Non-energy minerals and surficial geology of the continental margin of Maryland

Abstract The surficial sediments have been mapped and the shallow geologic framework outlined of the Maryland inner continental shelf. The initial study encompassed a small area offshore of Assateague Island but was extended northward to include the Ocean City area and eastward across several linear shoals. The surficial sediments are predominantly sand with mean grain sizes ranging from 0.40 to 2.89∅. Mud and gravel are the mappable components of the surficial sediments. Muds are distributed along a N-S-trending band seaward of the shoreface. Gravels are mapped farther offshore in 18–22 m of water. Four distinct seismic units are identified from seismic reflection profiles. The lowermost unit, T1, exhibits high-angle clinoforms truncated at the top by a locally prominent near-horizontal reflector. Above this reflector are concordant strata with parallel to subparallel bedding designated as Q2. Incised into Q2 is an extensive channel, Q3, that trends both coast-parallel and coast-normal. The upper unit, Q4, overlaps portions of units Q2 and Q3 along the eastward edges of the study area and is represented in the nearshore by (Holocene inlet?) channeling adjacent to the shoreface. Note that this excludes the modern shelf and “sheet”.