Earth and Planetary Sciences ETDs

Publication Date

11-21-1977

Abstract

Petrography, scanning electron microscopy (SEM), porosity and permeability, radiography, x-ray diffraction (clay mineralogy), whole rock wet chemistry and organic analysis are used to examine the texture, fabric and composition of fine-grained terrigenous sediments from the Graneros Member of the Mancos Shale, San Juan Basin, New Mexico. Grain content is highly variable and determines the configuration of the fabric during compaction. A scale of the degree of parallel orientation is compared to grain content and reveals a decrease in parallelism with an increase in grain content. Grain content also affects permeability, thus controlling he degree of authigenic mineralization. Although clay composition is consistent throughout the Graneros, clay morphologies vary considerably. Authigenic clays occur as primary void (interstitial) fillings, secondary void fillings (pits on grain surfaces, basal cleavage partings), pore-lining, fracture filling and alteration surfaces. SEM analyses reveals the following paragenesis of authigenic components: (l) pyrite, (2) overgrowths on quartz and anatase, (3) calcite and dolomite, (4) illite-montmorillonite and illite, (5) cabbage-head type structures and other authigenic clays except kaolinite and (6) kaolinite. Matrix-supported fabrics contain contorted pore-fluid channels. Contorted pore-fluid channels and authigenic mineralization occur during initial thermal dehydration. The maturation and transformation of organic material into petroleum and subsequent migration of petroleum from source beds to reservoir rock occurs during initial thermal migration. Level of organic metamorphism (LOM) calculations reveal that the portion of the Mancos Shale below the Carlisle-San Juan Basin generated the oil that occurs in the basin. Organic analyses and LOM studies of probable source beds are excellent exploration tools for oil and gas. Authigenic mineralization may result in petroleum accumulations in unlikely structural positions. Thick accumulations of montmorillonite-rich fine-grained terrigenous sediments that have undergone initial thermal dehydration might be excellent nuclear waste disposal sites.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Rodney Charles Ewing

Second Committee Member

Raymond Vail Ingersoll

Third Committee Member

Stephen G. Wells

Fourth Committee Member

Barry Stephen Kues

Language

English

Document Type

Thesis

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