Brief Introduction on New Advances on the Origin of Ooids
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摘要: 鲕粒的成因一直是一个谜一样的沉积学难题。Brehm等在2006年的实验室研究的结果表明，将鲕粒的形成可以与叠层石进行类比，是一个特殊的球状微生物席的产物，从而将鲕粒归为微生物成因。最近，来自于巴哈马现代鲕粒的研究，Duguid等在2010年认为，鲕粒形成与微生物活动不存在一个直接的关系，重新强调了鲕粒形成的化学过程，即：当鲕粒处在沉积物—水界面（活跃相）的时候，凭借一个在鲕粒上的非晶质钙碳酸盐（ACC）沉淀物的微薄层，鲕粒开始形成；这个ACC微薄层后来结晶成文石针，从而形成新的鲕粒皮层（静止相）。两种观点的直接对立，代表了对鲕粒成因研究的新进展。来自于华南下三叠统的巨鲕、以及华北寒武系鲕粒，特殊的显微组构似乎更多地支持了鲕粒形成的微生物作用机制的学说。Abstract: The origin of ooids represents a sedimentogical problem like an enigma. On the basis of experiment studies, Brehm et al. (2006) concluded that the ooid can be analogical to the stromatolite, i.e. the ooid is the product resulted from the activities of a special spherical microbial mat. Recently, studies on modern ooids in Bahamian Archipelago by Duguid et al. (2010) indicate that microbes do not play a role in ooid formation; thus, a new chemical model for the ooid formation has been proposed, i.e. whereby a veneer of ACC precipitates on an ooid while it is at the sediment water interface (the active phase) and this veneer of ACC later recrystallizes to aragonite needles and a new cortex layer is formed (the stationary phase). Two different views represent the new advances on studies of the ooid origin. Whereas, the particular microscopic fabrics for both the giant ooids of the lower Triassic in south China and the ooids of the Cambrian in north China provide more supporting evidence for the microbial origin of the ooid formation.
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Key words:
- microbial action
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