Day Four - Papers
Hundreds of dikes, sills, laccoliths, and stocks were emplaced within the crystalline Precambrian basement and the overlying Phanerozoic strata of the Black Hills uplift during the Paleocene and early Eocene. The great volume of plutons was sufficient to swell the basement forming the Bear Lodge, Tinton, and Lead-Deadwood domes (Fig. 1) and produced laccolithic clusters in the Phanerozoic section, such as those of the Black Buttes, Vanocker, Gilt Edge, and Theodore Roosevelt complexes. Individual plutons, such as Bear Butte and Devils Tower, are abundant outside the larger complexes. The alkalic igneous rock suite includes rhyolite, quartz latite, trachyte, and phonolite. Associated with the plutons are numerous bodies of breccia including diatremes, breccia pipes and intrusion breccias. These fragmental rocks are the theme of this paper.
There appear to be distinguishing internal features as well as differing spatial distribution between the intrusion breccias, breccia pipes and diatremes. For the purposes of distinguishing amongst them the following criteria are proposed.