Foraminifera and ostracods from the Carrizal Bajo coastal wetland (southern Atacama Desert). Applications to recent Quaternary palaeoenvironmental reconstruction

Abstract

This work analyzes the texture and meiofauna (foraminifera and ostracods) of recent sediments from Carrizal Bajo (southern Atacama Desert, northern Chile). A transect carried out from the infralittoral zone to the inner margin of an active wetland has made it possible to differentiate sectors based on the distribution and abundance of these faunal groups. The shallow marine areas (sector 1) are composed of bioclastic sandy sediments extremely rich in foraminifera and ostracods, which contrasts with the marked scarcity or absence of these groups in the adjacent intertidal-supratidal zones and washover fans (sector 2). Scarce resedimented shells of ostracods and the gastropod Heleobia copiapoensis copiapoensis characterize the bottom of the lagoon (sector 3), a hostile environment for the groups studied due to an intermittent anoxic environment and frequent changes in salinity. The inner margin of the wetland (sector 4) has a rich freshwater meiofauna in the vicinity of springs, as well as a surprising record of resedimented marine foraminifera 600 m inland. These results can be applied in future researches related to the environmental degradation of these systems, the reconstruction of paleoenvironments in recent Quaternary deposits or the identification of Holocene tsunamigenic layers along this coastline.