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ABSTRACT: The Algonquin Arch: An Upper Silurian Analogue of the Sinai Block

Simon J. Haynes

Detailed lithostratigraphic mapping of the Salina Group A and B Units at three gypsum mines near the Algonquin arch has revealed that lagoonal, coastal salina, and sabkha evaporite sequences may all be present within a vertical height of 10 m and a lateral distance of 55 km. A modern analog is the semi-arid coast of northern Egypt, where coastal salinas are separated from evaporite lagoons by sabkhas, at distances similar to those over the Algonquin arch. Also, the mudstone sequences of the Salina A and B Units, which thicken toward the Appalachian basin to become the Vernon and Syracuse shales, are comparable to the deltaic lagoons and offshore fans about the Nile Delta.

It is suggested that the present day Mediterranean basin is a tectonostratigraphic equivalent to the Upper Silurian Appalachian basin, and that the Sinai block is equivalent to the Algonquin arch. It is likely that terrestial ephemeral lake environments of the modern Sinai are present in the Salina Group over the Algonquin arch and may be represented by, at least in part, the Salina A Unit halite of the Michigan basin. The southern Sinai (Gulf of Aquaba/Red Sea), bordered by modern marine salinas and sabkhas, is similar in setting to the halite of the Michigan basin (an incipient rift?). Alternatively, the Michigan basin halites may represent tectonic drawdown of a marine basin.

Although the significance of this tectonostratigraphic comparison to oil and gas is unknown, it does explain why subaqueous, supratidal, and subaerial environments were mutually inclusive during the deposition of the Salina Group.

AAPG Search and Discovery Article #90998 AAPG Eastern Section Meeting, London, Ontario, Canada, September 10-12, 1990