Genesis of Boston Harbor drumlins, Massachusetts
Newman WA and Mickelson DM. 1994. Genesis of Boston Harbor drumlins, Massachusetts. Sedimentary Geology. 91:333-343
Drumlins in Boston Harbor are composed of two superposed silty-sandy diamicton units and subordinate sand and gravel. The lower, compact, undifferentiated, diamicton is interpreted as a pre-Wisconsin till, based on truncated weathering profiles preserved below an erosion surface. The upper, less compact, diamicton contains numerous, discontinuous and poorly sorted lenses and stringers of sand and sandy gravel that tend to parallel the erosion surface. The upper diamicton and subordinate sandy gravel lenses are interpreted to date from the late Wisconsin glaciation. Along the exposed sections of the Long Island drumlin complex, the preserved weathering profile on the lower diamicton is thicker beneath the drumlin axes and is either thin or missing in the inter drumlin areas. This suggests that glacial erosion and streamlining of pre-Wisconsin deposits and their weathering profile took place after the weathering profile developed and before subsequent deposition of the overlying diamicton unit. The latter drapes the erosional drumlin form without contributing substantially to relief of the drumlin form.
- Type
- Journal Article
- Authors
- Newman, W; Mickelson, D
- Units
- BOHA
- Keywords
- Geology, Sediment