Named for exposures along Cocalico Creek, Lancaster Co., southeastern PA. Consists of dark-gray shale containing graptolites of Normanskill type and thin crinoidal limestone at base; gray, green, and purple slates and green impure sandstone above. Thickness is 1000 ft, more or less. Overlies Beekmantown limestone northeast of Lancaster. Age is Ordovician.
Source: GNU records (USGS DDS-6; Reston GNULEX).
Revised the Cocalico to the Cocalico Formation in southeastern PA.
Source: GNU records (USGS DDS-6; Reston GNULEX).
The Cocalico Formation is probably closely related to the Hamburg sequence of PA. Consists of gray, phyllitic shale, maroon shale, and silty siliceous shale with some interbedded argillaceous and quartzose sandstone. Unit is of Ordovician age.
Source: GNU records (USGS DDS-6; Reston GNULEX).
The Cocalico Formation is divided into two informal members [relative position of members not stated]. The shale member consists of gray, highly phyllitic, moderately well and thin-bedded shale with some interbedded red shale. The shale member is slightly resistant to weathering. The sandstone member consists of argillaceous and quartzose, well and thick-bedded sandstone that is highly resistant to weathering.
Source: GNU records (USGS DDS-6; Reston GNULEX).
Age of the Cocalico Formation is shown as Late Cambrian through Late Ordovician.
Source: GNU records (USGS DDS-6; Reston GNULEX).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
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