The Geology of Delaware

Share

First State Geology Newsletter Signup

First State Geology has been the newsletter of DGS for over 25 years.

Click here to signup!

Choptank Formation

Tch
Geologic Time Period: 
middle to upper Miocene
Coastal Plain - Primarily Subsurface Unit

Description published in GM14 Geologic Map of Kent County, Delaware, Ramsey, K.W., 2007:

Light gray to blue gray, fine to medium, shelly, silty, quartz sand and clayey silt. Discontinuous beds of fine sand and medium to coarse quartz sand are common. Base of the unit is marked by a coarse to granule sand that fines upwards to a medium to fine silty sand. This sand is the Milford aquifer (Ramsey, 1997; McLaughlin and Velez, 2006). In southern Kent County, can be subdivided into upper and lower unit. Lower unit consists of the fining-upward sequence from the basal sand to a hard clayey silt to silty clay that ranges in color from grayish brown to bluish gray. Upper unit consists of clean to silty, fine to medium, moderately shelly sands with thin silty clay beds. Rarely found in outcrop in the upper reaches of some of the more deeply incised streams. Outcrops are too small to be shown on this map. Found in the southern half of Kent County. Up to 140 feet thick in the southernmost part of the county.