Grigg tongue

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This is an informal unit. A formal description has not been peer-reviewed or published.

Lithostratigraphy: Pearl Formation >>Grigg tongue
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Pleistocene Series

Primary source

GRIMLEY, D. A., and N. D. WEBB, 2010, Surficial Geology of Red Bud Quadrangle, Randolph, Monroe, and St. Clair Counties, Illinois: Illinois State Geological Survey, Illinois Geologic Quadrangle Map, IGQ Red Bud-SG, 2 sheets, 1:24,000; report, 15 p.

Contributing author(s)

D. A. Grimley and N. D. Webb

Name

Original description

Grigg tongue, Pearl Formation (Grimley and Webb, 2010).

Derivation

Town of Grigg, Illinois, on Red Bud Quadrangle.

Other names

Formerly basal sand in Glasford Formation (e.g., Grimley and Webb, 2009; Grimley, 2010).

History/background

The Grigg tongue of the Pearl Formation is a basal tongue of Illinois Episode sand and gravel that occurs below the Glasford Formation in some areas of the middle and lower Kaskaskia Basin, typically within a few miles of the present day valley in its type area (Grimley and Webb, 2010). The presence of this unit is based on stratigraphic test holes as well as numerous water well engineering boring logs. These data convincingly indicate its occurrence in the lower Kaskaskia Valley and many private water wells locally tap into this aquifer material (Grimley and Webb, 2010). The origin of this unit is likely proglacial sand and gravel deposited in front of an advancing Illinois Episode ice sheet.

The Pearl Formation was originally restricted to Illinois Episode outwash that overlies or extends beyond Illinois Episode till (mainly Glasford Formation). Prior to use of the Grigg tongue, sand and gravel outwash below Glasford till was typically referred to as “Glasford sand”. Sedimentologically and lithologically, the Grigg tongue is similar in character to this main body of the Pearl Formation, but lies stratigraphically below the Glasford Formation. Because the sand and gravel below Glasford till conceptually connects to the main body of the Pearl Formation beyond the limit of glaciation, this unit is defined as a tongue of the Pearl Formation (analogous to the Ashmore tongue of the Henry Formation for Wisconsin Episode deposits; Hansel and Johnson, 1996). The portion of the Pearl Formation above Glasford Formation till has locally been termed the Mascoutah facies (Grimley, 2010), in order to distinguish it from the Grigg tongue and Hagarstown Member of the Pearl Formation. The use of the Grigg tongue, and other tongues of the Pearl Formation between Glasford till units (McKay et al., 2008), allows the Glasford Formation to be mainly restricted to diamicton (till and debris flow deposits).

Type section

Type location

Stratigraphic test core RBD-7; Red Bud Quadrangle; API no. 121572661600; 3200’ SL, 600’ WL, Sec.8-T4S-R7W, Randolph County, IL.

Type author(s)

Grimley and Webb (2010).

Type status

Archived core in ISGS Geological Samples Library; Core #C 15448 (0' - 43').

Reference section

Reference location

Stratigraphic test core KSP-11; Keyesport Quadrangle; API no. 120272718900; 2800’ NL, 450’ WL, Sec. 11, T2N, R2W, Clinton County, IL.

Reference author(s)

Grimley and Walkowska (2015).

Reference status

Archived core in ISGS Geological Samples Library.

Stratigraphic relationships

The Grigg tongue occurs below diamicton (mainly till) of the Glasford Formation and above the Banner Formation, preglacial sediments, or bedrock. Conceptually, the Yarmouth Geosol would separate the Grigg tongue from older pre-Illinois Episode units, but in reality the paleosol is typically not preserved and the outwash lies directly on older materials. Laterally, the Grigg tongue conceptually connects with the main body of the Pearl Formation, but this connection is not always present where younger valley fills or glacial sedimentary deposits truncated the strata.

Extent and thickness

Up to 50 feet thick where the unit has been mapped in the middle and lower Kaskaskia Basin region. Stratigraphic equivalents are known to occur in other parts of Illinois such as in Kane County, in east-central Illinois, and in Clark County. The occurrence of the Grigg tongue is typically centered on paleo-valleys or paleo-lowlands, many of which were filled or buried by till units during Illinois or Wisconsin Episode glacial advances.

Lithology

Sand and gravel; typically brown to light olive brown; ranges from fine-medium sand to gravelly coarse sand; generally ranges from 0 to 30 % gravel, mainly < 5 cm diameter; moderately to well sorted; loose; calcareous; commonly water saturated (below water table); lithic fragments includes various rock types such as carbonate, sandstone, mudstone, coal, chert, and granite; subrounded to subangular.

