He concluded that the older rocks outcrop only in the submarine canyons. He found no consistent depth ranges for the series of Miocene and Upper Cretaceous rocks obtained.
Figure 20.—Georges Bank canyons
Chart shows position of sounding lines and dredge hauls used to construct projected profile and inferred geologic section shown in Figure 21 (a). Sounding lines from Coast and Geodetic Survey Chart 1313.
In the Georges Bank area a series of prominent benches continues along the continental slope. If these are structural benches we should be able to trace them up the canyons and thus determine the dip of the formations. If the benches are the result of step faulting or landslide scars they would not extend up the canyons. In order to test these alternatives, a series of profiles has been plotted from the surveys of the Coast and Geodetic Survey. A line was drawn which paralleled most of the contours of the continental slope for 20 miles or more (Fig. 20). A second line was drawn at right angles to this first strike line. All sounding lines in the area were projected to this second dip line along lines parallel to the strike line, and plotted as a composite projected profile (Fig. 21). If the first line was essentially the strike of rock layers then we should be able to determine the dip of the beds by picking the successive benches as they occur on successive profiles across the canyon. In Figure 21 the results of the analysis of Oceanographer and Hydrographer canyons are presented. The dredge hauls by Stetson (1949) have also been projected on this profile. We see that a major bench occurs at A which passes below the hauls in which fossiliferous Navarro (Upper Cretaceous) was obtained and through the upper limit of the hauls where Matawan (Upper Cretaceous) was obtained. Thus if this horizon or one closely parallel to it is the Navarro-Matawan contract, the apparent discrepancies of the depth ranges of Stetson's dredge hauls are explained. Much more important to the present study is the dating of a prominent structural bench.
Figure 21.—Two projected profiles of Georges Bank canyons
Location of soundings for profile (a) shown in Figure 20. Soundings projected along strike to construct profile. Soundings for both profiles taken from Coast and Geodetic Survey Chart 1313.