泌阳凹陷南部陡坡带核桃园组沉积体系研究

对泌阳凹陷南部陡坡带古近系核桃园组砂层组沉积体系进行了研究,认为研究区核桃园组属扇三角洲-湖泊沉积体系。根据沉积环境和沉积物特征可划分为扇三角洲平原、扇三角洲前缘及前扇三角洲亚相,以三角洲前缘亚相为沉积主体。湖泊沉积体系可分为浅湖亚相、半深湖、深湖亚相。沉积物主要来源于平氏、杨桥南部。     

大民屯凹陷古近系沙河街组三段扇三角洲前缘沉积生物扰动特征

为探究陆相扇三角洲前缘沉积生物扰动特征,以辽河拗陷大民屯凹陷沈检5井古近系沙河街组三段扇三角洲前缘沉积岩芯为研究对象,对生物遗迹化石进行了鉴定,统计了垂向剖面上生物扰动层厚度和扰动指数的分布特征.依据主微量元素参数反映的沉积条件,探讨了生物扰动层厚度和扰动指数与沉积环境的响应关系.研究结果表明,沈检5井S34Ⅱ和S34...     

Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation,Gwalior Group,central India

The ∼20 m thick coarse-grained clastic succession in the basal part of Palaeoproterozoic Par Formation, Gwalior Group has been investigated using process-based sedimentology and deductive palaeohydraulics. Bounded between granitic basement at its base and shallow marine succession at the top, the studied stratigraphic interval represents products of an alluvial fan and its strike-wise co-existent braided river system that possibly acted as a tributary for the fan. Detailed facies, facies association analysis allowed identification of two anatomical parts for the fan system viz. proximal and mid fan. While thin proximal fan is represented by products of rock avalanche and hyperconcentrated flows with widely varying rheology, the mid fan is represented by products of sheet floods and flows within streamlets. The interpretation found support from palaeoslope estimation carried out on the fluvial part of the mid fan that plot dominantly within the alluvial fan field demarcated by Blair and McPherson (1994). Dry climatic condition suggested from dominance of stream flow over mass flow deposition within the Par alluvial fan. Strike-wise, the fan is discontinuous and juxtaposed with a braid plain system. In contrast to the fluvial part of fan system, the palaeoslope data from the braid plain system dominantly plot within the ‘natural depositional gap’ defined by Blair and McPherson. A raised palaeoslope for the river systems, as suggested from Proterozoic braid plain deposits around the Globe, is found valid for the Par braid plain system as well. From preponderance of granular and sandy sediments within the alluvial fan and braid plain systems and a pervasive north-westward palaeocurrent pattern within the fluvial systems the present study infers a gently sloping bevelled source area in the south-southeast of the basin with occurrence of steep cliffs only locally.