Sedimentary Rock Facies

Preferred fluid migration pathways are influenced by porosity and permeability, sedimentary sequences, facies architecture, and fractures. Porosity is a measure of pore space per unit volume of rock or sediment and can be divided into two types absolute porosity and effective porosity. Absolute porosity (n) is the total void space per unit volume and is defined as the percentage of the bulk volume that is not solid material. The equation for basic porosity is listed below ... 

Feldspars are the most abundant minerals of igneous rocks, where their ubiquity and abundance of their components influence normative classifications. They are also abundant in gneisses, and may be observed in several facies of thermal and regional metamorphic regimes. Notwithstanding their alterability, they are ubiquitously present in sedimentary rocks, as authigenic and/or detritic phases. Only in carbonaceous sediments is their presence subordinate. 

In each of the different parageneses outlined here, the instability of a mineral can be denoted by its replacement with one or usually several minerals. The rocks in these facies are typified by multi-phase assemblages which can be placed in the K-Na-Al-Si system. This is typical of systems where the major chemical components are inert and where their masses determine the phases formed. The assumptions made in the analysis up to this point have been that all phases are stable under the variation of intensive variables of the system. This means that at constant P-T the minerals are stable over the range of pH s encountered in the various environments. This is probably true for most sedimentary basins, deep-sea deposits and buried sedimentary sequences. The assemblage albite-potassium feldspar-mixed layered-illite montmorillonite and albite-mixed layered illite montmorillonite-kaolinite represent the end of zeolite facies as found in carbonates and sedimentary rocks (Bates and Strahl,... 

As far as one can tell from the data presented, verdine facies minerals are found on the surface of shallow marine sediments (Odin, 1988 Thamban and Rao, 2000 Kronen and Glenn, 2000). Berthierine in sedimentary rocks (Fritz and Toth, 1997 Moore and Hughes, 2000) formed at temperatures below 70 °C (Hornibrook and Long-staffe, 1996). It can apparently form from verdine facies minerals or by various mineral reactions during diagenesis (Fritz and Toth, 1997 Velde, 1989). Verdine facies minerals, mixed layered in nature, are therefore of low-temperature oceanic origin, while berthierine can possibly form as a pure phase under these conditions or under diagenetic conditions and temperatures up to 70 °C. 

James, H.L., 1954. Sedimentary facies of iron formations. Econ. Geol., 49 235—293. James, H.L., 1966. Chemistry of the iron-rich sedimentary rocks. U.S. Geol. Surv. Prof. Pap., 440-W, 60 pp. 

For those ancient sedimentary rocks that have attained metamorphic grades exceeding perhaps greenschist facies, thermal alteration has proceeded beyond the stage where the original isotopic compositions can be precisely reconstructed. In addition to... 

The Bowers Terrane is located east of the Wilson Terrane and is separated from it by the Lanterman fault zone which has been traced from the Bowers Mountains on the Oates Coast to the Lady Newness Bay on the Borchgrevink Coast of the Ross Sea. The Bowers Terrane appears to be a sliver of a much larger land-mass that originally included an oceanic island-arc system. It is composed of oceanic tholeiites interbed-ded with and overlain by fossiliferous sedimentary rocks that were deposited in a marine environment. The rocks were compressed by westward-directed forces that caused the rocks to be folded and faulted. However, the metamorphic grade is lowermost green-schist facies. The eastern boundary of the Bowers... 

Fig. 19.8 The Meyer Desert Formation of the Sirius Group in the Dominion Range has a fine grained yellowish-tan matrix of sand, silt, and clay that encloses angular boulders of dolerite of the Ferrar Group and of sedimentary rocks of the Beacon Supergroup. This facies of the glacial deposits closely resembles the diamictite on Mt. Sirius in Fig. 19.5b. However, the section in the Dominion Range also includes thin bedded and well-sorted fluvial and lacustrine sandstones and sUtstones that formed in peiiglacial environments that existed between episodic advances of the East Antarctic ice sheet during the late Pliocene (Photo by G. Faure)...

Effects due to metamorphism are discussed in section 7.2. Although greenschist-to-amphibolite-facies metamorphism of regional extent commonly affects sedimentary rocks, no perceptible mobility of the lanthanides occurs. 

Most of the hydrocarbons (gas and oil) occur in sedimentary rocks that were generated in different depositional environments (e.g. river charmels, delta systems, submarine fans, carbonate mounds and reefs). Seismic waves penetrating into and reflected within sedimentary rock bodies yield a seismic image of their external shape and of their internal texture. Therefore, the analysis of the external shape of seismic bodies and its internal textures, which is called seismic facies analysis [2], helps to specify the depositional environment of the investigated sedimentary rocks. An analysis of the seismic facies is a must in seismic interpretation to determine the depositional environment and to locate potential reservoirs, especially in complex oilfields. 

Generally, different sedimentary rocks yield different seismic facies. The seismic facies of a buried carbonate mound or reef, for example, differs significantly from a submarine fan or a delta system. Hence, each depositional system has its particular seismic facies. 

In every exploration program it is a must to find out in what kind of deposi-tional environment the investigated rocks were generated. To locate reservoirs it has to be known if they were generated in a deltaic, fluvial or reef environment. Reservoir sands in a reef environment show a different seismic facies than sands of a fluvial environment. If the depositional environment of a sedimentary rock is known then further exploration and production strategies can be refined and optimised. A tool to describe depositional environments out... 

In our approach, we consider that reflections of seismic waves within sedimentary rock bodies produce an image of their external shape and internal configuration or texture. The study of these external shapes and internal textures is also referred to as seismic facies analysis. For further details on this, we refer to the chapter [37] of Schlaf and Randen. For instance a meandering channel produces an external shape that can be filled with different seismic... 

The youngest eruptive event is of Paleocene age ( 60 Ma) whereas the youngest preserved host rocks capping the Buffalo Head Hills are of Campanian age ( 78 Ma). In this instance, the only record of now eroded latest Campanian through Paleocene host rocks is provided by sedimentary xenoliths preserved in the truncated intra-crater facies ultramafic bodies (e.g., K1 body). 

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