Sedimentology Lecture 3. transitional depositional systems
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This document discusses river deltas, including their definition, classification, and importance. It begins by defining a delta as a deposit built by a river into a body of permanent water, consisting of both terrestrial and marine/lacustrine strata. Approximately 25% of the world's population lives on deltaic coastlines and deltas host close to 30% of oil, coal, and gas deposits. Common classifications of deltas include geomorphology-based (e.g. lobate), stratigraphy-based (e.g. shelf-type), and process-based approaches (e.g. river-, wave-, or tide-dominated). Key delta types discussed include the river-dominated Mississippi delta and the wave-dom
Sedimentology Lecture 3. transitional depositional systems
- 2. Continental systems alluvial fans glaciers lakes rivers embayments aeolian dune fields estuaries TRANSITIONAL SYSTEMS Marine systems
- 3. DELTAS
- 4. WHAT ARE DELTAS, AND WHY ARE THEY IMPORTANT? The concept of delta dates back to Herodotus (c. 400 BC), who recognized that the alluvial plain at the mouth of the Nile had the form of the capital Greek letter Δ. The first study of ancient deltas was that of Gilbert (1885), who described Pleistocene fresh-water gravelly deltas in Lake Bonneville, Utah. Barrell (1912) defined a delta as: «a deposit partly subaerial built by a river into or against a body of permanent water. The outer and lower parts are necessarily constructed below water level, but its upper and inner surface must be land maintained or reclaimed by the river building from the sea. A delta, therefore, consists of a combination of terrestrial and marine, or at least lacustrine strata, and differs from other modes of sedimentation in this respect»
- 5. About 25% of the world’s population live on deltaic coastlines and wetlands (Syvitski et al., 2005). Significant fresh-water resources also occur in delta deposits From the economic perspective, deltas have been estimated to host close to 30% of all of the world’s oil, coal, and gas deposits (Tyler and Finley, 1991). However, as production declines and global energy needs continue to grow, new and better facies models will be required to improve the extraction of oil and gas. WHAT ARE DELTAS, AND WHY ARE THEY IMPORTANT?
- 6. TYPES OF DELTAS In nature, there is a very enourmous variety of river deltas that change in their aspect on the basis of a wide range of factors, including: climate influencing sediment supply, energy and types of the marine forces (waves, tides, currents), tectonic setting and, recently, the anthropogenic pressure.
- 7. 7 Definition of river deltas A depositional system that lies both on the continent and above the sea is called transitional, because its component environments develop in subaerial and subaqueous conditions. One of the most representative transitional system is a river delta. When a river debouches into a basin, since it loses its transportation capacity, sediments become to be distributed and deposited. Then, a delta develops. The Nile delta
- 8. subaqueous sector upper delta plain lower delta plain DELTA CANYONS distributary channels 8 emerged sector River deltas: main depositional environments
- 9. MOST COMMON (=USED) CLASSIFICATIONS OF DELTAS GEOMORPHOLOGY-BASED APPROACH CONSTRUCTIVE DELTAS cuspate digitate arcuate estuarine tides waves lobate A first pioneeristic approach based on the coastal shape (in-plant view) of a delta and an attempt to correlate forms with processes (fluvial and marine). based on Fisher, 1967 Nile Mississippi Gange Rio Plata
- 10. STRATIGRAPHY-BASED APPROACH A widely- but often improperly-used classification based on the dominant depositional architecture of the deltaic strata. This method was often confusing because erroneously associated to a specific tectonic setting. Massari & Colella, 1988 SHELF-TYPE DELTA SLOPE-TYPE DELTA GILBERT-TYPE DELTA Crati Basin Messina Strait Logudoro Basin MOST COMMON (=USED) CLASSIFICATIONS OF DELTAS
- 11. PROCESS-BASED APPROACH The Galloway’s scheme is the one most commonly used by sedimentologists. It has gained much popularity among researchers of river deltas, and has also been adopted fro fan deltas.. Galloway, 1975 Orton & Reading, 1988 process-based/grain size approach MOST COMMON (=USED) CLASSIFICATIONS OF DELTAS
- 12. 12 Rivers, tides, waves, and currents, in varying proportions, all play a role in the ultimate distribution of deltaic sediment along different coastlines. A six-fold subdivision of deltas is one of the most common way to classify deltas, on the function of the respective influences of waves, tides, and rivers. Bhattacharya and Walker (1992) With deltaic reservoirs of hydrocarbons, it is essential to determine the type of deltaic deposit in order to maximize reservoir development and production. Errors are easily made in interpreting types of deltas in the subsurface environment, where we have only scattered wells and limited cores or image logs from which to identify depositional processes and environments. Transitional systems: deltas
