciation of the Pleistocene (A. Cardich, 1958, 1968, 1964). Radiocarbon dating of deposited organic material confirms the assumed age and defines simultaneously an Interstade (Interstade Agua-miro, 12,500 B.P.). The glacial advance prior to this date were more important, not only in their extension and in the thickness of ice (up to 800 m) but also in their duration. The later advances were less extensive and of shorter duration, as may be concluded from the smaller volume of the glacial deposits. A comparison with other regions studied confirms mostly the earlier given classification with regard to the 14C-dating.En la regi6n central del Peril, la Cordillera Raura (alrededor de 10° 25' de latitud sur y 76° 45' de longitud) es un centro de origen de ríos y un nilcleo de glaciación importantes. En la vertiente qne corresponde a las nacientes del rio Marafión o Amazonas se encuentra Lauricocha, una zona donde se habían una serie de rasgos y depósitos originados por antiguos avances del glaciar procedente de Raura. Estas huellas glaciates fueron señaladas por nosotros como correspondientes a la última glaciación del Pleistoceno de los Andes y que luego de otras observaciones y estudios nombramos como Glaciación Lauricocha (A. Cardich, 1958, 1968, 1964). Esta edad estimada se confirma con el fechado por radiocarbono que presentamos en este trabajo y además fija un interstadial (interstadial Aguamiro) que tiene la caracteristica de determinar dos momentos diferentes en el proceso de esta Glaciación: los avances del hielo anteriores a esa fecha fueron de mayor importancia tanto por la mayor extensión como por un mayor espesor de los glaciates que habrian alcanzado alrededor de los 800 m, como por la mayor duración de estos estadios. Los avances glaciarios posteriores a la aludida fecha radiocarbónica alcanzaron extensiones algo menores y ante todo han sido de corta duración como se advierte por el mucho menor volumen de los depósitos de origen glaciar. Haciendo un ordenamiento de otros acontecimientos a partir del fechado radiocarbonífero y mediante correlaciones con otras zonas estudiadas se confirma en gran parte las sistematizaeiones adelantadas anteriormente.Facultad de Ciencias Naturales y Muse

Reconstructing the Deep Population History of Central and South America

We report genome-wide ancient DNA from 49 individuals forming four parallel time transects in Belize, Brazil, the Central Andes, and the Southern Cone, each dating to at least 9,000 years ago. The common ancestral population radiated rapidly from just one of the two early branches that contributed to Native Americans today. We document two previously unappreciated streams of gene flow between North and South America. One affected the Central Andes by 4,200 years ago, while the other explains an affinity between the oldest North American genome associated with the Clovis culture and the oldest Central and South Americans from Chile, Brazil, and Belize. However, this was not the primary source for later South Americans, as the other ancient individuals derive from lineages without specific affinity to the Clovis-associated genome, suggesting a population replacement that began at least 9,000 years ago and was followed by substantial population continuity in multiple regions

Disease: A Hitherto Unexplored Constraint on the Spread of Dogs (Canis lupus familiaris) in Pre-Columbian South America

Although debate continues, there is agreement that dogs (Canis lupus familiaris) were first domesticated in Eurasia, spreading from there to other parts of the world. However, while that expansion already extended as far as Europe, China, and North America by the early Holocene, dogs spread into (and south of) the tropics only much later. In South America, for example, the earliest well attested instances of their presence do not reach back much beyond 3000 cal. BC, and dogs were still absent from large parts of the continent – Amazonia, the Gran Chaco, and much of the Southern Cone – at European contact. Previous explanations for these patterns have focused on cultural choice, the unsuitability of dogs for hunting certain kinds of tropical forest prey, and otherwise unspecified environmental hazards, while acknowledging that Neotropical lowland forests witness high rates of canine mortality. Building on previous work in Sub-Saharan Africa (Mitchell 2015) and noting that the dog’s closest relatives, the grey wolf (C. lupus) and the coyote (C. latrans), were likewise absent from South and most of Central America in Pre- Columbian times, this paper explores instead the possibility that infectious disease constrained the spread of dogs into Neotropical environments. Four diseases are considered, all likely to be native and/or endemic to South America: canine distemper, canine trypanosomiasis, canine rangeliosis, and canine visceral leishmaniasis caused by infection with Leishmania amazonensis and L. colombiensis. The paper concludes by suggesting ways in which the hypothesis that disease constrained the expansion of dogs into South America can be developed further

Calcareous benthic foraminifera from the upper central Peruvian margin : control of the assemblage by pore water redox and sedimentary organic matter

We studied 'living' (stained) benthic foraminifera in the upper border of the Peruvian oxygen minimum zone (OMZ) to determine the relationship between species' distribution and pore water and sediment geochemistry under oxygen deficiency. Superficial sediments were sampled between 2009 and 2011 from 2 bathymetric transects off central Peru (45 to 300 m depth). The quantity (total organic carbon, total nitrogen and chloroplastic pigment equivalents [CPE]) and quality (chlorophyll a/phaeopigments ratio) of organic matter (OM) were evaluated. Benthic foraminifera were sampled in the top 5 cm of sediment. Commonly, the inner shelf sediments were sulfidic and labile OM-rich, whereas the outer shelf and upper slope sediments exhibited postoxic conditions (e.g. anoxic and non-sulfidic) with less labile OM, typical of OMZ core sediments. Mixed conditions were found in shelf sediment samples from April 2010, when the effects of El Nino 2009/2010 were withdrawing. Foraminiferal assemblages exhibited differences according to redox conditions and OM quality, and were concentrated in the topmost sediment. A canonical correspondence analysis and non-parametric correlations indicated that Bolivina costata, Nonionella auris and Virgulinella fragilis were characteristic of sulfidic/labile OM sediments, thriving slightly deeper in the sediment. In contrast, Bolivina pacifica headed the assemblage representative of postoxia/less labile OM. Bolivina seminuda and Buliminella tenuata (both dominant under postoxia) were not associated with any specific measured parameter, although were present in sulfidic sediments, suggesting other factors were involved in their distribution