The IODP (Integrated Ocean ?Drilling Program) Expedition 336 had explored North Pond located in the western flank of Mid-Atlantic Ridge. The principal objective of IODP Expedition 336 is to explain the fundamental microbiology containing the nature of the subseafloor deep biosphere by using the relationship of oceanic hydrology, geology and biogeochemistry. As a part of the principal objective, the chemostratigraphy and biostratigraphy of the three holes (U1382B, U1383D and U1384A) drilled in North Pond were studied in this thesis.
The major minerals of North Pond are calcite and quartz, which are main skeletal components of the calcareous microfossil and a constituent of clay minerals respectively. The minor amount of clay minerals (illite, kaolinite and chlorite) might be derived from adjacent continent by wind and/or oceanic current. Therefore, the sediments of North Pond are mainly composed of pelagic biogenic sediment with minor terrigenous clay mineral.
The major elements of North Pond are CaO and SiO2 and they are mostly originated from calcareous microfossils and diatoms respectively. The minor amount of Al2O3 and Fe2O3 may indicate the input of clay minerals into North Pond. The sediments of North Pond are divided into three units based on XRF results. Unit Ch1 represented by the high content of SiO2, Al2O3, Fe2O3 and low CaO might be affected by basement contact sediments. Unit Ch2 represented by the increase of CaO and decrease of SiO2, Al2O3, Fe2O3 mainly consist of pelagic biogenic sediment. Unit Ch3 characterized by the increase of SiO2, Al2O3, Fe2O3 and decrease of CaO is considered to be strongly affected by eolian matter
The common species of the calcareous nannofossils of North Pond sediments are Discoaster brouweri, D. quinqueramus and Ceratolithus telesmus with minor amount of D. challengeri, which are used for biostratigraphic boundary.
NN9-NN11B Zone (Unit N1) is represented by the conjunction of D. challengeri and D. quinqueramus with D. brouweri and is considered to be an age of Late Miocene. NN11-NN16 Zone (Unit N2) indicating late-Late Miocene to Middle Pliocene is characterized by the conjunction of D. brouweri and D. quinqueramus. NN16-NN21 Zone (Unit N3) is recognized by the conjunction of C. telsmus and D. brouweri and is thought to be an age of Late Pliocene to Pleistocene.
The common to abundant occurrences of discoaster species in NN11-NN16 Zone and NN9-NN11B Zone indicates a warm surface water temperature during the Late Miocene-Middle Pliocene.
The results between chemo- and bio-stratigraphy are generally well correlated, that is, Unit Ch1 was deposited in Late Miocene (Unit N1), Unit Ch2 was deposited from late-Late Miocene to Middle Pliocene (Unit N2), and Unit Ch3 was deposited in Late Pliocene to Pleistocene (Unit N3).