The Decade of North American Geology 1983 Geologic Time Scale

Palmer, Allison R.

doi:10.1130/0091-7613(1983)11<503:tdonag>2.0.co;2

Cited by 564 publications

(273 citation statements)

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“…The Decade of North American Geology (DNAG) time scale, which will be used in this paper, is derived from the calibration of this magnetic polarity pattern to fossiliferous magnetostratigraphic sections (e.g., Lowrie et al, 1980;Ogg et al, 1984;Lowrie and Ogg, 1986), combined with a few radiometric dates on associated stage boundaries and the simplifying assumption of a constant regular spreading rate for formation of this Hawaiian lineation "M-sequence" (Kent and Gradstein, 1985;Palmer, 1983;see version in Shipboard Scientific Party, 1990a).…”

Section: Ridge Configuration and Oceanic Plateausmentioning

confidence: 99%

“…Notes: Statistics are primarily from the corresponding site chapters (Shipboard Scientific Party, 1973a, 1973b, 1975a, 1975b, 1975c, 1975d, 1975e, 1981, 1990b, 1990c. Geological and magnetic anomaly ages are converted to Ma following the Leg 129 time scale (Shipboard Scientific Party, 1990a), which incorporates the DNAG time scale (Kent and Gradstein, 1985;Palmer, 1983) and magnetic anomaly age assignments according to Ogg et al (1991). In cases where oceanic crust was not drilled, depth to crust is from the seismic interpretation in the corresponding site chapters, or estimated from crustal age and apparent sedimentation rates.…”

Section: Ridge Configuration and Oceanic Plateausmentioning

confidence: 99%

“…data, 1992) by applying inclination statistics (method of Kono, 1980) to paleomagnetic sample suites spanning different biostratigraphic age intervals (data are displayed in Steiner and Wallick, this volume; number of samples are those having high-quality data within the selected age interval). Age in Ma is the midpoint of the sampled paleomagnetic interval, with geological ages converted according to the DNAG time scale (Kent and Gradstein, 1985;Palmer, 1983). Paleolatitude of basalts at Site 802 is from Wallick and Steiner (this volume).…”

Section: Implications Of Paleolatitude Motion During Late Jurassic Tomentioning

confidence: 99%

“…Depths of depositional surfaces on oceanic plateaus (e.g.. Sites 305, 306, and 463) were computed by the same subsidence curve, but with an appropriate initial depth according to the estimated crustal age and total sediment thickness. Results of depth calculations were rounded to the nearest 100 m. Absolute ages (Ma) for geological stages are from the DNAG time scale (Palmer, 1983;Kent and Gradstein, 1985) with modified magnetic anomaly ages (Ogg et al, 1991). Sediment facies for each age interval are according to our examination of the cores or are according to core descriptions in the respective Initial Reports site chapters (Shipboard Scientific Party, 1973a, 1973b, 1975a, 1975b, 1975c, 1975d, 1975e, 1981, 1990b, 1990c.…”

Section: O Plmentioning

confidence: 99%

“…Age in Ma is the midpoint of the sampled paleomagnetic interval, with geological ages converted according to the DNAG time scale (Kent and Gradstein, 1985;Palmer, 1983). Paleolatitudes were derived from paleomagnetism of sediments recovered at DSDP Sites 462 (statistics recalculated from Steiner, 1981a, by Shipboard Scientific Party, 1985, 585, and 585A ) and of basalts recovered at DSDP Sites 289 (Hammond et al, 1975) and 462 (as drilled on Leg 89, but incorporating statistics recalculated from the earlier data set in Steiner, 1981b), 303, 304, and 307 (Larson and Lowrie, 1975.…”

Section: Referencementioning

confidence: 99%

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Jurassic through Early Cretaceous Sedimentation History of the Central Equatorial Pacific and of Sites 800 and 801

