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

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 useful to illuminate various storm processes.