Microanalytical study of an archived marine core from late Pleistocene submerged site GNL Quintero 1 (GNLQ1), Central Chile

This pilot study explores the use of micromorphology and automated mineral analysis to investigate the archived sedimentary record within a 73 cm long core collected from site GNL Quintero 1 (GNLQ1), a submerged (at −13 m) Late Pleistocene landscape located nearshore in Quintero Bay (32°S), Central Chile. Samples from the transported and untransported core half were analysed, with the former showing some homogenisation of sediments. Core T1 comprises four lithological units that have previously been interpreted to represent a transition from floodplain to freshwater lagoon, swamp and then marine depositional environment. Micromorphological and quantitative mineral analysis, using TESCAN Integrated Mineral Analysis (TIMA) broadly confirm this interpretation, and indicate a change from a quartz-rich assemblage, to a more ferruginous-dominated, and then siliciclastic assemblage. Several green mineral phases were identified by combining TIMA and petrology, including amphiboles, pyroxenes/clinopyroxenes, tourmaline and the phyllosilicates glauconite and chlorite. The latter, along with barite, occur as trace authigenic phases within the sediments and reflect late-stage marine influence. Trace micro-bone fragments exist throughout the profile, and despite evident localised reworking by burrowing bivalve Pholadidae, the macro-bones remain largely intact. The micro-analytical data provide useful baseline data to help correlate facies across Quintero Bay and map out the spatial extent of this unique inundated landscape.