Principle of Stratigraphic
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This document summarizes key concepts in stratigraphy and sequence stratigraphy. It discusses the principles of stratigraphy including superposition, original horizontality, and lateral continuity. It also describes unconformities and how they represent gaps in the stratigraphic record. Sequence stratigraphy divides rock sequences into systems tracts based on bounding surfaces and stacking patterns. Sequences are bounded by unconformities and composed of parasequence sets, which are made up of genetically related beds bounded by flooding surfaces.
Principle of Stratigraphic
- 1. Principle of Stratigraphic Lecture 8#
- 2. STRATIGRAPHIC Study about: Rock bedding (strata)-description- cluster – classification Stratigraphic unit, Age relative relation (bedding sequence), The process and the forming environment. The process sequences: relation between the process.
- 3. Rock strata fundamental principal: Superposition Original horizontality Lateral continuity
- 4. Superposition SUPERPOSITION (Steno, 1669) Original statement : At the time when any given stratum was being formed, all the matter resting upon it was fluid, and therefore, at the time when the lowest stratum was being formed, none of the upper strata existed. Modified statement : Law of Superposition : the younger strata at the top in an undisturbed sequence of sedimentary rocks (Anthony, 1955).
- 5. ….At the time when any given stratum was being formed, all the matter resting upon it was fluid…. (Steno, 1669)
- 6. Original Horizontality Original statement (Steno): As regards form, it is certain that at the time when any given stratum was being produced, its lower surface, as also its lateral surfaces, correspond to the surfaces of the lower substance and lateral substances, but that the upper surface was parallel to the horizon so far as possible; and that all strata therefore, except the lowest were bounded by two planes parallel to the horizon. Hence it follows that strata either perpendicular to the horizon or inclined toward it were art one time parallel to the horizon. Modified statement : Law of Horizontality : Sedimentary strata are laid down nearly horizontally and are essentially parallel to the surface upon which they accumulate (Anthony, 1955).
- 9. Lateral Continuity Original statement (Steno) : At the time when any given stratum was being formed it was either encompassed on its sides by another solid substance, or it covered the entire spherical surface to the earth. Hence it follows that in whatever place the bared sides of the strata are seen, either a continuation of the same strata must be sought, or another solid substance must be found which kept the matter of the strata from dispersion. Modified statement : Law of Original Continuity : The original continuity of water-laid sedimentary strata is terminated only by pinching out against the basin of deposition, at the time of their deposition (Anthony, 1955).
- 10. Principle of sedimentation 1. Sediment being deposit laterally until the end of the sedimentation boundary. 2. Sediment cannot be suddenly cut out laterally.
- 11. Classical unconformity; Hutton, 1785 1. Time gap exist 2. Depositional stop Process sequences: Uplift Folding and/or faulting Erosion Subsidence Re-Depositional
- 13. Arizona Grand Canyon Tilted sedimentary rocks of Precambrian age (lower half of photo) are overlain by younger sedimentary rocks of Phanerozoic age (Cambrian and younger, upper half of photo).
- 14. Types of classical unconformity; Hutton, 1785 • Angular unconformity • Disconformity • Non-conformity • Paraconformity
- 15. Angular Unconformity An angular unconformity is an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers Disconformity A disconformity is an unconformity between parallel layers of sedimentary which represents a period of erosion or non-deposition
- 16. Non-conformity A nonconformity exists when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock Paraconformity A paraconformity is in which strata are parallel; there is little apparent erosion and the unconformity surface resembles a simple bedding plane
- 17. Rock Strata Relationship: 1. Continue 2. Unconformity 3. Crosscutting : depend on the relative age and occurrence time
- 25. Definition of Sequence Stratigraphy: “It is a conceptual framework and methodology to get an integrated interpretation of strata units and their patterns from available data (seismic, well logs, cores, outcrops)…” Vail & Sangree, 1988
- 26. Eustasy, Relative Sea Lavel, and Water Depth
- 27. Accommodation “ The space available for sediments to accumulate at any point in time” (Jervey, 1988)
- 28. Fundamental Concepts of Sequence Stratigraphy The stratigraphic signatures result from the interaction of the following factors: 1. Tectonics 2. Eustasy (changes in the amount of water in the oceans, usually due to global climate change) 3. Sedimentation Tectonic and eustasy control the amount of the space available for sediments to accumulate accommodation Tectonic and Climate control the amount and types of sediments available to be accumulated Sediment supply Tectonic, Eustasy, and Climate control how much of the accommodation is filled by the sediments Sedimentary process control the detailed facies that fill the accommodation. Vall et al., 1990 Elmery & Myers., 1996
- 32. PARASEQUENCE Parasequence is a relative conformable succession of genetically related beds or bedsets bounded by marine flooding surface or their correlative surfaces Marine flooding surface is a surface separating younger from older strata across which there is evidence of an abrupt increase in water depth Parasequence have been identified in coastal plain, deltaic, beach, tidal, estuarine, and shelf environments It is difficult to identify parasequences in fluvial sections Parasequences are absent in the marine or marginal marine rocks which are deposited too far below sea level to be influenced by an increase in water depth
- 34. PARASEQUENCE SET Parasequence set is a relative conformable succession of genetically related parasequences forming a distinctive stacking pattern bounded by major marine flooding surface or their correlative surfaces. Stacking patterns of parasequences within parasequence sets are progradational, aggradational or retrogradational depending on the ratio of depositional rates to accommodation rates.
- 36. SEQUENCE Sequence is a relatively conformable succession of genetically related strata bounded by surfaces of unconformity or their correlative surfaces Surface of unconformity is a surface separating younger from older strata along which there is evidence of subaerial erosion, or subaerial exposure, with a significant hiatus indicated Surface of conformity is a surface separating younger from older strata along which there is no evidence of erosion (neither sub-aerial nor submarine) or non-deposition, and along which no significant hiatus is indicated.
- 37. SYSTEMS TRACTS Sequence can be subdivided into systems tracts based on objective criteria including types of bounding surfaces, parasequence set distribution, and position within the sequence System tract is a linkage of contemporaneous depositional systems Depositional system is a three dimensional assemblage of lithofacies, genetically linked by active (modern) or inferred (ancient) processes and environments There are several systems tract identified in sequences: •Lowstand systems tract •Transgressive systems tract •Highstand systems tract •Shelf-margin system tract