See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/222194352 Classification of clastic coastal depositional environments Article in Sedimentary Geology · October 1992 DOI: 10.1016/0037-0738(92)90037-R CITATIONS READS 495 654 3 authors: Ryan TJ Boyd Robert W Dalrymple Minnesota State University, Mankato Queen's University 15 PUBLICATIONS 1,553 CITATIONS 167 PUBLICATIONS 11,993 CITATIONS SEE PROFILE SEE PROFILE Brian Zaitlin Zaitlin Geoconsulting Ltd 43 PUBLICATIONS 4,183 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Late Neoproterozoic (Ediacaran) depositional environments View project Ediacaran discs: elucidating the form and function of the discoid fossils at the root of metazoan evolution View project All content following this page was uploaded by Robert W Dalrymple on 16 December 2015. The user has requested enhancement of the downloaded file. Sedimentary Geology, 80 (1992) 139-150 139 Elsevier Science Publishers B.V., Amsterdam Classification of clastic coastal depositional environments R. Boyd a, R. Dalrymple b and B.A. Zaitlin c a Centre for Marine Geology, Dalhousie University, Halifax, Nova Scotia, B3H 3J5, Canada b Department of Geological Sciences, Queens University, Kingston, Ontario KTL 3N6, Canada ¢ Esso Resources Canada Ltd., 2374th St. S.W. Calgary, Alberta, T2P OH6, Canada (Received December 1, 1991; revised version accepted March 2, 1992) ABSTRACT Boyd, R., Dalrymple, R. and Zaitlin, B.A., 1992. Classification of clastic coastal depositional environments. In: J.F. Donoghue, R.A. Davis, C.H. Fletcher and J.R. Suter (Editors), Quaternary Coastal Evolution. Sediment. Geol., 80: 139-150. This paper proposes a new classification for clastic coastal environments which includes the full range of major depositional settings including deltas, strand plains, tidal flats, estuaries and lagoons. This classification includes both morphologic and evolutionary components and is based on dominant coastal processes. It has the potential to predict responses in geomorphology, facies and stratigraphy. The significance of this classification is its evolutionary capability, and its inclusion of all major ctastic coastal depositional environments, making it more comprehensive than previous classifica- tions. We employ a ternary process classification with two axes. The first (horizontal axis) is defined as the relative power of wave versus tidal processes. The second (vertical) axis represents relative fluvial power (increasing upward). A ternary diagram defined by these axes can be used to illustrate the genetic process-response relationships between major coastal environments. The evolutionary classification combines the concept of two sediment sources (river and marine) with a relative sea-level parameter to classify embayed as well as linear and elongate/lobate shorelines. This approach identifies the evolutionary relationships between coastal sedimentary environments. The new ternary approach to process classification can be applied to estuaries and lagoons to define wave and tide end-member facies models, each consisting of a tripartite facies zonation. The evolutionary classification is compatible with sequence stratigraphy because sediment supply and relative sea level are included, and serves as a starting point for more refined coastal stratigraphic analyses. Introduction Shepard, 1973) or a range of marine processes such as Davies' (1980) use of wave type and tidal Classification of coasts has been a standard range. The approach of Curray (1964) employed approach for geomorphologists (Pethick, 1984) the variables of sediment supply and relative sea and most modern efforts date from Johnson level to distinguish regressive from transgressive (1919). These classifications concentrate on coasts. Successful classifications based on struc- grouping morphological features and often em- tural controls such as those of Bloom (1978) and ploy a sea-level criterion to distinguish emergent Inman and Nordstrom (1971) were usually em- from submergent coasts (e.g., Johnson, 1919; ployed only on a broad plate tectonic level. Valentin, 1952). Other classifications employ a From the mid part of the twentieth century, a genetic approach based on dominant processes, more geological approach to coastal classification using non-marine versus marine processes (e.g., evolved. Sedimentologists began to organise in- formation on the distribution and prediction of Correspondence to: R. Boyd, Department of Geology, Uni- reservoir facies or organic source rocks in single versity of Newcastle, Newcastle, NSW 2308, Australia (pre- depositional environments. Much early emphasis sent address). was placed on deltas (e.g., Fisher et al., 1969), 