Ancient Submarine Canyons and Fan Valleys

Abstract Many modern submarine canyons and deep-sea fans originated in pre-Pleistocene time. Similar submarine canyons, fans, and fan valleys are found in the geological record certainly as far back as the Precatnbrian. Criteria for recognizing ancient submarine channels include: (1) proved or inferred size comparable to modern canyons and fan valleys; (2) comparable geometry (e.g., high axial gradients diminishing seaward and steep wall slopes, some of which become vertical or overhanging) ; (3) similar locations ( or submarine canyons) between shallow-marine (shelf) and deep-marine (basin) environments and (for fan valleys) incision into inferred deep-sea fans at the lower ends of canyons; (4) similarities in lithologies, grain sizes, and primary structures of the fills and their variations along the length and width of the canyons or valleys; (5) similarities in the observed or deduced processes of fast cutting and filling, together with clean-cut channel contacts, concave upward form, minor channels at the base of or within channel fill, comoaction effects, and partial flushing out; and (6) similarities of multiple origin of faunas within the fill (indigenous, swept in from surrounding shelf areas, or derived from the canyon walls). These criteria emerge from a study of all available data on ancient submarine canyons and fan valleys from 32 areas. The information is grouped, tabulated, and discussed under eight stratigraphic and geographic headings: (1) Lower Paleozoic of the Caledonian-Appalachian Geosyncline, (2) Carboniferous of the Pennine Basin, (3) Upper Paleozoic of the Variscan Geosyncline, (4) Permian of the Delaware Basin, (5) Mesozoi and Tertiary of the Tethyan Geosyncline, (6) Mesozoic and Tertiary of California, (7) Tertiary of the Gulf Coast Basin, and (8) other areas. A study of these and future examples of ancient submarine canyons and fan valleys is important as an aid both in reconstructing the continental slopes and rises of geosynclinal and other basins and in the search for possible oil and gas traps. Further intensive studies of transitional areas between shelf and basin facies should reveal many more examples of ancient canyons and fan valleys.