English: Ferruginous quartz-pebble conglomerate from the the Pennsylvanian of Ohio, USA.

This rock is from an outcrop in southern Ohio that exposes the lowermost Pottsville Group, a Pennsylvanian-aged, cyclothemic succession in eastern Ohio that contains nonmarine shales, marine shales, siltstones, sandstones, coals, marine limestones, and chert ("flint"). The lower Pottsville dates to the late Early Pennsylvanian. The upper part dates to the early Middle Pennsylvanian. The Lower-Middle Pennsylvanian boundary is apparently somewhere near the Boggs Member (?).

At this site, the basal Pottsville is a spectacular quartz-pebble conglomerate, with a quartzose sandstone unit above it, plus coal and shale above that. The latter two units are visible, but not easily accessible for examination.

In eastern and northeastern Ohio, the conglomeratic base of the Pottsville Group is called the Sharon Conglomerate (a.k.a. Sharon Sandstone; Sharon Formation; Sharon Member). The literature points out that the Sharon elsewhere in Ohio is not directly correlatable with the conglomerate exposed at this site near Jackson, Ohio. Thus, it has been suggested that the unit at this locality be referred to as the "Sharon" Conglomerate.

Here, the rocks are generally massive (= non-bedded) quartz-pebble conglomerates. Other clast lithologies and sizes are also present, including angular shale clasts, angular sandstone clasts (both derived from erosion of the underlying Logan Formation of Early Mississippian age), rounded to irregularly-shaped ironstone clasts, rounded quartz sandstone pebbles, rounded quartzite pebbles, and rounded silicified limestone pebbles.

A very unusual clast type present at this outcrop is ferruginous quartz-pebble conglomerate (= conglomerate in conglomerate ! ) - the photo seen here depicts this material. The ferruginous conglomerate itself is older than the surrounding "Sharon" conglomerate matrix. On fresh crack surfaces, the ferruginous quartz-pebble conglomerate has pyrite cement between clasts. Hematite cement is also present on both weathered and fresh surfaces. Some limestone clasts are present - usually silicified. Also present are some angular clasts of sandstone.

Stratigraphy: "Sharon" Conglomerate, lowermost Pottsville Group, Lower Pennsylvanian

Locality: Jackson North Outcrop - roadcut along the southwestern side of Rt. 35, immediately southeast of the Rt. 35-Lloyds Bridge Road intersection (the northwestern intersection - there are two of them), north of the town of Jackson, northwest-central Jackson County, southern Ohio, USA (39° 06’ 32.94” North latitude, 82° 40’ 39.99” West longitude)