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Since sedimentary particles settle from fluids and experience the influence of gravity, the stratification was originally horizontal and when steeply inclined must have suffered subsequent disturbance. This is the second of the principles established in 1669 by Niels Stensen (alias Nicolaus or Nicolas Steno) (Dott and Batten, 1976).
Steno's three principles are still the fo undaformformtion of sedimentary stratigraphy. These are:
- principle of superposition, the crucial discovery that old rock layers underlie new rock layers.
- principle of original horizontality, that sediments are deposited as liquids, and like water, they are deposited horizontally, filling in irregularities at the bottom, but making a smooth surface at the top.
- Principle of lateral continuity, that layers of sediment are continuous, unless a barrier prevents the sediments from spreading during deposition, or subsequent changes in the landscape break those sediment layers apart.
References
Dott, Robert H. and Batten, Roger L., 1976, Evolution of the earth, McGraw-Hill, New York, ISBN 0070176191, 2nd edition, 504 p.
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Thursday, November 11, 2021