对“中白垩世(Albian-Santonian)热带大西洋表层海水温度记录”的评述

Forster等依据与δ18O无关的TEX86值来推算古温度的方法,获得了中白垩世(阿尔布期—三冬期)的表层海水温度(SST)记录。中白垩世期间,南美Demerara海隆位于热带大西洋西部,从赛诺曼期SST逐步升高(达31℃—35℃),至赛诺曼期-土仑期界线附近,SST的最高值明显高过35℃;土仑期内出现两次变凉事件(降温约2℃—3℃),打断了中白垩世稳定变暖的趋势;康尼亚克期,SST逐步下降,至三冬期降到了最低值(约32℃—33℃)。这一研究结果表明,在地质时期内,尽管中白垩世代表了典型的温室气候,但仍然很不稳定。驱动气候变化的因素是综合的,主要受地轴与地球赤道间的夹角变化、太阳辐射程度,及地球深部物质和构造运动等因素的影响,其他孤立的事件则很难影响全球性气候变化。气候的变化影响着生物的演化,古气候是研究重大地质事件的重要参数,古生物为研究古气候的最主要的标志之一。

A COMMENT ON "MID-CRETACEOUS (ALBIAN-SANTONIAN) SEA SURFACE TEMPERATURE RECORD OF THE TROPICAL ATLANTIC OCEAN"

By means of the TEX_ 86 proxy, which is independent from changes in the chemistry and oxygen isotopic composition of ambient seawater, Forster et al. obtained the of Mid-Cretaceous (Albian-Santonian) (sea surface temperatures) (SSTs) record of Demerara Rise, which was located in the western tropical Atlantic Ocean during Mid-Cretaceous. In the Mid-Cretaceous, a gradual getting warm trend, lasted up to the Turonian-Coniacian, of SSTs started since Cenomanian (ca. 31℃—35℃), and the maximal SSTs is over 35℃ near Cenomanian-Turonian boundary. However, two cooling events (ca. 2℃—3℃) disrupted the stable warming trend of Mid-Cretaceous. In Coniacian, the SSTs were stepwise declined, reaching the minimum in Santonian (32℃—33℃). Such results have shown, in the geological history, even during the extremely warm green house, the Mid-Cretaceous, the climate is unstable. The factors driving the climate changes are compositive, but mainly the variation of angle between the earth axis and the equator, the strength of the sun's radiation and the action of materials and structures in deep-earth level. Otherwise, any independent event hardly affects the global climate. Although climate does not directly influence the organic evolution, palaeoclimate plays an important role in studying major geological events including stratigraphic boundary, and fossil is, therefore of the most critical indexes of reconstructing the palaeoclimate.