This book is concerned almost wholly with a diverse suite of carbonate
rocks that were formed near the margins of shallow tropical seas during
the last 5-7 million years of the Permian period (300-251 Ma). These
unique rocks, collectively known as the Magnesian Limestone, have been
studied for more than 160 years and the names of some of the early
workers - Geinitz, Murchison, Phillips, Sedgwick, Sorby - would grace
any geological hall of fame. Despite this formidable assault, and the
efforts of a host of later workers, the Magnesian Limestone still
retains many of its secrets. Permian marine rocks crop out on both sides
of the Pennines, but those of the Zechstein Sea to the east are by far
the thicker and more varied, and in these lie all but one of the sites
selected for special protection. Detailed accounts of the rocks in 26
such sites form about half of this book and the normal and special
features of these sites are compared, contrasted and placed in their
mutual context in the remainder of the book. The sites were selected
according to a range of criteria, including uniqueness,
representativeness, historical importance and suitability for teaching
purposes and research; most are inland quarries but a few are in the
unrivalled coastal cliffs of classical County Durham where the main
difficulty lies in deciding what not to select.