Sedimentary rocks are laid down in layers called beds or strata. Typically this will involve a cover of sandstone overlying limestone strata undergoing solution. The floors inside are visible from the exterior like geological strata. Some of the later Permian limestone strata are rich in well-preserved fossils. This goaf collapses under the weight of the overlying strata. The geology consists of the Proterozoic, Cenozoic, and Paleozoic strata and Mesozoic intrusive granite. They lie upon an angular unconformity which cuts across pre-basin strata. Most linguists today refer to these remnants as dialectal strata or substrata. Many of the stones are carved including those of residences belonging to various social strata. Emigration focused mainly on the lower strata of society who abandoned the countryside. The poorest strata of Cambodian society benefited from these reforms. Marriage across social strata and caste lines has been taboo, states Saskia Brand. Age did not matter with victimization crossing the generational strata entirely. Lexical influences cut across the different social strata of Chile. It consists of two strata, superficial and deep.