Geology Reference
In-Depth Information
offset over a wider area, which makes it possible for more of the displacement to be
accommodated by folding rather than faulting. This helps a large fault die out into a
fold. The master fault may continue straight in the region of fault splays (Fig. 8.34), or
all the splays may have different orientations from that of the master fault.
Splay faults are ultimately bounded in all directions by branch lines and tip lines.
The leading edge of a structure is its termination in the transport direction, and the
trailing edge is in the opposite direction (after Elliott and Johnson 1980). For a thrust
fault, the leading edge of a splay is a tip line and the trailing edge is a branch line
(Fig. 8.36a). The leading hangingwall and footwall cutoff lines of a unit carried on a
splay join and end at the tip line of the leading fault (Fig. 8.36b). The trailing bed cutoff
line continues along the trailing thrust beyond the tip of the splay.
Fig. 8.36.
Splay faults at the leading edge of a thrust fault.
a
Fault surfaces in three dimensions.
b
Bedding
cutoff lines of a unit transported on the lower splay. (After Diegel 1986)
Fig. 8.37.
Fault horse bounded on all sides by fault surfaces that end in all directions at a closed branch-
line loop.
a
Main fault and branch lines.
b
Bedding cutoff lines for a stratigraphic unit within the fault
horse. (After Diegel 1986)
