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Sequence stratigraphy

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Facies Analysis, Facies Associations, Facies Sequences, and Facies Models; Sedimentary Depositional Environments; Types of Sedimentary Environments; Depositional Environment Setting; Classification of Clastic Sedimentary Rocks; Stratigraphy; Actualism ; Lithostratigraphy; Stratigraphy Boundaries; Types of Unconformities; Sedimentary (litho) facies; Depositional Systems Analysis; Facies Analysis, Facies Associations, Facies Sequences, and Facies Models; Sedimentary facies Changes; Carbonate Depositional Environments; Generalized (Siliclastic) Shoreline Profile with depositional facies of the Shelf and the Shoreface Facies Association; Common Siliciclastic Stratigraphic Successions; L-Bar and T-Bar Sequences, Braided River Deposits; Point-Bar Sequence, Meandering River Deposits; Hummocky Sequence, Storm Shelf Deposits; Bouma Sequence, Turbidite (Submarine Fan) Deposits; Barrier system; Mahakam delta; Deep-water fan morphology; Sequence Stratigraphy Concepts; Base Level; Relative Sea Level; Causes of sea-level change; Facies Analysis and Walther’s Law; Transgression and Regression;Paleomagnetism; Curie Point; Thermal Remanent Magnetism (TRM); Chemical Remanent Magnetism; Depositional Remanent Magnetism; Virtual Magnetic Pole; Apparent Polar Wander (APW) path

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Sequence stratigraphy

  1. 1. @Hassan Z. Harraz 2019 Sequence stratigraphy Prof. Dr. Hassan Z. Harraz Geology Department, Faculty of Science, Tanta University hharraz2006@yahoo.com Spring 2019
  2. 2. Outlines  Introduction  Sedimentary Depositional Environments  Types of Sedimentary Environments  Depositional Environment Setting  Classification of Clastic Sedimentary Rocks  Stratigraphy  Principles of Stratigraphy (revisited)  Actualism and "Genetic Stratigraphy“  Lithostratigraphy  Objective Subdivision of the Stratigraphic Record Into Distinct Lithostratigraphic Units  Stratigraphy Boundaries  Types of Unconformities  Sedimentary (litho) facies  Depositional Systems Analysis  Facies Analysis, Facies Associations, Facies Sequences, and Facies Models  Sedimentary facies Changes  Carbonate Depositional Environments  Common Sedimentary Facies Associations in Carbonate Dominated Environments  Generalized (Siliclastic) Shoreline Profile with depositional facies of the Shelf and the Shoreface Facies Association 2  Common Siliciclastic Stratigraphic Successions 1) L-Bar and T-Bar Sequences, Braided River Deposits 2) Point-Bar Sequence, Meandering River Deposits 3) Hummocky Sequence, Storm Shelf Deposits 4) Bouma Sequence, Turbidite (Submarine Fan) Deposits 5 ) Barrier system 6) Mahakam delta 7) Deep-water fan morphology  Sequence Stratigraphy Concepts:  Base Level  Relative Sea Level  Causes of sea-level change  Walther’s Law  Facies Analysis and Walther’s Law  Transgression and Regression  Paleomagnetism  Curie Point; Thermal Remanent Magnetism (TRM); Chemical Remanent Magnetism; Depositional Remanent Magnetism; Virtual Magnetic Pole; Apparent Polar Wander (APW) path @Hassan Z. Harraz 2019 Sequence stratigraphy
  3. 3. Fig 1: Major clastic sedimentary environments (bright-gray). The three major depositional environments (Level 1) are continental (non-marine), mixed (marine to non-marine or coastal setting), and marine (submarine). Each of these deposits has a characteristic set of processes and resulting deposits which form different reservoir types. 3 • Physical • Biological • Chemical Sedimentary Depositional Environments @Hassan Z. Harraz 2019 Sequence stratigraphy
  4. 4. Types of Sedimentary Depositional Environments  Types of sedimentary environments I) Continental (Terrestrial)  Dominated by Stream erosion and deposition 1) River: i) Fluvial ii) Meandering Stream iii) Flood-plain 2) Alluvial Fan 3) Lacustrine (Lakebeds) 4) Evaporites 5) Eolian Deposit: Sand dunes (Strong winds) 6) Glacial II) Transitional  Deltaic (Delta)  Tidal (Tidal Flat)  Lagoonal (Barrier Island-Lagoon)  Beach (Barrier Beach) III) Marine  Shallow (to about 200 meters):  Continental Shelf  Continental Slope  Continental Rise  Reef (Carbonate Barrier)  Submarine canyon  Deep Sea Fan:  Submarine (or Abysaal) Fan  Turbidite Fan  Deep sea floor (Carbonate Platform, Basin Floor) • Areas of the Earth’s surface where distinct processes generate specific geological (sedimentary) products: @Hassan Z. Harraz 2019 Sequence stratigraphy
