Sediment Dynamics and Depositional Systems of the Mahakam Delta, Indonesia: Ongoing Delta Abandonment On A Tide-Dominated Coast

Abstract A quantitative analysis of the depositional processes on the Mahakam Delta indicates that it is presently subsiding and is, in essence, a drowned delta that is being transgressed and modified by marine processes. Calculations of sediment transport rate indicate that most, if not all, fluvially derived sand is being stored onshore in the distributaries, whilst finer-grained sediment moves offshore. A fining-upward and increasingly marine-upward succession is being deposited in the distributaries, which is analogous to nearby outcropping and subsurface successions that have previously been interpreted as progradational. The mixed fluvial and tide-dominant shoreline morphology is not solely a product of the deltas present-day processes. The fluvial component is a relict feature from a phase of progradation that preceded the ongoing transgression and is now being modified by tidal processes. Facies distribution is a much better indicator of modern depositional processes than delta morphology on the Mahakam Delta, suggesting that facies-based delta classifications are more accurate than morphology-based classifications. All the apparently anomalous components of the sedimentology and morphology are reconciled by a transgressive interpretation, including the overly deep distributaries, gently dipping subaqueous delta plain, penetration by benthic marine organisms far into the distributaries, widespread Nypa palm on the lower delta plain, and the long, mud-filled gap between sand in the distributaries and on offshore bars.

[1]  J. Lambiase.  The Stacked-Channel Reservoir Sands of SE Asia (New Depositional Concepts and Implications for Reservoir Prediction) , 2011 .

[2]  H. Reading,et al.  Sedimentary Environments: Processes, Facies And Stratigraphy , 2011 .

[3]  W. Helland‐Hansen.  Facies and stacking patterns of shelf‐deltas within the Palaeogene Battfjellet Formation, Nordenskiöld Land, Svalbard: implications for subsurface reservoir prediction , 2010 .

[4]  P. Plink-Björklund,et al.  Process Regime Changes Across a Regressive to Transgressive Turnaround in a Shelf–Slope Basin, Eocene Central Basin of Spitsbergen , 2009 .

[5]  G. Hampson,et al.  Facies architecture of a net transgressive sandstone reservoir analog: The Cretaceous Hosta Tongue, New Mexico , 2008 .

[6]  Janok P. Bhattacharya,et al.  Basic Building Blocks and Process Variability of a Cretaceous Delta: Internal Facies Architecture Reveals a More Dynamic Interaction of River, Wave, and Tidal Processes Than Is Indicated by External Shape , 2007 .

[7]  J. Bhattacharya,et al.  Terminal Distributary Channels and Delta Front Architecture of River-Dominated Delta Systems , 2006 .

[8]  R. Dalrymple.  Incised Valleys in Time And Space: An Introduction to The Volume and an Examination of the Controls On Valley Formation and Filling , 2006 .

[9]  S. Kroonenberg,et al.  Late-Holocene evolution of the Mahakam delta, East Kalimantan, Indonesia , 2005 .

[10]  P. Plink-Björklund,et al.  Stacked fluvial and tide‐dominated estuarine deposits in high‐frequency (fourth‐order) sequences of the Eocene Central Basin, Spitsbergen , 2005 .

[11]  J. Lambiase,et al.  Facies distribution and sedimentary processes on the modern Baram Delta: implications for the reservoir sandstones of NW Borneo , 2002 .

[12]  G. P. Allen,et al.  Sedimentation in the modern and Miocene Mahakam delta , 1998 .

[13]  R. Soulsby,et al.  Threshold of Sediment Motion in Coastal Environments , 1997 .

[14]  R. Soulsby.  Dynamics of marine sands : a manual for practical applications , 1997 .

[15]  G. P. Allen,et al.  Reservoir Facies and Geometry in Mixed Tide and Fluvial-Dominated Delta Mouth Bars: Example from the Modern Mahakam Delta (East Kalimantan) , 1994 .

[16]  H. Reading,et al.  Variability of deltaic processes in terms of sediment supply, with particular emphasis on grain size , 1993 .

[17]  R. Gastaldo,et al.  Sediment facies, depositional environments, and distribution of phytoclasts in the Recent Mahakam River delta, Kalimantan, Indonesia , 1992 .

[18]  B. Caline,et al.  New Insight into the Recent Evolution of the Baram Delta from Satellite Imagery , 1992 .

[19]  R. Dalrymple,et al.  Estuarine Facies Models: Conceptual Basis and Stratigraphic Implications: PERSPECTIVE , 1992 .

[20]  José Maria Landim Dominguez,et al.  Controls on Quaternary coastal evolution of the east-northeastern coast of Brazil: roles of sea-level history, trade winds and climate , 1992 .

[21]  É. Dutrieux.  Study of the ecological functioning of the Mahakam delta (east Kalimantan, Indonesia) , 1991 .

[22]  S. Penland,et al.  Transgressive Depositional Systems of the Mississippi Delta Plain: A Model for Barrier Shoreline and Shelf Sand Development , 1988 .

[23]  C. Caratini,et al.  Paleogeographical evolution of the Mahakam delta in Kalimantan, Indonesia during the quaternary and late pliocene , 1988 .

[24]  P. Carbonel,et al.  Late Quaternary paleoenvironments of the Mahakam delta (Kalimantan, Indonesia) , 1987 .

[25]  Van Rijn,et al.  Closure of "Sediment Transport, Part III: Bed Forms and Alluvial Roughness" , 1984 .

[26]  L. Rijn.  Sediment Transport, Part II: Suspended Load Transport , 1984 .

[27]  Van Rijn,et al.  Sediment transport; Part I, Bed load transport , 1984 .

[28]  T. Oki,et al.  Geology of the Handil Field (East Kalimantan--Indonesia) , 1980 .

[29]  D. Laurier,et al.  Sediment Distribution Patterns in the Modern Mahakam Delta , 1976 .