Ancient flood-dominated fan-delta and river-delta systems of tectonically-active basins can be viewed as essentially small and immature fluvial systems (in the sense of Schumm, 1977) with relatively high-elevation catchment basins, short and high-gradient transfer zones, and marine depositional zones where transport and deposition are dominated by hyperpycnal flows. The delta-front deposits of these ancient systems are represented by facies and facies associations whose stratigraphic and sedimentological importance has been largely overlooked in previous literature. Both fan-delta and river-delta systems contain a common and very distinctive terminal depositional element consisting of sharp-based and parallel-sided, graded sandstone beds commonly containing HCS. These sediments, herein termed "flood-generated delta-front sandstone lobes", form impressive sedimentary accumulations in many basins worldwide. Commonly mistaken for storm-dominated nearshore and shelfal deposits, these sandstone lobes probably represent the most genuine expression of fluvial-dominated delta-front sedimentation. In ancient river-delta systems, river-mouth deposits show a great variability in terms of geometry and facies types, essentially recording the locally prevailing conditions ranging from extensive erosion and sediment bypass to deposition of the entire sediment load carried by sediment-laden stream flows entering seawaters. Flood-related processes are intrinsically catastrophic and, as such, under-represented in modern settings. It thus appears that ancient flood-dominated fluvio-deltaic systems cannot be described and interpreted following current sedimentological models for fluvial and deltaic sedimentation. Actually, these models are largely derived from modern depositional environments dominated by "normal" fluvial and marine processes. There are, on the other hand, impressive similarities between ancient flood-dominated fluvio-deltaic systems and turbidites - another category of catastrophic deposits which is under-represented in modern basins. Comparing facies and processes of these two groups of sediments deposited by density currents can provide significant insight into both types of sedimentation.
Delta-front associations of ancient flood-dominated fluvio-deltaic systems / Mutti, Emiliano; Tinterri, Roberto; DI BIASE, Davide; L., Fava; N., Mavilla; S., Angella; L., Calabrese. - In: REVISTA DE LA SOCIEDAD GEOLÓGICA DE ESPAÑA. - ISSN 0214-2708. - 13:(2000), pp. 165-190.
Delta-front associations of ancient flood-dominated fluvio-deltaic systems
MUTTI, Emiliano;TINTERRI, Roberto;DI BIASE, Davide;
2000-01-01
Abstract
Ancient flood-dominated fan-delta and river-delta systems of tectonically-active basins can be viewed as essentially small and immature fluvial systems (in the sense of Schumm, 1977) with relatively high-elevation catchment basins, short and high-gradient transfer zones, and marine depositional zones where transport and deposition are dominated by hyperpycnal flows. The delta-front deposits of these ancient systems are represented by facies and facies associations whose stratigraphic and sedimentological importance has been largely overlooked in previous literature. Both fan-delta and river-delta systems contain a common and very distinctive terminal depositional element consisting of sharp-based and parallel-sided, graded sandstone beds commonly containing HCS. These sediments, herein termed "flood-generated delta-front sandstone lobes", form impressive sedimentary accumulations in many basins worldwide. Commonly mistaken for storm-dominated nearshore and shelfal deposits, these sandstone lobes probably represent the most genuine expression of fluvial-dominated delta-front sedimentation. In ancient river-delta systems, river-mouth deposits show a great variability in terms of geometry and facies types, essentially recording the locally prevailing conditions ranging from extensive erosion and sediment bypass to deposition of the entire sediment load carried by sediment-laden stream flows entering seawaters. Flood-related processes are intrinsically catastrophic and, as such, under-represented in modern settings. It thus appears that ancient flood-dominated fluvio-deltaic systems cannot be described and interpreted following current sedimentological models for fluvial and deltaic sedimentation. Actually, these models are largely derived from modern depositional environments dominated by "normal" fluvial and marine processes. There are, on the other hand, impressive similarities between ancient flood-dominated fluvio-deltaic systems and turbidites - another category of catastrophic deposits which is under-represented in modern basins. Comparing facies and processes of these two groups of sediments deposited by density currents can provide significant insight into both types of sedimentation.File | Dimensione | Formato | |
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