Sites 102, 103, 104: Blake-Bahama Outer Ridge (Northern End)

Hollister, C.D.; Ewing, John; Habib, Daniel; Hathaway, John C.; Lancelot, Y.; Luterbacher, Hanspeter; Paulus, F.J.; Poag, C. Wylie; Wilcoxon, J.A.; Worstell, P.

doi:10.2973/dsdp.proc.11.105.1972

Cited by 14 publications

(9 citation statements)

References 7 publications

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“…The clastic materials that occur on this portion of the rise have been carried southward along the continental margin by the Western Boundary Undercurrent (Hollister, Ewing et al, 1972). During Leg 11, it was determined that some of the clay minerals had origins that could be uniquely traced to Labrador.…”

Section: Drilling Areamentioning

confidence: 99%

“…These low-reflectivity zones (or seismic blank zones) may be produced by pervasive gas hydrate cementation, which reduces the acoustic impedance contrasts (Lee et al, 1993). level of the BSR had been penetrated and it corresponded with a hard layer at the base of the hole (Hollister, Ewing, et al, 1972), this interpretation was based on estimates of sediment velocity that are lower than those that actually occur at this site, on the basis of subsequent work. Therefore, we question whether DSDP Leg 11 actually penetrated to the level of the BSR.…”

mentioning

confidence: 93%

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Gas Hydrate Sampling on the Blake Ridge and Carolina Rise

Paull¹,

Matsumoto²,

Wallace³

1995

ODP Scientific Prospectus

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Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, the participating agencies, Joint Oceanographic Institutions, Inc., Texas A&M University, or Texas A&M Research Foundation. This Scientific Prospectus is based on pre-cruise JOIDES panel discussions. The operational plans within reflect JOIDES Planning Committee and thematic panel priorities. During the course of the cruise, actual site operations may indicate to the Co-Chief Scientists and the Operations Superintendent that it would be scientifically or operationally advantageous to amend the plan detailed in this prospectus. It should be understood that any proposed changes to the plan presented here are contingent upon approval of the Director of the Ocean Drilling Program in consultation with the Planning Committee and the Pollution Prevention and Safety Panel. ABSTRACTODP Leg 164 will be devoted to refining our understanding of the in situ characteristics of natural gas hydrates. The program involves drilling four sites to 750-m depths on the Blake Ridge that extend down through the zone where gas hydrates are stable and into the sedimentary section below. Short holes (50 m) will also be drilled at three sites on the crests of two diapirs on the Carolina Rise where gas hydrate-bearing sedimentary sections have been disturbed by the intrusion of diapirs. Because of the ephemeral nature of the gas hydrates, emphasis will be placed on downhole measurements and sampling strategies that allow the in situ conditions of the gas hydrates to be reconstructed.The objectives of Leg 164 include 1) assessing the amounts of gas trapped in extensively hydrated sediments, 2) contributing to an understanding of the lateral variability in the extent of gas hydrate development, 3) refining the understanding of the relationship between bottomsimulating reflectors and gas hydrate development, 4) investigating the distribution and in situ fabric of gas hydrates within sediments, 5) establishing the changes in the physical properties (porosity, permeability, velocity, thermal conductivity, etc.) associated with gas hydrate formation and decomposition in continental margin sediments, 6) determining whether the gas captured in gas hydrates is produced locally or has migrated from elsewhere, 7) investigating the role of gas hydrates in the formation of authigenic carbonate nodules, 8) refining our understanding of chemical and isotopic composition of gas hydrates, 9) determining the gas composition, hydration number, and crystal structure of natural gas hydrates, 10) determining the role of gas hydrates in stimulating or modifying fluid circulation, 11) investigating the potential connection between major slumps and the breakdown of gas hydrate, and 12) establishing the influence of the Carolina Rise diapirs on the gas hydrates as well as the origin of the diapirs themselves.

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Section: Drilling Areamentioning

confidence: 99%

mentioning

confidence: 93%

Gas Hydrate Sampling on the Blake Ridge and Carolina Rise

Paull¹,

Matsumoto²,

Wallace³

1995

ODP Scientific Prospectus

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“…From these studies we know that the Blake Outer Ridge formed by the complex accretion of hemipelagic muds controlled in some way by contourfollowing currents (Heezen et al, 1966). On the basis of drilling at DSDP Sites 102, 103, and 104 (Hollister, Ewing, et al, 1972a), we believe that sedimentation rates are relatively rapid in the area (5-15 cm/1000 yrs. ).…”

Section: Background and Objectivesmentioning

confidence: 98%

“…Moreover, seismic studies in other areas indicate the presence of similar acoustic features that are suspected to be gas hydrates; thus the occurrence of such features as BSRs is not unique to the Blake Outer Ridge (Shipley et al, 1979). Some acoustic observations on the Blake Outer Ridge that support the hypothesis that gas hydrates are present are listed as follows: 1) Evidence of relatively high compressional-wave seismic velocities (2.0-2.5 km/s) between the BSR and seafloor (Hollister, Ewing, et al, 1972a;Dillon et al, 1980;Shipley et al, 1979).…”

Section: Background and Objectivesmentioning

confidence: 99%

“…This unit shows striking variations in microfossil assemblages, in calcium carbonate content, and in color that are associated with the climate variations during the Pleistocene. Unexpectedly low levels of reworked nannofossils point to predominantly Quaternary sources of the elastics, such as are found along the continental SITE 533 It has been suggested that the Blake Outer Ridge was formed by sediment transported by geostrophic contour currents (Heezen et al, 1966;Ballard, 1966;Ewing et al, 1966;Markl et al, 1970;Ewing and Hollister, 1972;and Hollister et al, 1972a). Although there is substantive evidence for this conclusion in the research just cited as well other work (e.g., Amos et al, 1971), the lack of obvious current-derived structures in the visual observations of cores at Site 533 on the Ridge led to significant shipboard discussion concerning the depositional processes that produced those sediments, as well as the implications of the genetic term "contourite.…”

Section: Lithology and Agementioning

confidence: 99%

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