Paleomagnetism of Ocean Drilling Program Leg 101 Sediments: Magnetostratigraphy, Magnetic Diagenesis, and Paleolatitudes

Sager, William W.

doi:10.2973/odp.proc.sr.101.153.1988

Cited by 21 publications

(19 citation statements)

References 32 publications

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“…The cores described here were recovered with the advanced hydraulic piston corer (APC) and the extended core barrel (XCB). The best paleomagnetic results were obtained on the generally well-preserved APC cores, as was previously found by Sager (1988).…”

Section: Introductionsupporting

confidence: 82%

High Southern Latitude Magnetostratigraphy and Rock Magnetic Properties of Sediments from Sites 747, 749, and 751

Heider¹,

Leitner²,

Inokuchi³

1992

Proceedings of the Ocean Drilling Program

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The magnetostratigraphy of Sites 747, 749, and 751 of Leg 120 that was established by shipboard measurements was extended and confirmed. Five hundred and eighty sediment cubes were stepwise demagnetized with alternating fields to determine their characteristic remanence. We obtained a rather complete magnetostratigraphy from the Oligocene to the Pliocene for the nannofossil oozes of Site 747. Alternating-field demagnetization experiments on laboratory-induced magnetization, hysteresis measurements, and low-temperature experiments showed that the magnetic carriers are single-domain and small pseudo-single-domain (titano)magnetite particles. A fraction of these Fe-Ti oxides seems to reside as microlites in the vitric volcanic ash particles that were enriched in the magnetic separates. The natural remanent magnetizations seem to be of detrital origin with small Fe-Ti oxide grains in the volcanic glass particles as carriers of the stable paleomagnetic signal.

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Section: Introductionsupporting

confidence: 82%

High Southern Latitude Magnetostratigraphy and Rock Magnetic Properties of Sediments from Sites 747, 749, and 751

Heider¹,

Leitner²,

Inokuchi³

1992

Proceedings of the Ocean Drilling Program

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“…At this point, primary magnetization becomes too weak to measure. The interval between 10 and 20 mbsf, in which high coercivity secondary components appear to have been acquired, may correspond to an interval observed by Sager (1988) in carbonate oozes in Holes 632A and 633A from ODP Leg 101. Mean destructive fields increased in these holes as intensities decreased downhole.…”

Section: Reduction and Magnetization Intensitymentioning

confidence: 62%

Site 806

1991

Proceedings of the Ocean Drilling Program

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Principal results: Ocean Drilling Program (ODP) Site 806 (proposed Site OJP-1) is located on the northeastern margin of the Ontong Java Plateau, close to the equator (latitude 0°19.1'N, longitude 159°21.7'E) in 2520 m of water, roughly 125 km northeast of Deep Sea Drilling Project (DSDP) Sites 289/586. The site represents the shallow end member on a transect that was designed to detect depthrelated paleoceanographic signals in Neogene sediments. We occupied this site with the objective to obtain a high-resolution carbonate record in an undisturbed setting, which could serve as a standard section for studies of ocean history, including biostratigraphy, chemostratigraphy, and acoustic stratigraphy. Site 806 was positioned at the proposed location (OJP-1), on a 2-km-wide terrace interrupting a gentle incline sloping to the northeast. We used a single-channel-seismic (SCS) line acquired by the Thomas Washington during ROUNDABOUT Cruise 11 (0600 UTC, 21 December 1989). The seismic profile shows a full set of reflectors, comparable with those at Sites 289/586, with little or no disturbance.Three holes were drilled, using the advanced hydraulic piston corer (APC) and the extended core barrel (XCB), with full recovery with the APC. Hole 806A, a dedicated hole, was cored with the APC to 83.7 mbsf into upper Pliocene sediments. Hole 806B was cored with the APC to 320 mbsf, at which point refusal occurred within the lower upper Miocene. The hole was continued with XCB coring to 743.1 mbsf, with 423.1 m of sediment cored and 331.2 m recovered (78%). Coring ended in the lowermost Miocene because of poor recovery. The hole was then logged. Hole 806C was cored with the APC to 309.6 mbsf and coring with the XCB was then begun. The aim was to core with the XCB to the lower middle Miocene a second time, and then drill ahead to search for the Oligocene/Miocene boundary. The attempt was successful. Drilling terminated in uppermost Oligocene sediments at 776.4 mbsf, with 278 m cored for a recovery rate of 73% and 188.8 m drilled without coring. SITE 806The entire sedimentary sequence encountered is considered as one lithologic unit (Unit 1), consisting of upper Oligocene to Pleistocene foraminifer nannofossil ooze and chalk to nannofossil ooze and chalk with foraminifers. Foraminifer abundances mostly range between 15% and 30%, with occasional excursions to 10% and 50%. Radiolarians are a minor constituent throughout the section. The ooze-chalk transition was placed between 338 and 340 mbsf; it is gradational and shows alternation of layers of varying induration, beginning at about 200 mbsf. The age of the sediments at the transition is ca. 10 Ma. Sedimentation throughout the time interval represented seems to have been continuous at this site.Unit I is divided into two subunits at the ooze-chalk transition, as follows:Subunit IA (0-339 mbsf) consists of Pleistocene to upper middle Miocene foraminifer nannofossil ooze to nannofossil ooze with foraminifers. Carbonate content generally ranges from 90% to 95%, except in the Pleistocene...

