TIME-SERIES STATISTICAL ANALYSIS OF BAINBRIDGE CRATER LAKE SEDIMENT RECORD OF EL NIÑO/SOUTHERN OSCILLATION EVENTS

The gray-scale intensity data of finely-laminated sediments from Lake Bainbridge Crater, Galápagos, and laminae thickness data were subjected to time series analysis. The sediment record preserved in this volcanic maar provides a continuous history of past El Niño/Southern Oscillation (ENSO) events over the last 6200 years. Gray-scale intensity data from analyses of x-radiography images of a 4.1 m long core from this basin were divided into two parts: the more recent part of stratigraphic sequence, which was deposited since 3000 yr BP; and the earlier part of record between 6200 and 3000 yr BP. After this the linear sedimentary rate may be considered approximately constant. A periodicity in 600 years was established for both parts of gray-scale intensity data. Considering the laminae thickness data as a function of the ordering number of laminae periodicity in 12th laminae was found. This means that the characteristics of 12th laminae, such as thickness (0.52 cm) and the number of the year for its forming (6 years) are repeated in each 12th laminae.