山东省中部上寒武统碳酸盐风暴沉积的综合模式

Integrative Depositional Model for Carbonate Tempestites in Upper Cambrian,Central Shandong Province

我国的碳酸盐风暴岩丰富多样,但前人对不同环境风暴岩的沉积作用、沉积序列和沉积模式的总结还不够完善.山东省中部上寒武统炒米店组碳酸盐风暴岩发育频繁,分布广,提供了全面分析风暴沉积作用的理想场所.基于该区详实的露头观察,可识别出冲刷面、渠模、丘状交错层理等典型的风暴沉积构造,以及砾屑灰岩、递变层理含砾砂屑灰岩-砂屑灰岩、纹层状粉-砂屑灰岩等风暴岩类型.根据砾屑颜色、磨圆度、排列方式、支撑结构、充填物等岩石学特征,研究区首要发育的砾屑灰岩可被细分为紧密堆积棱角状砾屑灰岩、基质支撑砾屑灰岩、砂屑支撑砾屑灰岩、水平-叠瓦状砾屑灰岩和放射状排列砾屑灰岩5种岩相类型,其分别归属于台前缓坡带原地-近源堆积、碎屑流、高密度-低密度浊流、风暴砾滩和风暴涡流沉积.对台前缓坡、台地边缘和开阔台地等不同环境的风暴沉积序列进行了归纳,建立了缓坡型碳酸盐台地风暴沉积的综合模式,并指出研究区频繁的风暴作用与全球气候变暖、海平面上升以及地震活动存在密切联系.研究表明较多台地边缘发育的大型渠模构造,其充填砾屑呈放射状排列,指示了渠模的风暴涡流成因.

Depositional processes, successions and models for various carbonate tempestites in different environments should be well documented in our country. The carbonate tempestites are frequently and widely developed in the Chaomidian Formation of the Upper Cambrian, central Shandong Province, providing an area favorable to comprehensively realize storm depositional processes. On the basis of outcrop observations in detail, typical storm sedimentary structures including scouring surface, gutter cast and hummocky cross-bedding, and tempestites including calcirudite, graded gravelly calcarenite, laminated calcisiltite and calcarenite were identified. Specially, according to petrologic features such as color, psephicity and arrangement mode of gravel and support fabric, the dominant calcirudites are classified as five sorts of lithofacies, including angular tightly-stacked calcirudite, matrix-supported calcirudite, sand-supported calcirudite, horizontal to imbricate calcirudite and radially-arranged calcirudite, which were attributed to autochthonous to near-sourced deposits at a fore-platform ramp, debris flow deposits, high-density to low-density turbidites, storm gravel beach deposits and storm vortex deposits respectively. Furthermore, storm depositional successes in the various environments of fore-platform ramp, platform margin and open platform were summarized, and an integrative depositional model for carbonate tempestites at the background of ramp platform was built up, Finally, the frequent tempestites were ascribed to warm climate, a sea-level rise and earthquakes. Significantly, many gutter casts occurred at the platform margin, and were commonly filled with radiate gravels indicative of storm vortex processes. Additionally, the integrative model is use{ul to illttminate various storm processes.