- 13. The Mississippi delta: a river-dominated system
- 14. The Mississippi delta: a river-dominated system
- 15. 15 The Mississippi River delta has long been considered the “type” river-dominated delta. Strong waves and currents do not impinge upon its protected shoreline, so sediment deposited at and near the shore zone is not reworked or dispersed laterally. With time, and sufficient accommodation space between the sea surface and seafloor to accept sediment, such a delta will prograde seaward, as will the delta zones. Sandy reservoir facies are deposits of distributary channels and distributary mouth bars. Interdistributary bays, marshes, and lagoons separate sandy facies and provide shale barriers in subsurface reservoirs, and sometimes, they provide hydrocarbon source rocks. The Mississippi deltas
- 17. The Subarnarekha delta: a wave-dominated system
- 18. 18 Wave-dominated deltas Symmetric and/or asymmetric, wave-dominated deltas, result from dominant redistribution of sediments by waves, once the sediments reach the shoreline. Sandy barrier bar complexes and associated prodelta muds form in the downcurrent portion of the delta and represent very good reservoirs! Tiber Delta, Italy St. Gheorghe lobe of the Danube delta, Romania
- 19. The Gange delta: a tide-dominated system
- 20. 20 In an embayed coastline, waves and tides can interact closely, depending upon the configuration of the embayment and the orientation of the incoming waves. Particularly in narrow embayments, tidal energy can build progressively landward, giving rise to a very large tidal range. Thus, the tide-dominated delta can be a very high-energy environment, and the sediments will berelatively coarse grained. Reservoir continuity and fluid-flow patterns are highly dependent upon depositional processes in this tide-dominated delta system. Reservoir sandstones exhibit good continuity and fluid-flow potential in the dip-elongate direction, but they have poor continuity in the strike-orientated direction. Advanced hydrocarbon-recovery strategies must account for this architectural style if production is to be maximized. Tide-dominated deltas
- 21. DELTA TERMINOLOGY: USES AND ABUSES FAN DELTAS? Nemec, 1990b The term ‘fan delta’ applied to sedimentary succession is correct only if there are evidences on the nature of the feeder system! In short: only if we are sure that the delta was feeded by an alluvial fan it can be descripted as a FAN DELTA or ALLUVIAL FAN DELTA
- 22. Shelf-type or shallow-water fan deltas encroach on to low-gradient shelves with very shallow water depths at and near the river mouth. They generally have only three physiographic zones, delta plain or subaerial fan delta comprising alluvial settings, delta front or transition zone affected by waves and the prodelta, below wave base, receiving hemipelagites. In very shallow- water basins the prodelta may not exist. There is a gradual distal dimimution of grain size (Colella, 1988; Massari & Colella, 1988; Wescott & Ethridge, 1990) from poorly bedded and poorly sorted coarse-grained gravels through wave imbricated, fine-grained gravel and planar- laminated and tabular cross-bedded sand to interbedded tabular cross-laminated sand and rippled sand giving a well-developed coarsening- upward delta front to delta plain sequence (Galloway, 1976). Shelf-type/ shallow-water delta (Wescott & Ethridge, 1990) Slope-type/ deep-water delta (Wescott & Ethridge, 1990) Slope-type, deep-water fan deltas have a slope separating a poorly-developed delta front from the prodelta. They normally include a deep-water fan system which may be mud dominated. The slope may be an inherent constructional element of the delta, a delta slope, or it may be a consequence of a faulted basin margin and therefore be separated from the delta front by a pronounced shelf/slope break. In such cases subaerial fan gravels may sometimes pass seaward into a significant coastal transition zone of beach, shoreface and shelf gravels and sands before passing into deep-water mass flow deposits of the slope and base-of-slope settings. Gilbert-type delta (Wescott & Ethridge, 1990) Gilbert-type fan deltas occur in both shallow- water and relatively deep water settings. They consist of subaerial topset, subaqueous foreset and bottomset beds. The topset beds are deposited by shifting channels and may be part of an alluvial fan, a braidplain or a braided river. Foreset beds form where bedload, dropped at the river mouth, continues down the delta front as grain flows or frictional debris flows. Bottomset beds, deposited from a mixture of suspended load and gravity flows, form a low-gradient prodelta. Wescott & Ethridge, 1990 DELTA TERMINOLOGY: USES AND ABUSES FAN DELTAS?
