ALBERT

Description: Leg 190 was the first of a two-leg program across the Nankai accretionary prism and Trough, offshore Japan, aiming to evaluate existing models for prism evolution and to constrain syntectonic sedimentation, deformation styles, mechanical properties, and prism hydrology (Moore, Taira, Klaus, et al., 2001; Moore et al., 2001). More than 400 volcanic ash and siliceous claystone (altered ash) layers were penetrated and sampled during drilling of the six sites from two transects across the accretionary prism (Sites 1173-1178). In sites from the subducting Shikoku Basin (Sites 1173 and 1177) and in the trench axis (Site 1174), recognition of ash layers and diagenetically altered ashes was initially important in defining major lithostratigraphic units. However, it is clear that understanding the diagenesis of the volcanic ashes has considerable implications for prism evolution, mechanical properties, prism hydrology, geochemistry, and fluid flow in the accretionary prism and associated subducting sediments (cf. Masuda et al., 1996, doi 10.1346/CCMN.1996.0440402). Particle size, chemical composition, temperature, depth of burial, and time are all thought to be factors that may affect volcanic ash diagenesis and preservation (Kuramoto et al., 1992, doi:10.2973/odp.proc.sr.127128-2.235.1992; Underwood et al., 1993, doi:10.2973/odp.proc.sr.131.137.1993). The overall aim of this research is to evaluate factors influencing volcanic ash diagenesis in the Nankai Trough area. This data report presents just the results of the sedimentological and petrographic analysis of the volcanic ashes and siliceous claystones from Sites 1173, 1174, and 1177. It is anticipated that when the results of additional geochemical analysis of these lithologies is available a more meaningful evaluation of factors influencing volcanic ash alteration will be possible.

Description: In Gobabeb, Namibia SWD, LWD and DIR are each measured redundant with two instruments of the same make (not in this data base). The differences between the pairs are used in the quality control. This is done manually by inspecting plots of half-day diurnal courses of the pairs and their differences. Values are removed mostly in the morning due to daily cleaning. Other reasons for larger differences are birds, insects, or people at the station. There are regular fog events varying in frequency over the year. Usually, the fog appears in the second half of the night and disappears a few hours after sunrise. The case temperatures of pyrgeometers practically never drop below dewpoint but there can be water deposition of the dome.

Description: In Gobabeb, Namibia SWD, LWD and DIR are each measured redundant with two instruments of the same make (not in this data base). The differences between the pairs are used in the quality control. This is done manually by inspecting plots of half-day diurnal courses of the pairs and their differences. Values are removed mostly in the morning due to daily cleaning. Other reasons for larger differences are birds, insects, or people at the station. There are regular fog events varying in frequency over the year. Usually, the fog appears in the second half of the night and disappears a few hours after sunrise. The case temperatures of pyrgeometers practically never drop below dewpoint but there can be water deposition of the dome.