A lazy warm breeze rustles through the trees on a grassy hill slope. A herd of hippopotamuses are wallowing down in the valley as a rhinoceros wanders over to a watering hole to take a refreshing drink. Just audible, bellowing in the distance are a herd of elephants. It’s the end of a pleasant day near Skipton during the Ice Age… Hang on, I hear you all say, the Ice Age!? You’re probably all hoping for the rhinoceros to be wool-clad and the distant elephants to be of the shaggy-haired variety. Although these images aren’t wrong, they’re not the whole picture, as the Ice Age (also known as the Pleistocene) was a time of alternating warm and cold climates. During these warm intervals Yorkshire was visited by a host of animals with a distinctly more African feel. The Pleistocene spanned from around 2.58 million years ago through to 12 thousand years ago. Across that time there were repeated cycles in the climate. These can be divided into glacial (episodes when the ice sheets advanced as temperatures plummeted) and interglacial periods (the warm and pleasant intervals when the ice sheets retreated). These climatic changes were the result of cyclical shifts in the earth’s orbit around the sun and changes to the angle and direction of the earth’s axis. There were many of these glacial and interglacial periods, with the last glacial interval only ending around 12 thousand years ago. The preceding interglacial warm period, known as the Ipswichian, ran from approximately 130 -115 thousand years ago, and was the only time that hippos migrated northwards into Britain (Gascoyne et al. 1981). It is estimated that Britain was up to 5 degrees warmer during the Ipswichian than today (Candy et al. 2016). So how do we know there were hippos, rhinos and elephants roaming around near Skipton? During the 1870s a quarry at Lothersdale, just southwest of Skipton, exposed an ancient fissure in the limestone filled up with clay, sand, pebbles and bones! This became known as the Raygill Fissure. During the Ipswichian, the fissure would have been a steep sided pothole, with an opening at the surface few meters across. In 1880 the Yorkshire Geological Society set about excavating the fissure fill and a fund was set up to raise the £50 necessary to conduct the exploration. In June of that year the fund reached a mighty £60, and work commenced (Green et al., 1880). The team excavated some 40m of the near vertical pothole. The fossil teeth and bones were found in a distinct layer towards the lower portion of the excavation along with rounded pebbles of locally derived stones (Green et al., 1880). The fossils included remains of straight-tusked elephant (Palaeoloxodon antiquus), narrow-nosed rhinoceros (Stephanorhinus hemitoechus) and teeth belonging to hyena (Crocuta crocuta). There were other bones too, a molar and part of a tusk from a hippo (Hippopotamus amphibius) and even reports of a tooth from a brown bear (Ursus arctos) and cave lion (Panthera spelaea). Many of these bones were donated to the Leeds Museum and are now held in the collections at the Leeds Discovery Center. They Raygill material held there comprises many dozens of teeth from the elephant Palaeoloxodon and the rhino Stephanorhinus, but with very few bones. This may be due to the way the Raygill material was deposited and the way in which it was preserved. The bones were well and truly embedded into the rock by a natural cement. In the original excavation report, they remark how they were unable to extract the bones whole from the matrix as they would just splinter, and most were already just fragments anyway. Combined with this, the predominance of teeth could be from the way the bones accumulated in the fissure. Unlike the famous Kirkdale Cave in Kirkbymoorside (discovered some 50 years earlier) and Victoria Cave in the Yorkshire Dales, the bone in Raygill were not brought in by hyenas. The Raygill fossils were found in a layer of sand and rounded stones and many of the teeth have a battered appearance, which tells us that flowing water was involved in the deposition of the fossil-yielding layer. The presence of only the most robust bone and teeth adds to the suggestion that the bones were either washed into the fissure, or were from animals that got to close to the edge of the fissure and fell in with their bones later scattered and eroded by water. It still leaves an interesting question about the hippo bones. The entrance to the fissure would have been on a hill 160 m above the valley floor, not exactly where one would expect to find a wallowing hippo... Could it have been that hippos had a slightly different lifestyle during the Ipswichian, grazing on the hillslopes (O’Connor and Lord, 2013)? Or, could it be that a partial carcass was dragged up from the valley by a predator, the bones only to later be washed into the fissure? As the quarry continued its operations more of the fissure was exposed until the excavations were eventually abandoned as it became increasingly difficult and dangerous to continue. Nonetheless, the quarry continued to work its way through the fissure, destroying possibly one of the richest Ipswichian bone deposits in Yorkshire. The Quarry itself eventually closed in the 1980s to become a fishing lake, although sadly there are no hippos swimming there today. We wish to thank the Leeds Discovery Centre for allowing us access to the Raygill Fissure material, and Paul Kabrna (Craven and Pendle Geological Society) for photographs. Author: Jed Atkinson References:Candy I, White TS and ELias S. 2016. How warm was Britain during the Last Interglacial? A critical review of Ipswichian (MIS 5e) palaeotemperature reconstructions. Journal of Quaternary Science. v. 31(8), p. 857-868.
Gascoyne M, Currant AP and Lord TC. 1981. Ipswichian fauna of Victoria Cave and the marine palaeoclimatic record. Nature. v.294, p. 652-654. Green AH, Miall LC, Briggs J and Davis JW. 1880. Report of the Raygill Fissure exploration committee. Proceedings of the Yorkshire Geological Society. v.7, p.300-306 O'Connor, T and Lord T. 2013. Cave Palaeontology, Chapter 15, p. 225-238 IN Caves and Karsts of the Yorkshire Dales. Eds. Waltham T and Lowe D. British Cave Research Association
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