Abstract:

Based on paleogeography and tectonic settings, strata spatial distribution characteristics, basic geochemistry indexes and
mineral composition, we compared lower part of Lower Silurian Gaojiabian Formation of Lower Yangtze area and middle Devonian
Marcellus Formation in the Appalachian basin. The results show that the two sets of shales shared similar paleogeography and tectonic
settings, both accumulated in tranquil anoxic basinal waters and their euxinic depositional site allowed the preservation of the finely
organic detritus. The stratigraphy and thickness trends of both formations reflect the interplay of tectonism during the formation time
and the later stage. These events shaped the stratigraphic architecture of both formations and can impact the exploration and production
strategies of shale gas. Both formations are considered to be good source rocks for the exploration of shale gas and they both have high

thermal maturity and contain relatively high total organic carbon (TOC) content, as well as large amount of brittle minerals. Compared
with Marcellus shale, Gaojiabian Formation contains less TOC content, has a deeper burial depth burial depth and has been reworked
by multicycle tectonism, which bring higher risks for the exploration of shale gas.

Key words: Lower Yangtze area, Lower Silurian, Appalachian basin, Marcellus shale, shale gas