  5. 5. Figure 7.CDistribution of marine sediments @Hassan Z. Harraz 2019 Sequence stratigraphy
  6. 6. Examples of Sedimentary EnvironmentsRed – continental environments Blue – transitional environments Black – marine environments Flood-plain @Hassan Z. Harraz 2019 Sequence stratigraphy
  7. 7. Schematic diagram showing the main sedimentary depositional Environments 7@Hassan Z. Harraz 2019 Sequence stratigraphy
  8. 8. Depositional Environment Setting 8@Hassan Z. Harraz 2019 Sequence stratigraphy
  9. 9. A very basic classification of all sedimentary rocks is based on the type of material that is deposited and the modes of deposition. The Classification of Clastic Sedimentary Rocks Factors which influence clastic depositional systems @Hassan Z. Harraz 2019 Sequence stratigraphy
  10. 10. Stratigraphy 10  Any package of sedimentary strata bounded above and below by an unconformity (of any kind) is a SEQUENCE.  Traditional sedimentology and stratigraphy judge formations to be the fundamental units of the rock record, and interpretation of sedimentary environments to be the essential product of stratigraphic studies.  Sequence stratigraphy makes sequences the fundamental units of the rock record, and hence emphasizes periods of deposition and nondeposition (closely related to episodes of rising and falling sea level) as the essential information. Sequence stratigraphy grew out of seismic stratigraphy; unconformities are easily distinguished in seismic records, but lithology is often unknown.  Sedimentary accumulation (hence the boundaries of sequences) is controlled by changes in base level, the elevation to which sediments will accumulate if the local land surface is too low, or erode is the local land surface is too high. @Hassan Z. Harraz 2019 Sequence stratigraphy
  11. 11. Principles of Stratigraphy (revisited) Recall the fundamental principles of stratigraphy: original horizontality, superposition, cross- cutting A more detailed study brings up three major themes: Uniformitarianism: the interpretation of ancient deposits by analogy to modern, observable environments. Cyclicity: climate, sea-level, annual, tidal variations, etc., all generate repeating cycles of sedimentation. Hierarchy: basic stratigraphic principles apply across a wide range of space and time scales 11@Hassan Z. Harraz 2019 Sequence stratigraphy
  12. 12. 12 Actualism and "Genetic Stratigraphy" Recognition of Uniformitarianism the relationship between modern processes of sedimentation and the rock record @Hassan Z. Harraz 2019 Sequence stratigraphy
  13. 13. 13 Lithostratigraphy Definitions of stratigraphic elements: Rock units are organized into a hierarchy of classifications Formations, Members, Groups, ..etc. Material Units and "Classical Layer Cake Stratigraphy“ • Catastrophism: continuous layering = time equivalence NO!  Further organization and subdivision of the rock record otbo  Relative age: Superposition, unconformities, cross cutting relationships, included fragments  Original Horizontality  Lateral Continuity  There are also supergroups and subgroups, used when original group definitions later prove inadequate to describe important associations. Name Typical thickness Lateral Continuity Group > 1000 m Continent-wide Formation 100-1000 m 1000 km Member (Lens, Tongue) 10-100 m 100 km Bed or Flow 1-10 m 10 km @Hassan Z. Harraz 2019 Sequence stratigraphy
  14. 14. 14 Objective Subdivision of the Stratigraphic Record Into Distinct Lithostratigraphic Units Formations with a type section, geographic or lithologic name, and definition based on:  limited and distinctive lithologic variability  consistent stratigraphic context  “extensive” map distribution in the surface or subsurface Groups and Supergroups  Are formations lumped otbo stratigraphic association Members and beds  Subdivisions of Formations  lithostrat units with less areal extent defined as it is useful @Hassan Z. Harraz 2019 Sequence stratigraphy
  15. 15. Stratigraphy Boundaries The boundaries between rock units can be conformable or unconformable. Conformable is meant to describe continuous deposition with no major breaks in time or erosional episodes. This definition is somewhat scale-dependent – just how long or large a gap is an unconformity depends on the size and time significance of the units being divided. A vertical succession of strata represents progressive passage of time, either continuously at the scale of observation (conformable) or discontinuously (unconformable). A lateral succession of strata represents changing environments of deposition at the time of sedimentation or diagenesis. Each recognizable environment in a lateral succession is called a facies. 15@Hassan Z. Harraz 2019 Sequence stratigraphy
