【摘要】 东濮凹陷下第三系沙三段发育风暴沉积,主要特征有:(1)具重力流沉积特征的变形构造;(2)反映风暴作用的丘状交错层理、冲刷-充填构造(渠模)、浪成沙纹层理、和震荡波痕;(3)与风浪作用相关的生物活动,包括潜穴、钻孔和生物逃逸现象;(4)可与海相风暴岩对比的“似鲍马层序”以及(5)多变的砂层顶面形态。根据风暴砂层的性质,可将风暴岩系划分为三个微相:(1)水道充填沉积;(2)漫溢沉积微相;(3)末稍沉积微相。更多还原

【Abstract】 Storm deposits are well-developed in the Shasan Member of Oligocene in Dongpu Depression. The lacustrine tempestites have many sedimentary features. (1) Pene-contemporaneous deformation structures are well-developed including load structures, ball-and-pillow structures, flame structures, clastic dykes, concolute beddings, etc, The formation of these structures is related to sediment liquefaction and drai- nage, reflecting the characteristics of gravity flows. (2) Scour-and fill structures are conspicuous and they can be divided into two types, sand-filled scours and themud-filled ones cut into sands. The erossional structures, especially the mud-filled scours, seem to be uncommon in turbidite facies. They are the evidence of storm activity. (3) Sandstone tops of Bouma-like sequeces often disply oscillatory ripples. Parting lineations are often found in the parallel lamination sandstones. (4) Hummocky crosss-tratifications are characterized by gently curved, lowangle cross-lamination. Most researchers have specifically inferred their origin results from powerful oscillatory dominant or multidirectional flows. Despite uncertainty regarding the dynamics of formation, hummocky cross-stratification is now regarded as the best indicator of a storm influence in ancient sedimentary sequences. The absence of tidal currents in the lake greatly enhanced the potential for preservation of hummocfcy cross-stratification. (5) Biogenetic sedimentary structures are distinct. Storm activity may have mixed oxygen-rich surface water with stagnant basin water so as to provide more favorable conditions for development of benthic communities. After the storm is over, the sediment surface is then populated by burrowing infauna. The presence of escape burrows reflects a quick depositional event.The sedimentary sequences of the storm sand layers can be compared with Bouma Sequence, but they display more variable sand-stone tops. There are five principal types: (a) sandstone tops modified by subsequent organic reworking; (b) wave-rippled sand-stone tops; (c) sandstone tops displaying mud-filled scours; (d)sandstone tops displaying starved ripples; and (e) sharp sandstone tops.The storm layers vary between proximal and distal types: (a) channel-filled deposits, consisting of massive sandstones; (b) interchannel deposits with complete Sb-Se sequeccesf and (c) distal deposits, mainly consisting of thin silt beds with Sc-e, Sde. Based on single-well microfacies analysis and comparison of well-to-well correlations as well as their paleostructures, paleoclimaes, sources and nature of sand layers, a facies model is presented.更多还原