Lab%203 - a S e d i m entology nd S tr atigr aPhY 3...

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Sedimentology and StratigraPhY Laboratory 3 Carbonate SedimentarY Rocks Purpose: In this exercise, you will examine samples of various carbonate rocks in order to become familiar with carbonate rock classification and the concept of facies. Method: The exercise consists of two parts. For Part l, you will examine and classify hand samples limestone types. In Part ll, you will utilize thin sections of limestone to classify the associated rocks by name and Part I In this part of the exercise hand specimens of some common kinds of carbonate rock, and classify each one according to textural, compositional, and structural features. For each sample you will: A. determine nature of the binding material B. determine abundance and distribution of allochems C. determine sizes D. determine types of allochems E. determine structure of rock F. assign an appropriate Procedure: 1) Enter all data on Table l. 2) Using the binocular microscope, and especially looking at any available edges of rock, determine whether the rock is bound primarily by sparry cement or by matrix. The cement will usually appear to be glassy, allowing allochems below the rock surface to be seen through the cement. Matrix will be extremely fine grained and opaque. 3) Determine whether allochems make up 10% or more of the rock. Note whether the allochems are dominantly 'floating' or touching each other. 4) Using your grain comparator, determine the average size of allochems. 5) Determine are ooliths (rounded clasts of micrite with concentric rings), peloids (ovoid, very fine grained, no trace of concentric lamina), lithoclasts (large micrite clasts), or skeletal (fossil fragments). 6) Does the rock have any obvious overall structural features, such as cross bedding, lamination, in situ skeletal framework, etc.? 7) Using the attached Embry & Klovan (1971) classificatory scheme (modified after Dunham (1962)), each of the hand samples, 8) Add modifying adjectives as necessary. Examples might be: skeletal wackestone of coralline framestone. 9) Specify the energy level of the system. 10) Which of the carbonate facies described by Wilson (1975) (attached) best describes this sample? 11) Repeat the above procedure with each of the six samples provided.
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Part ll ln this part of the exercise, you will examine carbonate rocks in thin section, and classify each rock according to allochem composition. For each sample you will: A) determine the overall abundance of allochems the relative proportions of each major allochem type B) determine the nature of the binding material C) determine the degree of neomorphism D) classify the rock F) assign the rock to an appropriate facies. Procedure: 1) Enter all data in Table ll. 2) Using the petrographic microscope, estimate percentages of each the major allochem types. Appropriate categories for allochem type include: brachiopods, bivalves, gastropods, bryozOans, Corals, foramS, algae, trilObites, peloids, intraclasts, ooids, oncoids, etc. Estimations can be made by using the attached visual estimation charts. 3) Estimate percentage of the sample which is, or was, micrite. 4) Estimate
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Lab%203 - a S e d i m entology nd S tr atigr aPhY 3...

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