Trilobite cranidia as paleocurrent indicators

Trilobite cranidia are not usually thought of as paleocurrent indicators. Indeed, not all of them can be used as such. For example, Dikeocephalus has been shown to not align with the paleocurrent (S.P. Hasselbo, 1987, Palaios, 2:605-608). However, in one slab from East Crum Creek, we measured the orientation of 269 aligned Amplexograptus praetypicalis graptolites and 15 aligned cranidia of Triarthrus beckii. The rose diagrams of each is shown below. The mean direction of the cranidia is 115.0 degrees; the mean direction of the graptolites is 114.3 degrees, with a measurement accuracy of only two degrees.

Sangrey, W.F., and Gildner, R.F., 1989, A test of trilobite cranidia as paleocurrent direction indicators: GSA Abstracts with Programs, v. 21, p. 64.