The Niobrara formation is composed of the Fort Hays limestone and the Smoky Hills chalk members. The Fort Hays member is in the neighborhood of 50 feet
thick, topped by 100 feet of Smoky Hills chalk. The geologic map of Russell suggests that both members should be present in the area under discussion
and would overlie the Blue Hills shale, a strata of great prominence in other areas of the county.|
From the image at left, this is not evident. The lower part of the outcrop appeared to be a very weak sandstone topped by a single layer of limestone. This caused some confusion on my part as I am a mere amateur as a geologist. There is also no mention of a sandstone layer on the Russell map; and the limestone was nowhere near 50 feet thick, let alone 150 feet.
Examination of the Ellis County map provided some explanation. This map shows a layer of Codell sandstone atop the Blue Hills Shale member (this can be seen in the previous chart). From this it was divined that the exposed limestone was the remainder of the Fort Hays member, and that this outcrop did not contain any Smoky Hills chalk. It is possible that the Smoky Hills is in evidence at the peak of the hill to the east, but has probably been eroded away to a great extent, as the elevation of the hill above the road is only 65 feet.
The Ellis County map mentions that the Codell sandstone is visible in outcrop, but not in plan. This is not surprising as it is a very weak stone that is easily worn away by rubbing with the fingers. The layer is only 25 feet thick and probably doesn't last long when exposed directly to weathering. As can be seen from the image, the sandstone at this location is protected by the overlying limestone, but there was no evidence of it beyond the bluff. It can be seen how readily this stone is eroded by water dripping from the edge of the bluff.
The limestone is described as being massive chalk beds separated by thin layers of chalky shale. This is apparent in the image where the blocks of stone are separated by a horizontal plane. There are large blocks of this stone at the foot of the bluff; evidence of the continued erosion of the layer. It can also be seen that the vegetation on the hill is contributing to the erosion, as the stone at the top is being turned to rubble by root infestation.
The sandstone is very homogenous and contained few inclusions of interest (at least to this untrained eye), but there were many interesting features in the