Petrographic Characterization and Maceral Controls on Porosity in Overmature Marine Shales: Examples from Ordovician-Silurian Shales in China and the U.S.

Figure 4

(a) Photomicrographs of groundmass pyrobitumen in Wufeng-Longmaxi shale samples under a microscope in incident white light under oil immersion. (b) Scanning electron microscopy (SEM) of the pyrobitumen disseminated in the shale matrix in the same area as (a). (c, d) Pyrobitumen accumulated in interparticle pores and microfractures. (e, f) Pyrobitumen filling the mineral outline. Zooclast and pyrobitumen distributing along the shale matrix. (g, h) Single large pyrobitumen particle of several micrometers in diameter. The larger rectangles in (i, j) are enlarged areas of the related smaller rectangles. This type of pyrobitumen consists of bacteria-like aggregates.

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