A number of hydrological, botanical, macro- and micro-climatological processes are involved in the formation of patterned peatlands. La Grande Tsa at 2336 m a.s.l. is probably the highest bog in the central Swiss Alps and is unique in its pattern. In two of five pools there is in the contact zone between the basal peat and the overlying gyttja an unconformity in the depth-age models based on radiocarbon dates. Palynostratigraphies of cores from a ridge and a pool confirm the occurrence of an unconformity in the contact zone. We conclude that deepening of the pools results from decomposition of peat. The fact that the dated unconformities in the two pools and the unconformity in the ridge-core all fall within the Bronze Age suggest they were caused by events external to the bog. We hypothesize that early transhumance resulted in anthropogenic lowering of the timberline, which resulted in a reduction in the leaf-area index and evapotranspiration, and in higher water levels and thus pool formation.

A sediment core 7.2 m long from Lake Mirabad, Iran, was examined for loss-on-ignition, mineralogy, oxygen-isotopic composition of authigenic calcite, and trace-element composition of ostracodes to complement earlier pollen and ostracode-assemblage studies. Pollen, ostracode-inferred lake level, and high Sr/Ca ratios indicate that the early Holocene (10000 to 6500 cal yr BP) was drier than the late Holocene. Low delta O-18 values during this interval are interpreted as resulting from winter-dominated precipitation, characteristic of a Mediterranean climate. Increasing delta O-18 values after 6500 cal yr BP signal a gradual increase in spring rains, which are present today. A severe 600-yr drought occurred at ca. 5500 cal yr BP, shortly after the transition from pistachio-almond to oak forest. During the late Holocene, two milder droughts occurred at about 1500 and 500 cal yr BP. Within the resolution of the record, no drought is evident during the collapse of the Akkadian empire (4200-3900 cal yr BP). Rather, a decrease in delta O-18 values to early-Holocene levels may indicate the return to a Mediterranean precipitation regime. (c) 2006 University of Washington. All rights reserved.

Pollen studies of the four European interglacial intervals indicate a strong similarity in vegetational sequence: a pretemperate phase (I) marks the late glacial, early temperate (II) and late temperate (III) phases mark the interglacial proper, and a posttemperate phase (IV) represents the beginning of the next cold period. A grossly similar record is now known for the last interglacial (Sangamon) of central and southeastern United States. The Holocene sequence in both Europe and America are completely typical of the interglacial sequence, although much more is known of the geographic variations.Estimates for the duration of the interglacials range from 10,000 to more than 30,000 yr, according to counts of the annually laminated sediments (organic varves).The Holocene has already run a course of at least 10,000 yr. If it is like earlier interglacials, it will end soon, giving way to gradually developing cold conditions, which may not lead to glacial maxima for tens of thousands of years.