over past 41,000 years
03 June 2009 Plataforma SINC
The examination of the fossil remains of rodents and insectivores from
deposits in the cave of El Mirón, Cantabria, has made it possible to
determine the climatic conditions of this region between the late
Pleistocene and the present day. In total, researchers have pinpointed
seven periods of climatic change, with glacial cold dominating during
some of them, and heat in others.
In 1996, an international team of scientists led by the University of
Zaragoza (UNIZAR) started to carry out a paleontological survey in the
cave of El Mirón. Since then they have focused on analysing the fossil
remains of the bones and teeth of small vertebrates that lived in the
Cantabrian region over the past 41,000 years, at the end of the
Quaternary. The richness, great diversity and good conservation status
of the fossils have enabled the researchers to carry out a
paleoclimatic study, which has been published recently in the Journal
of Archaeological Science.
"We carried out every kind of statistical analysis over a six-month
period at the University of New Mexico, analysing around 100,000
remains, of which 4,000 were specifically identified, and catalogued
according to species and the number of individuals in each stratum",
Gloria Cuenca-Bescós, lead author of the study and a researcher in the
Paleontology Department of the UNIZAR's Institute for Scientific
Research (IUCA), tells SINC.
The resulting study involves climatic inferences being drawn on the
basis of the fossil associations of small mammals whose remains have
been deposited in El Mirón over the past 41,000 years. The fossil
associations of these mammals reveal the composition of fauna living
around the cave at the time, and have made it possible to develop a
paleoclimatological and paleoenvironmental reconstruction of the
environment.
The research shows that there have been seven periods of cooling and
warming in the Cantabrian cornice over the past 41,000 years. An
analysis carried out by other authors on data relating to pollen,
marine isotope stratigraphy, and materials deposited by glaciers backs
this up this result.
The water rat was king of the Late Pleistocene
According to the study, there were four unstable cold periods, two
more stable ones, and a temperate climatic period at the El Mirón
cave. The scientists are unsure about dating the seventh and last
period ended, as this "could correspond with the Bronze Age, the Ice
Age, or the start of agricultural expansion by human beings, which
certainly would have impacted on the wild animals living close to the
caves.
However, the study shows that during earlier periods at the end of the
Late Pleistocene, the species that predominated during cold periods
were rodents and insectivores that were well-adapted to environments
with only sparse vegetation. "When climatic conditions became more
mild at the end of the last cold pulse of the Late Pleistocene, known
as the Dryas III, forest-dwelling rodents and insectivores flourished
and become more frequent in the associations", explains Cuenca-Bescós.
We now know that the water vole (Arvicola terrestris) dominated in
this period.
According to the researcher, this domination by woodland species
started to decline in the area only at the end of the Holocene, when
human activities began to change the landscape, and when deforestation
resulting from permanent settlements and agriculture can be observed
"even though the climate continued to be favourable to these kinds of
organisms".
The study has also shown that the majority of the Pleistocene taxa
became extinct around 10,000 years ago while "some cold-adapted
species, which had managed to survive, moved to the north of Europe,
leaving our warmer latitudes behind", the scientist concludes.
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