科研之友
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摘要
During the Serpukhovian (early Namurian) icehouse conditions were initiated in the southern hemisphere. However, nearfield evidence is inconsistent: glaciation appears to have started in limited areas of eastern Australia in the earliest Serpukhovian, followed by a long interglacial, whereas data from South America and Tibet suggest glaciation throughout the Serpukhovian. New farfield data from the Woodland, Throckley and Rowlands Gill boreholes in northern England allow this inconsistency to be addressed. delta(18)O from well-preserved late Serpukhovian (late Pendleian to early Arnsbergian) Woodland brachiopods vary between -3.4 and -6.3 parts per thousand, and delta(13)C varies between -2.0 and +3.2 parts per thousand, suggesting a delta(18)O seawater (w) value of around -1.8 parts per thousand VSMOW, and therefore an absence of widespread ice-caps. The organic carbon delta(13)C upward increasing trend in the Throckley borehole (Serpukhovian to Bashkirian; c. -24 to c. -22 parts per thousand) and the Rowlands Gill borehole (Serpukhovian; c. 24 to c. 23 parts per thousand) suggests large-scale burial of organic material, probably in burgeoning lycophyte-dominated coal forest, implying a fall in pCO(2). pCO(2) reduction appears not to have caused large-scale glaciation until the early Bashkirian, but a scenario of coalescing upland ice-caps through the Serpukhovian with a background of decreasing pCO(2) appears to be similar to the process that initiated Cenozoic Antarctic glaciation.
- 出版日期2010-12
