(Table T1) Scanning electron microscope (SEM) analyses of IODP Site 321-U1338

The late Miocene to early Pliocene carbonate-rich sediments recovered at Integrated Ocean Drilling Program (IODP) Site U1338 during the Expedition 320/321 Pacific Equatorial Age Transect (PEAT) program contain abundant calcareous nanno- and microfossils. Geochemical proxies from benthic and planktonic foraminiferal and coccolithophore calcite could be very useful at this location; however, good preservation of the calcite is crucial for the proxies to be robust. Here, we evaluate the preservation of specific benthic and planktonic foraminifer species and coccolithophores in fine fraction sediment at Site U1338 using backscattered electron (topography mode) scanning electron microscopy (BSE-TOPO SEM). Both investigated foraminiferal species, Cibicidoides mundulus and Globigerinoides sacculifer, have undergone some alteration. The C. mundulus show minor evidence for dissolution, and only some specimens show evidence of overgrowth. The Gs. sacculifer show definite signs of alteration and exhibit variable preservation, ranging from fair to poor; some specimens show minor overgrowth and internal recrystallization but retain original features such as pores, spine pits, and internal test-wall growth structure, whereas in other specimens the recrystallization and overgrowth disguise many of the original features. Secondary electron and BSE-TOPO SEM images show that coccolith calcite preservation is moderate or moderate to poor. Slight to moderate etching has removed central heterococcolith features, and a small amount of secondary overgrowth is also visible. Energy dispersive spectroscopy analyses indicate that the main sedimentary components of the fine fraction sediment are biogenic CaCO3 and SiO2, with some marine barite. Based on the investigations in this data report, geochemical analyses on benthic foraminifers are unlikely to be affected by preservation, although geochemical analyses on the planktonic foraminifers should be treated cautiously because of the fair to poor and highly variable preservation.

(Table 1) Heavy minerals in silt and sand samples of IODP Site 301-U1301

The northwestern Cascadia Basin of western North America accumulated high-sedimentation-rate sequences during the Pleistocene sea-level low-stands. The continental shelf was largely exposed at that time, and rivers and estuaries delivered large sediment fluxes directly to the deep ocean. The IODP EXP1301 core, which was taken from the middle portion of the Cascadia Basin, is well preserved and exhibits the deeper and - more distal sedimentary facies. The lithology in this location is composed of two units, 1) hemipelagic mud with a thin sand layer and 2) thick, coarsening upward silt-sand turbidites with a small proportion of granules at the top. We will focus on the detailed sand-grain proportions in order to understand the origin of these sediments. We determined the modal proportions of the heavy minerals, and the chemical composition of olivine and orthopyroxene in fourteen samples. These are characterized by an abundance of amphibole, pyroxenes and epidote, and the presence of minerals derived from peridotite. There is no drastic change in the modal and mineral compositions of the sands and silts between the turbidite and hemipelagic sequences. There were two probable drainage systems on the continent, the Frazer and Columbia rivers, which shed turbidites into the Cascadia Basin after 1.6 Ma, especially at 0.46-0.76 Ma. Based on a comparison of the modal and mineral compositions, the Northern Cascadia Basin has been supplied with sediments, mainly from the Frazer River, through the Straits of Juan de Fuca, by Pleistocene to Holocene turbidites.

Temperature observation of CORK installation during ODP Leg 168

Four boreholes, drilled a few tens of meters into igneous basement on the eastern flank of the Juan de Fuca Ridge during ODP Leg 168, were sealed and instrumented for long-term monitoring to observe the hydrologic state of young sediment-sealed oceanic crust. The thermal regime is dominated by the effects of rapid fluid circulation in uppermost igneous basement driven by very small non-hydrostatic pressure gradients. Upper basement temperatures are uniform laterally between pairs of holes over distances of hundreds of meters to kilometers. In the case of two holes drilled into a sediment-buried basement ridge and adjacent valley, basement temperatures differ by less than 2 K despite the 2.2 km lateral separation of the sites and the 2.5:1 contrast in sediment cover thickness. Under conductive conditions, upper basement temperatures would differ by roughly 50 K. By comparison with modeling results, the observed degree of isothermality suggests a fluid flux of at least 10**-6 m/s (30 m/yr), and an effective permeability in the range of 10**-10 to 10**-9 m**2 in the uppermost igneous crust. The pressure difference available to drive this rapid flux between the ridge and valley, estimated by comparing the observed pressures via the isothermal upper basement hydrostat that is inferred to connect the two sites, is small (~2 kPa) and also suggests high permeability. Relative to the hydrostats defined by the local conductive sediment geotherms, substantial super-hydrostatic pressure (+18 kPa) is present within the buried basement ridge, and sub-hydrostatic pressure is present in the adjacent valley (-26 kPa). Such pressure differentials are the direct consequence of the advection-dominated thermal regime and small pressure losses in high-permeability basement, and are available to drive fluid seepage through sediment sections vertically up above and horizontally away from buried ridges, and down above valleys. No constraints are provided by any of the observations on the depth in the crust to which thermally or chemically significant flow might extend, although just as in the overlying sediments, the pattern of deep flow may be affected by the near-isothermal and near-hydrostatic conditions present in the permeable uppermost crustal section.