Morphology and Vertical Sedimentary Sequences in Holocene Transgressive Sand Barriers: ABSTRACT

Abstract

Studies of the barrier ridges and beaches along the presently transgressing mid-Atlantic coastal area have been used to formulate morphologic and vertical sequence models for transgressive beaches. Each type of barrier is a response to the topography being inundated in the ongoing transgression as well as to wave and current conditions. Four major types of sand-gravel barriers may be identified in coastal Delaware: (1) bay-mouth barriers, (2) beach against highlands, (3) estuarine barriers, and (4) spit complex. The bay-mouth barriers, between enclosed lagoons and the open Atlantic Ocean, are characterized by a vertical transgressive sequence of sedimentary environments identical with the horizontal sequence in the direction of the transgression. In the beach against highland barrier, beach-bern system impinges on low-lying Pleistocene highlands (20-30 ft) which are being eroded and provide a partial source of sediment to the beach system. Estuarine barriers occur as long arcuate shorelines of large estuaries such as Delaware Bay. A barrier of sand and gravel is formed with small width (30 ft) and thickness ( End_of_Article - Last_Page 856------------