3. Autoclastic chert
General Atlantic, Tjaden 1A1 WIW # 1, 4346 ft, autoclastic chert breccia with mottled oil staining and fractures. Scale is 2 cm. Upper photomicrographs, 4331 ft, shelter porosity. Lower, 4331.5 ft, boundary between interpenetrating clasts of highly porous chat. Boundaries defined by “dirty” clay rim. Interior of clasts contain varying amounts of microcrystalline quartz and associated fine vuggy and moldic porosity. Scale bars are 0.1 mm. Plane polarized light and blue epoxy impregnation.