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Home > Explore! > Coastal Marine Geology > Saco Bay Sand Resource > Discussion


Assessment of Sand and Gravel Resources along the Inner Continental Shelf of Maine

Discussion

Large rivers that enter the Gulf of Maine, such as the Merrimack, Kennebec, and Penobscot, are all associated with deltas built at times of lower-than-present sea level (Belknap and others, 2004; Kelley and others, 2003). These rivers gathered their sand as new rivers that formed in the post-glacial period and eroded down into glacial sediment as local, relative sea level fell. The Merrimack and Kennebec actively contribute sand to the inner shelf today (FitzGerald and others, 2004), as does the Saco (Kelley and others, 2004). The Penobscot River does not carry sand to sea today and its paleodelta is buried under 10 m of mud in Penobscot Bay apparently due to drainage derangement in the early Holocene (Belknap and others, 2005).

Even though the Saco River actively contributes sand to the shelf today, it possesses a discharge that is an order of magnitude smaller than the Kennebec or Merrimack Rivers. This may account for its lack of a lowstand paleodelta. In its upper reaches, the Saco also passes through extensive wetlands and a pond (Kezar Pond, Fryberg, ME) where it may have deposited much of its early sand load before reaching the sea.

Although it lacks a deltaic landform, the shoreline complex in outer Saco Bay still contains an abundance of sand (Table 2). In assessing the sand volumes in the eight basins of outer Saco Bay, seismic coverage was not dense enough in any one basin to construct an isopach map because of the highly irregular basement bathymetry. Maximum and minimum values were attached to the sand volumes in the basins based on extrapolations from the thickness of sand collected in the cores (Table 2). A maximum volume of sand was estimated at 3.1 x 107 m3, with a minimum volume of about 8 x 106 m3. The deposits extend beyond the study area into shoreline deposits to the northeast cored in earlier years (Kelley and others, 2003) and landward, up the Shelf Valley (Basin 1). Since no deltaic landform was recognized in these areas, it is unlikely that more than an additional 1 x 107 m3 could be found in these areas.

Introduction   Previous Studies   Geologic Setting   Methods   Results   Discussion   References   Appendix

Last updated on October 30, 2006