A REEXAMINATION OF PENNSYLVANIAN “FILLED-SINK” DEPOSITS IN EAST-CENTRAL MISSOURI: ARE THEY PENNSYLVANIAN AND

ARE THEY FILLED SINKS?

William W. Little

Missouri Department of

Natural ResourcesGeological Survey and Resource Assessment Division

Small circular outcrops

DickiteDisturbed bedding

Stratigraphic position

Evidence Supporting Pennsylvanian Sink and Cave Fill Features

Oc

Oc“Psf”

“Psf” (rimrock)

Oc

Oc

Mc

“Psf”

“Psf” (rimrock)

Oc

Oc

Mc

“Psf”

Mc

“Psf” (rimrock)

“Psf”

A B

C D

B

D

Mc

Oc

Paleokarst unconformity

Mb?

Mc

Oc

Paleokarst unconformity

Mb? B

A

Mc

Oc

Mc

Mb?

Oc

“Psf” (rimrock)

Remnant paleokarst hills

Oc

“Psf” (rimrock)

Remnant paleokarst hills

Oc

Oc

Mb

Mc

ds

Interbeddedss, ms, & ds}

PaleokarstHill on Oc

ds

Interbeddedss, ms, & ds}

PaleokarstHill on Oc

ds

ds

ds

ss & ms

Middle O Everton Fm on I-55

“P sink-fill” on Hwy 50

Outcrop pattern and measured sections for Middle Ordovician strata

GeneralizedSection

MeasuredSections

Cave Hill RdExposure

“Psf” (rimrock)

Mr

“Psf” (rimrock)

Mr

“Psf” (rimrock)

Mr

Versailles

Mr

“Pss”

Goerlisch Ridge

Mr

“Pss”

Vichy

Mr

“Pss”

Otterville East

Mr

“Psf”

Oc

Morrison

Mr“Pss”

Fredricksburg

Mr“Pss”

New Melle

Mr

“Pss”

Washington East

Mr“Pss”

“Pss”

Mr

“Pms”

Mississippian Residuum from atop a Pennsylvanian sandstone

Modern stream gravel from same area

Mississippian Residuum from atop a Pennsylvanian sandstone

Glacial erratics from the Troy area

Oc

“Psf”

“Psf” (rimrock)

Oc

“Psf”

“Psf” (rimrock)A

B

Oc

“Psf”“Psf” (rimrock)

ss

ms

South side of hwy North side of hwy

Differential Compaction

Oc“Pss” Oc

.• In some places, these deposits are interbedded with carbonates of Ordovician age.

• In other localities, they underlie Mississippian-age limestones.

• As shown on the state geologic map, small remnants of Devonian and Mississippian-age strata locally overlie these deposits.

• Cobbles and small boulders of fossiliferous Mississippian-age chert are found on the surface above these deposits throughout their mapped extent.

Evidence Supporting a Pre-Pennsylvanian Age

Most deposits are flat-lying with disturbed strata being restricted to lateral margins.

The regional distribution pattern of sandstone resembles that of an integrated drainage system and commonly forms a sheet.

Internal structures of sandstones indicate deposition by moving water.

Sandstone bodies are often flanked by stratified successions of interbedded claystone, siltstone, and thinner sandstones.

Evidence Supporting a Paleovalley Origin