Charles Lapworth, graptolites and Birkhill Cottage

BGS image ID: P015041

 Charles Lapworth  1842-1920 - portrait.

An English geologist known for first describing the Ordovician period. This was carefully worked out by his new technique of faunal analysis of 'index fossils' especially graptolites. He was also a key participant in the 'Highland Controversy' when he was first to say that there were older rocks lying over younger and suggesting the cause being complex folding or faulting.

BGS iamge ID: P217123

Plaque on Birkhill Cottage commemorating Charles Lapworth. The inscription reads:

Birkhill Cottage where between 1872 & 1877 Charles Lapworth recognized the value of Graptolites as a clue to the geological structure of these hills. Erected by Scottish Geologists, 1931.

BGS image ID: P5211147

A fossil specimen of Torquigraptus linterni sp. nov. A fossil graptolite. (Graptolithina). Pot Burn, Ettrick Valley, Southern Uplands, Selkirkshire, Scotland.

Torquigraptus linterni sp. nov. is an Ordovician graptolite from the Birkhill Shales, Moffat Shale Group. British Geological Survey Biostratigraphy Collection number GSE 15158. The specimen has a coiled uniserial rhabdosome. The type area of the Birkhill Shales is the famous Dobb's Linn near Birkhill Cottage at the head of Moffat Water. The Birkhill Shales is a series of black graptolitic mudstones found in bands between 0.1 and 0.3 metres thick overlain by alternations of black and grey mudstones. It is famous for its graptolite fauna. Graptolites are of value in geology as stratigraphic indicators and the sequence of graptolite faunas has been used for the subdivision of the Ordovician and the Silurian rocks since the time of Charles Lapworth.

BGS image ID: P521143

A fossil specimen of Diplograptus truncatus Lapworth var. pauperatus Elles and Wood. A fossil graptolite. (Graptolithina.) Dobb's Linn, Moffat Water, near Birkhill about 9.5 miles north-east of Moffat, Dumfriesshire, Scotland.

Diplograptus lived between the Middle Ordovician to the Lower Silurian (Llanvirn to Landovery). This specimen is from the Lower Hartfell Shales. British Geological Survey Biostratigraphy Collection number GSE 8231. It is biserial, it has two rows of thecae arranged back to back and grew in an upwards direction away from the sicula and scandent (stipes grow upwards from the sicula with the thecae growing outwards). Graptolites are related to the living Protochordata. They consisted of colonies of tiny individuals enclosed in a common horny sheath. They were widely distributed as they floated in the surface waters of the ancient oceans. On death the sheaths sank to the ocean floor and were buried and preserved.

Bob McIntosh