Major erosional events are seen on seismic line 12-81 where the reflector clinoforms, which have been identified by coloring the horizons, on lap onto the shelf as Yellow (11), Olive Green and Rust (14 - 15), and Purple (19) horizons. Our interpretation is that the slope of the clinoforms in this section are represented by the Torok Formation. The horizontal onlapping reflectors of the crest of the Torok Formation clinoforms represent the Nanushuk Group. The same pattern is to be seen in the other seismic lines that follow.
Major erosional events are seen on the seismic line 26-74 at events Orange (7), Green and Navy Blue (14-15), and Olive Green (19).
Major erosional events are seen on the seismic line 27-81 at reflectors Orange and Olive Green (11-12).
Major erosional events are seen on the seismic line 37-81 at reflectors Orange and Olive Green (16-17).
Proposed Sea Level events
||Sequences in the Nanushuk Group and Torok Formation clinoforms were identified on the seismic data and numbered from 5 through 24. The areal extent of the sequence boundaries were then placed in order in a spread sheet and then displayed as a chronostratigraphic chart. On the basis of the earlier work by Palmer (1983) and Bird and Molenaar (1991) that suggests that the eastern most part margin of the progradational Torok Formation and Nanushuk Group were Cenomanian in age, the major lows in sea level and unconformities were identified and were assumed to be related to the major lows on the Haq and others (1987) chart for the Cenomanian, for 98 my, 96 my and 94 my.
Evolution of Basin Margin
Mapping the position of selected Nanushuk Group and Torok Formation clinoforms observed in the seismic data set indicate the paleo-shoreline was oriented northwest southeast.
The crests of the basin margins are indicated on Figure 12 below.