摘要
通过对依舒地堑汤原断陷古近系的岩芯观察和描述,结合测井和粒度分析,发现研究区存在湖底扇沉积。依据岩石岩性、沉积构造、垂向组合,将湖底扇划分为内扇、中扇和外扇。内扇主要发育碎屑流(水下泥石流);中扇以颗粒流和浊流最为常见;外扇发育远源浊积岩。在三级层序中湖底扇沉积体系有两类组合形式:①退积型:即内扇→中扇→外扇,反映了一个从进积型到退积型准层序组的叠加方式,揭示了从低水位体系域到水进体系域变化趋势;②进积型:外扇→中扇→内扇,反映了一个从加积型到进积型准层序组的叠加方式,揭示了从高水位体系域到水退体系域变化趋势。湖底扇主要发育于低水位体系域和水退体系域。
Sublacustrine fan is found in Tangyuan fault depression of Yishu Oraben under the observation and description of cores, borehole log and grading analysis. Based on the lithology, sedimentary structure and the vertical sequence, the sublacustrine fan is divided into inner- ,middle- and outer fans. The debris flow developed in the inner fan. The grain flow and turbidite flow are common in the middle fan. The turbidite rocks are found in the outer fan. In three-grade sequence,the sublacuslrine fan is divided as two types： （1）. retrogradational type （ inner fan →middle fan→ outer fan）, showing a stacking pattern of the parasequence sets from progradation to retrogradation, and reflecting the change from lowstand system tract （LST） to transgressive system tract （TST） （2） progradational type （outer fan → middle fan→ inner fan）, showing a stacking pattern of the parasequence sets from aggradation to progradationand, reflecting the change from highstand system tract （HST） to resgressive system tract （RST） .The sublacustrine fan developed mainly in the lowstand system tract （LST） and resgressive system tract （RST）.
出处
《世界地质》
CAS
CSCD
2006年第1期23-28,共6页
World Geology
基金
国家油气专项(XQ-2004-07)
关键词
湖底扇
沉积
层序
汤原断陷
sub lacustrine fan
sedimentary
sequence
Tangyuan fault depression
