Showing papers on "Speleothem published in 1982"

Speleothem dates, Quaternary terraces and uplift rates in New Zealand

Abstract: Previous isotopic research on calcite stalagmites, stalactites and flowstones (speleothems) from New Zealand caves has focused on palaeotemperature reconstruction1,2. I report here the use of 230Th/234U and 14C age data from speleothems to investigate the relationships between cave levels, emerged coastal terraces and uplift rates. In the north-west of the South Island of New Zealand, at least seven terraces, provisionally assigned to various stages in the Quaternary, are known to occur to at least 200m above sea level3,4. The terraces sometimes cut across limestones which contain caves formed in association with past sea levels. Uplift, followed by water table lowering and abandonment of cave passages by active streams, permitted speleothem deposition. Dating of these deposits gives a minimum age for the cave level and hence also for any terrace to which it may be related, while successive dates at different levels yield an uplift rate for the area. Data are presented from two localities, which suggest differential emergence rates of 0.27+0.28 −0.09 mm yr−1 and 0.14+0.05 −0.03 mm yr−1. Thus re-evaluation is required of other largely qualitative evidence on the uplift of these parts of the Southern Alps5.

Stratigraphic evidence of quaternary climatic change at Echo Cave, transvaal, and a paleoclimatic record for Botswana and northeastern South Africa

Abstract: Summary Changes in climate at Echo Cave during the last 35,000 years caused ground water levels to fluctuate by > 29 m. There was little speleothem deposition during dry climatic phases because of a lack of moisture and only localized deposition during very wet phases when water levels rose and most cave passages were flooded. The most massive speleothems were laid down in transitional periods between very wet and dry conditions when water levels were low enough for many passages to be air filled and the climate wet enough for rapid deposition of travertine. Data from Echo Cave and from other sites in Botswana and northeastern South Africa suggest that there were three cooler and wetter phases during the Holocene at 9,700-7,600, 4,300-2,200, and 1,700-400 yr B.P.; that the Late Glacial climate (12,000-10,000 yr B.P.) was warm and dry; and that the climate during the Upper Pleniglacial (18,000-13,000 yr B.P.) and Middle Pleniglacial (38,000-30,000 yr B.P.) was cooler and wetter than today but warmer and drier than the first 12,000 years (30,000-18,000 yr B.P.) of the Upper Pleniglacial.