Derwent South - Information
The deeply incised River Derwent drops below the 100m contour in its course through the spectacular gorges at Matlock, while the limestones rise steeply up dip to over 300m to the west and south west.
Unfortunately large vadose caves and risings are unknown. Drainage and cave development are largely governed by lavas and mineral veins within the limestone, and possibly by the occurrence of dolomitic limestones.
The thermal springs constitute a proportion of the total drainage, along with surface streams and the few steeply dipping but immature stream caves. The greatest proportion of the drainage emerges from lead mine soughs, indicating the extent to which the natural drainage has been modified by mining.
The majority of the known caves have been intersected by the miners, and there are some classic examples of ancient mineralised solution caves.
Dolomitisation of the limestone probably took place during the Permian. This was followed by mineralisation when hydrothermal mineral fluids dissolved limestone along major joints, and deposited the well known range of Derbyshire minerals.
The Tertiary and Pleistocene saw the re-invasion of these cavities by streams flowing under phreatic or epiphreatic conditions, and many were filled with sediment during several glaciations. The source of these sediments is still in some doubt, but a lot of material was undoubtedly derived from the overlying gritstone.
The interesting story of the geological history of the area is not within the scope of this book. A great deal has been written about it elsewhere, and the reader is referred to the cited references for further information.
Many of the mines are still being systematically explored and surveyed, and much work remains to be done.