  16. 16. Types of Unconformities ii) Disconformity is used when beds above and below are parallel but a well-developed erosional surface can be recognized, by irregular incision, soil development, or basal gravel deposits on top. iii) Paraconformity is used for obscure unconformities where correlation with time markers elsewhere indicates missing strata, even though no evidence of a gap is present locally. iv) Nonconformity is used for deposition of bedded strata on unbedded (usually igneous or metamorphic) basement. 16 • Unconformities are usually divided into four types: i) Angular unconformity is used when layers below are clearly tilted or folded and then eroded before deposition continues on the eroded surface @Hassan Z. Harraz 2019 Sequence stratigraphy
  17. 17. 17 Sedimentary (litho) Facies and (litho) Facies Analysis Sedimentary (litho) facies  Lithostratigraphic Units (time independent)  Defined by sum total of (relevant) rock properties  Reflects processes during genesis and may include:  Lithology  Sedimentary Structures  Fossils  Bedding style and geometry (on various scales)  Paleo-sediment transport indicators  It is possible to more precisely determine the sum total of processes active at the site of deposition and interpret “Depositional Environment”  Facies sequences are recurring (in the geological record) facies associations which occur in a particular order due to the inherent temporal changes in depositional conditions in particular depositional environments e.g.: Hummocky Cross Stratified, Zoophycus burrowed, fine- to medium- grained, sandstone @Hassan Z. Harraz 2019 Sequence stratigraphy
  18. 18. 18 Depositional Systems Analysis • Depositional Systems: (lithostratigraphic units) • Three dimensional assemblages of lithofacies, which are interpreted to be genetically linked by process and environment @Hassan Z. Harraz 2019 Sequence stratigraphy
  19. 19. 19 Facies Analysis, Facies Associations, Facies Sequences, and Facies Models Facies Models are a general summary of a given depositional environment or depositional system:  Lithostratigraphic unit representing depositional processes and geographic location The apparent existence of order in Nature suggest that there are (and have been through geological time) a limited number of different and recognizable depositional systems These depositional systems are identified through the use of Facies Models @Hassan Z. Harraz 2019 Sequence stratigraphy
  20. 20. Sedimentary facies Changes:  Different sediments often accumulate adjacent to one another at the same time  Each unit (facies) possesses a distinctive set of characteristics reflecting the conditions of a particular environment  Merging of adjacent facies is a gradual transition @Hassan Z. Harraz 2019 Sequence stratigraphy
  21. 21. 21 Model prediction of shelf sediments…Facies Changes. @Hassan Z. Harraz 2019 Sequence stratigraphy
  22. 22. Carbonate Depositional Environments 22@Hassan Z. Harraz 2019 Sequence stratigraphy
  23. 23. Common Sedimentary Facies Associations in Carbonate Dominated Environments • Carbonate sediment dominated, rimmed shallow marine shelf • RIMMED CARBONATE SHELF SYSTEM 23 Rimmed Carbonate Platform 23@Hassan Z. Harraz 2019 Sequence stratigraphy
  24. 24. Generalized (Siliclastic) Shoreline Profile with depositional facies of the Shelf and the Shoreface Facies Association 24@Hassan Z. Harraz 2019 Sequence stratigraphy
  25. 25. 25 Common Siliciclastic Stratigraphic Successions  Vertical successions characterized by lithology, associations and vertical arrangement of sedimentary structures:  Indicative of particular sedimentary depositional environments  Expression of Walther’s Law  Reflects Autocyclicity:  stratigraphic variability inherent to a particular depositional environment.  Four Common Stratigraphic Sequences are recorded, namely: 1) L-Bar and T-Bar Sequences, Braided River Deposits 2) Point-Bar Sequence, Meandering River Deposits. 3) Hummocky Sequence, Storm Shelf Deposits, 4) Bouma Sequence, Turbidite (Submarine Fan) Deposits Four Common Stratigraphic Sequences and their Environmental Interpretations @Hassan Z. Harraz 2019 Sequence stratigraphy
