Magnetostratigraphy&lt;subtitle&gt;A Powerful Tool for High-Resolution Age-Dating and Correlation in the Miocene Monterey Formation of California: Results from Shell Beach Section, Pismo Basin&lt;/subtitle&gt;

Omarzai, Sheraz Khan; Coe, Robert S.; Barron, John A.

doi:10.2110/pec.93.49.0095

Cited by 5 publications

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“…Previous paleomagnetic studies of these rocks in Southern California (e.g. Hornafius, 1985;Omarzai et al, 1993) have identified magnetite as the primary detrital magnetic phase. We thus expected magnetite to be the primary detrital magnetic phase in Zaca Lake.…”

Section: Rock Magnetismmentioning

confidence: 99%

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Paleomagnetic chronostratigraphy of late Holocene Zaca Lake, California

Lund

Platzman

2015

The Holocene

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We have developed a paleomagnetic secular variation (PSV) record from Zaca Lake, California, that spans the last ~3200 years. The record is derived from detailed (2 cm) sampling of core 09-1C, which is 873 cm in length. The paleomagnetic remanence is carried jointly by magnetite and greigite. The greigite appears to form in the anoxic bottom water of the lake and/or at the sediment/water interface. The paleomagnetic remanence has a very simple characteristic remanence, which demagnetizes straight to the origin between ~10 and 80 mT. This remanence has strong serial correlation and a pattern of variability that strongly matches 15 other published PSV records from Western North America. In all, 23 radiocarbon-dated PSV features, which were identified in the core, provide an independent timescale for dating the Zaca Lake core and an independent means of correlating Zaca Lake sediments to other Holocene lakes of the Western United States. We have also compared our paleomagnetic chronology with a previously published radiocarbon-based chronology from Zaca Lake (Feakins et al., 2014; Kirby et al., 2014). Our chronology is not significantly different from the radiocarbon-based chronology for the last 2000 years. However, the radiocarbon dates appear to be anomalously young in the older part of the lake record where correlatable PSV features suggest ages that are ~300–500 years older than the radiocarbon dates. Our analysis suggests that the PSV feature ages are a better estimator of lake sediment age in this interval.

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Section: Rock Magnetismmentioning

confidence: 99%

“…Rocks surrounding Zaca Lake are predominantly Miocene carbonate/silica-rich deep-sea sediments of the Monterey Formation (e.g. Omarzai et al, 1993) and Paleogene marine forearc-basin clastic-rich sediments.…”

Section: Zaca Lake Settingmentioning

confidence: 99%

Paleomagnetic chronostratigraphy of late Holocene Zaca Lake, California

Lund

Platzman

2015

The Holocene

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Application of magnetostratigraphy to Brent Group reservoir zonation in the Visund Field

Hauger¹,

Veen

1995

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Magnetostratigraphy has been applied to an increasing number of oil fields in the North Sea region with promising results for detailed chronostratigraphic reservoir correlation. However, the magnetization processes in hydrocarbon reservoir successions, and the potential use of magnetostratigraphy for reservoir zonation purposes, are not very well known. Therefore, aspects of these subjects are discussed on the basis of a magnetostratigraphic study of three different wells covering the Middle Jurassic Brent Group at the Visund Field, northern North Sea. Results from scanning electron microscopy and remanent coercivity analysis suggest that the primary magnetization defining the magnetozones in the Brent Group is a combination of detrital remanent magnetization and a chemical remanent magnetization, probably acquired contemporaneously shortly after deposition. Detailed thermal demagnetization has uncovered an important secondary magnetization component in most of the core samples. This magnetization is probably due to cooling of the cores from a reservoir temperature of about ll0~ to surface temperature, and it causes the main disturbances in the palaeomagnetic results. Based on analyses of individual core samples, characteristic remanent magnetization components have been defined. The magnetopolarity stratigraphy for the individual wells is based on these components and the results are comparable from well to well. The well correlation covers a rock sequence with a thickness of about 200m, and both magnetostratigraphic and biostratigraphic results have been used in combination with the lithostratigraphy. The acme of Corollina represents the most important palyno-event, and the top and bottom of this palynozone is used as the main tie-level for two of the wells. Sixteen additional correlation lines have been derived from the magnetostratigraphic results, six of these considered as tentative. The correlation reveals that the magnetostratigraphic results are facies independent and some of the lithostratigraphic formation lines appear to be diachronous within this deltaic mega-sequence. Although the magnetostratigraphy only provides a relative time framework for the Brent Group, the results are encouraging and suggest the possibility of achieving high resolution chronostratigraphic well correlations for Middle Jurassic reservoir sequences in the northern North Sea area.The application of magnetostratigraphy in the oil industry is rapidly increasing and the method has been used in several oil fields world-wide (e.g. Rey et al. 1993; Hauger et al. 1994; Belkaaloul et al. this vol.; Bryant et al. this vol.).The potential uses of magnetostratigraphy are many and in hydrocarbon reservoir research may reflect: (1) on a regional scale, magnetopolarity stratigraphy can be used for dating and duration assessments of sequences and individual formations (Haq et al. 1988;Harland et al.

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Carbonaceous and Phosphate-Rich Sediments of the Miocene Monterey Formation at El Capitan State Beach, California, U.S.A.

John

Föllmi

Kaenel³

et al. 2002

Journal of Sedimentary Research

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Phosphogenesis and accumulation of phosphate were dynamic processes, which started with local phosphogenesis leading to the formation of phosphatized particles, as well as stratigraphically bound phosphogenesis leading to the formation of phosphate laminae and lenses. Phases of subsequent sediment reworking resulted in the concentration of phosphate particles in phosphate-rich layers, and repeated phases of sediment reworking and phosphogenesis ultimately resulted in the formation of the complex phosphate condensed horizons. Preservation of organic matter was favored by high productivity rates and by the development of dysaerobic bottom-water conditions. The dynamic sedimentary environment likely led to the formation of early diagenetic phosphatic lids (which may have sealed off subjacent organic-rich layers) as well as to the rapid deposition of entire layers in the form of mud flows, thereby eventually enhancing the potential of organic-matter preservation.Our new age data suggest that at the El Capitan State Beach section the intervals characterized by high TOC values and maximum TOC accumulation rates (red marl), as well as significant quantities of in situ phosphates appeared in the late middle Miocene, i.e., during and after the major cooling phase at around 14.5 Ma. This implies that deposition of phosphate and organic carbon continued well after this cooling phase, thereby underlining the observation that preservation of organic carbon in the Monterey Formation is not only dependent on climate change during the mid Miocene but also on regional conditions.

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Magnetostratigraphy<subtitle>A Powerful Tool for High-Resolution Age-Dating and Correlation in the Miocene Monterey Formation of California: Results from Shell Beach Section, Pismo Basin</subtitle>

Cited by 5 publications

References 0 publications

Paleomagnetic chronostratigraphy of late Holocene Zaca Lake, California

Paleomagnetic chronostratigraphy of late Holocene Zaca Lake, California

Application of magnetostratigraphy to Brent Group reservoir zonation in the Visund Field

Carbonaceous and Phosphate-Rich Sediments of the Miocene Monterey Formation at El Capitan State Beach, California, U.S.A.

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