Search results for "Evolution"

New tree-ring evidence for the Late Glacial period from the northern pre-Alps in eastern Switzerland

2018

Abstract The rate and magnitude of temperature variability at the transition from the Last Glacial Maximum into the early Holocene represents a natural analog to current and predicted climate change. A limited number of high-resolution proxy archives, however, challenges our understanding of environmental conditions during this period. Here, we present combined dendrochronological and radiocarbon evidence from 253 newly discovered subfossil pine stumps from Zurich, Switzerland. The individual trees reveal ages of 41–506 years and were growing between the Allerod and Preboreal (∼13′900–11′300 cal BP). Together with previously collected pines from this region, this world's best preserved Late…

2020

To place recent hydroclimate changes, including drought occurrences, in a long-term historical context, tree-ring records serve as an important natural archive. Here, we evaluate 46 millennium-long ...

Concord and discord among Northern Hemisphere paleotemperature reconstructions from tree rings

2019

Abstract We review the current generation of large-scale, millennial-length temperature reconstructions derived from tree rings and highlight areas of agreement and disagreement among these state-of-the-art paleotemperature estimates. Although thousands of tree ring-width chronologies are now available from temperate and boreal forest sites across the Northern Hemisphere, only a small fraction of those records are suited as proxies for surface temperature. Maximum latewood density is clearly a superior temperature proxy but is less available, with few densitometric records that are both long and up-to-date. Compared to previous efforts, the newest generation of tree-ring reconstructions cor…

Oxygen isotope analysis of Equus teeth evidences early Eemian and early Weichselian palaeotemperatures at the Middle Palaeolithic site of Neumark-Nor…

2019

Abstract Here we present phosphate oxygen isotope (δ 18OPO4) data from horse (Equus sp.) tooth enamel (bioapatite) from early Eemian and early Weichselian find levels at the archaeological site of Neumark-Nord 2, Germany. Based on the relationship between δ18OPO4 of bioapatite, body water, local precipitation and air temperature, these data are used to reconstruct palaeoclimatic conditions contemporary to the different phases of Neanderthal activity at the site. Bulk enamel samples representing one year of growth were taken from horse teeth from early Eemian (NN2/2b [∼121 ± 5 ka], and NN2/1c) and early Weichselian (NN2/0; ∼93 ± 7 ka) find levels, and δ18OPO4 values were then utilised to cal…

Improving the accuracy of small vertebrate-based palaeoclimatic reconstructions derived from the Mutual Ecogeographic Range. A case study using geogr…

2019

Abstract Understanding past climate and the mechanisms of climate change remain major challenges in scientific research. The Mutual Ecogeographic Range (MER) method for climatic reconstruction uses the current geographical distribution of fossil assemblages to infer palaeoclimatic conditions. Current species distributions used in the MER method are usually obtained from biogeographic atlases that record the absence/presence of species in a 10 × 10 km grid. A 10 × 10 km area is quite broad and the method only records presence/absence, without considering the real area occupied by any given species. Thus, the method overlooks the fact that environmental heterogeneity is strongly related to to…

Vegetation and climate record from Abric Romaní (Capellades, northeast Iberia) during the Upper Pleistocene (MIS 5d−3)

2019

This study addresses the pollen record of Abric Romani archaeological site and the climate evolution of the last interglacial and glacial stadials in the Iberian Peninsula. The new pollen record spans the interval from 110,000 to 55,000 years ago. In general, the glacial/stadial vegetation is characterized by a steppe and herbaceous communities indicating dry and cold climatic conditions, whereas the vegetation optimum of past interglacials can be described as pine-oaks with mediterranean forest indicating milder and moister climatic conditions. During the first half of the MIS 5a and the MIS 5c, the region was warmer, which is characterized by temperate forests. However, the existence of A…

Turia river delta and coastal barrier-lagoon of Valencia (Mediterranean coast of Spain): Geomorphological processes and global climate fluctuations s…

2019

Abstract Extensive drillings and 31 new C-14 datings were used to establish the geomorphological evolution of the Turia river delta and coastal barrier-lagoon system of Valencia (Spain) over the last three millennia. Integration of geomorphological, stratigraphic, malacological, sedimentological and geoarchaeological data enables us to relate river Turia avulsions and alluvial episodes to the development of coastal spits and barriers. Geomorphological changes in the study area may also be associated with global climate events, sea-level fluctuations or anthropogenic periods in the Turia catchment. Six phases may be differentiated: (1) a major early alluviation phase during the Iberian perio…

Caribbean hydroclimate and vegetation history across the last glacial period

2019

Abstract We present a new speleothem trace element and stable isotope record, which extends previous paleoclimate evidence from Cuban speleothems to the last 96 ka. Multiple proxies were used to reconstruct Caribbean hydroclimate and vegetation variability on orbital to millennial timescales. In particular, our proxies indicate a shift to more abundant C4 (compared to C3) vegetation and/or reduced soil activity during the Last Glacial Maximum. Our results confirm the close link of Caribbean precipitation to North Atlantic climate variability, insolation and the strength of the AMOC. The associated variations in Caribbean SSTs and the shift of the ITCZ led to substantial changes of the hydro…

Hydroclimate variability of western Thailand during the last 1400 years

2020

Mainland Southeast Asia is located on the moisture transport route of the Indian summer monsoon (ISM) where hydroclimate records from speleothems have rarely been investigated. Here, we present a new multi-proxy (δ18O and δ13C values, trace element concentrations, and grayscale values) data set of stalagmite KPC1 from Khao Prae cave in western Thailand spanning the last 1400 years (500–1900 CE; the Common Era). These multi-proxy data reveal a high variability between the wet and dry periods during 500–850 CE and 1150–1300 CE, stable climate conditions during 850–1150 CE, and overall dry conditions since 1300 CE. The δ13C values, trace elements concentrations, and grayscale values show cente…

Human occupation and environmental change in the western Maghreb during the Last Glacial Maximum (LGM) and the Late Glacial. New evidence from the Ib…

2019

With the onset of the Last Glacial Maximum (LGM), hunter-gatherers of the so-called Iberomaurusian techno-complex appeared in what is now the Mediterranean Maghreb. During a period of about seven thousand years, these groups left sandy occupation layers in a limited number of archaeological sites, while at the beginning of Greenland Interstadial (GI) 1, the sudden shift towards the deposition of shell-rich sediments and the increase in number of sites document clear changes in subsistence strategies as well as occupation density. It is highly likely that these shifts in human behaviour are related to paleoenvironmental changes in the area, which, so far, are poorly documented in geological …