ACTIVITY 6.5 Sediment Analysis, Classification, and Interpretation Date: Name: C

Question

ACTIVITY 6.5 Sediment Analysis, Classification, and Interpretation Date: Name: Course/Section: Complete parts 1 through 6 for each sample below. Refer to FIGURES 6.2 and 6.3 as needed SAMPLEA 1. Grain sine range in man 2. Percent of cach Wenrworth sine class 3. Grain sorting (circk) 4 Grain roundness (cirde): 5. Sediment composition (circle): clay silt sand gravd Poor Moderate Well Subround Well-rounded Biochemical Chemical (Siliciclastic) (Bioclastic) Detrical 6. Describe how and in what environment (FIGURE 6.10) this sediment may have formed. SAMPLE B o 1 2mm 1. Grain size range in mm 2- Percent of each wentworth size class: clay- sile gravel _ 3. Grain sorting (circle 4. Grain roundness (cincle) 5. Sediment composition (circle): 6. Describe how and in what environment (FIGURE 6.10) this sediment may have formed Poor Moderate Well Angular Subround Well-rounded Detrital (Siliciclastic)Biochemical (Bioclastic) SAMPLEC 0 10 mm 1. Grain size range in mm: 2. Percent of each Wentworth size class: clay salt sand- gravel 3. Grain sorting (circle): 4. Grain roundness (circle): 5. Sediment composátion (circdle): Moderate Well Angular Subround Well-rounded Detrital (Siliciclastic) (Bioclastic) Biochemical Chemical 6. Describe how and in what environment (FIGURE 6.10) this sediment may have formed. D. REFLECT& DISCUSS Imagine that these sediments are rocks. Which of the samples do you think would be the least diagnostic of a specific ancient environmente Why 178

Explanation / Answer

SAMPLE: A

1) In the photo, almost all of the grains are almost 0mm to less than 1mm measured by photographic scale.

2) Accroding to wentworth scale, the sand grains vary in size from 1mm to 1/16 mm . In the pictures percentage of wentworth size class are clay-0%,silt-0%,sand-100%,gravel-0%.

3) Sorting is varience in grain size such that same size clasts or low varience indicates well sorting. In the picture grains sorting are moderate because grains are showing moderate varience, as within same size clasts, some different size clasts are present.

4) Roundness is degree of smoothing due to abrasion of sedimentary particles. It is ratio of the curvature of the corners and curvature of the inscribed sphere. In the photo the grains are sub-rounded.

5) Siliciclastic rockes are those which are made up of silica or sand grains. As all the grains are siliciclastic or made up of sand grains. So the rocks are clastic or detrital.

6) As all the grains are sand size, sub angular, moderate sorting, so the depositional environment is fluviatile. Because energy of fluviatile environment is very high.

SAMPLE: B

1) In the photo, almost all of the grains varies in size from 0.5mm t0 2mm photographic scale.

2) Accroding to wentworth scale, the sand grains vary in size from 1mm to 1/16 mm . in the pictures percentage of wentworth size class are clay-0%, silt-0%, sand-100%, gravel-0%.

3) Sorting is varience in grain size such that same size clasts or low varience indicates well sorting. In the picture grains are moderate to poor sorting because grains are showing moderateto low varience. Because different size clasts are present.

4) Roundness is degree of smoothing due to abrasion of sedimentary particles. It is ratio of the curvature of the corners and curvature of the inscribed sphere. In the photo the grains are sub-angular.

5) As all the grains are siliciclastic or made up of sand grains. So the rocks are detrital (siliciclastic).

6) As all the grains are sand size, sub-angular, moderate to poor sorting, so the sediments are deposited by high engery environment or the depositional environment is fluvio-glacial.

SAMPLE: C

1) In the photo, almost all of the grains varies in size less than 1mm but organic substances varies from 0 to 10 mm in size.

2) Accroding to wentworth scale, the grains varies in size less than 1/16 mm . Grain size can not be identified by naked eye in the picture. Accroding to percentage of wentworth size class are clay~20%, silt~80%, sand~0%, gravel~0% most probably.

3) Sorting is varience in grain size, such that same size clasts or low varience indicates well sorting. In the picture grains are moderate to poor sorting because grains are showing moderate to low varience. Because different size clasts are present.

4) Roundness is degree of smoothing due to abrasion of sedimentary particles. It is ratio of the curvature of the corners and curvature of the inscribed sphere. In the photo the grains are angular to sub-angular.

5) Biochemical or bioclastic rocks are those which contains clastic grains with organic substances. In the photo, as organic substances are present with clastic grains, so the rocks are bioclastic or biochemical.

6) As all the grains are silt to clay size, angular to sub-angular, moderate to poor sorting with organic substances, so the depositional environment is shelf to shallow marine environment because shelf to shallow marine environment is dominated by organic substances.

D. Sample C is the least significant to expose ancient environment,because sample C rocks are showing different grains with very low grain size. Oraganic substances are present with those. Sorting, grain size, roundness can not be identified by properly due to very small in size. Sample-c components are not resistant comapared with Sample-A and Sample-B. With increasing time the organic substances become disappeared dut to the pressure of late pahase diagenesis, working of weathering substances etc. So, the sample- C is the least diagnostic of a specific ancient environment.

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