Presentation Title

The Monterey Formation at Point Dume, California: Controls on Facies Cyclicity

Start Date

November 2016

End Date

November 2016

Location

HUB 302-#112

Type of Presentation

Poster

Abstract

The mid-Miocene Monterey Formation, deposited between roughly 7-18 Ma, is exposed along much of California’s southern and central coastline. It is the major source rock for California’s petroleum reserves, and is important for understanding the impact of geologically rapid organic carbon burial on global climate. The Monterey Formation at Point Dume is composed of rhythmically bedded decimeter-scale pairs of two fine-grained facies, both with relatively minimal diagenetic alteration. The lack of diagenetic alteration is in stark contrast to most Monterey Formation sections, which have undergone significant diagenetic alteration. The excellent preservation at Point Dume allows the application of various published accumulation rate models to predict the average time interval separating turbidity flows. Furthermore, the section studied is well-preserved over approximately seven meters and may permit the use of image processing to test for a multi-millennial climate signal, perhaps associated with orbital cycles. A variety of methods were, and are, being used to understand the lithology of the section and controls on deposition more fully, including hand sample analysis, thin section analysis, examination of polished thin sections using SEM, percent carbonate in both facies, microfossil examination and digital images of the facies couplets processed to show any stratigraphic trends. Preliminary results of thin section analysis, percent carbonate determination and application of accumulation rate models provide the following findings: 1) facies A is a silty mudstone with scattered angular quartz and feldspar grains and interpreted to represent turbidites; 2) facies B is a calcareous mudstone with a clotted carbonate fabric interpreted to represent background sedimentation; 3) the timing of a couplet of facies A and B together is millennial in scale, depending on the rate model applied. Ongoing work seeks to test for the presence of cyclicity at a longer time-scale, possibly related to orbital cylces and tied to changes in climate.

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The Monterey Formation at Point Dume, California: Controls on Facies Cyclicity

HUB 302-#112

The mid-Miocene Monterey Formation, deposited between roughly 7-18 Ma, is exposed along much of California’s southern and central coastline. It is the major source rock for California’s petroleum reserves, and is important for understanding the impact of geologically rapid organic carbon burial on global climate. The Monterey Formation at Point Dume is composed of rhythmically bedded decimeter-scale pairs of two fine-grained facies, both with relatively minimal diagenetic alteration. The lack of diagenetic alteration is in stark contrast to most Monterey Formation sections, which have undergone significant diagenetic alteration. The excellent preservation at Point Dume allows the application of various published accumulation rate models to predict the average time interval separating turbidity flows. Furthermore, the section studied is well-preserved over approximately seven meters and may permit the use of image processing to test for a multi-millennial climate signal, perhaps associated with orbital cycles. A variety of methods were, and are, being used to understand the lithology of the section and controls on deposition more fully, including hand sample analysis, thin section analysis, examination of polished thin sections using SEM, percent carbonate in both facies, microfossil examination and digital images of the facies couplets processed to show any stratigraphic trends. Preliminary results of thin section analysis, percent carbonate determination and application of accumulation rate models provide the following findings: 1) facies A is a silty mudstone with scattered angular quartz and feldspar grains and interpreted to represent turbidites; 2) facies B is a calcareous mudstone with a clotted carbonate fabric interpreted to represent background sedimentation; 3) the timing of a couplet of facies A and B together is millennial in scale, depending on the rate model applied. Ongoing work seeks to test for the presence of cyclicity at a longer time-scale, possibly related to orbital cylces and tied to changes in climate.