Dating sediments in Pearl cays, Pearl lagoon, South Caribbean of Nicaragua, using additional techniques to 210Pb

Abstract

This report presents the historical reconstruction of a sediment profile for the 150 years approximately, collected in July 2016 in Pearl cays (Pearl lagoon, South Caribbean of Nicaragua) and the sedimentation and sediment accumulation rates were estimated using the nuclear technique ²¹⁰Pb. The Buttonwood NIC II sedimentary profile was dominated by the silt fraction and exceeded 50% of the particles, followed by clay (19% - 27%) and sand (7% - 24%). According to the grain size and its distribution, the sediment profile presented the silty loam texture. Magnetic susceptibility values registered variations with respect to depth, observing five different drastic changes in the quality of sediment particles deposited at depths of 5,5 cm, 11,0 cm, 17,5 cm, 18,5 cm and 28,5 cm. The age of the different sections of the sediment profile was carried out with the constant flow method (CRS) and ranged from 2,14 to 130,1 years, recording the history of the last 128 years. The results in the sedimentation rate ranged from 0,022 to 0,725 cm.year^-1 between 2014 - 1886; abrupt changes were observed from 1965. The sediment accumulation rate varied between 0,016 to 0,308 g.cm^-2.year^-1 between 2014 - 1886 showing an increase from 1970, suggesting that these changes are related to various factors such as population increase and the influence of natural phenomena (hurricanes and tropical storms).