The Kupferschiefer (German for Copper Shale, Copper Schist or Copper Slate) or Kupfermergel (Copper Marl), (T1 or Z1) is an extensive and remarkable sedimentary unit in Central Europe. The relatively monotonous succession is typically 30 to 60 centimetres (12 to 24 in) and maximum 2 metres (6.6 ft) thick, but extends over an area of 600,000 square kilometres (230,000 sq mi) across the Southern Permian Basin. The Kupferschiefer can be found in outcrop or in the subsurface straddling six countries, including parts of the southern North Sea. The lateral equivalent outcropping in England is called Marl Slate. Despite its distinctive nature, the Kupferschiefer is not ranked as a formation but is officially declared a sub-unit of the Werra Formation, the lowest formation of the Zechstein Group, overlying the Rotliegend Group. The unit has been dated to 257.3 ± 1.6 Ma, placing it in the Wuchiapingian stage of the Late Permian. The Kupferschiefer comprises black shales, bituminous marls, mudstones and limestones deposited mostly in an open marine setting, with the borders of its extension deposited in a shallow marine environment. At time of deposition, the area what is now northern Europe was covered by an enclosed sea; the Zechstein sea, characterized by anoxic conditions. The Kupferschiefer is renowned for hosting one of the most important copper deposits in the world, which were mined at least since 1199 AD. Other mineral resources found in the unit include zinc, vanadium, lead and silver. The Kupferschiefer is also an important lagerstätte; having provided fossils of early Archosauromorph reptiles, the ancestors to modern crocodiles and extinct dinosaurs, as well as pareiasaurs, many fossil fish, including Coelacanthus granulatus, Dorypterus hoffmanni and Palaeoniscum freieslebeni, flora and other fossils. Famous finds from the unit include Parasaurus geinitzi, Protorosaurus speneri, Weigeltisaurus jaekeli and Glaurung schneideri.
Description
The Kupferschiefer is a regional stratigraphic unit stretching across an area of 600,000 square kilometres (230,000 sq mi) in the Southern Permian Basin of north-central Europe. The unit is typically 30 to 60 centimetres (12 to 24 in) thick. In the Rossenray 2 shaft, the unit reaches a maximum thickness of 2 metres (6.6 ft). The Kupferschiefer unconformably overlies various formations of the Rotliegend Group and the Varsican basement and forms the basal unit of the Zechstein Group. In some parts of the Zechstein Basin, the Kupferschiefer is underlain by the Mutterflöz Limestone, an organic-lean thin limestone unit. Despite its distinctive nature, the Kupferschiefer is not ranked as a formation but is officially declared a sub-unit of the Werra Formation, the lowest formation of the Zechstein Group. The Kupferschiefer is overlain by the Zechstein Limestone sub-unit of the Werra Formation. The unit has been dated to 257.3 ± 1.6 Ma, placing it in the Wuchiapingian stage of the Late Permian. The age of the unit corresponds to the Ilinskoe part of the Sokolki Assemblage Zone of European Russia and the Tropidostoma Assemblage Zone of the Karoo Basin of South Africa. The Kupferschiefer contains up to 30% organic matter, with variations across its extent. The basinal facies shows values of between 5 and 25% TOC, while the marginal facies present values up to 7% TOC and swell facies are much poorer in organic matter with values below 1%.
Basin history
Depositional environment The Kupferschiefer was deposited in a highstand setting, in a deep enclosed basin, covered by the Zechstein sea that was present on the paleocontinent Laurussia, the northern part of Pangea. The basin possibly had periodic connections to the Paleo-Tethys Ocean. Sedimentation rates during Kupferschiefer deposition were low, estimated at 5 millimetres (0.20 in) per thousand years. The climate of the Late Permian was extremely variable, with polar icecaps present near the south pole and hot and arid conditions prevailing in the tropic and paleotemperate regions of the northern and southern hemispheres. The Zechstein sea in the Late Permian was located at paleolatitudes around 15 to 16 degrees north. Large areas of Pangea were covered by deserts and arid conditions also prevailed near the Zechstein sea of the time. Apatite oxygen isotope analysis has revealed that the Late Permian was characterized by a drastic increase in global temperatures, accompanied by a strong rise of eustatic sea level. The rise in oxygen isotope values was possibly related to an increase in volcanic activity. The Permian-Triassic extinction event, the biggest extinction event in geologic history, is thought to have been caused mostly by large volcanic provinces of the Siberian Traps.
Mining
Prehistoric finds of slag and bronze from smelting sites on top of or immediately adjacent to outcropping Kupferschiefer ores at Wettelrode, Mohrungen, and Bottendorf in Central Germany evidence Early to Middle Bronze Age mining of the Kupferschiefer ores. The medieval mining history of the Kupferschiefer ores is documented in written sources since at least 1199 A.D. from the Mansfeld district in Central Germany. The Counts of Mansfeld developed several copper mines, smelters, and a mint at the town of Eisleben, where copper and silver coins were minted from the metals of the Kupferschiefer ores.
Germany
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