Core(s)

Photograph(s)

Contacts

The upper contact is below Glasford Formation till and is typically a sharp contact.

The lower contact is unconformably above pre-Illinois Episode deposits (Banner Formation) or bedrock. A Yarmouth Geosol may be found below the sand but is typically eroded and not present. Thus, the inclusion of pre-Illinois episode sand within basal portions of the unit is sometimes possible.

Well log characteristics

This unit occurs in numerous water well logs in its type area near the town of Grigg (Grimley and Webb, 2010) and in many other areas in the middle and lower Kaskaskia River Basin (Grimley and Gemperline, 2015; Grimley and Walkowska, 2015; Grimley and Phillips, 2015).

Fossils

None recognized.

Age and correlation

Illinois Episode; marine oxygen isotope stage 6 (~ 190 to 135 ka)

Environments of deposition

Glaciofluvial, primarily outwash related to advancing Illinois Episode glaciers.

Economic importance

Utilized as a groundwater supply.

Remarks

Similar deposits mapped in the New Athens East and Mascoutah Quadrangles were referred to as a basal sand in the Glasford Formation (Grimley and Webb, 2009; Grimley, 2010). Deposits in a similar stratigraphic position in the Martinsville area, Illinois, were classified informally as the Martinsville sand (Curry et al., 1994). Sand and gravel in a similar stratigraphic position in Kane County were in places mapped as Glasford sand (e.g., Curry, 2007; Curry et al., 2013).

References

CURRY, B. B., 2007, Surficial geology of Elgin Quadrangle, Kane and Cook Counties, Illinois: Illinois State Geological Survey, Illinois Geologic Quadrangle Map, IGQ Elgin-SG, 3 sheets, 1:24,000, report, 14 p.
CURRY, B. B., D. A. GRIMLEY, and A. R. BRUEGGER, 2013, Surficial Geology of Kane County, Illinois: Illinois State Geological Survey, USGS-STATEMAP contract report, 3 sheets, 1:62,500.
CURRY, B. B., K. G. TROOST, R. C. BERG, 1994, Quaternary geology of the Martinsville alternative site, Clark County, Illinois, a proposed low level radioactive waste disposal site: Illinois State Geological Survey Circular 556, 85 p.
GRIMLEY, D. A., 2010, Surficial Geology of Mascoutah Quadrangle, St. Clair County, Illinois: Illinois State Geological Survey, Illinois Geologic Quadrangle Map, IGQ Mascoutah-SG, Revision, 2 sheets, 1:24,000; report, 9 p.
GRIMLEY, D. A. and J. M. GEMPERLINE, 2015, Surficial Geology of Stolletown Quadrangle, Bond and Clinton Counties, Illinois: Illinois State Geological Survey, IGQ Stolletown-SG, 2 sheets, 1:24,000; report, 11p.
GRIMLEY, D. A., and A. C. PHILLIPS, editors, 2015, Ridges, Mounds, and Valleys: Glacial-Interglacial History of the Kaskaskia Basin, Southwestern Illinois, 55th Midwest Friends of the Pleistocene Field Conference: Illinois State Geological Survey Guidebook 41, 124 p.
GRIMLEY, D. A. and K. A. WALKOWSKA, 2015, Surficial Geology of Keyesport Quadrangle, Bond and Clinton, and Fayette Counties, Illinois, Illinois State Geological Survey, STATEMAP Keyesport-SG, 2 sheets, 1:24,000; report, 10p.
GRIMLEY, D. A. and N. D. WEBB, 2009, Surficial Geology of New Athens East Quadrangle, St. Clair County, Illinois: Illinois State Geological Survey, Illinois Geologic Quadrangle Map, IGQ New Athens East-SG, 2 sheets, 1:24,000; report, 12 p.
GRIMLEY, D. A., and N. D. WEBB, 2010, Surficial Geology of Red Bud Quadrangle, Randolph, Monroe, and St. Clair Counties, Illinois: Illinois State Geological Survey, Illinois Geologic Quadrangle Map, IGQ Red Bud-SG, 2 sheets, 1:24,000; report, 15 p.
McKAY III E. D., R. C. BERG, A. K. HANSEL, T. J. KEMMIS, & A. J. STUMPF, 2008, Quaternary deposits and history of the Ancient Mississippi River Valley, north-central Illinois: Illinois State Geological Survey Guidebook 35, 106 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation
0000
pl-g