In the case of mudstone to be a source rock, the uncompacted mudstone would have a strong capability of hydrocarbon concentation sealing to seal gas in diffusive phase.
And the boundary of them has the same lithologic character: the ravinement surface of river course or exposure mudstone of flooding plain and root clay.
Nonsandstone reservoirs between salt beds of Qianjiang Formation in the Qianjiang Sag of the Jianghan Basin are mainly composed of dolomicrite,glauberite rock,mudstone and their peperite.
You're searching for fossils in the Harrison Formation -- a big swath of siltstone, sandstone, and volcanic ash dating back to the Miocene Epoch some 22 million years ago.
In this quarry, the dinosaurs are being found in something called mudstone, silt stone or a shale and these rocks are very fine grained and they represent quiet water environments.