Tracking the early Silurian post-extinction faunal recovery in the Jupiter Formation of Anticosti Island, eastern Canada: A stratigraphic revision

Refinement of the 105-115 m thick Llandovery Jupiter Formation provides a more precise view of the tropical faunal recovery and radiation on the eastern margins of Laurentia. The formation spans the late Aeronian through mid-Telychian (438-434 Ma) and preserves an 'experimental laboratory' for evolution of tropical benthic communities in Laurentia, with a mixture of endemic and immigrant genera. Brachiopod communities, for the first time during the Llandovery, differentiated into those that became firmly ensconced as deeper-water inhabitants, and those that inhabited shallower depths. Following deposition of the Aeronian coral patch reef complex (East Point Member, Menier Formation) on Anticosti Island, sealevel rise resulted in the deposition of the Richardson Member shales (basal Jupiter Formation). This featured relatively deep-water, locally rich assemblages dominated variously by Dicoelosia, Triplesia, Striispirifer, Gotatrypa, Lissatrypa or Zygatrypa, accompanied by common graptolites. Progressive shallowing marked the overlying Cybele Member, characterised by diverse suites of pentamerides (e.g. Phricoclorinda, Chiastodoca, Microcardinalia, Ehlersella) and abundant atrypides ('Gotatrypa', Zygatrypa, Clintonella, Lissatrypa). In the Jupiter Formation, spiriferides appeared in pulses, beginning with Striispirifer in the Richardson Member, Eospirifer in the Cybele Member, and Cyrtia in the Pavillon Member. Corals are generally rare, locally with small favositids, heliolitids and solitary rugosans. The succeeding lower Ferrum Member reflects a shallow, quiet-water, possibly lagoonal setting, with a less diverse benthic shelly assemblage dominated by shellbeds of large Gotatrypa. The upper Ferrum Member features the recurrence of Pentamerus, abundant Eocoelia, common crinoids, rare tabulate corals and small solitary rugosans, and common hardgrounds. The Pavillon Member at the top of the formation is marked by the first appearance of Pentameroides and Costistricklandia, indicating a mid-Telychian age. It has diverse stromatoporoids, solitary and colonial rugose corals, including the first Telychian coral-sponge patch reefs at South Point, a precursor to the reef-crinoid meadow ecosystem preserved in the overlying Chicotte Formation (mid-?late Telychian).