The Stellwagen Bank region off eastern Massachusetts: a Wisconsin glaciated Cenozoic sand banks/delta?

Abstract

Stellwagen and Tillies banks, Jeffreys Ledge, the erosional remnants shoreward of the banks in Massachusetts Bay, Cape Cod Bay and beneath Cape Cod may define an Eocene sand banks/delta. The present configuration of the region is due to a combination of pre-Wisconsin fluvial erosion, Wisconsin proglacial, subglacial and marine processes and Holocene marine processes. Wisconsin sediments south of Jeffreys Ledge experienced deformation and the formation of sag basins by the sinking of the overlying sediments into the underlying fine grained mass with the sediments between the basins being squeezed up to producing diapirs. The western part of Jeffreys Ledge rising tens of meters above its surroundings is a moraine created during a local re-advance when the overall Laurentide ice was retreating prior to 14 000 years ago. This re-advance resulted in the deformation of Coastal Plain and Wisconsin strata.