BIOSTRATIGRAPHICAL ANALYSIS FOR SUPERFICIAL SAMPLES FROM THE SHINKAI 6500, STUDY OF THE SOUTHERN MARIANA FOREARC

The retrieval of samples from the ocean floor in the studied area 11º 35'N, 143º5'E to 13º20'N, 145º10'E., occurred during the summer of 2008, as part of the YK08-08 Leg 2 Cruise. It was supported by the Japan Agency for Marine-Earth Science and Technology. The submersible Shinkai 6500 dives were designed to observe and collect a suite of igneous rocks associated with what could be termed a “supra-subduction zone ophiolite” along the forearc south and east of Guam. It formed during the initiation of the subduction. The main scope of the expedition was to study and collect material associated with igneous processes. However in order to provide biostratigraphic control a total of nine sedimentary samples were collected during four dives at depths ranging from 2,300 to 5,830 meters. These samples exhibit a diverse and abundant Neogene association of deep and medium depth sediments. Radiolarians, sponge spicules and silicoflagellates correspond to the deeper association and foraminifera and ostracods are from the shallower levels (over the CCD). The biostratigraphy is presented here in relation to the submarine topography where the samples were retrieved. Besides the obvious interest in the biostratigraphy of the area this samples are used also as a research training tool for undergraduate and graduate students in the Geosciences Department, University of Texas at Dallas.