Pearya: a composite terrane with Caledonian affinities in northern Ellesmere Island

Abstract

In Ellesmere Island, the Canadian Shield and Arctic Platform are flanked on the northwest by the lower Paleozoic Franklinian mobile belt, which comprises an unstable shelf (miogeocline) and a deep-water basin, divisible into an inner sedimentary belt and an outer sedimentary–volcanic belt. Both are tied to the shelf by interlocking facies changes, but additional exotic units may be present in the outer belt.Pearya, bordering the deep-water basin on the northwest, is divisible into four successions. Succession I comprises sedimentary and(?) volcanic rocks, deformed, metamorphosed to amphibolite grade, and intruded by granitic plutons at 1.0–1.1 Ga. Succession II consists mainly of platformal sediments (carbonates, quartzite, mudrock), with smaller proportions of mafic and siliceous volcanics, diamictite, and chert ranging in age from Late Proterozoic (Hadrynian) to latest Cambrian or Early Ordovician. Its concealed contact with succession I is tentatively interpreted as an angular unconformity. Succession III (Lower to Middle Ordovician?) includes arc-type and ocean-floor volcanics, chert, mudrock, and carbonates and is associated with fault slices of Lower Ordovician (Arenig) ultramafic–mafic complexes–possibly dismembered ophiolites. The faulted contact of succession III and the ultramafics with succession II is unconformably overlapped by succession IV, 7–8 km of volcanic and sedimentary rocks ranging in age from late Middle Ordovician (Blackriverian = early Caradoc) to Late Silurian (late Ludlow?). The angular unconformity at the base of succession IV represents the early Middle Ordovician (Llandeilo–Llanvirn) M'Clintock Orogeny, which was accompanied by metamorphism up to amphibolite grade and granitic plutonism. Pearya is related to the Appalachian–Caledonian mobile belt by the Grenville age of its basement, the age of its ultramafic–mafic complexes, and evidence for a Middle Ordovician orogeny, comparable in age and character to the Taconic. By contrast, the Franklinian mobile belt has a Lower Proterozoic (Aphebian) – Archean basement and was not deformed in the Ordovician. Stratigraphic–structural evidence suggests that Pearya was transported by sinistral strike slip as three or more slices and accreted to the Franklinian deep-water basin in the Late Silurian under intense deformation. The inferred sinistral motion is compatible with derivation from the northern Caledonides.

The High Arctic LIP in Canada: Trace element and Sm–Nd isotopic evidence for the role of mantle heterogeneity and crustal assimilation

“…Again, like the Th/La data (Fig. 17), there is a strong divergence between the data and the cratonic mixing curve, indicating further that cratonic and metavolcanic rocks that, in northern Ellesmere Island, constitute the Pearya terrane (Trettin, 1987;Malone, 2012). Lying unconformably above the cratonic basement is the Cambrian-Devonian Franklinian Mobile Belt with sediments derived from underlying cratonic (>450 Ma) as well as Caledonian sources from the northeast (<450 Ma) on the basis of Nd and traceelement geochemistry (Patchett et al, 1999).…”

Tropical weathering of the Taconic orogeny as a driver for Ordovician cooling

“…The colliding Taconic arc system extended west (paleocoordinates in Fig. 1) into 82 the southern Appalachians as far as Alabama (Hibbard, 2000), and east along the 83 Greenland margin to Ellesmere Island (Trettin, 1987). This elongate east-west exposure 84 of the arc system was all within a similar latitude band (Fig.…”

Multistage Cretaceous magmatism in the northern coastal region of Ellesmere Island and its relation to the formation of Alpha Ridge – evidence from aeromagnetic, geochemical and geochronological data

“…Intrusive rocks related to the Mid Ordovician M'Clintock orogeny (Trettin et al, 1982) . The Pearya Terrane is bounded by faults, among others the Peterson Bay Fault and the M'Clintock Glacier Fault (Trettin, 1987;Trettin & Frisch, 1987;Piepjohn et al, 2013), against Early Palaeozoic metasedimentary rocks of the Franklinian Basin in the south (Fig. 3B).…”