  26. 26. 26 1) L-Bar and T-Bar Sequences, Braided River Deposits • High gradient, low sinuosity, sand and gravel dominatedBraided River System @Hassan Z. Harraz 2019 Sequence stratigraphy
  27. 27. 27 2) Point-Bar Sequence, Meandering River Deposits Low Gradient, high sinuosity, mud to sand dominatedMeandering River System @Hassan Z. Harraz 2019 Sequence stratigraphy
  28. 28. 28 3) Hummocky Sequence, Storm Shelf Deposits hummocky cross stratified, Zoophycus burrowed, fine- to medium-grained, sandstoneStorm Shelf, Hummocky Sequence @Hassan Z. Harraz 2019 Sequence stratigraphy
  29. 29. 29 4) Bouma Sequence, Turbidite (Submarine Fan) Deposits Sediment gravity flow-dominated (Turbidity Currents), “deep” water sediment dispersal Deep OceanSubmarine Fan System @Hassan Z. Harraz 2019 Sequence stratigraphy
  30. 30. Barrier system 30@Hassan Z. Harraz 2019 Sequence stratigraphy
  31. 31. Mahakam delta 31@Hassan Z. Harraz 2019 Sequence stratigraphy
  32. 32. This reef was built by algae, sponges, and bryozoa. Skeletons help trap sediments, aid in build-up. Deep-water fan morphology @Hassan Z. Harraz 2019 Sequence stratigraphy
  33. 33. 33 Example: Reservoir potential of turbidite facies @Hassan Z. Harraz 2019 Sequence stratigraphy
  34. 34. 34@Hassan Z. Harraz 2019 Sequence stratigraphy
  35. 35. Components of Sequences Components of sequences, their log responses, and predicted and observed seismic reflection pattern 35@Hassan Z. Harraz 2019 Sequence stratigraphy
  36. 36. Sequence Stratigraphy Concepts Sequence Stratigraphy highlights the role of allogenic controls on patterns of deposition, as opposed to autogenic controls that operate within depositional environments: Eustasy (Sea Level) Subsidence (Basin Tectonics) Sediment supply (Climate and hinterland tectonics) 36@Hassan Z. Harraz 2019 Sequence stratigraphy
  37. 37. Representation Sequence Stratigraphy 37@Hassan Z. Harraz 2019 Sequence stratigraphy
  38. 38. Base Level 38 On land, base level is set by the equilibrium profile of river systems. In marginal marine settings, base level is often the same as sea level In the deep sea there is no base level and sedimentation is controlled only by sediment supply. Changes in base level allow the sedimentary record to preserve evidence of geological events:  Relative sea level change is the most important determinant of changes in base level.  Local tectonic uplift or subsidence changes base level and leads to erosion or accumulation.  Changes in water supply or sediment load affect the equilibrium profile of a river and therefore the base level downstream. @Hassan Z. Harraz 2019 Sequence stratigraphy
  39. 39.  Changes in Sea Level: i) Eustatic Sea Level Changes  Climate (Ice Ages)  Tectonic (development of Mid-Ocean Ridges) 39 ii) Local Sea Level Changes:  Uplift  Subsidence @Hassan Z. Harraz 2019 Sequence stratigraphy
  40. 40. Base Level 40 The parameters of the curve for each river are different, and depend on various parameters. Changes in these parameters will cause the river to aggrade or incise to reach a new equilibrium base level. Parameters include the elevation of the headwaters, which may change by uplift or erosion; the elevation of the mouth, which may change up uplift or sea- level change; the sediment supply, the water discharge, the type of rock being cut. • On land, base level is set by the equilibrium longitudinal profile of river systems, which evolve to a characteristic shape: @Hassan Z. Harraz 2019 Sequence stratigraphy
  41. 41. Base Level 41 The placing of an artificial knickpoint in a river by building a dam has curious consequences, both upstream and downstream. A waterfall must retreat because it is steeper than the equilibrium gradient for the reach of the river below the falls. A sudden drop in base-level leads to the formation of river terraces A knickpoint (resistant bed or lake) where the form of the river is interrupted leads to a nested set of river profiles. @Hassan Z. Harraz 2019 Sequence stratigraphy
