Petrology of Lower and Middle Eocene Carbonate Rocks, Floridan Aquifer, Central Florida: ABSTRACT
9
Citation
0
Reference
10
Related Paper
Abstract:
ABSTRACT Study of cores from a U.S. Geological Survey test well near Polk City indicates that the Avon Park-Lake City (Claibornian) and Oldsmar (Sabinian) Formations, which comprise most of the Floridan aquifer in central Florida, can be divided into six microfacies: foraminiferal mudstone; foraminiferal wackestone-packstone; foraminiferal grainstone; nodular anhydrite; laminated dolomicrite; and replacement dolomite. Dolomite containing variable amounts of nodular anhydrite forms more than 90 percent of the Avon Park-Lake City interval, whereas the Oldsmar is chiefly limestone. The depositional model inferred for these units is a broad, shallow-water marine platform with environments ranging from supratidal-sabkha to shallow-water shelf. Diagenetic pathways vary with rock type, but generally include: (1) marine phreatic -- grain micritization, and radially fibrous cementation within foraminiferal tests; (2) meteoric vadose -- minor leaching of aragonitic grains; and (3) meteroic phreatic -- neomorphism of unstable grains, dissolution of aragonitic allochems, formation of isopachous equant calcite cement and coarse spar in grainstones, and syntaxial calcite overgrowths on echinoderms. Several episodes of dolomite formation are recognized. Laminated dolomicrite formed syngenetically in a supratidalsabkha environment. Crystalline dolomite with nodular anhydrite formed early by replacement of limestone through reflux of dense, Mg-rich brines. Replacement dolomite not associated with evaporites and containing limpid crystals probably formed later by a mixed-water process in the subsurface environment. Late diagenetic processes affecting crystalline dolomites include hydration of anyhdrite to gypsum, partial dissolution of gypsum, alteration of gypsum to calcite (minor), and dissolution of calcian dolomite cores in stoichiometric crystals. Crystalline dolomite and grainstone are the only rock types that have high enough porosities and permeabilities to provide significant yields of water. Medium and finely crystalline dolomites show best values of porosity and permeability because they have high percentages of intercrystal and moldic pores that are well connected. Filling of pores by anhydrite or gypsum can significantly reduce porosity and permeability.Vietnam has a carbonate rock distribution area of about 60,000 km2, accounting for nearly 20% of the territory's area. Carbonate rocks in Vietnam are located in many different stratigraphy, their ages from Pre Cambrian to Triassic. Carbonate rocks in Vietnam include limestone, marble, and dolomite. Carbonate rock has been made up for hundreds of millions of years. However, the use of carbonate rock resources in Vietnam is inconsequential, reducing its value. The author of the article introduces an overview of carbonate rock resources in Vietnam, and the reality of exploiting and processing carbonate resources in Vietnam. Since then, gave warnings about illogical in the use of carbonate rock resources. At the same time, it also makes recommendations for the rational use of carbonate rock resources for sustainable development.
Cite
Citations (0)
According to the amount of argillaceous material in formations that determines the surface soil thickness,the petrologic assemblages in carbonate area in Guizhou Province can be divided into three types: homogenous carbonate rock,carbonate rock intercalated with clastic rocks,and carbonate/clastic rock alternations.With the average weathering dissolving rate of carbonate rocks in Guizhou being 49.67 mm/ka,the pedogenesis rates of different petrologic assemblages in carbonate area have been calculated and used as the value of soil loss tolerance in carbonate areas.The soil loss tolerance in homogenous carbonate rocks area is lower than 6.84 t/(km~2·a),45.53 t/(km~2·a) in carbonate rock intercalated with clastic rock areas and 103.46 t/(km~2·a) in carbonate/ clastic rock alternations areas.Therefore,this three area are utmost sensitive,severe sensitive and moderate sensitive to soil erosion separately in these carbonate areas.As a result,there exists a spatial heterogeneity of the classification indices for soil erosion intensity in carbonate areas of Guizhou Province.Karst rocky desertification is predominately distributed in homogenous carbonate assemblages whose soil loss tolerance is lower than 6.84 t/(km~2·a),especially,in homogenous limestone assemblage.
Cite
Citations (14)
The feedback from studies of Recent carbonate sediments to studies of ancient carbonate rocks is small. The reason for this unfortunate state of affairs is that the approaches used in the two problems are so different. For example, the materials are different; carbonate sediments are conventionally nearly pure carbonate, whereas carbonate rocks contain up to 50 per cent non-carbonates. Sediment studies usually involve rather elaborate size analyses, mineralogic studies, and individual particle descriptions. For most carbonate rocks diagenetic alteration has made size analysis difficult or meaningless, the minerals have changed, and only a part of the original particles can even be recognized. The best understanding of carbonate rocks comes from conventional isopachous maps, stratigraphic associations, insoluble-residue studies, and fossil content. Only in a few cases can petrographic studies of size or particle type do more than support conclusions based on field relations. The writers do not see any immediate way of changing drastically the methods for studying carbonate rocks. However, new approaches are possible in the study of sediments. By simply enlarging the End_Page 457------------------------------ definition of carbonate sediments to include those containing more than 50 per cent carbonate minerals, many new parameters can be studied and new and useful information can be incorporated in studies of carbonate rocks. It is obvious that, by enlarging the definition, consideration of insoluble residues and stratigraphic associations is possible. Further, the geographic range of carbonate sediments is enlarged, permitting study of a wider variety of environmental conditions. Finally, a greater variation in thickness of Recent carbonate sediments is found, a fact which should allow a better understanding of sedimentation rates. End_of_Article - Last_Page 458------------
Cite
Citations (0)
The current research on the dissolution of carbonate rocks in the Karst of Trieste indicates that the average degradation of surfaces exposed to atmospheric agents is 0.028 mm/year with an average rainfall of 1350 mm. The maximum levels (0.031 mm/year) correspond to micro-crystalline limestones, the minimum values (0.014 mm/year) to dolomites.
Cite
Citations (13)
Carbonate minerals
Cite
Citations (3)
Summary he paper focuses on the relationship among the karst collapse sinkholes, extensional fault trends, and associated offset talus debris observed on several Miocene carbonate platforms of Central Luconia, Sarawak. The Central Luconia province is divided into several tectonic highs i.e. Mega Platform, G Fields High, Bunga Pelaga High, and Southern Field High. The carbonate platforms studied for the analysis are carbonate platforms located on the Bunga Pelaga High. As of now, there have been no in-depth studies concentrating on establishing the first Central Luconia's Carbonate Karst Island Model. Each of these carbonate platforms actually creates the ideal background platform to further analyse the aforesaid carbonate island karst model. Sea-level changes are a critical factor that influences the distribution and the density of the karst formation. The type of karst features formed on a carbonate platform is also influenced by the rise and fall of the sea-level because these changes of sea-level will influence the period of exposure which in turn, will determine the duration of Stillstands that is needed to create the karst features. Therefore, to further analyse these carbonate platforms, results of this analysis will help construct the carbonate karst island model for the Bunga Pelaga High carbonate platforms.
Sinkhole
Carbonate platform
Cite
Citations (0)