Hadley Gravel Member

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Lithostratigraphy: Embayment Megagroup >>Baylis Formation >>Hadley Gravel Member
Chronostratigraphy: Mesozoic Erathem >>Cretaceous System >>Gulfian Series

Primary source

Willman, H. B., Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, and Jack A. Simon, 1975, Handbook of Illinois Stratigraphy: Illinois State Geological Survey Bulletin 95, 261 p.

Contributing author(s)

H. B. Willman and John C. Frye


Original description

The Hadley Gravel Member, the basal member of the Baylis Formation (Frye et al., 1964, p. 4, 8).


Named for Hadley, Pike County, 4 miles northwest of the type section.

Other names


Type section

Type location

The type section for the Hadley Gravel Member is the same as that for the Baylis Formation, an exposure and small pit along a branch of Kiser Creek (NW SW SE 31, 4S-4W).

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

Extent and thickness

The member is generally present in the outcrop area of the formation. It is as much as 15 feet thick but is generally less than 10 feet and in places is only a layer of pebbles.


The Hadley Gravel Member is predominantly pebbles and small cobbles of brown, dark gray, and red chert, but 20-30 percent of the pebbles are quartz, and 1-2 percent are quartzite. It differs only slightly from the Grover Gravel of the Tertiary System, which probably was largely reworked from the Cretaceous gravels, but in the Grover Gravel the brown chert pebbles are more abundant, rounder, and more highly polished. Some of the isolated patches of chert gravels long assigned to the Tertiary may be remnants of the Hadley Gravel Member, which originally may have had wide distribution in western and northern Illinois.




Well log characteristics


Age and correlation

Environments of deposition

Economic importance



FRYE, J. C., H. B. WILLMAN, and H. D. GLASS, 1964, Cretaceous deposits and the Illinoian glacial boundary in western Illinois: Illinois State Geological Survey Circular 364, 28 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation