Seafloor Engineering in the Central and Western Pacific

Storms, M.A.; Natland, J.H.

doi:10.2973/odp.proc.ir.132.101.1991

Cited by 9 publications

(19 citation statements)

References 4 publications

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“…Biostratigraphic data show that the recovered sediments from Hole 810C range in age from Maastrichtian to Pleistocene (Storms, Natland, et al, 1991;Premoli Silva et al, this volume). What is more, sedimentological and magnetic susceptibility data (Storms, Natland, et al, 1991) indicate that there is a significant Pliocene-Pleistocene section that appears to record the effects of glacial/interglacial climate cycles.…”

Section: Introductionmentioning

confidence: 95%

“…Fifteen APC cores (132-810C-1H through -15H) were recovered along with one extended core barrel core (132-810C-16X). The total recovery was 105.7% and the sediments consisted mostly of nannofossil ooze (Storms, Natland, et al, 1991).…”

Section: Introductionmentioning

confidence: 97%

“…Results, 132 tary section. Four holes were drilled at Site 810, but only one (810C) had significant penetration and recovery (Storms, Natland, et al, 1991). Hole 810C penetrated 136.1 m below seafloor (mbsf) and was drilled primarily with the advanced hydraulic piston corer (APC) to obtain relatively undisturbed, high-recovery cores from the Cenozoic oozes that rest atop the target Cretaceous section.…”

Section: Introductionmentioning

confidence: 99%

“…What is more, sedimentological and magnetic susceptibility data (Storms, Natland, et al, 1991) indicate that there is a significant Pliocene-Pleistocene section that appears to record the effects of glacial/interglacial climate cycles. As a consequence, climate-proxy studies of Hole 810C cores were undertaken by several groups of investigators.…”

Section: Introductionmentioning

confidence: 99%

“…We also discovered that a mistake in wiring the cryogenic magnetometer caused shipboard paleomagnetic measurements to give the opposite sign in inclination and added 180° to declination. This caused incorrect interpretations of the magnetic stratigraphy in the Initial Reports volume (Storms, Natland, et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

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Magnetic Polarity Reversal Stratigraphy of Hole 810C, Shatsky Rise, Western Pacific Ocean

Sager¹,

Polgreen²,

Rack³

1993

Proceedings of the Ocean Drilling Program

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A magnetic stratigraphy study was undertaken on Hole 8 IOC cores to provide age constraints and to characterize sedimentation on the summit of Shatsky Rise. Sediments from this hole are mostly nannofossil oozes recovered by the advanced hydraulic piston corer which gave virtually complete recovery to 136 m below seafloor. High-resolution magnetic measurements were made aboard ship with a pass-through cryogenic magnetometer, and these results were confirmed with discrete samples also measured with a cryogenic magnetometer. The sediments give clearly defined magnetic polarity zones within the upper 100 m below seafloor. It was possible to make a convincing match with the polarity reversal time scale from the surface to 76.8 m below seafloor, through the base of the Gilbert Chron near the Pliocene/Miocene boundary. Because of slow sedimentation and hiatuses punctuating the middle to upper Miocene section, the match with the time scale is less certain below this depth. For core recovered beneath 100 m below seafloor, it was mostly impossible to define clear polarity zones, except for a section of reversed polarity in Maastrichtian sediments, from 113.1 to 116.4 m below seafloor, that is tentatively correlated with Chron 3 lr. The magnetic stratigraphy shows that sediment accumulation was slow (about 2.5 m/m.y.) during the late Miocene, but increased to 15.0 to 18.5 m/m.y. during the late Pliocene and Pleistocene. Missing sections within the Matuyama Chron and an extended Brunhes Chron suggest that actual sediment accumulation rates were at times higher and lower than these averages. Furthermore, differences in sediment accumulation between Site 810 and nearby Site 577 suggest that the normal pelagic sedimentation regime atop Shatsky Rise is perturbed by bottom currents resulting in locally patchy sediment accumulation.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Magnetic Polarity Reversal Stratigraphy of Hole 810C, Shatsky Rise, Western Pacific Ocean

Sager¹,

Polgreen²,

Rack³

1993

Proceedings of the Ocean Drilling Program

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Introduction, Background, and Scientific Objectives: Engineering Leg 142 at the East Pacific Rise

Party¹

1993

Proceedings of the Ocean Drilling Program

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Design and Performance of Subsea Hardware

Holloway¹

1993

Proceedings of the Ocean Drilling Program

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EXECUTIVE SUMMARYThe East Pacific Rise (EPR) provided a difficult and challenging arena in which to test the diamond coring system (DCS) and associated subsea hardware. Information gained from Ocean Drilling Program (ODP) Legs 124 and 132 proved invaluable in further developing hardware to withstand the difficult drilling conditions anticipated at the sediment-free fast-spreading mid-ocean ridge. The coordinates of the primary site (EPR-2) are latitude 9°30.85'N and longitude 104°14.66'W. Water depth at the site is approximately 9020 ft (2570 m). Recent surveys using ARGO and studies conducted from the submersible Alvin have confirmed the surface crust to be a layer of massive basalt. The location selected for drilling appears to be in a ponded lava flow with relatively zero relief. This ponded flow is underlain by 164-197 ft (50-60 m) of low-velocity material suspected to be very thin sheet flows, lobate pillows fragments, or intact lobate pillows filled with lava.The reconfigured six-sided hard-rock guide base (mini-HRB) was used to establish a drilling template from which to initiate diamond coring. The mini-HRB provided a three-legged structure with counterbalanced reentry cone. The base was designed for seafloor slopes up to 25°. Because of the difficult drilling conditions expected at EPR, a nested drill-in bottom-hole assembly (DI-BHA) was developed after proving a single-stage version viable on Leg 132. The nested system provides two stages of casing which can be deployed to assist the DCS in isolating unstable formations. The drill-in concept is designed to eliminate any redlining or reaming of the initial hole that might be necessary due to instability of the formation or size of borehole attempted. Auxiliary hardware to support the nested system components are also described in detail.The ODP drill string was again used as a riser for supporting the DCS tubing. A comprehensive study conducted by an outside consultant of the whole mini-riser system was performed to verify the earlier studies conducted for Leg 132. Discussion of the findings and suggested improvements are described in detail. The drill string was again held in tension with a redesigned tensioning tool and new break-away safety joint. The safety joint provides the mechanical fuse to release from the mini-HRB in case a sudden drive-off situation were to occur from loss of the dynamic positioning system. This component replaced the shear bolts used on Leg 132 between the tapered stress joint (TSJ) and tensioning tool.The equipment tested during Leg 142 performed without any mechanical problems throughout the entire leg. The fine volcanic glass did at times cause situations in which both tools and drill strings became stuck due to the problems associated with cuttings reentering the hole. Problems with fill reentering the borehole occurred to such an extent that the second-stage DI-BHA was installed to isolate the material. Some minor changes in hardware are suggested in order to enhance a" system that appears to have survived the rigors of...

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Seafloor Engineering in the Central and Western Pacific

Cited by 9 publications

References 4 publications

Magnetic Polarity Reversal Stratigraphy of Hole 810C, Shatsky Rise, Western Pacific Ocean

Magnetic Polarity Reversal Stratigraphy of Hole 810C, Shatsky Rise, Western Pacific Ocean

Introduction, Background, and Scientific Objectives: Engineering Leg 142 at the East Pacific Rise

Design and Performance of Subsea Hardware

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