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Abstract

A geosyncline occupied northern parts of the Arctic Islands in late Proterozoic time. It received sediments from the continent and deepened in a northerly direction. A northwestern belt, which included northernmost Ellesmere Island and the present shelf off Ellesmere and Axel Heiberg Islands, underwent orogeny in latest Proterozoic or Cambrian time. The orogen behaved as an intermittently rising geanticline and remained a site of volcanism, plutonism, and metamorphism from Cambrian to Devonian time.

Sediments derived from the geanticline accumulated in a clastic basin on its southeast side. The basin was flanked on the southeast by a subsiding carbonate shelf, in turn grading southward to a stable carbonate platform.

Three phases of sedimentation are recognized in the clastic basin in northeastern Ellesmere Island: (1) Middle to Upper Cambriani?) post-tectonic deltaic deposition; (2) Early to Middle Ordovician deep-water deposition of starved-basin type (radiolarian chert, graptolitic shale, etc.); and (3) late Middle Ordovician to Middle Silurian deep-water deposition of flysch type (graywacke, shale, etc.).

The trough must have formed by subsidence of the continental crust rather than by sea-floor spreading, because the deep-water strata lie on shallow-water strata and not on volcanic rocks. The trough, which was separated from subaerial parts of the geanticline by a shelf on which carbonate, clastic, and volcanic materials were deposited, expanded until about mid-Silurian time, then migrated southeast, ahead of the southeast-migrating geanticline. The southeast flank of the trough, characterized by graptolitic shales and limestones, has been traced from northwestern Greenland to northwestern Melville Island. There, starved-basin conditions persisted from Early Ordovician to Early Devonian time.

A north-trending belt in the central islands, extending from the stable platform to the geanticline, was elevated in the Early Devonian. The uplift, which wcs basement controlled, reflects Precambrian basement trends unrelated to the early Paleozoic basin configuration.

An orogeny of the entire northern regions, locally accompanied by intrusion of quartz diorite, occurred in Middle Devonian to Mississippian time. Deformation and uplift proceeded from northwest to southeast.

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