PALEOCLIMATIC SIGNALS IN THE QUATERNARY SEDIMENTS IN LAKE IZABAL, GUATEMALA, CENTRAL AMERICA

Lake sediments may record high-frequency paleoclimatic signals reflecting marine and terrestrial interactions. Lake Izabal is 672 sq. km, located in eastern Guatemala on the eastern slope of the Cordilleran. Currently, it is shallow with a maximum depth of 15 m, polymictic, hydrologically open, and connected to Amatique Bay of the Caribbean Sea via the Dulce River. It has developed in a pull-apart basin along the northern margin of the Caribbean Plate since Miocene. An 80-cm segment of a sediment core from depth 578-657 cm at the east part of the lake contains sub-mm-to-mm laminae composed of organic-rich and -poor couplets; dark organic-rich and light organic-poor laminae are 0.1-0.98 and 0.1-0.85 mm thick, respectively. The gray scale of the sediments reflects relative concentration of organic matter, with dark laminae interpreted to represent periods of high riverine influx. Current age model based on three radiocarbon dates constrains the age of the segment to 5627-6757 years BP with a total duration of 1130 years. The gray-scale series was subject to spectral analysis using a wavelet-transform algorithm. The analysis was performed for the entire segment and 10 subsections, each of which is ~15 cm thick and overlaps with adjacent subsections at half length. The spectrogram of the whole segment shows peaks with periods of 30, 100, 330, and 1250 years. The spectrograms of the subsections show higher-frequency peaks with periods ranging from 10 to 140 years, with the 12 and 30-year peaks as the most prominent. However, the 330 and 1250-year peaks are not present in the spectrograms of the subsections. The periods of all peaks on the spectrograms of subsections and the entire section are generally persistent with small variations, indicating persistent signals in the record. Similar to other precipitation records from Central America, the dominance of specific peaks in the spectra highlights a significant role of sea-surface temperature fluctuations on precipitation in the region. The 30-year peak may reflect a potential connection to the Atlantic Multidecadal Oscillation and the 12-year peak to El Niño Southern Oscillation. Future improved chronological constraints will allow more accurate assessment of the paleoclimatic signals and their causes in the Lake Izabal record to reconstruct the paleoclimatic evolution in the region.