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AAPG Bulletin


Volume: 26 (1942)

Issue: 5. (May)

First Page: 765

Last Page: 792

Title: Geological Extrapolation and Pseud-Abyssal Sediments

Author(s): W. G. Woolnough (2)


It is considered conceivable that the processes of dynamical geology which are active at the present day are unlikely to have been equally dominant throughout the whole of geological history. Late Neogene time has been a period of intense orogenic activity comparable with earlier epochs of the same character like those of the Caledonian and Hercynian movements. We are now living in an orogenic period, perhaps in its dying phases; but, nevertheless, earth processes are dominated thereby.

Reasons are adduced for considering that throughout the intervening quiescent periods, which were presumably of much longer duration than those of active orogeny, a totally different combination of earth processes from those with which we are familiar was dominant. It is suggested that during some parts of geological time accumulation in the sea of terrigenous materials carried down by rivers may have been subordinate. The dominant processes were probably marine deposition on extensive continental shelves, affected by terrigenous detritus to an extent much less than is the case now. The reason for this relative subordination was that the continental lands, though near the sea in point of actual distance, remained in an "ultra-base-levelled" condition for enormously long periods.

Certain corollaries of this thesis are dealt with, including sedimentation in barred basins. It is diffidently suggested that elaboration of this idea may solve certain paradoxes in historical geology, and may explain many puzzling problems, such as the origin of the Jurassic (?) radiolarites of the East Indies, and possibly even some of the much debated anomalies in Devonian and Culm stratigraphy of Europe, and of the Triassic and Jurassic "transgressions" in the Alps.

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