The Late Ordovician Dawson Point Formation (Timiskaming outlier, Ontario): key to a new regional synthesis of Richmondian–Hirnantian carbonate and siliciclastic magnafacies across the central Canadian craton

Abstract

Current paleogeographic reconstructions extend Late Ordovician Taconic-derived siliciclastics across the central Canadian craton prior to the terminal Ordovician glacioeustatic lowstand. Revision of the Late Ordovician Dawson Point Formation of the Timiskaming outlier greatly reduces the distribution of these siliciclastics, and documents a greater spread of shallow-water carbonate of Richmondian age. As revised, the Dawson Point Formation contains two informal members: a deep-water graptolitic shale that grades upward into shallow-water siliciclastic redbeds, and an upper member of shallow-water, muddy, crinoidal limestone with interbedded shale, likely representing low-energy shoals on a muddy shelf. Deep-water shale accumulation began in the upper manitoulinensis graptolite Zone following foundering of the regional foreland carbonate platform.

High‐resolution seismic reflection profiling of neotectonic faults in Lake Timiskaming, Timiskaming Graben, Ontario‐Quebec, Canada

“…Schreurs, ; Storti et al ., ; Shamir, ), during one or more Palaeozoic Appalachian orogenies marking the amalgamation of Pangea (e.g. Dix & Molgat, ; Dix & Robinson, ; Dix et al ., ). Faure et al .…”

Late Ordovician (Chatfieldian) catastrophic volcanism and abrupt carbonate platform-interior subsidence: A tectonic link across a Taconian foreland basin (Quebec Embayment) due to inherited crustal weakness

“…This association youngs to the west, through the Ottawa Embayment and into the Canadian craton interior (Dix et al, 2007). Subsequent deepwater dysoxic basinal sediments were succeeded by a westward progradational, basin-fill, flysch succession leading to marginal marine conditions of the Queenston Formation (Sharma et al, 2003;Sharma and Dix, 2004).…”

The Role of Regional and Local Structure in a Late Ordovician (Edenian) Foreland Platform-to-Basin Succession Inboard of the Taconic Orogen, Central Canada

“…By the Late Ordovician, reversal of subduction polarity established a retroarc foreland basin [23]. Westerly directed diachronous foundering of the regional foreland platform spanned the Chatfieldian to early Maysvillian interval [1][2][3][4] extending as far west as the Timiskaming graben [24] in the craton interior ( Figure 1). Along the Laurentian margin, initial deep-water black shale represented by the regional Utica or Indian Castle facies [1,5] is replaced by a northwesterly directed, shallowing-upward succession of oxic siliciclastic facies, an expression of a northwesterly progradational clastic wedge from the Taconic orogen [25,26].…”