- 23. Shelf-type/ shallow-water delta (Wescott & Ethridge, 1990) Slope-type/ deep-water delta (Wescott & Ethridge, 1990) Gilbert-type delta (Wescott & Ethridge, 1990) DELTA TERMINOLOGY: USES AND ABUSES FAN DELTAS?
- 24. Mellere et al., 2017
- 25. An outcrop case study from southern Italy
- 26. 1. Introduction to the general geological setting of the Calabrian Arc Calabria and the southern Apennine Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy)
- 27. The Calabrian Arc is a small orogeny, presently located in the southern Italy, which connects the NNW-trending Southern Apennine Chain with the Maghrebian Chain of Sicily. The Calabrian Arc mainly consists of Hercynian metamorphic and intrusive rocks, tectonically superposed on ophiolite-bearing units of Tethyan affinity, in turn overlying Mesozoic carbonate platform limestone of Apennine affinity . The sedimentary cover of the Hercynian basement is represented by Mesozoic redbeds passing upwards to Jurassic platform limestone. 1. Introduction to the general geological setting of the Calabrian Arc Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy)
- 28. Structure of the Calabria Terrane 28 1. Introduction to the general geological setting of the Calabrian Arc Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) The present-day arc-shaped setting of Calabria is the result of a tectonic superimposition onto the Apennine Chain during the middle Miocene after the opening of the Tyrrhenian back-arc basin.
- 29. 29 Origin of the Calabrian terrane 1. Introduction to the general geological setting of the Calabrian Arc Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) Southeast-ward migration of Calabria since 10 Ma Importance of strike-slip fault zones Tectonics and sedimentation: an example from the Paola Basin
- 30. The main Neogene-to-Quaternary basins Ghisetti & Vezzani (1981) 30 1. Introduction to the general geological setting of the Calabrian Arc Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) Strike-slip and extensional tectonics, possibly connected with blocks rotation, induced a structural fragmentation of the Calabrian Arc from the Middle Miocene onwards, and favored the formation of structural highs which separated grabens and half-grabens, including the Amantea and the Crati basins, which were filled by alluvial, to shallow-water to deeper marine sediments. Some of these basins formed narrow- linear marine seaways where amplification of tidal currents generated the accumulation of important volumes of sediment. Today these successions exhibit recurrent large-scale (> 3 m thick) cross-stratification motifs. In other sectors, tectonics generated small engulfed basins dominated by interior deltaic sedimentation
- 31. 31 2. Introduction to the Crati Basin Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) T h e C r a t i B a s i n The Pliocene-Quaternary Crati Basin occupies the northern Calabrian Arc . It is bounded by the Sila Massif crystalline terranes to the East, and by the crystalline and sedimentary rocks of the Coastal Range to the West and South. Its northern basin margin is represented by Mesozoic sedimentary rocks of the Pollino Range. On the basis of its tectono- stratigraphic features, the Crati Basin was divided into several sub-basins, including the N-S oriented Crati Trough and the E-W oriented Sibari Trough. The sedimentary deposits filling the Crati Basin are organized into transitional (= deltaic) and sublittoral depositional systems, whose stratal architectures and vertical stacking were strongly conditioned by active normal fault arrays (i.e., the so-called “Crati Fault System”). Siliciclastic sediments of the basin fill mostly derived from the tectonic uplifting of the marginal areas, whereas the bioclastic fractions were due to local shallow-water factories. Spina et al., 2013 Tansi et al., 2013 SILA MASSIF IONIAN SEA
- 32. 32 SOUTH NORTH 2. Introduction to the Crati Basin Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) T h e C r a t i B a s i n The south-eastern basin margin Fabbricatore, unpublished
- 33. 33 2. Introduction to the Crati Basin Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) T h e C r a t i B a s i n The Arente Section The Rose-Vetere Section The Zumpano Section The Meritani Section The Pescara Section
- 34. 34 2. Introduction to the Crati Basin Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) T h e C r a t i B a s i n
- 35. 35 10 m 50 m 5 m 1 m 2. Introduction to the Crati Basin Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) T h e C r a t i B a s i n The Spezzano Albanese Section
