Date Awarded

1986

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Abstract

A total of 68 vibra-cores and 14-box cores in conjunction with high-resolution seismic records are used to describe the late Quaternary development of a twin-barrier island complex. Based on the stratigraphy, radiocarbon dates, and microfossils, a transgressive outer Holocene and inner Pleistocene barrier island complex are recognized. The two subaerial sub-parallel barriers are a result of separate marine transgressions that occurred before and after late Wisconsin glaciation. Pollen assemblages and ten radiocarbon dates from the lagoonal sediments below the older island concur on a date of approximately 30,000 years B.P., hence a probable mid-Wisconsinan age for the overriding barrier island. The uncertainty surrounding a sea level near today's position 30,000 years ago is not unnoticed; neotectonics may be an important consideration in this apparent rise in sea-level. Holocene sediments deposited in the backbarrier environment show a general shallowing and fining upward sequence. The Holocene stratigraphic sequence indicates a narrowing of the backbarrier region, a decrease in the tidal prism, and an increase in marsh and tidal flat infilling associated with calmer water conditions. Most backbarrier sediments are introduced through tidal inlets. Despite Holocene, backbarrier deposits greater than 8 meters thick, only 2 meters may be preserved below 75-100 cm thick nearshore sands in some areas. Inlet fill deposits will not be preserved. However inner barrier sands and lower Holocene backbarrier sands and muds have a strong preservational potential. The stacking of transgressive barrier deposits, albeit those from different transgressions, may provide a stratigraphic oil trap.

DOI

https://dx.doi.org/doi:10.25773/v5-xn6m-nr31

Rights

© The Author

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