SandyForth Opencast
Contribution by Steve Livesley

Click on the photos to enlarge
SandyForth Opencast One exposure I have collected after the shutdown of Crockhey is called Sandyforth Opencast near to Winstanley in the Wigan area, located approximately 1 mile north of the SandyForth OpencastCrockhey exposure. The last mining operator went bankrupt, leaving the site open for a good number of years, which allowed a longer than usual period of time to collect fossil material from there.
Recent research suggests the area encompassed by the exposure has been opencast mined on four occasions previously starting in 1948 accessing the close to the surface seams. The area is also crossed by a number of geological faults, one being named the Crows nest Fault, which throws the seams out of alignment approximately 40 m and bringing differing coal seams closer to the surface within the boundaries of the opencast. (See strata diagram)

My recent experiences at Crockhey Opencast made me initially looking for siderite nodules, but for some reason at Sandyforth, although not completely devoid, these seemed to be very few and what was evident seemed not completely formed.
At Crockhey, most of the fossil bearing nodules came from above the Wigan 2 foot seam. Although here, that seam had been extensively worked previously, the sparse nodules that were actually present, seemed to be relatively fresh from the most recent excavations. Some nodules could be present in the form of previous opencast backfill. Due to the lack of nodules I started to determine other possible sources for fossil material from the site, and focused on a very dark siltstone band that would possibly contain fish remains if laid down as a silt sediment during periods when the area was under water.

The alternative, to concentrate on a dark silt layer, started to prove successful. Sections of this I found up to 300 millimetres thick, where at Crockhey I had only observed a similar material up to 50 mm thick. The silt was very fine as well, so I presumed the area must have been a very slow moving water way if not a lagoon. It became quite frequent in this layer to discover individual fish scales and teeth, nice finds.
But then I found a lower jaw bone, which had the teeth still embedded within it. This is attributed to a juvenile rhizodont, a species of fish from an extinct group of predatory lobe-finned fishes. These fossils are found in many areas of the world with the earliest known being about 377 Ma, the latest around 310 Ma.
In addition to the normal type of scale, I came across a grouping of scale type attributed to Strepsodus anculonamensis. A further discovery from within the same silty sediment proved to be the spine of a xenacanthida, which is a freshwater shark that appeared during the Lower Carboniferous. At two exposures previously, I have found fossil shark eggcases, and it's nice to finally find part of the shark that (possibly) produced them. The spine I found was from a species possibly Anodontacanthus triangularis
. Click on the photos.

Rhizodont scale
Scale of Rhizodont

Rhizodont jaw
Jaw of Rhizodont

Strepsodus scales
Scales of Strepsodus

Anodontacanthus scales
Spine of Anodontacanthus (?)

All these fossil specimens appear to come from juveniles of the species, which for carboniferous fish is very rare indeed. So I think it can be determined that this area during the upper carboniferous period was possibly  not a section through a constant river channel, but more likely a marginal section of a levee. Marginal shallow areas are often used as sanctuary by smaller fish to prevent predation from their larger relatives. Another clue to this was the discovery of some ripple marks contained within a mudstone, suggesting the area’s could have had shallow marginal edges, where water rises and falls slowly creating the ripples.

From the same area two quite poorly preserved Bellinurus trilobitoides horse shoe crabs were also discovered.These were the only ones we found, which was confusing, as I would have expected this environment to be an ideal home for these creatures to flourish.

Insects are present usually with an abundance of well preserved fossil plant material, which wasn’t the case at Sandyforth. There was very little sign of anything of this nature until I discovered a small area that contained some promising nodules within the characteristic light blue mudstone. It was only after it has rained that this material stood out from the rest and appeared to be worth further investigation. It produced five examples of a syncarid crustacean (a small shrimp) called Palaeocaris.
A section of an insect wing was found fossilised as well, with the condition of the nodule suggesting it to be from a previous exposure at the site. Some larger individual fish scales up to 25 mm in size were also collected in siderite nodules as well from this material.
Furthermore there were a few plant fossils in the nodules. Click on the photos below to see some of them.
All in all a very pale environment, different from Crockhey, and very hard to actually find quality fossils, but certainly worth recording for future study…..





Finally some very fine fossils from the collection of Sean Sale: a tooth of a shark, an unidentified wing and an unidentified milliped.

Tooth of Ctenoptychius
Tooth of Ctenoptychius

Unidentified wing from Sandyforth

Unidentified milliped from Sandyforth