Related by context. Frequent words. (Click for all words.) 64 Carboniferous 60 Paleocene 58 Late Cretaceous 57 Precambrian 56 stromatolites 56 Lower Cretaceous 56 Pliocene 56 Cretaceous 56 Eocene 56 Jurassic Period 55 Silurian 55 depositional 55 Burgess Shale 55 Mesolithic 55 marine sediments 54 igneous rock 54 Palaeolithic 54 microfossils 54 midden 53 lavas 53 Ordovician 53 hydrothermal vent 53 middens 53 Devonian 52 Namib Desert 52 Cretaceous Period 52 alluvial deposits 52 sandstone 52 ironstone 52 sediments 52 ammonites 52 inter tidal 51 continental crust 51 basaltic 51 sedimentary rock 51 magmas 51 Upper Cretaceous 51 neolithic 51 embayment 51 relict 51 Mesozoic 50 fossil 50 calcareous 50 moraines 50 faunal 50 surficial 50 carbonate rocks 50 Triassic 50 oceanic crust 50 radiocarbon dated 50 Jurassic 50 Oligocene 50 fossils 49 trilobites 49 silts 49 graben 49 lineaments 49 stalactite 49 haematite 49 Geologically 49 sandstone formations 49 fossilization 49 Paleozoic 49 basalts 49 mudstone 49 Proterozoic 49 basalt 49 lake sediments 49 limestones 49 alluvium 49 abiotic 49 igneous rocks 49 limestone 48 gravels 48 escarpments 48 mudflat 48 clasts 48 temperate forests 48 lava tubes 48 kerogen 48 isotopic composition 48 snail shells 48 barrens 48 geological formations 48 moorlands 48 preindustrial 48 Lake Vostok 48 grassy plains 48 massive sulphide deposit 48 Quaternary 48 Pleistocene 48 igneous 48 prehistoric 48 carbonaceous 48 geologically 48 ocher 48 salt crystals 47 bauxite deposits 47 aridity 47 biogenic 47 siliceous