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“…First, pyrite was observed in several cores, indicating potential complications posed by reduction diagenesis. The effect of reduction diagenesis on magnetization properties, first documented in hemipelagic regions (Karlin andLevi, 1983, 1985;Karlin, 1990;Leslie et al, 1990), has more recently been noted in pelagic sediments (Sager, 1988), including those having very high carbonate values (Musgrave et al, 1993) similar to those of Site 866. The presence of pyrite implicates sulfate reduction and the production of H 2 S, which combines with ferric iron in the magnetite lattice (Canfield and Berner, 1987).…”

Section: Discussionmentioning

confidence: 91%

Early Cretaceous Magnetostratigraphy and Paleolatitudes from the Mid-Pacific Mountains: Preliminary Results Bearing on Guyot Formation and Pacific Plate Translation

Tarduno¹,

Sager²,

Nogi³

1995

Proceedings of the Ocean Drilling Program, 143 Scientific Results

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Detailed thermal demagnetization experiments applied to some weakly magnetized shallow-water carbonates recovered at Site 866 (991-1622 mbsf) yield a characteristic remanent magnetization having maximum unblocking temperatures of 500° to 580°C, after the removal of one or more overprints. Alternating field (AF) demagnetization yields a similar characteristic component. This magnetization shows both polarities, which form 10 polarity zones that we correlate to the upper Mesozoic "M-sequence" of the marine magnetic anomaly record. Using tie points derived from paleontologic and isotopic studies, we tentatively assign the polarity zones to CM1 through CM7. Such an assignment requires that basement at Site 866 be of M7 age (or older), broadly consistent with radiometric age data that suggest an age of 128 Ma. Using this interpretation, at least one major hiatus and several substantial changes in sedimentation rate are required in the carbonate sequence.Paleolatitude data from the Site 866 carbonates (14.6°S) are within error of an early Aptian data set from nearby Site 463 (13°S), suggesting little (or no) latitudinal transport during the later part of the Early Cretaceous. Comparisons with younger data sets also suggest that total latitudinal translation from the time of edifice formation to the mid-Cretaceous was minor (±5°). These data do not support drift toward extreme southerly latitudes as a cause of platform drowning. This near-stationary behavior of the Pacific Plate over an area of vigorous mantle convection may account for some patterns of subsidence that are implied by the magnetostratigraphic data.

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Paleomagnetism of Ocean Drilling Program Leg 101 Sediments: Magnetostratigraphy, Magnetic Diagenesis, and Paleolatitudes

Cited by 21 publications

References 32 publications

High Southern Latitude Magnetostratigraphy and Rock Magnetic Properties of Sediments from Sites 747, 749, and 751

High Southern Latitude Magnetostratigraphy and Rock Magnetic Properties of Sediments from Sites 747, 749, and 751

Site 806

Early Cretaceous Magnetostratigraphy and Paleolatitudes from the Mid-Pacific Mountains: Preliminary Results Bearing on Guyot Formation and Pacific Plate Translation

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