We studied the shale deposited during the Late Ordovician-Early Silurian in Upper and Middle Yangtze regions to investigate the link between paleogeographic evolution and marine shale deposition in southern China.The graptolite-bearing shales from 24 shale gas wells that can be used to stratigraphic division are the focus of the study.Combined with the outcrop data from the GBDB database and previous data

we proposed the classification scheme in the facies-sub-fa- cies-micro-facies sequence

that is three sedimentary facies(continental shelf

tidal-flat and delta)

including eight sub-facies and several micro-facies

according to the characteristics of sediments

sedimentary setting

geo-chemical parameters and logging data.It’s made certain that during the Late Ordovician-Early Silurian

the Upper and Middle Yangtze regions were in a restricted low-energy epicontinental shallow sea environment surrounded by paleo-uplifts

and the favorable se-dimentary facies zones for shale reservoirs therein were the restricted deep shelf facies.The lithofacies paleogeographic framework of the Katian

Hirnantian

Rhuddanian

Aeronian stages in a row for the study area was reconstructed by taking the sedimentary facies profile/wells covering the whole region as controlling points

employing the “favorable facies” approach and taking chronostratigraphic “stage” as the research unit

and thus the boundaries of paleo-uplifts during va- rious stages can be predicted effectively.The thicknesses of graptolite-bearing shale intervals were accurately measured by taking the “stage” as the ruler

and the temporal-spatial distribution of sedimentary systems and shale distribution pattern in each stage were summarized.The results suggest that the distribution of black shales is controlled by global sea-level rise

regional tectonic movement and plaeogeographic framework

while the thickness of black shales is apparently controlled by the pattern of alternating uplifts and depressions.The depositional model is a type of “one depression entrapped by two uplifts”

with the shale gas enrichment area located within the depression restricted by two uplifts on both sides.Graptolite-bearing shale intervals are absent to various extents at the regions near the uplifts.Such regions as well as uplifts should therefore be undesirable in terms of shale gas exploration and development.