Sedimentological and geochemical characteristics of recent sediments from Paracas Bay, Pisco (2013, 2014, and 2015)

Abstract

During 2013, 2014, and 2015, we analyzed the sedimentological and geochemical characteristics of recent marine surface sediments from Paracas Bay, as part of the projects “Integrated Study of the Dynamics of Physical and Biogeochemical Processes in Coastal Edge Ecosystems” and “Global Environment Facility”. At Paracas Bay, recent sediments correspond to clayey silt, silty clay, and sandy silt textures, which are associated with low current intensities. The sandy sediments were recorded near the coastline and the mouth of the Pisco River, the presence of gravel is very scarce (<1%) found north of the river. The current and waves increase in the coastal area, transporting finer material to places where the current is lower. The highest values of total organic matter correspond to the fine fraction made up of silt and clay, which is conditioned by the contribution of biogenic material related to the high biological productivity in the water column, and also by the presence of very fine particles of urban and industrial waste, which are incorporated to the bottom by transport and sedimentation processes. The greatest variation was found in the southern part of the bay between Puntilla and El Chaco, with values ranging from 12.21 to 17.80%; while the lowest total organic matter contents are associated with sediments dominated by the sand fraction and were found north of the Pisco River, with values of 3.16 to 3.21%, corresponding to evaluations conducted in spring 2014 and winter 2015. The inner bay is occasionally affected by anthropogenic pollutants due to north winds and southward marine circulation.