paleogene middle britannica eocene paleogeography basins tertiary neogene
phanerozoic eras scale time mesozoic geological paleozoic cenozoic eon into divided three eons which life units longest
alluvial illustrates geomorphic drainages faults
pleistocene hominin phylogeny plio generalized homo characterized
given geological vertebrates evolutionary representation diagrammatic periods correct
pleistocene figure pliocene stratigraphic record california basin mecca andreas deformation evolution fault