Formation of fifths
The fifths formation (also Quintner-lime) is in the geological a lithostratigraphic rock unit of Helvetikum in the Swiss Alps. It is dated to the Upper Jurassic and the Lower Cretaceous .
Concept history
Hans Michael Mohr and Hanspeter Funk used the term fifth formation several times in 1995 in their work The Development of the Helvetian Carbonate Platform in Eastern Switzerland (Tithonian - Berriasian): A sequence stratigraphic approximation . In this work, however, the term can only be described as informal, since the two authors did not determine any type locality. Nevertheless, the lithostratigraphic unit was adopted in 2006 by the Swiss Stratigraphic Committee (SKS). This is not entirely correct, because the term fifth formation was already used in Hans Michael Mohr's dissertation. The Swiss Stratigraphic Committee, however, did not recognize this work as the first description of the fifth formation, probably for formal reasons. The term basically goes back to Arnold Escher von der Linth in a lecture by Isidor Bachmann in 1863, who first published the term in the form of quintener lime . Bachmann himself favored the name Hochgebirgskalk. Other names for this rock unit are: Malmkalk, Tithonkalk, Jurassic limestone from Au, Auerkalk, Obertithonbreccie, Schwarzer Quintnerkalk, Unterer Quintnerkalk, Oberer Quintnerkalk, Tros-Kalk and Margelband. The original type locality is Quinten am Walensee ( Canton St. Gallen , Switzerland ).
Definition, absolute dating, correlation and subdivision
The base of the fifth formation is defined by the insertion of thick-bank limestone over the slightly brownish limestone-marl alternating layers of the Schilt formation . At the same time, it forms the upper limit of the lying Schilt formation. The fifth formation is overlaid by the cement stone formation and in northern eastern Switzerland also by the Öhrli formation . The boundary is formed by the onset of a lime-marl alternate storage (cement marl formation) or the onset of two lime and two marl members of the Öhrli formation.
The fifth formation consists of fine-grained to dense, dark gray to almost black, massive to thick-banked, locally also thin-banked limestone, which can reach a thickness of 200 to 450 meters. The limestones are also locally sandy-dolomitic (e.g. the marl band member) and can contain inclusions of pebbles or limestone breccias. In the so-called Northern Facies of Eastern Switzerland, where the Quinten Formation is overlaid by the Öhrli Formation, coral-bearing limestones have also developed in the upper part of the formation, which are known as Tros-Members (or Tros-Kalk).
The fifth formation is chronostratigraphically dated in the Upper Oxfordian ( Upper Jurassic ) to the Lower Berriasian ( Lower Cretaceous ); geochronologically, this corresponds to the period from 157.7 to 141.9 million years ago.
The fifth formation is currently divided into two members:
- Marl band member (also Plattenkalk member)
- Tros-Kalk-Member (only developed in the North Facies)
Individual evidence
- ↑ Mohr, Hans & Hanspeter, Funk (1995): The development of the Helvetian carbonate platform in Eastern Switzerland (Tithonian-Berriasian): a sequence stratigraphic approximation. Eclogae Geologicae Helvetiae, Vol. 88/2, pp. 281-320, Basel. doi : 10.5169 / seals-167676
- ↑ a b Lithostratigraphic Lexicon of Switzerland - Fifth Formation ( Memento of the original from October 28, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Mohr, Hans Michael (1992): The Helvetian Shelf of Eastern Switzerland at the transition from the late Jura to the early Cretaceous . Diss. ETH No. 9805, Swiss Federal Institute of Technology, Zurich.
- ↑ Bachmann, Isidor (1863): About the Jura formation in the canton of Glarus. Announcements of the natural research society in Bern, pp. 559–562: 145 Online at archive.org
- ↑ Stratigraphic overview in the Sargans area (Eastern Switzerland)
- ^ Burger, Hans (1985): Palfris formation, Öhrli formation and Vitznau marl (basal chalk of the Helveticum) between the Reuss and the Rhine. Stratigraphic, facial, mineralogical and paleogeographical investigations. Messages from the Geological Institute of the Swiss Federal Institute of Technology and the University of Zurich, New Series, 254: 237 S., Zurich. PDF
