File:Honeycomb weathering (Black Hand Sandstone, Lower Mississippian; Picnic Rock, Black Hand Gorge, Ohio, USA) 3.jpg

English: Quartzose sandstone in the Mississippian of Ohio, USA.

The Black Hand Sandstone is a prominent, cliff-forming sedimentary unit in the Mississippian of parts of eastern Ohio, USA. This photo was taken at the type locality - Black Hand Gorge in Licking County, Ohio, where an American Indian pictograph formerly existed. The "Black Hand" was destroyed long ago by canal builders. The pictograph represented an early "highway sign" that roughly indicated directions to Flint Ridge, where arrowhead-quality flint was quarried.

The Black Hand Sandstone consists of horizontally bedded and cross-bedded quartzose sandstones, granulose sandstones, pebbly sandstones, plus minor quartz-pebble conglomerate. Stratigraphically, the unit was traditionally considered as a coarse-grained upper member of the Cuyahoga Formation (Lower Mississippian) and represented a delta deposit.

A revised understanding of the Black Hand Sandstone was published in the 2000s by West Virginia geologists. The unit is now understood to be temporally and genetically unrelated to the Cuyahoga Formation, and therefore cannot be considered one of its members. The Black Hand Sandstone is now interpreted as an incised valley fill deposit.

The Black Hand Sandstone in parts of Ohio produces some oil and natural gas. Oil drillers refer to the Black Hand as the “Big Injun Sandstone”.

The pitting present on this outcrop is a distinctive weathering style called honeycomb weathering. It is most commonly seen on steep sandstone faces. It forms by differential erosion. Slight variations in the degree of cementation causes some areas of the rock to have grains removed more quickly by erosion than other areas.

Stratigraphy: Black Hand Sandstone, Lower Mississippian

Locality: outcrop at the western end of Black Hand Tunnel (part of the long-abandoned Ohio Electric Railway interurban line) at Red Rock/Tunnel Rock/Picnic Rock, Black Hand Gorge, far-eastern Licking County, eastern Ohio, USA

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Some references on the Black Hand Sandstone:

Ver Steeg, K. 1947. Black Hand sandstone and conglomerate in Ohio. Bulletin of the Geological Society of America 58: 703-727.

Szmuc, E.J. 1970. The Mississippian System. pp. 23-67 in Guide to the Geology of Northeastern Ohio. Cleveland. Northern Ohio Geological Society.

Walker, D.A. 1978. Paleontology and Paleoecology of the Cuyahoga and Logan Formations of Central Ohio. Senior Thesis. Denison University, Granville, Ohio, USA. 9+102+11+(1)+2 pp. 11 pls.

Bork, K.B. & R.J. Malcuit. 1981. Cuyahoga and Logan Formations of central and eastern Licking County, Ohio. Ohio Sedimentary Geology III. 21 pp.

Kammer, T.W. & D.L. Matchen. 2002. Biostratigraphic constraints on the timing of valley incisement and deposition of the Lower Mississippian Black Hand Sandstone of Ohio. Geological Society American Abstracts with Programs 34(6): 428.

Matchen, D.L. & T.W. Kammer. 2002. Reinterpretation of the Black Hand Sandstone (Lower Mississippian) of Ohio as incised valley fill. Geological Society of America Abstracts with Programs 34(6): 277.

Matchen, D.L. & T.W. Kammer. 2006. Incised valley fill interpretation for Mississippian Black Hand Sandstone, Appalachian Basin, USA: implications for glacial eustasy at Kinderhookian-Osagean (Tn2-Tn3) boundary. Sedimentary Geology 191: 89-113.