Time Series Analysis of Recent (1 kyr) euxinic sediments of the Black Sea: A case study
Duliu, Octavian G.; Oaie, Gheorghe; Preoteasa, Florentin
published: Nov 1, 2013
ArtNo. ESP155027002003, Price: 29.00 €
A 0.5 m core of unconsolidated Holocene sediments was collected at a depth of 600 m on the slope of the Western Continental Platform of the Black Sea, offshore from the city of Constantza (Romania). The sediments, belonging to the so-called Lithological Unit I, were deposited under euxinic conditions. A high resolution computed tomography scan evidenced the presence of c. 250 coupled laminae which comprise interlaminated coccolithic ooze and fine argillaceous silt (subsequently confirmed by mineralogical analysis), whose maximum age, previously determined by 137Cs and 210Pb was 940 y BP. A longitudinal gray-scale tomographic image was converted into a corresponding time series consisting of 3500 equally spaced intervals. Further Time Series as well as Wavelet Analysis, revealed the presence of additional sedimentary cycles, whose periods varied between 7 and 350 y, reflecting both regional climate changes and large scale drivers such as the North Atlantic Oscillation. Moreover, the lamina pattern showed a significant increase in high frequencies between c, 1600 and 1800 AD, which could be ascribed to the end of the European Little Ice Age as well as to the onset of industrialization in Western Europe. Fractal Analysis of the time series gave a Hurst exponent equal to 0.8, indicating that the laminar structure represents a “memory effect” which could be considered as reflecting the external influences on the depositional processes for this sedimentary succession.