  42. 42. Relative Sea Level 42 Relative sea level is the depth of water relative to the local land surface.  Relative sea level can change due to local vertical tectonic motions or due to eustatic sea level variations (i.e. global changes in the volume of ocean water or of the ocean basins).  In both sequence and traditional stratigraphy, the critical events that determine the locations of environments and unconformities are transgressions and regressions. A transgression is a landward shift in the coastline, and hence a landward shift in all marginal marine environments. A regression is a seaward shift in the coastline.  A drop in relative sea level always causes a regression. A transgression hence requires rising relative sea level. However, rising sea-level can result in transgression, stationary shorelines, or regression depending on sediment supply.  This asymmetry results because sediment flux from land is always positive, and because transgression during sea-level fall would create unstable, over- steepened long-valley profiles. @Hassan Z. Harraz 2019 Sequence stratigraphy
  43. 43. Factors effect on Stratigraphic Sequences 1)Sedimentation Rate 2)Change in Relative Sea Level 3)Subsidence rate 4)Rate of eustatic sea level change 43 Examples  Eustatic Sea Level is Constant  Sedimentation > Subsidence Rate – Regression  Sedimentation < Subsidence Rate - Transgression  Sedimentation = Subsidence Rate  Sea Level Rises – Transgression  Sea Level Falls – Regression i) Regression Sequence (offlap sequence) ii) Transgression Sequence (onlap sequence) Types of Stratigraphic Sequences @Hassan Z. Harraz 2019 Sequence stratigraphy
  44. 44. Relative Sea Level 44 • Whether transgression or regression occurs controls the preservation potential and vertical succession of environments like barrier islands • rising sea-level can result in transgression, stationary shorelines, or regression depending on sediment supply. @Hassan Z. Harraz 2019 Sequence stratigraphy
  45. 45. 45 Causes of sea-level change Relative sea level can change due to local or regional tectonics, which cause vertical motions (uplift and subsidence). Global sea level can only change by altering either the volume of sea water or the volume of the ocean basins themselves. On time scales of 103–105 years, glaciation can quickly tie up and release enough water to change global sea level by ~200 m. But Sloss cycles have time scales of 108 years and amplitudes of 1000 m! Changes in the global configuration of continents and the working of plate tectonics can affect global sea level by changing the volume of the oceans:  when continents are assembled into supercontinents, the area of shallow shelves is greatly decreased and the mean age of the ocean crust is a maximum, because there are few small oceans and one big one. This should lead to a big fall in sea level (Permian through Jurassic regression?).  when continents rift, a new, shallow ocean is created at the expense somewhere of an old, deep ocean. Sea level should rise.  an increase in spreading rate of the global ridge system leads with time to increase in the volume of water displaced by the mid-ocean ridges and a sea-level rise (cause of Cretaceous transgression?). @Hassan Z. Harraz 2019 Sequence stratigraphy
  46. 46. Walther’s Law 46 We are now ready to state the third fundamental tenet of traditional stratigraphy, lateral continuity, which is expressed by Walther’s Law: In a conformable vertical succession, only those facies that can be observed laterally adjacent to one another can be superimposed vertically. That is, if the lateral shifting of sedimentary environments is controlled by continuous changes in base-level, each point accumulating sediments vertically passes through all intermediate environments continuously. Thus, e.g., deep-sea sediments directly overlying a terrestrial flood-plain facies demands an unconformity in between. Consider again the vertical succession of beach facies, which maps the lateral succession of beach facies onto a single point as the beach progrades outwards during a regressive relative sea-level rise. @Hassan Z. Harraz 2019 Sequence stratigraphy
  47. 47. 47 Facies Analysis and Walther’s Law “It is a basic statement of far reaching significance that only those facies and facies areas can be super imposed primarily that can be observed beside each other at the present time”. Gradational (vertical) transitions from one facies to another indicate original adjacency and genetic relationship during formation. Sharp/erosional (vertical) contacts between facies provides NO evidence of contemporaneous genetic relationship of depositional environments. @Hassan Z. Harraz 2019 Sequence stratigraphy
  48. 48. Transgression and Regression 48  In vertical succession, transgression is recognized by progression from inland towards deep water sediments moving up section; regression, if preserved, is recognized by progressively shallower water facies moving towards continental settings as you go up section. @Hassan Z. Harraz 2019 Sequence stratigraphy
