Mesozoic radiolarians and radiolarian‐bearing sequences in the circum‐Pacific regions: A report of the symposium‐‘Radiolarians and Orogenic Belts’

Abstract

This paper contains extended abstracts of the seven papers presented at the symposium 'Radiolarians and Orogenic Belts' held at the seventh meeting of the International Association of Radiolarian Paleontologists (INTERRAD). Important results of the symposium include the following: (1) Upper Paleozoic and Mesozoic cherts are widely distributed within accretionary complexes in the circum-Pacific orogenic belt. Radiolarian dating reveals that long durations of chert sedimentation in a pelagic environment are recorded on both sides of Pacific-rim accretionary complexes (e.g. New Zealand, Japan, Russian Far East, Canadian Cordillera). (2) Triassic radiolarian faunas from New Zealand and the Omolon Massif, northeast Siberia are similar in composition and are characterized by the absence of typical Tethyan elements. This suggests that radiolarian faunal provincialism may have been established as early as the Triassic. High-latitude radiolarian taxa exhibit a bi-polar distribution pattern.(3) The Lower Triassic interval in chert dominant pelagic sequences is mechanically weaker than other levels and acted as a dkcollement in accretionary events. This lithologic. contrast in physical property is considered to reflect radiolarian evolution, such as the end-Permian mass extinction.

Logan Medallist 1. Seeking the Suture: The Coast-Cascade Conundrum

“…The only clearly 'exotic' faunas (as opposed to individual species) of Permian through Middle Jurassic age occur in the accretionary complexes that form the Cache Creek and Bridge River terranes in Canada, and the innermost part of the Chugach terrane (McHugh Complex) in southern Alaska (Clark 1971, p. A54;Monger and Ross 1971;Cordey 1996;Orchard et al 2001). These faunas are akin to those today in eastern, southeastern and central Asia and probably lived far out in Panthalassa, and in Paleotethys and Tethys oceans.…”

“…1, 2, 3; Friedman and Armstrong 1995; Bustin et al 2013). Of these terranes, the Bridge River near latitude 51° comprises fragmented, faulted and folded Early Carboniferous through Middle Jurassic (~350-160 Ma) basalt, radiolarian chert, argillite, ultramafic rock, small carbonate olistoliths, and rare Late Triassic blueschist (Cordey and Schiarizza 1993;Schiarizza et al 1997) and may in part grade into Late Jurassic and earliest Cretaceous clastic rocks in Tyaughton-Methow basin (Mahoney and Journeay 1993;Cordey 1996). The Cadwallader and Methow terranes also were founded on Permian oceanic lithosphere and overlain by Triassic and local Middle Jurassic arc-volcanic rocks and associated clastic strata.…”

“…Both the Bridge River and Cache Creek terranes are considered to be remnants of the floor of Panthalassa (Cordey et al 1992;Cordey and Schiarizza 1993;Cordey 1996;Orchard et al 2001). In southern British Columbia they are separated from one another by rocks of the TyaughtonMethow basin and Cenozoic volcanic rocks and by the Yalakom and FraserStraight Creek faults, but father north the Cache Creek lies entirely within the Intermontane superterrane, sandwiched between Stikinia and Quesnellia (Figs.…”

“…Both terranes contain Late Triassic blueschist, but differ in that the Bridge River terrane is generally 'more pelagic' with abundant radiolarian chert and rare, small, carbonate olistoliths whereas Cache Creek terrane is characterized by enormous masses of Late Carboniferous to Late Triassic shallow water carbonate, as well as widely distributed remnants of a Permian-Triassic (~250 Ma) intraoceanic arc (Schiarizza et al 1997;Schiarizza 2012). Furthermore, the Bridge River terrane is at least as young as Callovian (~164 Ma) in chert-rich facies and may grade into clastic facies as young as earliest Cretaceous (≥ 130 Ma; Mahoney and Journeay 1993;Cordey 1996), whereas no strata younger than latest Early Jurassic (~180 Ma) are known from the Cache Creek terrane. Although both the Bridge River and Cache Creek terranes probably originated in Panthalassa, the former evidently faced open ocean until trapped in the Early Cretaceous (≤130 Ma) behind the arc rocks in the southwestern Coast Mountains, whereas in northern British Columbia the Cache Creek terrane was thrust southwestward over Stikinia in the earliest Middle Jurassic (~174 Ma) (Mihalynuk et al 2004), and in southern British Columbia was thrust eastward over Quesnellia probably in the Late Jurassic (≤ 160 Ma) (Travers 1978).…”

Allochthonous Mesozoic marine sequences of northeastern Asia and western North America: Correlation of the stratigraphic levels and geodynamic depositional settings

“…bonate concretions, which yielded a Callovian assem blage of radiolarians with high conical parvicingulids similar to that from coeval rocks of the Nauchirynai River basin [72]. According to [75,80,89], the Canadian Cordille ras are formed by a system of terranes: the Bridge River, Hozameen, Cache Creek, Slide Mountain, and others (Fig. 6).…”