Chemocline instability and isotope variations of the Ediacaran Doushantuo basin in South China

Stable isotope analyses in sections across a shelf to basinal transect of the Ediacaran Doushantuo basin show substantial isotope variabilities. In Songlin section where sediments were deposited in an intrashelf basin, δ 13C values are persistently negative (_3‰ to _5‰, VPDB) through the entire Doushantuo Formation, similar to those obtained from the slope section in Wuhe (_5‰ to _10‰, VPDB). Shallow water sections in Weng'an and Duoding show two broad δ 13C anomalies overprinted with significant meter-scale variations, but none of the curves has similar absolute δ 13C values compared to the Yangtze Gorges areas in South China and other sections globally. Such isotope variations, if partially recording ancient seawater signature, imply spatial and temporal chemocline instability in the Doushantuo basin. In combination with available δ 13C records from other Ediacaran successions globally, the data from the Doushantuo basin are consistent, in first order, with the existence and oxidation of a large dissolved organic carbon (DOC) reservoir in Ediacaran oceans, but imply local environmental controls on Neoproterozoic isotope values and call attentions for using δ 13C anomalies as time lines in stratigraphic correlation.

The characteristic pattern of multiple colored layers in coastal stratified lakes in the process of separation from the White Sea

An unusual feature of the saline stratified lakes that were formed due to ongoing postglacial uplift on the White Sea coast is the presence of several differently colored thin layers in the zone with sharp gradients. Colored layers in five lakes at various stages of separation from the sea were investigated using optical microscopy, spectrophotometry, spectrofluorimetry, and photobiology. The upper greenish colored layer located in the aerobic strata of all lakes near the compensation depth of 1% light penetration contains green algae. In the chemocline, another layer, brightly green, red or pink, is dominated by mixotrophic flagellates. Despite the very low light intensities and the presence of H 2 S, active photosynthesis by these algae appears to be occurring, as indicated by high values of the maximum quantum yield of primary photochemistry, electron transport activity, photosynthetic activity of photosystem II, the fraction of active centers, and low values of heat dissipation. In the reduced zone of the chemocline, a dense green or brown suspension of anoxygenic phototrophs(green sulfur bacteria) is located.

DISTRIBUTION AND RESIDENCE TIME OF BORON IN CLOSED LAKE VANDA, ANTARCTICA

I. INTRODUCTIONVanda Lake, located in Wright Valley of Antarctic Trase Mountains, 77 32’S, 161 31’ E, is one of the salt lakes in Antarctica. The lake spreads from east to west, and is bordered by the high rock walls of Asgard and Olympus Mountains on the north and south. The area of the lake is covered by exposed granite with intruded lamprophyre and overlying