  49. 49. Transgression and Regression 49 The ideal sequence consists of a transgressive clastic formation, a carbonate formation deposited when essentially the whole continent was flooded, and a regressive clastic formation (less often preserved after erosion). On a regional-continental scale, transgression is recognized by lateral migration of environments with time, from the coast towards the interior, and regression by migration of environments towards the coast. @Hassan Z. Harraz 2019 Sequence stratigraphy
  50. 50. Paleomagnetism 50 A magnetic mineral crystallized above the Curie point and then cooled through it acquires a Thermal Remanent Magnetism (TRM) in the same direction as and with intensity proportional to the applied field. As we have already discussed, the Earth’s magnetic field varies with time and records of the paleomagnetic field are preserved in rocks. Let’s look in more detail. Magnetization of rocks: At high temperatures, all materials are paramagnetic, meaning their magnetization is proportional to the applied field, and zero in the absence of an applied field Materials with unpaired electron spins can undergo a phase transition to ferromagnetic behavior at a temperature called the Curie Point. Material Curie Point (°C) Specific Magnetization (A m2 /kg) Fe 770 227 Magnetite (Fe3O4) 578 93 Hematite (Fe2O3) 675 0.5 @Hassan Z. Harraz 2019 Sequence stratigraphy
  51. 51. Paleomagnetism 51 If a magnetic mineral is formed by chemical alteration or metamorphism at temperatures below its Curie Point, it acquires a Chemical Remanent Magnetism. If a given rock cooled at one time with some magnetic minerals and was altered later to grow new magnetic minerals, the TRM and CRM may point in different directions. They can be separately measured by progressive demagnetization of a sample with increasing temperature. If magnetic particles are eroded from a source, transported, and deposited in a new rock under appropriate conditions, all below the Curie Point, they will have a preferred orientation governed by the magnetic field at the time of sedimentation, a Depositional Remanent Magnetism. This will typically be ~1000 times weaker than the magnetic moment in a lava where each little dipole is perfectly aligned, but it is measurable. @Hassan Z. Harraz 2019 Sequence stratigraphy
  52. 52. Paleomagnetism 52 Measurement of the vector remanent magnetic field in a rock sample gives the declination and inclination of the field at the time and location of acquisition. If the terrestrial magnetic field was a simple dipole at the time of acquisition, this measurement gives a Virtual Magnetic Pole: The declination gives the orientation of the great circle on which the pole lies, and the inclination gives the magnetic latitude of the sample. @Hassan Z. Harraz 2019 Sequence stratigraphy
  53. 53. 53 Paleomagnetism A measured virtual magnetic pole reveals several facts: Magnetic polarity at time of magnetization, assuming you know which hemisphere the sample was in and have some rough idea of horizontal Intensity of the field at the time of magnetization, if you correct for the susceptibility of the particular sample. @Hassan Z. Harraz 2019 Sequence stratigraphy
  54. 54. Paleomagnetism 54  The apparent latitude of the sample at the time of magnetization. If it does not match the present latitude, you can infer that the sample has moved north or south. • There are terranes on the west coast of North America whose magnetic inclinations imply motions of thousands of kilometers. • You get no information on longitude, which is a limitation in the reconstruction of positions of continents in the past; this is particularly serious before the Mesozoic, when there are no marine magnetic anomalies to go by.  Tectonic rotations about a vertical axis show up through anomalies in the measured declination.  A sequence of virtual magnetic poles from a series of rocks of different ages attached to one stable continent defines an Apparent Polar Wander (APW) path. • “Apparent” because it is not clear without a fixed frame of reference whether it is the continent or the pole that has wandered. • However, the difference between APW paths for two different continents gives an accurate measurement of the relative motion between the two continents. @Hassan Z. Harraz 2019 Sequence stratigraphy
  55. 55. Examples 55@Hassan Z. Harraz 2019 Sequence stratigraphy

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