北海马里福斯盆地东部晚侏罗世深水重力流沉积特征及沉积序列

Depositional characteristics and sedimentary sequence of Late Jurassic deep-water gravity flows in Eastern Moray Firth Basin,North Sea

通过大量岩心观察,钻测井资料分析,结合重力流沉积理论,对北海马里福斯盆地北东地区上侏罗统深水重力流沉积特征、沉积过程、沉积模式进行了系统分析。研究表明,研究区重力流沉积可以分为砾质碎屑流沉积、砂质碎屑流沉积、泥质碎屑流沉积、浊流和二次滑塌沉积等,其中块状砂质碎屑流沉积最发育。根据重力流沉积过程中,不同期次的不同流态或相同流态沉积物垂向相互叠加模式,建立了3种深水重力流沉积垂向序列;不同沉积序列对应不同沉积环境和沉积模式,以碎屑流沉积为主的沉积序列常见于限制性水道,碎屑流为主、频繁夹杂浊流的沉积序列多发育于弱限制性水道,浊流和底流互层的沉积序列则常见于末端朵叶复合体内。

Through a large number of core observations,drilling/logging data analysis,and combined with gravity flow deposition theory,a systematic analysis was carried out on the aspects of depositional characteristics,depositional processes,and sedimentary modes of the Upper Jurassic deep-water gravity flow in the northeastern Moray Firth Basin,North Sea.Research shows that the gravity flow deposits in the study area can be divided into gravel debris flow deposition,sandy debris flow deposition,argillaceous debris flow deposition,turbidity current and the secondary slumping deposition.Among them,massive sandy debris flow deposition is the most developed one.According to the vertical superposition mode of different or identical flow regimes in different stages during the gravity flow depositions,three vertical sequences of deep-water gravity flow deposition have been established;different deposition sequences correspond to their unique depositional environments and depositional modes.Sedimentary sequences dominated by debris flow deposition are often found in restricted channels,sedimentary sequences dominated by debris flow and frequently interbedded with turbidity currents are mostly developed in weakly restricted channels,and sedimentary sequences composed of turbidity currents and undercurrent interbeds are commonly observed in the distal lobe complex.