Five of the primary proposed sites are located on the Kerguelen Plateau and one is on Broken Ridge (Tables 1, 2; Figs. 2, 3, 4). Site surveys for all of the primary sites on the Kerguelen Plateau were undertaken by Australia (Australian Geological Survey Organisation) in 1997 and by France (École et Observatoire des Sciences de la Terre, Université Louis Pasteur, Strasbourg) in 1998. The high-quality multichannel seismic data acquired during the site surveys have been critical to candidate site selection. On behalf of the entire Leg 183 shipboard scientific party, the designated co-chief scientists wish to acknowledge and commend France and Australia for their allocation of significant resources in support of ODP objectives on the Kerguelen Plateau.
The Pollution Prevention and Safety Panel (PPSP) has approved six primary sites (KIP-2E, KIP-3F, KIP-6C, KIP-7B, KIP-9B, and KIP-13B) and alternates for each (KIP-2C, KIP-3C, KIP-6D, KIP-7C, KIP-9C, and KIP-13A). PPSP has also approved three secondary sites (KIP-1D, KIP-10C, and KIP-14C) and alternates (KIP-1E and KIP-10D). In case drilling objectives at the six primary sites are met ahead of schedule, or conditions do not permit reaching our objectives at the primary sites and their alternates, the highest priority secondary site, KIP-1D, will be targeted.
Primary Sites (Alternate Sites)
Igneous basement of the NKP has never been sampled apart from the Kerguelen Isles. A site north of the Kerguelen Archipelago is required to establish the age, composition, and construction environment of the NKP (presumed to be Cenozoic in age), as well as to document tectonic events and to test plate reconstructions.
Several distinct, roughly circular bathymetric and gravity highs form a linear trend between the Kerguelen Archipelago on the NKP and the active Heard and McDonald Islands on the CKP (Figs. 2, 4). This site was selected because it is on one of several aligned gravity highs that may reflect a hot-spot track between Heard/McDonald and Kerguelen Islands. Drilling is necessary to determine the age, composition, and extrusion environment of one of the presumed volcanoes.
This site is on Elan Bank, which is a prominent east-west-oriented bathymetric and gravity high west of the CKP (Figs. 2, 4). This major morphotectonic component of the Kerguelen Plateau province is unsampled; drilling at this site will constrain its age, composition, construction environment, and tectonic history.
This site in the CKP is ~100 km north of ODP Site 747. The radioisotopic age of basalts at Site 747 is ~85 Ma, which represents the only sampled basement of Late Cretaceous age found on the Kerguelen Plateau. Drilling at Site KIP-7B will evaluate the areal extent of Late Cretaceous crust, its composition, and extrusion environment. In addition, the sedimentary section will help constrain the post-constructional tectonic history.
This site on the Southern Kerguelen Plateau is located on a bathymetric and gravity high (Figs. 2, 4). The location was selected to evaluate the areal extent of continental crustal contamination north of Site 738 (Figs. 2, 5), as well as the age and formation environment of this part of the plateau. Several hundred meters of sediment will help to constrain the tectonic history.
This site on the Eastern Broken Ridge will provide the first in situ basement samples from the entire Broken Ridge (Fig. 3). It is located near Dredge 8, whose lavas are similar in age (88 Ma) to lavas from Site 747. Unlike lavas from the central part of the Kerguelen plateau, dredge site 8 lavas contain a continental lithosphere component (Fig. 5). This site will define the spatial extent of this component as well as the age, extrusion environment, and tectonic history of this part of Broken Ridge.
Primary Secondary Site (Alternate)
This site is on Leclaire Rise (aka Skiff Bank), which has been proposed as the current site of the Kerguelen hot spot but has never been sampled. A site here is required to establish the age, composition, and construction environment of Skiff Bank as well as to test plate reconstructions and ideas of hot-spot fixity.
Ancillary Secondary Sites (Alternates)
This site lies in the Enderby Basin, presumed oceanic crust southwest of Kerguelen that has never been sampled. This reference site will establish the age and composition of the Enderby Basin, and may record the history of Kerguelen plume activity in its sediment. The site will help to constrain plate tectonic reconstructions.
This site is in the Labuan Basin, a deep-water portion of the Kerguelen Plateau province that has yielded dredges of metamorphic and granitic rock but has never been drilled. This site will establish the age and composition of the Labuan Basin and may contain a sedimentary record of Kerguelen plume activity. The site will also help to constrain plate tectonic models.
To Sampling Strategy
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