Biostratigraphic data, based mostly on radiolarian assemblages, establish synchronous deposition in the northern Sierra terrane and the Havallah basin beginning in the Late Devonian and extending into the early Late Permian. Lower Mississippian and mid-Permian arc-derived volcaniclastic debris was deposited in parts of the Havallah basin during episodes of arc volcanism in the northern Sierra terrane. Between these episodes of arc volcanism, from late Early Mississippian to at least Middle Pennsylvanian, the northern Sierra terrane collected siliceous pelagic deposits that correlate with dominantly chert-argillite sections in the Havallah sequence. These intermixed lithic assemblages suggest shared stratigraphic evolution and geographic proximity between the Sierran arc terrane and the Havallah basin during the late Paleozoic.
During Late Devonian and Early Mississippian arc volcanism in the northern Sierra terrane, lower Paleozoic rocks of the Roberts Mountains allochthon were thrust over coeval deposits on the North American shelf. Chert-quartz-rich siliciclastic debris, derived from the Antler orogenic belt, is interbedded with Upper Devonian and Lower Mississippian distal volcanic rocks in the northern Sierra terrane and with Kinderhookian volcaniclastic rocks and chert in the Schoonover sequence. These quartzose-clastic deposits not only provide an independent lithologic link between the Sierran arc terrane and the Havallah basin, they also tie the arc terrane and basin to North America at the time of the Antler orogeny.
Late Devonian and Early Mississippian arc volcanism in the northern Sierra terrane occurred in an extensional regime. Extensional tectonism began locally in the Havallah basin during the Famennian and continued into the early Meramecian. Contemporaneous extension in the arc and basin during emplacement of the Roberts Mountains allochthon is difficult to reconcile with existing arc-continent collision models for the Antler orogeny.
