Cowling: Stonehead Beck

© Craven & Pendle Geological Society

Eumorphoceras beta sp
Arnsbergian Stage (E2C3 Horizon)

Nuculoceras nuculum
Arnsbergian Stage (E2C3 Horizon)

Isohomoceras subglobosum
Chokerian Stage (H1a1-3 Horizon)

Ammonoids of Stonehead Beck
Altogether there are four important ammonoid tax that are used in recognising the Mid-Carboniferous boundary interval. They are Eumorphoceras beta sp. nov., Fayettevillea darwenensis (MOORE), Isohomoceras subglobosum (BISAT), and Nuculoceras nuculum (BISAT).

At Stonehead Beck ammonoids are the dominant marine fauna. They are concentrated in thin horizons between variable intervals of barren strata. Their low diversity but high abundance suggest that they lived in stressful conditions where oxygen levels were low and salinity levels fluctuated considerably.

This genus is recorded from Eurasia, North Africa and North America. It is commonly found in rocks belonging to the Pendleian and Arnsbergian Stages. It is thought that the genus is derived from the late Brigantian girtyoceratid Sulcogirtyoceras.

This genus is known only from late Arnsbergian strata of Europe. The origin of Nuculoceras is uncertain but may have been a descendant of Cravenoceratoides.

Isohomoceras belongs to the family Homocertatidae and is known only from Europe and North Africa in strata assigned to the Chokerian, Alportian and maybe Kinderscoutian Stages. In Britain though it appears to be restricted to the Chokerian Stage.

Other marine faunal associations found in Stonehead Beck include Lingula, Bivalves, and Cephalopods.

Arnsbergian marine Band

Arnsbergian Marine Band

This is a good example of typical bluey-grey marine band lithology associated with Stonehead Beck. Here you can see that early lithification has assisted in the preservation of uncrushed macrofauna, in this case the ammonoid Nuculoceras nuculum and its juvenile forms.

Also notice the typical plant fragments though these are more commonly found in the silty beds.