Abstract: Otto Fiord Formation--Evidence of Subaqueous Evaporite Deposition in Carboniferous of Sverdrup Basin, Canadian Arctic Islands

D. L. Christie, Graham R. Davies, N. C. Wardlaw

The Carboniferous Otto Fiord Formation is a widespread evaporite unit within the Sverdrup basin of the Canadian Arctic Islands. Outcrops of this formation, which are as much as 600 m thick, are characterized by thick units of anhydrite (some in excess of 65 m) lying above thinner limestone units in cyclically alternating couplets, each of which is bounded by unconformities. The sequence bears some similarity to that of classic sabkha deposits, but detailed examination reveals features not related to a sabkha environment. Vertical faunal changes within the limestones, primary bedding structures preserved within the sulfates, and the regional basin geometry of shelf deposits surrounding a central evaporite facies all serve to indicate that each cycle represents a period of ontinuous subaqueous deposition. The upward change in lithology from limestone to sulfate, through an interlaminated contact, records increasing levels of salinity of the depositing brines as the basin became progressively more isolated from the influence of normal marine waters.

The limestone-anhydrite couplets of the Otto Fiord Formation, with their bounding unconformities, are interpreted to be the result of alternating periods of transgression (limestone deposition) and regression (sulfate deposition). Information from drilling within the Sverdrup basin indicates that tectonic activity during the Carboniferous, in the form of block faulting, may have been an important factor in initiating and localizing evaporite deposition.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC