非暖水碳酸盐岩:沉积学进展与油气勘探新领域

非暖水碳酸盐岩是碳酸盐岩沉积学中的重要组成部分,结合国内外关于碳酸盐岩的最新研究成果,综述了非暖水碳酸盐岩的研究内涵,将表面海水温度20℃的非暖水碳酸盐岩的沉积环境划分为温暖-温水区(15~20℃)、凉水-温水区(5~15℃)和冷水-极地区(5℃)。与暖水-热带区碳酸盐岩中含有大量光合自养生物组合不同,非暖水碳酸盐岩中的生物类型主要为非营光合作用的异养生物组合。非暖水碳酸盐岩的沉积速率很低,凉水碳酸盐岩的沉积速率大多不到1m/ka,一般都只有每千年几厘米。由于缺乏造礁生物,非暖水碳酸盐岩的沉积环境缺乏生物礁,主要为无障壁的缓坡以及开阔的大陆架。由于缺乏灰泥支撑,非暖水碳酸盐岩主要为颗粒支撑结构,早期成岩作用中很少见到镁方解石或文石胶结。由于胶结作用大都发生于深埋藏环境,具有大量碳酸盐岩生物碎屑堆积的非暖水碳酸盐岩体系可以保存大量的优质粒内孔和粒间孔等储集空间,可能成为未来油气勘探的新领域。非暖水碳酸盐岩概念的出现,对岩相古地理分析具有重要影响,如果将现代非暖水碳酸盐岩研究、古生物资料以及古海水研究应用到古老碳酸盐岩研究中,则现在划分的古纬度可能将需要进行较大的改变。

Non-tropical carbonate:progress in sedimentology and new field of petroleum exploration

Non-tropical carbonate is a significant component of carbonate sedimentology. Combined with latest carbonate research achievements, this paper focuses on the connotation of non-tropical carbonate realm with surface marine water temperature <20℃, which could be divided to warm-temperate realm (15-20℃), temperate-cool water realm (5-15℃) and polar cold water realm (<5℃). The biota types in non-tropical carbonate are mainly heterozoan association, which is different from the phtozoan association in tropical carbonate. The non-tropical carbonate has very low accumulation rate. The accumulation rate of cool-water carbonate is no more than 1m/ka, mostly only some centimeters per millennium. Because of the lack of reef-building organisms, there is reef deficiency in non-tropical carbonate, mainly are ramp with no barrier and open shelf. Lack of lime mud supporting, it is grain-supporting structure in non-tropical carbonate. There is little Mg-calcite or aragonite cementation in early stage diagenesis of non-tropical carbonate. Because the cementation is mainly in deep burial environments, the non-tropical carbonate system with abundant carbonate bioclasts accumulation can preserve plenty of high-quality intra-grain pores and inter-grain pores, which might be the new field of future petroleum exploration. The appearance of the concept non-tropical carbonate has significant influence on lithofacies paleogeography analysis. If the modern non-tropical carbonate study, paleontological material and paleo-ocean water study were applied into the ancient carbonate study, the present paleo-latitude division might be greatly changed.