The Jurassic Entrada Formation in Ghost Ranch area is eolian in origin. It is composed of quartz with minor amounts of feldspar and rock fragments. Observed cements are smectite as grain coatings, and calcite and kaolinite as pore fillings. Smectite and calcite were formed during very early to early diagenesis, whereas kaolinite formed during late diagenesis. Dust storms played an important role in the diagenesis of the Entrada Formation as a source of cements and as a controlling factor in diagenetic processes. The Entrada Formation is highly porous. These pores show many characteristics of secondary origin. Calcite and feldspar dissolution resulted in kaolinite formation. / The Cretaceous Dakota Formation has three units. The fluvial lower unit was cemented with kaolinite and silica. The middle unit was deposited in a transitional environment and was cemented with silica and calcite. The marine upper unit is cemented with silica and kaolinite. Sources of cements in Dakota Formation have been interpreted as being water of shale compaction and ground water for silica; shells and calcareous particles for calcite; and feldspar and other alumino-silicate grains for kaolinite. / Entrada and Dakota sandstones have several similar characteristics. Both have similar mineralogical composition and grain size, are tectonically undisturbed, and have not been deeply buried. However, even though the Dakota Formation is stratigraphically above the Entrada Formation, it is much more coherent than the latter. / The friable nature of the Entrada Formation is believed to be the result of very early cementation. Early smectite coatings prevented potentially available silica cementation, which would have produced a more durable sandstone. Early calcite cementation kept the formation from being extensively compacted. Early calcite cement and feldspar grains were dissolved, in part, later, resulting in a highly porous (secondary) and friable sandstone. / Well developed quartz overgrowths, generally interlocked, made the Dakota sandstones relatively coherent. / Cementation patterns are not formation-boundary dependent. Lower Morrison sandstones have the Entrada cementation pattern, whereas Upper Morrison sandstones are more like the Dakota. / Source: Dissertation Abstracts International, Volume: 50-05, Section: B, page: 1817. / Major Professor: William F. Tanner. / Thesis (Ph.D.)--The Florida State University, 1989.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_78018 |
| Contributors | Orhan, Hukmu., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 168 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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