4. Nodular-bedded chert
General Atlantic, Tjaden 1A1 WIW # 1, 4379 ft, nodules of chat in overpacked fabric with interpenetrating clasts. Variable brown oil staining identify separate clasts and associated relative differences in microporosity. Individual clasts show variations in staining along discontinuous fracturing. Scale is 2 cm. Photomicrograph from 4379.5 ft from within a chat nodule containing micro-, moldic, and vuggy porosity. Some micritic calcite preserved stained with alizarin-red. Scale bar is 0.1 mm.