rocks, age, period, time, strata, limestones, limestone, sediments, times, system, beds, fossils, formations, trilobites, shales, silurian, deposits, sequence, boundary, faunas, fauna, seas, radiation, succession, conodonts, sandstones, slates, graptolites, extinction, sea, brachiopods, shale, stratigraphy, devonian, formation, forms, carbonates, permian, sandstone, aquifer, lower, species, sequences, series, dolomite, rock, event, sedimentation, communities, genera, dolomites, radiations, upper, cephalopods, margin, bentonites, genus, paleogeography, onwards, arc, units, volcanics, corals, quartzite, basin, zones, vertebrates, algae, greywackes, outcrops, reefs, bedrock, successions, slate, bryozoans, lavas, pelecypods, facies, trilobite, provinces, erratics, gastropods, geology, outcrop, palaeogeography, geography, transgression, era, extinctions, record, volcanism, glaciation, contact, schists

late, early, cambro, middle, lower, cambrian, upper, latest, mid, earliest, uppermost, pre, later, basal, lowermost, lowest, post, fossiliferous, earlier, folded, typical, norwegian, end, upturned, marine, medial, deformed, probable, regional, terminal, subsurface, sinian, eroded