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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 53 (1969)

Issue: 3. (March)

First Page: 740

Last Page: 741

Title: Geologic Implications of Cenozoic Subsidence and Fragmentation of Continental Margins: ABSTRACT

Author(s): David W. Scholl, Roland E. Von Huene

Article Type: Meeting abstract

Abstract:

Lithified rocks are exposed or underlie a thin layer of Cenozoic deposits, at the sea floor at depths exceeding 2.0 km along major segments of the continental margin forming the northern and eastern flanks of the Pacific basin. For example, indurated and deformed sedimentary units of Mesozoic age underlie the surface of the shelf and continental slope off southern and southwestern Alaska, submerged plutonic and metamorphic rocks crop out on the margin off central California and central and southern Baja California, and they are the most likely rock type underlying the shelf and slope off northern and central Chile.

Because crystalline and metamorphic rocks do not form at the sea floor, their juxtaposition with seawater on continental slopes signifies that large masses of formerly superjacent crustal rocks have been removed to form the surfaces of these margins. Unless massive early Tertiary submarine erosion is invoked, stripping of the superjacent rocks could have been effected by (1) submarine decollement sliding, or (2) a more acceptable hypothesis (to the writers) of crustal uplift (including possible horizontal shifting of continental blocks), deep subaerial erosion, and subsequent submergence.

Studied segments of continental margins that are underlain by deformed and indurated sedimentary rocks appear also to have undergone a history of

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uplift, erosion, and subsidence. Evidence for this conclusion comes from regional geologic and tectonic mapping and the collection of samples of shallow-water deposits of Cenozoic age at depths exceeding 1-2 km that lie on surfaces cut across deformed and indurated Mesozoic deposits.

Although the writers recognize that the origin of submerged surfaces on continental margins that are underlain by lithified rocks cannot everywhere be ascribed to subsided erosional surfaces, this explanation appears to be more generally applicable than others that have been considered. The broader implications of this conclusion are: (1) postulated offshore landmasses, e.g., Appalachia and Cascadia, may indeed have existed and foundered along former continental edges, (2) continental accretion may be interrupted by relatively long episodes of continental regression or wasting, and (3) the widespread evidence for marginal foundering suggests that a general mechanism of crustal thinning, possibly including "oceanization," is involved.

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Copyright 1997 American Association of Petroleum Geologists