Ten years of studies on Maryland's inner continental margin and coastal bays

During the past ten years of the Association of American State Geologists-M ineral Management Service Continental Margins Program, the Maryland Geologi cal Survey investigated the sedimentological, paleontological, stratigraphi cal and geophysical character of Maryland's inner continental shelf Based o n seismic records and sedimentological analyses completed during the first four years, a late Quarternary stratigraphic model was developed. Five dist inct stratigraphic units were identified and described on the Maryland inne r shelf These units represent late Pleistocene interglacial deposits, the o ldest of which corresponds to pre-Illinoian (oxygen-isotope stages 7 and/or 9) transgressive shelf sands. Overlying the Q1 unit, the Q2 unit is a 6-me ter thick mud sequence of oxygen-isotope stage 5 (128-75 ka) age. Units Q3 and Q4 representing fluvial and leading edge estuarine deposits (oxygen-iso tope stages 4, 3 and 2) filled numerous paleochannels that were incised int o units Q2 and Q1. Modem trailing-edge transgressive shelf shoals (Unit Q5) discontinuously cap the sequence. The 5th and 6th years studies reported on the economic minerals of surficia l and cored sediments. Vibracores collected off the Maryland's shelf during previous studies were analyzed for mineral types and abundances, weight pe rcent of general size fractions, and heavy mineral (HM) content. Mineralogi c maturity indices were compiled to correlate the THM and economic heavy mi nerals (EHM) abundances with position offshore, sediment type, and the indi ces themselves. For the 7th year; the Maryland Geological Survey re-examine d geophysical records and lithological data originally collected by the Arm y Corps of Engineers to locate and assess beach fill borrow areas for the O cean City Beach Replenishment Project. Data from 163 vibracores and over 30 0 kilometers of high-resolution seismic profile records collected off Ocean City, Maryland, supported the stratigraphic model developed by MGS during the first four years of the AASG-MMS program. The Maryland coastal bays became the focus of study during the 8th and 9th years during which seismic records, cores and surficial sediment were colle cted in Isle of Wight and Assawoman Bays. Shallow pretransgression surface was mapped, relating the existing streams to offshore paleochannels. The tenth year study focused on developing a repository for vibracores coll ected on Maryland's inner continental shelf.