Primary Sedimentary Structures

Primary Sedimentary Structures By Sardar Hashim Abbas

1. Presented by Sardar Hashim Abbas Roll # 02 Group Roll No. (1 to 8 ) BS-Geology 4 th Semester Presented to Aamir Asghar Sabz Ali Khan & Malli Khan Institute Of Earthsciences

2. PRIMARY FEATURES OF MARINE SEDIMENTARY ROCKS

3. Contents: Ripple mark: Cross bedding: Mud Crack: Graded Budding: Warm Tracks: Leaf Prints: Rip up: Rain Prints: Volcanic clast: Sole Marks: PRIMARY FEATURES OF MARINE SEDIMENTARY STRUCTURES

4. Sedimentary Rocks Rocks formed by the deposition & cementation of material at earth surface. Sedimentation is collective name of process that caused mineral and organic particles to settle in place.

5. Sedimentary Structures The majority of structure form by physical process before, during and after sedimentation. Sedimentary structure have variety of uses: For interpreting the depositional environment in term of water depth and wind strength. For determining the the way of rock succession in area of complex folding. For determining the paleocurrent pattern and paleogeographic .

6. Sedimentary Structures

7. Depositional Sedimentary structure When sediments erroded & transported in response to unidirectional aquous flow such a flow of river,tidal,or stream current. A wide range of sedimentary structure arises from water flowing overall sedimentary surface. With tidal current the flood produce further sedimentary structure.

8. Ripple mark Ripple and dunes are Asymmetric bed form that gradually moved down stream as sediment is transported to erosion of upstream faces and its deposition on downstream faces. Ripple marks usually form in conditions with flowing water, in the lower part of the Flow Regime. There are two types of ripple marks Symmetrical ripple marks: Asymmetrical ripple marks:

9. Ripple mark

10. Symmetrical ripple marks: Often found on beaches, they are created by a two way current, for example the waves on a beach (swash and backwash). This creates ripple marks with pointed crests and rounded troughs, which aren't inclined more to a certain direction

11. 2 . Asymmetrical ripple marks: These are created by a one way current, for example in a river, or the wind in a desert. This creates ripple marks with still pointed crests and rounded troughs But which are inclined more strongly in the direction of the current.

12. formed on an ancient beach formed on modern beach

13. Cross Bedding . Cross bedding include ripples and dunes, or any cross stratification caused by currents. The "cross" refers to the angle between flat bedding and the inclined bedding of the cross bed, typically about 34 degrees.

14. Paleocurrents are best found from cross bedding

15. Mud Cracks Mud cracks are common in fine grain sediments and form through breakup of rocks due to hydrolic pressure of water. They are commonly in tidal flate species. As the water is lost the volume is reduced and clay mineral pull apart developing cracks in surface under sub aerial condition.

16. a poly gonal pattern of cracks develop when muddy sediments dries completely . These are desiccation cracks the spacing of desiccation cracks depends upon the thickness of layer of wet mud. Mud Cracks

17. Mud Cracks – Environment that periodically dries out

18. Gradded Bedding: This feature relate to the grain size changes through a bed and mostly develop in response to changes in flow condition during sedimentation. There are four types of gradded bedding: Contect gradding: Reverse gradding : Normal gradding : Coarse tail grading:

19. Gradded Bedding

20. 1.Contect gradding: A gradual decrease in the average grain size up through the bed is called contect gradding. 2.Reverse gradding: A pattern of increasing in average size from base to top is called reverse gradding.

21. 3.Normal gradding : A grain size in a bed is usually variable and may show pattern of over all decrease in grain size from base to top.

22. 4. Coarse tail gradding: A gradual upword decrease in size of coarse grain. Multiple gradding where there are several grade sub unit in a bed occur. Reverse or inverse gradding where grain size increase upthrough the bed is not common.

23. Warm Tracks: A fossil is remain of living plants and animals that were preserved in rocks and other material . That organism lived for short period of time in many areas these are called warm tracks. Specific index fossil found in different layer in different rocks. They are used to describe fossil fuel like oil,coal and petroleum.

24. Warm Tracks: Fossilization and preservation of organism can occured in several way: Preservation without change: Complete replacement by mineral: Formation of imprints: Formation of thin film of carbon: Filling of holospace by mineral:

25. Leaf Prints: In fine grain sedimentary rocks some prints of leaf are preserved due to some activities like earthquake. There preserved parts are known as fossil. These preserved bodies are used to identify the older and younger rocks.

26. Rip up: When over there was deposition of sand stone a particle of clay is eroded and preserved in sand stone. Rip up are also known as shot rock that are used to armor shore line. A foundation or wall of stone or concrete thrown together without order as in deep water make slope to erosion

27. Rip up:

28. Sole Marks: Small scale erosion feature on the bed surface are referred as sole marks. They are preserved in the rock record when an other layer of sediments is deposit on the top leaving the feature on bedding plane. Sole mark may be divided into those that form as a result of turbulance in water causing erosion.

29. Sole Marks:

30. Rain Prints: Rain print are commonly formed in mud rocks of continental and shore line environment. Raindrop impressions form on exposed sediment by raindrop impacts.

31. Volcanic clast: Claustic sedimentary rocks are rock composed of broken pieces or claust of older weathered and eroded rock. A claustic rock composed of fragments and clast of preexisting minerals and rock . A clast is fragment of broken rock that are form by weathering.

32. Importance Of Field Study

33. Geological field work require to be properly organised even if the visit is for a short duration. The extent of preparation and planning will depend on the nature of the project. But there are certain basic things which must be attended to for making it a success. Geological field work is a serious exercise and any casual approach may affect its accuracy and therefore its usefulness.

34. Field study is designed to provide student with the opportunity to examine social problems. Evaluate the merit of ideas presented in the classroom. Learn and practice method of naturalistic field research,data collection,theory testing or program evaluation & social intervention. Develop interpersonal and professional skills & technical competencies.

35. Participate in the ongoing activities of an organization. Through field study upper division student and faculty engage with our community to study issues,build capacity & impact social change.

36. THANKS