Paleopebble from the Mississippian of Ohio, USA. (54 millimeters across at its widest)

The Black Hand Sandstone is a prominent, cliff-forming sedimentary unit in the Mississippian of parts of eastern Ohio, USA. The type locality is 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 is no longer considered to be one of its members. The Black Hand Sandstone is currently 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 specimen shown here is a large, iron-oxide stained, quartz pebble eroded from the Black Hand. In sedimentology, pebbles are defined as sediment grains between 4 and 64 millimeters in size. The long axis of this sample is 54 millimeters. This is the largest Black Hand paleopebble I've ever observed.

Stratigraphy: Black Hand Sandstone, lower Osagean Stage, Lower Mississippian

Locality: Hanover, eastern Licking County, eastern Ohio, USA

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.