May 2008 GEOLOGY media highlights

Rapid ecosystem response to abrupt climate changes during the last glacial period in western Europe, 40–16 ka
Barbara Wohlfarth et al., Department of Geology and Geochemistry, Stockholm University, 106 91 Stockholm, Sweden. Pages 407-410.

Current and future climate change may lead to dramatic consequences for our remaining natural ecosystems, but how fast may these occur and how severe might these be? Looking into the future is quite difficult, but a glimpse into the past offers an excellent opportunity to further our understanding of the impact and rapidity of climatic changes. Wohlfarth et al. recovered and analyzed sediments from the bottom of the former lake at Les Échets in central France, which offer such a glimpse into the past. Their careful study revealed that the lake’s ecosystem and the lake’s surroundings responded distinctly and within 40-230 years to climatic changes between 40,000 and 20,000 years before present. The observation that the lake’s response, and response time, were unique for each of these climatic shifts clearly shows how sensitive ecosystems are once critical thresholds are crossed.

Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases
James W. Head et al., Department of Geological Sciences, Brown University, Box 1846, Providence, Rhode Island 02912, USA. Pages 411-414.

A terrain type characterized by lineated terrain oriented parallel to the strike of long valleys fills many valleys along the distinctive boundary between the southern uplands and the northern lowlands of Mars. This lineated valley fill has been interpreted as glacial in origin, representing the former presence of extensive glaciation at these mid-latitudes. A glacial flow lobe trending uphill for over 900 meters elevation provides impressive evidence that the glaciation was even more extensive than previously thought. Taken together with the elevation of the lineated valley fill, Head et al.'s new data suggest that a glacial land system at least 2 km thick extended over these regions of Mars in recent geological history.

Optical dating of abrupt shifts in the late Pleistocene East Asian monsoon
Thomas Stevens et al., School of Earth Science and Geography, Kingston University, Penrhyn Road, Kingston upon Thames, Surrey, KT1 2EE, UK. Pages 415-418.

Chinese loess (wind-blown silt) contains one of the most important records of terrestrial Quaternary climate change. The deposits contain a detailed and long-term record of the alternating influence of part of the monsoon system responsible for sustaining two-thirds of the world's population. However, previous findings from loess have been limited by the lack of independently dated sequences. Using optically stimulated luminescence dating at high sampling resolution, Stevens et al. provide time-continuous chronologies for two sites on the Chinese Loess Plateau. The age models shed new light on loess sedimentation rates, monsoon forcing, response, and dynamics. This new information is only obtainable using radiometric dating and allows the first independent comparison to other regional records of monsoon change.