- 36. 36
- 37. Slope-type/ deep-water delta (Wescott & Ethridge, 1990) Slope-type, deep-water fan deltas have a slope separating a poorly-developed delta front from the prodelta. They normally include a deep-water fan system which may be mud dominated. The slope may be an inherent constructional element of the delta, a delta slope, or it may be a consequence of a faulted basin margin and therefore be separated from the delta front by a pronounced shelf/slope break. In such cases subaerial fan gravels may sometimes pass seaward into a significant coastal transition zone of beach, shoreface and shelf gravels and sands before passing into deep-water mass flow deposits of the slope and base-of-slope settings. 2. Introduction to the Crati Basin Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) Shelf-type or shallow-water fan deltas encroach on to low-gradient shelves with very shallow water depths at and near the river mouth. They generally have only three physiographic zones, delta plain or subaerial fan delta comprising alluvial settings, delta front or transition zone affected by waves and the prodelta, below wave base, receiving hemipelagites. In very shallow- water basins the prodelta may not exist. There is a gradual distal dimimution of grain size (Colella, 1988; Massari & Colella, 1988; Wescott & Ethridge, 1990) from poorly bedded and poorly sorted coarse-grained gravels through wave imbricated, fine-grained gravel and planar- laminated and tabular cross-bedded sand to interbedded tabular cross-laminated sand and rippled sand giving a well-developed coarsening- upward delta front to delta plain sequence (Galloway, 1976). Shelf-type/ shallow-water delta (Wescott & Ethridge, 1990) Gilbert-type delta (Wescott & Ethridge, 1990) Gilbert-type fan deltas occur in both shallow- water and relatively deep water settings. They consist of subaerial topset, subaqueous foreset and bottomset beds. The topset beds are deposited by shifting channels and may be part of an alluvial fan, a braidplain or a braided river. Foreset beds form where bedload, dropped at the river mouth, continues down the delta front as grain flows or frictional debris flows. Bottomset beds, deposited from a mixture of suspended load and gravity flows, form a low-gradient prodelta. Wescott & Ethridge, 1990 T h e C r a t i B a s i n
- 38. 38 2. Introduction to the Crati Basin Detection of outcrop analogues to the intra-Draupne sandstone unit of the Johan Sverdrup: Neogene-Quaternary basins of Calabria (southern Italy) T h e C r a t i B a s i n Fabbricatore, unpublished
- 39. ESTUARIES
- 40. • > Sediment supply < Accommodation Delta = Net transport seawards. Progradation • < Sediment supply > Accommodation Estuary = Net transport landwards. Infill of coastal bays Mawddach Estuary, (Wales, UK) Mekong Delta (Vietnam) Deltas versus Estuaries
- 41. Sedimentary Environments lake glaciers alluvial fans aeolian sands river & floodplain lagoon delta estuary mountains volcanic environments shelf epicontinental sea submarine fan shoreline ocean basin floor continental slope Shallow marine Continental Deep marine
- 43. Classification of coasts Modified after Hayes (1979)
- 44. Courtesy of Ron Boyd (2011) Classification of coasts Video 1
- 45. Estuaries Definitions: Seaward portion of a drowned incised valley which receives sediment from both fluvial and marine sources and which contains facies influenced by tide, wave and fluvial processes (Dalrymple et al., 1992); Transgressive coastal embayments with at least some amount of river influence (Dalrymple, 2010)
- 46. Definition of estuary Dalrympleet al. (1992)
- 47. Courtesy of Ron Boyd (2011) Classification of coasts
- 48. Cobequid Estuary, Nova Scotia Tide-dominated estuary
- 49. Tide-dominated estuary Dalrympleand Choi (2007) Zone 3 Zone 2 Zone 1
- 50. Tide-dominated estuary UFR = Upper Flow Regime
- 51. Zone 1 River-dominated “meandering” area Zone 1 Bay of Fundy, Canada
- 52. Zone 2 Mixed-energy “straight–meandering–straight” Zone 2 Bay of Fundy, Canada
- 53. Marine-dominated - elongate sand-bars Bay of Fundy, Canada Zone 3 Zone 3
- 54. Bay of Fundy, Canada Marine-dominated - elongate sand-bars
- 56. Tide-dominated estuaries Jade Estuary, Germany
- 57. Tide-dominated estuaries Jade Estuary, Germany Tidal sand bar Reineck, 1963
- 60. Tide-dominated estuaries Tidal channel (active during rising tide) Landward-migrating dunes produced during rising tide Small delta (an ebb tidal delta) Cross beds and ripples produced on falling tide are seaward directed
