4. CONTINUOUS SEDIMENTARY SEQUENCES FROM THE EASTERN MEDITERRANEAN SEA: COMPOSITE DEPTH SECTIONS1Tatsuhiko Sakamoto,2 Thomas Janecek,3 and Kay-Christian Emeis4 |
ABSTRACTWe have developed revised postcruise composite depth sections over the ~100-m-long, Pliocene–Holocene sediment sequences at four paleoceanographic sites (Site 964: Ionian Basin; Sites 966 and 967: Eratosthenes Seamount; Site 969: Mediterranean Ridge), which are located in different tectonic and oceanographic settings and water depths in the Eastern Mediterranean Sea. These revised composite sections were constructed using correlation intervals of a few centimeters instead of the 1- to 10-m intervals used in the shipboard composite construction procedure. These revised composite depth sections now take into account differential stretching and squeezing within a core and correct depth differences between holes caused by coring artifact and tectonic disturbances that resulted in attenuated and incomplete sections. The revised composite depth sections were constructed by combining digitized color images of split cores, visual core descriptions from shipboard operations, and color reflectance measurements with a 2-cm sampling resolution. The detailed revised depth sequences not only enable us to correlate sapropels between holes, but also other lithofacies, such as pale nannofossil oozes, reddish oozes, dark clays, and ash layers. Depending on the location of the drill site, over 80 individual sapropels are recognized in the revised composite depth sections. During Leg 160, use of the advanced piston coring system on the JOIDES Resolution typically resulted in an average gap between cores of 1-2 m, with a maximum of 8 m. Gaps within cores, resulting from faulting, slumping, or mass flows, also averaged 1-2 m in length. These revised composite depth sections can be used as starting points for the development of high-resolution time scales and paleoceanographic time series in the Mediterranean. |
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