0037-0738/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved 141i e, II(1~,I11 t ,',t culminating in Galloway's (1975) ternary classifi- stratigraphy. The significance of this classification cation based on wave, tide and river processes is its evolutionary capability, and its inclusion of and the approach of Wright (1977) based on all major coastal depositional environments, mak- statistical analysis of many process variables. ing it more comprehensive than previous classifi- Models have now been established in many envi- cations. ronments including alluvial (e.g., Miall, 1977), tidal inlets and barriers (e.g., Hayes, 1975), or Coastal classification continental shelves (e.g., Johnson and Baldwin, 1986). The most recent development in coastal General principles models involves sequence stratigraphy (e.g., Posa- mentier and Vail, 1988) which places the coastal The most effective method of classifying coastal facies in a classification defined by transgressive stratigraphy is to use a subdivision into regressive and regressive stacking geometries and based pri- and transgressive categories such as Reinson's marily on relative sea-level variations. approach (Reinson, 1984) or that of Frazier The objective for this paper is to provide a (1974). Curray's (1964) classification of transgres- classification for depositional coastal environ- sions and regressions has the potential to cate- ments which includes the full range of major gorise most coastal environments. Curray used elastic depositional settings including deltas, parameters of relative sea-level rise and fall plot- strand plains, tidal flats, estuaries and lagoons. ted against erosion and deposition to identify This classification includes both morphologic and several types of transgression and regression. The evolutionary components and is based on domi- same approach can be used (Fig. 1) to broadly nant coastal processes. It has the potential to distinguish between two groups of depositional predict responses in geomorphology, facies and sedimentary environments--transgressive and re- gressive. When the rate of sediment supply ex- ceeds the rate of relative sea-level rise, or sedi- RATE OF RSL CHANGE ment accumulates during a relative sea-level fall (area of darkest stipple on Fig. 1), regression results in the generation of elongate/lobate (de- lta) or linear (strandplain and tidal fiat) shore- lines (Fig. 2). The interaction between river sedi- ment input and the ability of marine processes to redistribute that input determines if the coast will be elongate/lobate or linear (Fisher et al., 1969; Galloway, 1975). Deposition during relative sea- level fall (upper right quadrant, Fig. 1) has re- cently been investigated by Plint (1988) and ESTUARY/SHELF DELTA, ~rRANIDPLAIN 1 TIDAL FLAT termed "forced regression" by Posamentier et al. Fig. 1. A plot of relative sea-level rise and fall rates against (1992). When the rate of relative sea-level rise erosion and deposition rates allows discrimination of trans- exceeds the rate of sediment supply (area of light gressive from regressive coasts, and depositional coasts (upper stipple on Fig. 1), transgression results in the half of figure) from erosional coasts (lower half of figure). Within the depositional field, this plot separates (transgres- generation of estuaries and lagoons on embayed sive) estuary/shelf environments from (regressive) deltas, coasts and the landward migration of the conti- strandplains and tidal flats. Each field represents equilibrium, nental shelf on all linear (tidal flat and strand- long-term positions for the environments. Greater distance plain) coasts (Fig. 2). Coastal plain estuaries and from the regression/transgression diagonal indicates in- lagoons are formed in a seaward location (Fig. 1) creased rates of transgression/regression. When continued but if the transgression extends further inland it over a long period, high rates of transgression result in land- ward migration from the zone of coastal plain estuaries to may encounter areas of higher relief and/or that of piedmont estuaries. (Based on Curray, 1964.) bedrock and produce piedmont estuaries and la- CLASSIFICATION OF CLASTIC COASTAL DEPOSITIONAL ENVIRONMENTS 141 goons (e.g., Ricketts, 1991). Depending on the deltas, estuaries, lagoons, strand plains and tidal balance between relative sea level and erosion flats (Fig. 3; see Zaitlin and Schultz, 1990, and (lower half Fig. 1), coasts may experience either Dalrymple et al., 1992, for earlier versions). We landward or seaward migrating marine uncon- use two axes for this classification. The first formities produced by the shoreface (often termed (horizontal axis) is defined as the relative power ravinement surfaces), tidal channels