FUNDAMENTALS LAWS OF STRATIGRAPHY

Stratigraphy

1. FUNDAMENTAL LAWS OF STrATIGRAPHY Presented by Kaijirsong Rongpi Class Roll No. 377 B.Sc. 5 th Semester Department Of Geology Arya Vidyapeeth College

2. Nicholas Steno (1638-1686) Nicholas Steno was a Danish scientist, a pioneer in both anatomy and geology who became a Catholic bishop in his later years. Importantly he questioned explanations for tear production, the idea that fossils grew in the ground and explanations of rock formations. His investigations and his subsequent conclusions on fossils and rock formation have led scholars to consider him one of the founders of modern Stratigraphy and modern Geology. The importance of Steno’s foundational contributions to geology may be gauged from the fact that half of the twenty papers in a recent miscellany volume on The Revolution in Geology from the Renaissance to the enlightenment focus on Steno, the preeminent Baroque polymath and founder of modern geologic thought. Steno was the first to established the theoretical basis for stratigraphy when he introduced law of superposition of strata, lateral continuity, original horizontality which he work on the fossilization of organic remains in the layer of sediments.

3. William smith (1769-1839) William Smith was an English Geologist, credited with creating the first detailed, nationwide geology of any country. At the time his map was first published he was overlooked by the scientific community; his relatively humble education and family connections prevented him from mixing easily in learned society. Financially ruined, Smith spent time in debtor’s prison. It was only late in his life that Smith received recognition for his accomplishments, and became known as the "Father of English Geology". He is also known as “ Father of stratigraphy “.

4. Charles Lyell (1797-1875) Charles Lyell was a Scottish geologist who demonstrated the power of existing natural causes in explaining Earth history. He is best known as the author of “ Principles of Geology .” He is largely responsible for the general acceptance of the view that all features of the earth’s surface are produced by physical, chemical, and biological processes through long periods of geological time

5. WHAT IS STRATIGRAPHY ? “Stratigraphy ” is a science of description, correlation and classification of strata in sedimentary rocks. The study of stratified rocks is known as stratigraphy. It is a branch of geology that deals with the correlation, interpretation, and description of stratified sediments and rocks that are found on or below the surface of the earth. Stratigraphy is a science that primarily deals with the study of layered sedimentary rocks(called strata) but may also include layered igneous rocks. Layered rocks may result from successive lava flows or from the formation of extensive igneous rocks.

6. Law of Superposition of Strata Law of Original Horizontality Law of Cross-cutting relationship Law of Lateral continuity Law of Inclusions Law of Faunal succession. The first 4 laws are proposed by Danish Geologist , Nicholas Steno. The 5 th law is proposed by Scottish Geologist , Charles Lyell. The 6 th law is proposed by English Geologist ,William Smith. FUNDAMENTAL LAWS OF STRATIGRAPHY

7. 1. Law of SUPERPOSITION OF STRATA According to law of superposition of strata, the overlying bed is younger than the underlying bed under the natural condition of sedimentation. This law can be used to determine the relative age of sedimentary rocks and volcanic rocks. But in the case of deformed rocks the top and bottom of beds at the time of their deposition are determined with the help of sedimentary structures like current bedding , ripple marks, etc. According to this law, we cannot find the exact date of a stratum but we can compare between two or more strata is younger or older then which strata.

8. Picture of superposition of strata Oldest Rock Youngest Rock

9. 2. Law of ORIGINAL HORIZONTALITY Law of original horizontality was proposed by Nicholas Steno. The law states that the strata that are now either perpendicular to the horizon or inclined to the horizon were at one time parallel to the horizon i.e., they are originally laid down horizontally under the action of gravity. It is Important for the analysis of folded and tilted strata. Sediments are deposited at the earth’s surface in flat layers

10. Picture showing Horizontal strata due to the gravity and tilted strata due to some geological factors

11. 3. law of CROSS CUTTING RELATIONSHIP Laws of cross cutting relationship was proposed by Nicholas Steno in 1669. According to this law if a body or discontinuity cuts across strata then it must have formed after the formation of that stratum or strata. Rock that are cut by another geologic feature are older than the feature that cuts them.

12. 4. Law of LATERAL CONTINUITY Principle of lateral continuity states that layers of sediments initially extended in all direction in other words, they are laterally continuous to some range. After deposition they may be separated by the action of some geological forces (valleys, mountains etc ). If a set of sedimentary layers found at a place shows similar properties as compared to another set of sediment layer found at another place then we can conclude that relative age of both the location is same i.e , formed at the same time.

13. 5. Law of PRINCIPLE OF INCLUSION According to this principle, clasts or the inclusion in a rock are older than the rock itself. If the enclosing rock is an igneous rock, the inclusions are called xenoliths. In either case, the inclusions had to be present before they could be included in the younger rock, therefore, the inclusions represent fragments of an older rock.

14. This principle is based on the appearance of fossils in sedimentary rocks. Fossils that were contained in the rock could also be used to determine relative age. It was first discovered by English geologist, William Smith (1769-1839). According to this principle, the layers of sedimentary rock in any given location contain fossil in a definite sequence. The same sequence can be found in the rock elsewhere

15. PICTURE SHOWING THE LAW OF FAUNAL SUCCESSION

16. CONCLUSION Stratigraphy deals with different periods of geological past by revealing their details from the earth’s birth to the present period. It also enables us to understand the details of geography, climate, glaciations, orogeny and how various factors affected the evolution and migration of plants and animals. Stratigraphic laws are basic principles that all geologists use in deciphering the spatial and temporal relationships of rock layers. Principle of stratigraphy reaffirms the vital importance of stratigraphy to the earth sciences.

17. BIBLIOGRAPHY Indian Stratigraphy by Ravindra Kumar A Textbook of Geology by P.K Mukherjee (Indian stratigraphy) Https://www.slideshare.net/principles_of_stratigraphy https://www.Wikipedia.org/principlesofstratigraphy https://www.Wikipedia.org/williamsmith https://www.Wikipedia.org/nicholassteno https://www.wikiepedia.org/charleslyell https://www.google.com/search?q=principle+of+inclusion+geology&client=firefox-b-d&sxsrf=ACYBGNSXwfeqepLW2dXbaGTCATHqZSDeOA:1568869081836&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi8pcnijNzkAhVOSX0KHcT1D4sQ_AUIESgB#imgrc=zvjZZZTN5ghkWM :

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