Analysing the origin of the Upper Cretaceous–?Lower Tertiary Rio Capim semi flint (Pará State, Brazil) under a sedimentologic perspective

摘要: Abstract The Rio Capim kaolin, one of the largest kaolin reserves in world currently under exploration, is typified by a lower and an upper unit represented soft, well-structured semi-flint respectively, latter term been applied here for flint-like fire clay consisting indurated kaolinite, which develops no plasticity when ground up. characterized its elevated hardness massive nature, has preliminarily attributed to stronger weathering relative underlying soft kaolin. Despite overall aspect, detailed sedimentologic investigation freshly exposed sections along open mines revealed variety structures that are primary sedimentary features. features include channel like forms having distinct lags quartz sandstones at their bottoms. These deposits intergrade with strata displaying series inclined lines, defining lobed bodies locally highlighted distinctively mud layers. lobes internally truncated undulating surfaces wave erosion. described this work related deposition either distributary channels mouth bar or tidal inlet delta areas associated deltaic wave-dominated estuarine settings, respectively. recognition these large implications analyze composition, must have primarily included sand grain sizes, least case strata. apparent muddy nature might be due, part, post depositional modification sandy composed most likely grains previously formed kaolinite derived from reworking unit.