灾变事件地层斜坡滑塌(带)堆积的特征——以滇西保山地区上三叠统南梳坝组为例

Catastrophic event characteristics of stratigraphic slope slumping accumulation: a case study of the Upper Triassic Nanshuba Formation in Baoshan area,western Yunnan Province

保山地块保山地区三叠系上统南梳坝组研究程度较差,以往的资料多侧重于岩石地层、生物地层的研究,沉积环境资料甚少。通过1∶5万保山幅等8幅区域地质调查,在南梳坝组中发现了灰岩滑塌岩块、下超面、饥饿沉积、水道砾岩、粒序层理、复理石韵律及槽模、沟模等一系列非常重要的沉积相资料,认为其沉积环境为斜坡-盆地环境,总体为一套浊积岩,其中的同沉积"褶皱"、同沉积断层、大量的滑塌面、各种类型的滑塌褶皱组成了3条较大规模的滑塌带,是斜坡环境的沉积物在地震作用触发下形成的,剖面结构"不合理",明显具有灾变事件地层的特征。灰岩滑塌岩块有极浓的油气味,显示出生储存油气的良好环境。因此,重塑三叠系上统南梳坝组的古地理环境,不仅对发展沉积学、地层学有重要意义,而且对于寻找烃源岩也有重要的现实意义。

Researches on Upper Triassic Nanshuba Formation（T3n） in Baoshan area of Baoshan block are very insufficient.In the 1∶50000 Baoshan sheet,the 1∶200000 Fengqin sheet and the 1∶250000 Dali City sheet have been completed,which,however,mainly lay emphasis on the study of rock-strata and biostratigraphy.The data of the sedimentary environment are very few.Through regional geological survey of 1∶50000 Baoshan sheet and other seven sheets,the authors found a series of very important data of sedimentary facies,such as limestone slumping rock-block,downlap surface,hunger deposition,channel conglomerate,graded bedding,flysch rhythm and flute cast and groove cast at the upper Triassic Nanshuba Formation in Baoshan area.The authors hold that the sedimentary environment is a slope-basin environment.On the whole,that exist a set of turbidites,which include contemporaneous folds,contemporaneous faults,large amounts of slumping surfaces,various types of slumping fold,which constitute three relatively large-scale slumping zones.The stratigraphic characteristics of the sediments were formed by the triggering of earthquakes in a slope environment,and the profile structure is unreasonable,suggesting obviously a catastrophic event.In the limestone slump,rock block has strong hydrocarbon flavor,implying a good environment for oil generation and storage.Therefore,the restoration of the geographic environment of Upper Triassic Nanshuba Formation not only has very important significance for the development of sedimentology and stratigraphy but also is of remarkable practical importance in search for hydrocarbon source rocks.