Search results for " sedi"
showing 10 items of 793 documents
Holocene treeline in the northern Andes (Ecuador): new evidence from soil charcoals
2006
Soil charcoals represent a record for palaeoecological studies. For the first time pedoanthracology is applied to northern Andes of Ecuador to study the Holocene treeline. The first results show that the upper treeline was lower than today in the late Pleistocene and in the Middle Holocene. A wide amount of charcoals dated ca. 13000 cal. yr. BP could be caused by fires linked to the first presence of man at these altitudes.
Polycyclic aromatic hydrocarbons and trace metal contamination of coastal sediment and biota from Togo
2011
The state of contamination of tropical environments, particularly in Africa, remains a relatively under explored subject. Here, we determined polycyclic aromatic hydrocarbon (PAH) and trace metal concentrations in coastal sediment and biota samples (fish and mussels) from Togo (West Africa). In the sediments, the ∑21 PAH concentrations ranged from4 ng g(-1) to 257 ng g(-1), averaging 92 ng g(-1). Concentration ratios of low molecular weight PAHs (2-3 rings) versus high molecular weight PAHs (≥4 rings) were always lower than 1 (ranging from 0.08 to 0.46) indicating that high molecular weight PAHs were dominant in all sediment samples, and that PAHs originated mainly from anthropogenic combus…
Sulfur isotope's signal of nanopyrites enclosed in 2.7 Ga stromatolitic organic remains reveal microbial sulfate reduction.
2018
18 pages; International audience; Microbial sulfate reduction (MSR) is thought to have operated very early on Earth and is often invoked to explain the occurrence of sedimentary sulfides in the rock record. Sedimentary sulfides can also form from sulfides produced abiotically during late diagenesis or metamorphism. As both biotic and abiotic processes contribute to the bulk of sedimentary sulfides, tracing back the original microbial signature from the earliest Earth record is challenging. We present in situ sulfur isotope data from nanopyrites occurring in carbonaceous remains lining the domical shape of stromatolite knobs of the 2.7-Gyr-old Tumbiana Formation (Western Australia). The anal…
Environmental drivers and abrupt changes of phytoplankton community in temperate lake Lielais Svētiņu, Eastern Latvia, over the last Post-Glacial per…
2021
Understanding the long-term dynamics of ecological communities on the centuries-to-millennia scale is important for explaining the emergence of present-day biodiversity patterns and for predicting possible future scenarios. Fossil pigments and ancient DNA present in various sedimentary deposits can be analysed to study long-term changes in ecological communities. We analysed recent compilations of data, including fossil pigments, microfossils, and molecular inventories from the sedimentary archives, to understand the impact of gradual versus abrupt climate changes on the ecosystem status of a regional model lake over the last ~14.5 kyr. Such long and complete paleo-archives are scarce in No…
OSL dating of Middle Weichselian age shallow basin sediments in Western Latvia, Eastern Baltic
2012
Abstract This paper presents the results of the first attempt to date the Quaternary sediments of western Latvia in the southeast Baltic region, using luminescence. The analyses have been carried out on sandy sediments of the Jurkalne Formation that are located between upper and lower Scandinavian sourced tills. Previous publications on the origin of the Quaternary sediments in the region are reviewed and it is found that there are a wide range of explanations for their processes of formation and their age of formation. It is concluded that although the sandy sediments were deposited in freshwater environment although they contain both marine and freshwater fauna and flora, a property that …
Materiales del Paleolítico Superior en Cova Negra (Xàtiva) y su interés para establecer los procesos de su secuencia estratigráfica
2017
En este trabajo se analizan los materiales líticos adscritos al Paleolítico Superior obtenidos en Cova Negra a lo largo de las campañas de excavación de los años 30, 50 y 80 del pasado siglo y en las campañas de 2013-2016. La atención se centra en el estudio de los soportes, los núcleos y el material retocado, y se efectúa una primera aproximación con respecto a la cronología y periodos a los que remiten las piezas retocadas. El principal interés de estos materiales reside en confirmar que la ocupación de la cavidad no se limitó al Paleolítico Medio, ni a momentos iniciales de la secuencia del Paleolítico Superior, lo que facilita una evaluación del alcance de los procesos de alteración pos…
Implications for paleomobility studies of the effects of quaternary volcanism on bioavailable strontium: a test case in North Patagonia (Argentina)
2020
Strontium isotopes (⁸⁷Sr/⁸⁶Sr) are used as geochemical tracers for paleomobility studies because they display predictable and stable patterns in ecosystems primarily controlled by the underlying geological regimes. While bedrock geology is stable over thousands of years, geomorphological processes can influence the ⁸⁷Sr/⁸⁶Sr in ecosystems over archeologically relevant timescales. Among these geomorphological processes, the deposition and reworking of volcanic sediments over Quaternary timescales are little studied but could be an important control of ⁸⁷Sr/⁸⁶Sr variations in many archeological regions. North Patagonia is a key archeological region to address animal and human movements, and a…
The microbial community of sub-surface sediment of a chronically contaminated SIC
2015
Hydrocarbons (HC), especially high molecular weight HC, are trapped in the sediments for a long time, making the benthic system a permanent pollution source, with several effects on the biota. Sediment bacterial communities play a significant role in the degradation of contaminants, both under aerobic and anaerobic conditions. In this work we focused on the bacterial communities of sediments (5-10 cm below surface), of a Site of Community Importance, the Priolo Bay, in Central Mediterranean Sea. The bay is situated in proximity to the Augusta Harbour, affected for decades by pollution from industrial and petrochemical plants. The microbial communities of sediments from six stations on two t…
Investigating the influence of climate changes on rodent communities at a regional-scale (MIS 1-3, southwestern France).
2016
25 pages; International audience; Terrestrial ecosystems have continuously evolved throughout the Late Pleistocene and theHolocene, deeply affected by both progressive environmental and climatic modifications, aswell as by abrupt and large climatic changes such as the Heinrich or Dansgaard-Oeschgerevents. Yet, the impacts of these different events on terrestrial mammalian communities arepoorly known, as is the role played by potential refugia on geographical species distributions.This study examines community changes in rodents of southwestern France between50 and 10 ky BP by integrating 94 dated faunal assemblages coming from 37 archaeologicalsites. This work reveals that faunal distributi…
Active faulting and continental slope instability in the Gulf of Patti (Tyrrhenian side of NE Sicily, Italy): a field, marine and seismological joint…
2016
The Gulf of Patti and its onshore sector represent one of the most seismically active regions of the Italian Peninsula. Over the period 1984–2014, about 1800 earthquakes with small-to-moderate magnitude and a maximum hypocentral depth of 40 km occurred in this area. Historical catalogues reveal that the same area was affected by several strong earthquakes such as the Mw = 6.1 event in April 1978 and the Mw = 6.2 one in March 1786 which have caused severe damages in the surrounding localities. The main seismotectonic feature affecting this area is represented by a NNW–SSE trending right-lateral strike-slip fault system called ‘‘Aeolian–Tindari–Letojanni’’ (ATLFS) which has been interpreted a…