Ogg¹,

Stattegger²,

Behl³

1992

Proceedings of the Ocean Drilling Program

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Sedimentation in the central Pacific during the Jurassic and Early Cretaceous was dominated by abundant biogenic silica. A synthesis of the stratigraphy, lithology, petrology, and geochemistry of the radiolarites in Sites 801 and 800 documents the sedimentation processes and trends in the equatorial central Pacific from the Middle Jurassic through the Early Cretaceous. Paleolatitude and paleodepth reconstructions enable comparisons with previous DSDP sites and identification of the general patterns of sedimentation over a wide region of the Pacific.Clayey radiolarites dominated sedimentation on Pacific oceanic crust within tropical paleolatitudes from at least the latest Bathonian through Tithonian. Radiolarian productivity rose to a peak within 5° of the paleoequator, where accumulation rates of biogenic silica exceeded 1000 g/cm 2 /m.y. Wavy-bedded radiolarian cherts developed in the upper Tithonian at Site 801 coinciding with the proximity of this site to the paleoequator. Ribbon-bedding of some radiolarian cherts exposed on Pacific margins may have formed from silicification of radiolarite deposited near the equatorial high-productivity zone where radiolarian/clay ratios were high. Silicification processes in sediments extensively mixed by bioturbation or enriched in clay or carbonate generally resulted in discontinuous bands or nodules of porcellanite or chert, e.g., a "knobby" radiolarite. Ribbon-bedded cherts require primary alternations of radiolarian-rich and clay-rich layers as an initial structural template, coupled with abundant biogenic silica in both layers. During diagenesis, migration of silica from clay-rich layers leaves radiolarian "ghosts" or voids, and the precipitation in adjacent radiolarite layers results in silicification of the inter-radiolarian matrix and infilling of radiolarian tests. Alternations of claystone and clay-rich radiolarian grainstone were deposited during the Callovian at Site 801 and during the Berriasian-Valanginian at Site 800, but did not silicify to form bedded chert.Carbonate was not preserved on the Pacific oceanic floor or spreading ridges during the Jurassic, perhaps due to an elevated level of dissolved carbon dioxide. During the Berriasian through Hauterivian, the carbonate compensation depth (CCD) descended to approximately 3500 m, permitting the accumulation of siliceous limestones at near-ridge sites. Carbonate accumulation rates exceeded 1500 g/cm 2 /m.y. at sites above the CCD, yet there is no evidence of an equatorial carbonate bulge during the Early Cretaceous. In the Barremian and Aptian, the CCD rose, coincident with the onset of mid-plate volcanic activity.Abundance of Fe and Mn and the associated formation of authigenic Fe-smectite clays was a function of proximity to the spreading ridges, with secondary enrichments occurring during episodes of spreading-center reorganizations. Callovian radiolarite at Site 801 is anomalously depleted in Mn, which resulted either from inhibited precipitation of Mn-oxides by lower pH of interstitial waters in...

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Section: Ridge Configuration and Oceanic Plateausmentioning

confidence: 99%

Section: Ridge Configuration and Oceanic Plateausmentioning

confidence: 99%

Section: Implications Of Paleolatitude Motion During Late Jurassic Tomentioning

confidence: 99%

Section: O Plmentioning

confidence: 99%

Section: Referencementioning

confidence: 99%

See 3 more Smart Citations

Jurassic through Early Cretaceous Sedimentation History of the Central Equatorial Pacific and of Sites 800 and 801

Ogg¹,

Stattegger²,

Behl³

1992

Proceedings of the Ocean Drilling Program

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Palaeozoic drift of Gondwana: Palaeomagnetic and stratigraphic constraints

Houten

Hargraves

1987

Geol. J.

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Currently available Palaeozoic palaeomagnctic data from Gondwanan continents can he interpreted in terms of either (a) a migration of the pole from northern Africa to southern Africa between Ordovician and late Palaeozoic times, or (b) a rapid excursion of the pole from northern Africa to southwest of South Africa during late Ordovician to early Silurian times, followed by a return to central Africa in late Devonian times, t h e r c a k r continuing southward again. With respect to this uncertainty, pertinent stratigraphical evidence from western Gondwana includes the distribution of glacial deposits and cold-water and warm-water faunas. This record, although meagre and to some extent contradictory, appears to favour a drift history consistent with the second (b) o f the APW alternatives that involves a rapid southerly excursion of the pole by early Silurian times.

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