Abstract

The Lower Devonian Compton Formation is the uppermost unit of the St. Francis Group in the Connecticut Valley – Gaspé synclinorium of southern Quebec. The Compton Formation is composed of three informal members. Five distinct sedimentary facies have been recognized in the lower two members of the Compton Formation. High-energy, shallow-marine, and channel sands dominate the Milan member. The overlying Lac Drolet member consists of below wave base mud and silt deposits with abundant turbidite sand. The Milan member is interpreted to represent deposits of a river-dominated delta-front environment, whereas the Lac Drolet member is suggestive of below storm-wave base pro-delta deposits. The transition from the Milan member to the Lac Drolet member is correlated with the deepening event recognized in coeval succession in the Gaspé Peninsula and known as the T2 event. There, the coeval Indian Point Formation is interpreted to represent pro-delta sediments. The new paleogeographic map for the Lochkovian illustrates the development of deltaic lobes from northern Gaspé to southern Quebec. In Lochkovian, deltaic regimes were established in southern Quebec and northeastern Gaspé, whereas the intervening successions (western Gaspé Peninsula – New Brunswick) experienced significant synsedimentary tectonic collapse.

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