Tectonic Controls of Foreland Basin Subsidence and Laramide Style Deformation, Western United States
- P. A. Allen and
- P. Homewood
Published Online: 5 MAY 2009
Copyright © 1986 The International Association of Sedimentologists
How to Cite
Cross, T. A. (1986) Tectonic Controls of Foreland Basin Subsidence and Laramide Style Deformation, Western United States, in Foreland Basins (eds P. A. Allen and P. Homewood), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303810.ch1
- Published Online: 5 MAY 2009
- Published Print: 22 DEC 1986
Print ISBN: 9780632017324
Online ISBN: 9781444303810
- Circum-Pacific and Western Americas;
- tectonic controls of foreland basin subsidence and Laramide style deformation, western United States;
- plate interactions from plate reconstructions;
- plate interactions inferred from history of magmatism;
- plate interactions inferred from subsidence in foreland;
- Sevier and Laramide orogenies - late mesozoic and early cenozoic deformation in rocky mountains;
- duration and geographical limits of Sevier;
- Laramide structures
A variety of Late Mesozoic to Early Cenozoic tectonic events in the Rocky Mountains region are temporally and spatially coincident with inferred variations in kinematics of plate interactions and subduction geometries. This coincidence suggests that these disparate events are the products of a single causal mechanism. The following tectonic features are regarded as genetic expressions of variations in subduction modes and geometries: (1) the history of igneous activity in the western United States; (2) the contrasting styles and loci of deformation along the foreland fold and thrust belt (Sevier style) and the basement-cored uplifts (Laramide style) bordering the northern and eastern margins of the Colorado Plateau; (3) the development and maintenance of the Colorado Plateau as a relatively rigid tectonic block; (4) the timing and geometry of subsidence in the foreland basin; and (5) the disjunct history of subsidence and subsequent uplift of the Colorado–Wyoming region beyond the foreland basin.
During a period of normal subduction (from before 92 to about 80 Ma), thin-skinned décollement style deformation occurred along the Sevier fold and thrust belt opposite the convergent margin. Coeval subsidence of the foreland basin was confined to a relatively narrow zone to the east of the Sevier belt. This subsidence is attributed to lithospheric flexure induced by supracrustal loading of thrust plates and sediment. Geohistory analyses of strata along the axis of the foreland basin indicate that foreland basin subsidence began as early as 115 Ma, with a major episode of rapid subsidence initiated by about 90 Ma.
During an ensuring period of low-angle subduction, the Colorado Plateau was underpinned by subducted lithosphere and behaved as a mechanically rigid block, a consequence of the doubled lithospheric thickness. From about 80 to 67 Ma, rapid subsidence occurred over an anomalously broad region centred about Colorado and Wyoming. This episode of subsidence is attributed to sublithospheric loading and cooling induced by the shallowly subducted oceanic plate. To the north and south of the Colorado–Wyoming locus, foreland basin subsidence continued without interruption coincident with continued foreland folding and thrusting. Another effect of low-angle subduction was the transfer of deformation from the Sevier belt (termination about 75 Ma) to the eastern and northern margins of the Colorado Plateau, coincident with the position of greatest contrast in mechanical properties of the lithosphere. This initiated Laramide style basement-cored uplifts at about 69 Ma. Decoupling of subducted lithosphere from overlying lithosphere at about 50 Ma caused regional uplift and erosional stripping of the Colorado–Wyoming region, lithospheric flexure to the east, and sediment accumulation on the High Plains following a long period of non-deposition.