English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Drilling in the deep basin west of Hawaii during DSDP Leg 6 revealed an extremely difficult situation. The thin to undetectable upper transparent acoustic layer was found to consist of soft sediments. The underlying opaque layer was discovered to be a chert chalk sequence, which was difficult to drill. The heavy bottom hole assembly will buckle and break off if not supported by the hole, and, therefore, 200 to 500 feet of easily penetrable sediments are desired in order to provide support for the assembly before the drilling of hard strata can be commenced. There are extremely few sites in the entire western Pacific which combine an upper, easily penetrable sediment and an underlying clear acoustic stratigraphic sequence which can be related to the overall stratigraphy of the Pacific basin. Those members of the JOIDES Pacific Panel who had access to original records searched every available profile to come up with a selection of less than one dozen possibilities for Leg 20, most of which were admittedly marginal. The prospective sites as initially selected would have taken the Glomar Challenger on Leg 20 from Japan eastward to about longitude 160°E and then south to the equator and ultimately to Fiji. It was planned that the Aries V expedition would first explore the final sites for Leg 17, then explore the Mid-Pacific Mountains, and finally pick up the proposed Leg 20 traverse near Wake and run it to Japan, detailing such areas as appeared promising. The R.V. Kana Keoki at the same time was to run the traverse from the vicinity of Wake to the Equator, making special surveys of three prospective sites. Reports on these surveys are found in a chapter by Zachariadis in this volume. In general, the abyssal clays which make up the upper transparent layer are far thinner than the minimum required by the drillers for bottom hole assembly support. Only in anomalous areas do the unconsolidated sediments approach, equal, or exceed the desired 180-foot minimum. Within about 1000 km of Japan, volcanic ash is carried out by the wind in sufficient quantities to provide an uppermost layer of sufficient thickness. This deposit was employed during Leg 20 to spud in Sites 194, 195, 196, and 197. Site 198 was located on an anomalous thickening on the archipelagic apron of Marcus Island. Site 51 of Leg 6 was located in a small turbidite pond while Site 52 was on the volcanogenic wedge east of the island arc. The survey carried out along 170°E effectively eliminated each prospect north of 5°N by demonstrating insufficient thickness of transparent sediment. The seismic reflection profiles run by ARIES V demonstrated the presence of attractive sites in the region of the Mid-Pacific Mountains. These sites were to have been drilled by Leg 17. Unfortunately, the drilling of these thick accumulations was not undertaken on that leg. In the deep basin west and northwest of the Mid-Pacific Mountains, the seismic profiler gave very little promise of providing minimum requirements for spudding-in. A prospect found on two Conrad profiles was further explored by ARIES V and given a more detailed study on ARIES VII. During the early stages of exploration, drilling objectives were easily modified to meet the limitations of drilling technique. However, most of the obvious sites in the west Pacific have now been drilled, and further exploration of the oldest areas by drilling will have to await development of techniques to spud-in without the present minimum of 180 feet of soft sediment.

R/V Thomas Washington Cruise Aries V: Reconnaissance Seismic Reflection Profiles of Prospective DSDP Sites in the Northwest Pacific