Search results for "Glacial period"

How do the 1982/83 and 1997/98 El Niños rank in a geological record from Peru?

2007

Two very strong El Nino events during the years 1982/83 and 1997/98 caused dramatic economical and social damages worldwide. However, it is quite uncertain how these events rank in a long-term perspective and how frequent events of similar magnitude were in the past. Very-high-resolution proxy data for flood events in the El Nino key region of Peru are presented. Strong flood events in the hyper-arid northern and northern central Peru coastal desert occur during El Nino events. The flood data are derived from a laminated marine sediment core. The proxy data reveal that both modern events were recorded as the strongest sediment discharges in the 106KL flood record over the last millennium. S…

STOP 3: Late-glacial and early postglacial environmental processes and the history of the River Triečupīte valley and surroundings, in the foreland o…

2014

A late Eemian aridity pulse in central Europe during the last glacial inception

2005

How do ice ages begin? It's an obvious question to ask as we enjoy the relative luxury of an interglacial, but a hard one to answer. A look at past transitions may give some clues as to how this period will one day come to an end. A climate reconstruction based on sediments found beneath a lake in the Eifel mountains in Germany provides evidence of an extreme climate event lasting 468 years right at the end of the last interglacial. Dust storms, aridity, bushfires and the loss of trees associated with a warm climate coincided with a southward shift of the warm waters of the North Atlantic drift. In terms of insolation — the rate of delivery of the Sun's radiation to Earth — conditions then …

Primary productivity variability on the Atlantic Iberian Margin over the last 70,000 years: Evidence from coccolithophores and fossil organic compoun…

2010

[1] This study analyzes coccolithophore abundance fluctuations (e.g., Emiliania huxleyi, Gephyrocapsa specimens, and Florisphaera profunda) in core MD01-2444 sediment strata retrieved at the Iberian Margin, northeastern Atlantic Ocean. Coccolithophores are calcareous nannofossils, a major component of the oceanic phytoplankton, which provide information about past ecological and climatological variability. Results are supported by data on fossil organic compounds (sea surface temperatures, alkenones, and n-hexacosan-1-ol index) and geochemical analyses (benthic δ13Ccc and planktonic δ18Occ isotopes). Three scenarios are taken into account for this location at centennial-scale resolution ove…

Size variations in the genus Gephyrocapsa during the Early Plaeistocene in the eastern Mediterranean

2014

The genus Gephyrocapsa, belonging to coccolithophores, hasoften been used in biostratigraphic and paleoceanographic studies ofthe late Cenozoic. This taxon exhibits a gradual increase in sizeduring the Early Pleistocene which has been ascribed to evolutiveand/or environmental processes and has been used for biostratigraphicpurposes.Here we show both biometric and relative abundance data ofspecimens of this genus between about 2.0 and 0.9 Ma, from sedimentsof the Ionian Sea (eastern Mediterranean). Measurements onthe long axis of placoliths highlight a gradual size increase betweenthe upper part of MNN 19a and the top of MNN 19d biozones. Onthe basis of the comparison with paleoenvironmental…

How dry was the Younger Dryas? Evidence from a coupled <i>δ</i><sup>2</sup>H–<i&gt…

2019

Abstract. Causes of the Late Glacial to Early Holocene transition phase and particularly the Younger Dryas period, i.e. the major last cold spell in central Europe during the Late Glacial, are considered to be keys for understanding rapid natural climate change in the past. The sediments from maar lakes in the Eifel, Germany, have turned out to be valuable archives for recording such paleoenvironmental changes. For this study, we investigated a Late Glacial to Early Holocene sediment core that was retrieved from the Gemündener Maar in the Western Eifel, Germany. We analysed the hydrogen (δ2H) and oxygen (δ18O) stable isotope composition of leaf-wax-derived lipid biomarkers (n-alkanes C27 an…

Is the Anthropocene really worthy of a formal geologic definition?

2014

Scientists are actively debating whether the Anthropocene, the geologic time span (GTS) we are now living in, should be considered a period, epoch, or age in the geologic timescale. The solution is not easy, because the beginning of this GTS is undefined and the end unknown. In fact, there is no agreement on when the Anthropocene began, the proposed dates ranging from the Second World War, when radioactive fallout branded soils and sediments all over the world, to little after the end of the last glacial period, i.e. 11.7 thousand years ago, therefore coinciding with the onset of the Holocene. We are in favour of a concurrence of the Anthropocene with the Holocene, although a major impact …

Chemostratigraphy of the early Pliocene diatomite interval from MIS AND-1B core (Antarctica): Palaeoenvironment implications

2013

The AND-1B drill core (1285m-long) was recovered, inside the ANDRILL (ANtarctic geological DRILLing) Program, during the austral summer of 2006/07 from beneath the floating McMurdo Ice Shelf. Drilling recovered a stratigraphic succession of alternating diamictites, diatomites and volcaniclastic sediments spanning about the last 14Ma. A core portion between 350 and 480mbsf, including a 80m-thick diatomite interval recording the early Pliocene warming event, was investigated in term of opal biogenic content and element geochemistry. Across the diatomite interval, in spite of the lithological uniformity, a fluctuating biogenic opal profile mirrors the δ18O record, testifying a decrease in prod…

Drivers of change and ecosystem status in a temperate lake over the last Post-Glacial period from 14.5 kyr

2020

AbstractUnderstanding the long-term dynamics of ecological communities on the centuries-to-millennia scale is important for explaining present-day biodiversity patterns. Placing these patterns in a historical context could yield reliable tools for predicting possible future scenarios. Paleoarchives of macro+ and micro-fossil remains, and most importantly biomarkers such as fossil pigments and ancient DNA present in various sedimentary deposits, allow long term changes in ecological communities to be analysed. We use recent compilations of data including fossil pigments, metabarcoding of sedimentary ancient DNA and microfossils together with data analysis to understand the impact of gradual …

LA OCUPACIÓN SOLUTRENSE DEL ABRIGO DE LA BOJA (MULA, MURCIA, ESPAÑA)

2013

El relleno pleistoceno del Abrigo de la Boja (ADB) empieza con un nivel adscrito al Magdaleniense superior, seguido de un potente paquete con ocupación difusa bajo el cual se desarrolla una secuencia depositada durante el último máximo glacial caracterizada por una serie de estructuras de combustión, de tipo hogar plano/amorfo (open hearth), existiendo también hogares de cubeta. Destaca un hogar enlosado, completo y muy bien conservado, excavado en 2012 y adscrito provisionalmente al Solutreogravetiense. Los niveles solutrenses subyacentes son ricos en elementos de adorno, entre los cuales conchas perforadas de Littorina obtusata y Smaragdia viridis; su industria lítica incluye raspadores, …