- 61. Land above high tide High water Low water Tide-dominated estuaries
- 63. Tidal channels Tidal creeks Mudflats Tide-dominated estuaries
- 64. Tide-dominated estuaries Amazon estuary, Brasil
- 65. Tide-dominated estuaries Sand deposited on bars in tidal channels
- 66. Tide-dominated estuaries Sand deposited on bars in tidal channels
- 67. Tidal creeks Mudflats Tide-dominated estuaries Tidal channels
- 68. Baie de Mont St Michel, France “La Masquerée” / “Vague primaire” (tidal bore) Video 2
- 69. “La Masquerée” / “Vague primaire” Baie de Mont St Michel, France
- 70. Baie de Mont St Michel, France Scour Herringbone x-beds Parallel lamination Sand-grade Fining up
- 71. Two main palaeoflow orientations represent: • Migration of bedforms landward during rising tide • Migration of dunes seaward during falling tide Tidal deposits: revision! Seaward Landward Reineck, 1963 Sigmoidal bedform Reactivation surface on lee slope Clay drape Current rippleson toesets Ebb tide cross-beds Flood tide cross-beds 2 m Flow
- 72. Tidal creeks Mudflats Tide-dominated estuaries Tidal mudflats and tidal creeks
- 73. Rootlets above high tide Bioturbation in intertidal zone Muds, mudflats Fine-grained sediments Ripple cross-lamination
- 75. Courtesy of Ron Boyd (2011) Classification of coasts
- 76. Tidal flat in different coastal environment Modified after Fan(2013) Wave-dominated estuary Tide-dominated estuary
- 77. Open-coast tidal flats shifting temporally from tide-dominated or mix-energy (tide-dominated) to wave-dominated regimes for a few days to weeks during summer/winter storms Tidal flat
- 78. Tidal creeks Tidal bars Tidal channels
- 79. 2006)
- 80. Barrier BarrierInlet Intertidal lagoon, New Jersey coast Tidal inlet T I D A L F L A T
- 81. Coastal tidal flat, South CarolinaCoastal tidal flat unprotected by beach barrier, Burma Tidal-flat systems EXAMPLES Fully tide-dominated Tide-dominated and wave- influenced
- 82. Intertidal flat with tidal channels and creeks. Example from the Pacific coast of California.
- 83. McArthur tidal flats, Alaska (A) Tidal channels on a coastal tidal flat (A) 2D dunes in a tidal channel A B Martha’s Vinyard, Massachusetts
- 84. Mont St Michel, France
- 85. Tidal Creek Mont St Michel, France
- 86. Mudflat Mixedflat Sandflat Heterolithic tidal bedding Flemming (2012) Reineck (1967) Dalrymple (2010)
- 87. Baronia Fm. (Eocene), Pyrenees Mudflat Mixed-flat Sandflat Sandflat
- 88. Bidirectional (‘herringbone’) cross-stratification in a tidal sandflat Photo courtesy of Mike Blum
- 89. Sinuous/meandering tidal channels in mangrove swamps, Niger delta plain. 30 km
- 90. Mixed-load tidal channel Sand-load river channel Allen (1982) COMPARISON
- 91. Lateral accretion bedding of a point bar in tidal channel; note the mud drapes extending to the point-bar base Photo courtesy of Mike Blum
- 92. Tidal channel filled by lateral accretion Pennsylvanian BreathittGroup of eastern Kentucky Photograph courtesy of Jostein Koldingsnes
- 93. Tidal channel filled by lateral accretion Photograph courtesy of Øystein Spinnagr
- 94. Terrestrial Marine Tidal flats Roots and bioturbation Tidal Channels Cross-bedded and cross- laminated sands with tidal indicators (e.g. mud drapes and bi- directional palaeoflow) Facies summary: Tide-dominated estuaries
- 95. Courtesy of Ron Boyd (2011) Classification of coasts
- 97. Estuaries
- 98. Tide-dominated estuary Boyd et al. (2006)
- 101. Wave-dominated estuaries Beach barrier and lagoon
- 104. Wave-dominated estuaries Sandy channel deposits
- 105. Wave-dominated estuaries Sandy channel deposits
- 107. OR BAYHEADDELTA FORMED BY RIVER Facies successions Allen (1991)
- 108. Wave-dominated estuaries Tuggerah «Lake», Australia
- 109. Wave-dominated estuaries Port Stephens, Australia Bay-headdelta Deeper central basin Tidal delta and barriers
- 110. Piedmont and coastal-plain incised valleys as possible sites for estuaries Video 3 Zaitlin et al., (1994)
- 111. • Form at the mouths of rivers • Do not build out into the sea (c.f. deltas) • Display a mixture of terrestrial and marine environment indicators • Often show evidence of tidal conditions Estuaries: a summary
- 113. Some take home questions:- What is the key difference between deltas and estuaries? List the key geomorphic features associated with different types of estuary What sedimentary facies would you expect in a sandy tidal channel? What criteria would you use to identify a tidal influence? What sedimentary facies would you expect to see on tidal flats?