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PoteauSyncline

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Geologic Map of the Adona Quadrangle, Conway and Perry Counties, ArkansasDigital Geologic Quad rangle MapAd ona Quad rangle, Arkansas

DGM-AR-00005

Descrip tion of Map U nits

Correlation of Map U nits

U nconform ity

U nconform ity

ÙhsÙm a

Ùau

Qal Holocene

Desm oinesian

Atokan

Pennsylvanian

Quaternary

T hrust faultÙal

U nconform ityQt Pleistocene

Ùhs

Ùau

Ùhs

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ÙalÙal?? ? ?

?

A'1000

500

-500

Sea L evel

A

1000

500

Sea L evel

-500

Petit Jean Mountain

Ada Anticline Poteau Syncline Rose CreekMountain Ross Creek Fault

ScaleV ertical: 1 inch = 500 feet

Horizontal: 1 inch = 2000 feet

Introd uction

Geology b y Boyd R. Haley, Charles G. Stone and Angela K. Chand ler2008

Arkansas Geological Survey, Bekki White, State Geologist

lower m em b er

up p er m em b er

AtokaForm ation

HartshorneSand stone

McAlester Form ation

Des Moinesian

Atokan

Pennsylvanian

Series

Stage

Formation

unconform ab le surface

silt, siltstoneand silty shale

sand stone

b lack fissileshale

coal

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McAlester Formation (Pennsylvanian, Desmoinesian) – Consists of very thin b ed d ed silty m icaceous shales and siltstones with occasional thin-b ed d ed sand stone. T he shales and siltstones are charcoal-gray to b lack on fresh surfaces b ut weather b uff to orange in color. T his form ation is exp osed on Round Mountain just south of Seven Hollows T rail and Petit Jean State Park. T his form ation contains p lant fossils and a thin coal b ed is id entified as the “lower Hartshorne coal seam ”. T he McAlester Form ation is conform ab le with the und erlying Hartshorne Sand stone. Ap p roxim ately 250-300 ft. thick in the Round Mountain area. Hartshorne Sandstone (Pennsylvanian, Desmoinesian) – A very fine to m ed ium -grained m icaceous sand stone that is thin to m assive-b ed d ed . T he m assive b ed s contain tab ular cross-b ed s. T he sand stone is usually a light red or orange to b uff or white on fresh surfaces b ut weathers a d ark-gray. T he q uartz grains are angular to sub -round ed . Also contains som e intervals of siltstone and shale. T he form ation is exp osed on top of Petit Jean Mountain and along the Seven Hollows T rail and contains the well known “turtle rocks” and b ox-work or “carp et rock” seen in the p ark. T he sand stone also form s the scenic rid ges along Rose Creek Mountain. T he Hartshorne Sand stone is unconform ab le with the und erlying Atoka Form ation. T he unconform ab le contact can b e seen b eneath Ced ar Falls ap p roxim ately 15 feet ab ove p ool level. Ap p roxim ately 200-300 ft. thick in this area.

Atoka Formation (Pennsylvanian, Atokan) – T he Atoka Form ation is d ivid ed into lower, m id d le and up p er m em b ers b ased on regionally m ap p ab le shale or sand stone intervals (McFarland , 1998). Only the up p er and lower m em b ers are exp osed on this m ap . T he m id d le m em b er is ab sent d ue to the action of the Ross Creek T hrust Fault in the lower p ortion of the m ap p ed area. Upper member – Consists of m icaceous silty shales, siltstones and thin-b ed d ed sand stones. T he shales and siltstones are charcoal-gray to b lack on fresh surface and weather a d ark-gray. Som e silty seq uences contain very thin-b ed d ed round ed concretions. T he sand stone is fine-grained with sub -angular to sub -round ed grains and is gray to b uff on fresh surfaces. T his unit contains lim onite p eb b le b ed s and occasional fossiliferous b ed s containing m ostly gastrop od s and b ivalves. More com m only seen are p lant fossils and trace fossils such as Conostichus. Coal stringers and thin coal b ed s less than one inch are ab und ant in this m em b er. T he up p er m em b er is p resent along the hillsid es of Petit Jean Mountain and in the surround ing valleys. Ap p roxim ately 650-700 ft. of section is exp osed in this area. Lower member – Consists of thin to thick-b ed d ed sand stone, m icaceous siltstone and b lack fissile shale (Stone et. al., 1981). T he siltstone and shale contain coalified p lant fragm ents and sid eritic iron concretions. T race fossils are ab und ant in this unit. T he lower m em b er is exp osed south of the Ross Creek Fault in the southern p art of the m ap . Ap p roxim ately 300-500 ft. of section is exp osed on southern p art of m ap .

