Sedimentary ‘Signatures’ of Foreland Basin Assemblages: Real or Counterfeit?
- P. A. Allen,
- P. Homewood
Published Online: 5 MAY 2009
Copyright © 1986 The International Association of Sedimentologists
How to Cite
Schwab, F. L. (2009) Sedimentary ‘Signatures’ of Foreland Basin Assemblages: Real or Counterfeit?, in Foreland Basins (eds P. A. Allen and P. Homewood), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303810.ch21
- Published Online: 5 MAY 2009
- Published Print: 22 DEC 1986
Print ISBN: 9780632017324
Online ISBN: 9781444303810
- petrography and stratigraphic techniques;
- sedimentary ‘signatures’ of foreland basin assemblages - real or count;
- Sandstone framework mineralogy - reflecting tectonic setting and provenance terranes;
- detrital sandstone modes and recycled orogenic source types;
- recycled orogen provenance—general characteristics;
- Western Wyoming foreland basin (Jackson ‘exogeosyncline’);
- mean detrital modes for sandstones - Appalachian foreland basin;
- bulk chemistry—foreland basins versus other basin types;
- comparative sediment accumulation rates
Can various aspects of the sedimentary fill of foreland basins be used to characterize such basins and distinguish them from other basin varieties? Data selected from ancient assemblages of the Ouachita, Appalachian, Cordilleran, and Alpine belts are compared with one another and with modern deep-sea and continental margin deposits.
(1) The mineralogical composition of foreland basin sandstones (modes compiled using QFL, QmFLt, QpLvLs and QmPK plots) show a wide range of provenance types. Quartz-rich, feldspar-poor detritus derived from continental blocks (intensely weathered cratons as well as locally uplifted basement) comprises large portions of the early fill of foreland basins, but the bulk of the detritus is less quartz-rich. Subsequent material is richer in rock fragments and is derived from subjacent orogenic source source areas: either much older continental margin deposits exposed in sedimentary and metasedimentary nappes and thrusts or from slightly older deformed sediments exposed within the fold-thrust belt itself. Only small amounts of material are derived from tectonically uplifted subduction complexes or from magmatic arcs, either because the fold-thrust uplands topographically shield such sources, or thanks to mainly longitudinal dispersal along the strike of the suturing orogenic belt.
(2) Systematic, through time secular variations in provenance related to unroofing and to secular dominance of distinct source rocks are not obvious based on bulk framework mineralogy, even though some orderly evolution appears to occur when more precise mineral suites can be defined.
(3) The estimated bulk chemical composition of the sediment fill of foreland basins most resembles the fill of ancient geosynclines in general, and eugeoclines (eugeosynclines) specifically, and markedly contrasts with the fill of aulacogens, forearc basins, ancient miogeoclines, and modern trench-abyssal plain sediments.
(4) The rate at which sediment accumulates in foreland basins (0.044 to 0.927 m/1000 yr; mean is 0.186 m/1000 yr) exceeds sediment accumulation rates for cratonic basins and the abyssal ocean floor by a factor of 5–30. Comparably high rates of sediment accumulation characterize ancient aulacogens and modern rift valleys, successor basins, and (surprisingly) some modern trenches.