Site U1460

Abstract

Site U1460 ended at 1945 h on 15 August. A total of 133 cores were recovered with the HLAPC system; of the 606.7 m cored, 592.2 m was recovered (recovery = 97%). Hole U1460A After arriving at Hole U1460A (27°22.4948′S, 112°55.4296′E), preparations for coring commenced. As a result of previous difficulty establishing the mudline core at Site U1459 (broken core barrel), the seafloor was tagged with the bit to determine its precise location and whether it was as hard as the previous site. A nonmagnetic HLAPC core barrel was dressed with a core liner, picked up, and run into the hole. Hole U1460A was started at 0115 h on 13 August. Based on the recovery of the mudline core, the seafloor depth was calculated to be 214.5 mbsl. Coring continued with the HLAPC system through Core 356-U1460A-64F to 298.2 m DSF. After the mudline core, each core was advanced 4.7 m despite partial strokes on Cores 2F, 9F, and 64F. Hole U1460A was cored to a final depth of 300.1 m DSF (Core 65F). During coring, a routine slip, cut, and retermination of the coring line was performed. At the conclusion of coring, the drill string was pulled back to 231.6 m DSF and the top drive was set back. The drill string was pulled back to just above the seafloor, clearing the seafloor at 0605 h on 14 August and ending Hole U1460A. Of 300.1 m cored, 291.39 m of material was recovered (recovery = 97.1%). The total time spent on Hole U1460A was 33.25 h. Hole U1460B After offsetting the vessel 20 m north of Hole U1460A, preparations were made to begin Hole U1460B (27°22.4867′S, 112°55.4265′E). A nonmagnetic HLAPC core barrel was dressed with a core liner, picked up, and run into the hole. Hole U1460B was started at 1920 h on 14 August. Based on the recovery of the mudline core, the seafloor depth was calculated to be 214.4 mbsl. Coring continued with the HLAPC system through Core 356-U1460B-68F to 306.6 m DSF. After the mudline core, each core was advanced by recovery in an attempt to cover any gaps from Hole U1460A. Of the 306.6 m cored, 800.81 m was recovered (recovery = 98%). Also in this hole, in situ temperature measurements were made with the APCT-3 before recovering Cores 12F, 20F, 28F, 33F, and 36F. During coring, a routine slip, cut, and retermination of the coring line was performed. At the conclusion of coring, the drill string was pulled back to 260.7 m DSF and the top drive was set back. The drill string was pulled from the hole and the advanced piston corer/extended core barrel bit cleared the rig floor at 1940 h. The thrusters and hydrophones were pulled and secured, and at 1945 h on 15 August, Site U1460 concluded. The total time spent on Hole U1460B was 37.75 h.

Hardened faecal pellets as a significant component in deep water, subtropical marine environments

“…From Hole U1460B, a 306 m long hydraulic piston core with 98% recovery was obtained (Figure ). The IODP site U1460 consists of two lithostratigraphic units (Ι, ΙΙ), with Unit I subdivided into three subunits (Ιa, Ιb, Ιc) (Gallagher et al., ). In this study, the focus is placed on the interval between 0 and 108 m core depth below sea floor (CSF‐A) belonging to Subunits Ia (0‐44.94 m CSF‐A) and Ib (44.94‐173.36 m CSF‐A) (Figure ).…”

“…(a) Lithostratigraphic summary for IODP Hole U1460B. Lithification varies between unlithified (1), partially lithified (2) and lithified (3) intervals (Gallagher et al., ). The presence of azooxanthellate corals is displayed in (b).…”

“…Unit I as defined in Gallagher et al. () consists mainly of unlithified to partially lithified skeletal packstone with minor skeletal wackestone, and some lithified intervals (Figure ). This unit is divided into three Subunits based on the abundances of macrofossils and sponge spicules and variation in diagenetic alteration.…”

“…The base of the lithified interval in Subunit Ia is defined by a hardground. The upper part of Subunit Ib is dominated by unlithified beige to light brown skeletal packstone and the lower part by partially lithified skeletal wackestone and mudstone (Gallagher et al., ).…”

“…Consequently, hardened faecal pellets were described only as a very minor component from cool‐water carbonate settings, such as the Great Australian Bight and Spencer Gulf (Betzler, Saxena, Swart, Isern, & James, ; O'Connell & James, ). Peloids have been recently reported from IODP site U1460 on the subtropical Southwest Shelf of Australia (Gallagher et al., , ). The aim of this study was to analyse the origin of these peloids using modal analysis and scanning electron microscopy (SEM) equipped with an energy‐dispersive X‐ray spectrometer (SEM‐EDX).…”