Ùau

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Bear Cave T railBoy Scout T railCanyon T railCed ar Creek T railCed ar Falls T railSeven Hollow T rail

T rails

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lower Hartshorne coal

Sym b ols

T he Ad ona q uad rangle was m ap p ed b y Boyd R. Haley and Charles G. Stone in 1995 through COGEOMAP, a coop erative m ap p ing p roject with the Oklahom a Geological Survey and the U .S. Geological Survey. T his area was revisited in 2007 for a State Park Series centered on Petit Jean State Park and as a result this m ap was d igitized and the layout com p iled as a Digital Geologic Map , DGM-AR-00005.

T he m ajority of the Ad ona q uad rangle is located in the Arkansas River V alley p hysiograp hic region. Several structures (anticlines and synclines) are p resent as a result of the tectonic forces from the Ouachita orogenic (m ountain b uild ing) event. T his area contains b road valleys consisting of non-resistant shales with resistant sand stones form ing the rid ges.

T he Ross Creek Fault m arks the northern ed ge of the Ouachita Mountain p hysiograp hic region which contains the m ajority of thrust faults. Several thrust faults are p resent south of the Ross Creek Fault system creating steep ly inclined southward d ip p ing rocks.

Alluvium deposits (Quaternary. Holocene) – Consists of alluvial d ep osits, tan to b uff in color, com p osed of sand , clay and gravel. Ap p roxim ately 30-40 feet is exp osed in northwestern corner of q uad rangle. Terrace deposits (Quaternary, Pleistocene) – Consists of various low to high level terrace d ep osits, red d ish-orange in color, com p osed of sand , clay and gravel. Ap p roxim ately 30-50 feet of section is exp osed along the Petit Jean River.

M

F

o12

Form ation contact

Syncline

Anticline

Strike and d ipof inclined b ed d ing

T hrust fault(b arb on up thrown p late)

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Bed d ing

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Arrow showing d irectionof fault m ovem ent

ucuc sw Gravel p it

Quarry (crushed stone)

Quarry (coal) References

Acknowledgments: T his geologic m ap is a com p ilation of the Ad ona q uad rangle that was m ap p ed in 1995 for COGEO, Coop erative Geologic Map p ing Program , a p rogram with the U S Geological Survey. Many thanks to Charlie Stone and Boyd Haley for their assistance in creating this d igital m ap with layout. Disclaimer: T his m ap was p rep ared in a d igital form at using ArcV iew 9.2, ArcGIS 9 software on com p uters at the Arkansas Geological Survey. T he Arkansas Geological Survey d oes not guarantee the accuracy of this m ap esp ecially when used on any other system or with any other software. As m ap p ing continues and is refined , the d ata p resented on this m ap m ay b e up d ated . For the latest ed ition of this p ub lication p lease contact our office. For inform ation on ob taining cop ies of this m ap and other Arkansas Geological Survey m ap s and p ub lications call: Pub lication Sales 501-296-1877

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Chand ler, Angela K., 2007, T he geologic story of Petit Jean State Park: Arkansas Geological Survey, State Park Series 2, 10 p ., 4 trail m ap s. Haley, Boyd R., and Stone, Charles G., 1995, Geologic m ap of

the Ad ona Quad rangle: Arkansas Geological Com m ission Geologic Worksheet, 1 sheet.

Haley, Boyd R., and Stone, Charles G., 1995, Geologic m ap of the Atkins Quad rangle: Arkansas Geological Com m ission Geologic Worksheet, 1 sheet.

Haley, Boyd R., and Stone, Charles G., 1995, Geologic m ap of the Perryville Quad rangle: Arkansas Geological

Com m ission Geologic Worksheet, 1 sheet. Howard , J.M., 2008, Arkansas m ineral com m od ity d atab ase; Arkansas Geological Survey, in house d ata. McFarland , John David , 1998, Stratigrap hic sum m ary of Arkansas: Arkansas Geological Com m ission Inform ation Circular, IC-36, 39 p p . Stone, Charles G., 1975, A b rief sum m ary of the Petit Jean Mountain Region: Arkansas Geological Com m ission Op en file rep ort, 8 p p . Stone, Charles G. and McFarland , John D. III, with the

Coop eration of Haley, Boyd R., 1981, Field guid eb ook to the Paleozoic rocks of the Ouachita Mountains and Arkansas V alley Provinces, Arkansas: Arkansas Geological Com m ission Guid eb ook 81-1, 140 p p .