Lower Jurassic

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system series step ≈ age ( mya )
higher higher higher younger
law Upper Jurassic Tithonium 145
⬍
152.1
Kimmeridgium 152.1
⬍
157.3
Oxfordium 157.3
⬍
163.5
Middle Jurassic Callovium 163.5
⬍
166.1
Bathonium 166.1
⬍
168.3
Bajocium 168.3
⬍
170.3
Aalenium 170.3
⬍
174.1
Lower Jurassic Toarcium 174.1
⬍
182.7
Pliensbachium 182.7
⬍
190.8
Sinemurium 190.8
⬍
199.3
Hettangium 199.3
⬍
201.3
deeper deeper deeper older

The Unterjura (also Lower Jura ) is the international chronostratigraphic name for the lower series of the Jura in geological history. In the older literature, e.g. Even in popular scientific literature, this chronostratigraphic section is often referred to as Lias or Schwarzer Jura (Black Jura). Today these terms are only understood as lithostratigraphic units. The Lower Jura follows the series of the Upper Triassic (or Upper Triassic) or the uppermost stage of the Triassic, the Rhaetium . The series of the Middle Jura (Middle Jura) follows above the Lower Jura. The Lower Jurassic corresponds roughly to the period from 201.3 to 174.1 million years .

Older terms

For this chronostratigraphic series of the Jura, the terms Schwarzer Jura (Schwarzjura) and Lias may not be used. They are reserved for rock units. In the context of the new lithostratigraphic structure of the South German Jura , the term Black Jura is used in the sense of a group of formations . In the Jura of northern and central Germany, however, the lowest lithostratigraphic group is provisionally referred to as Lias (in the form of North German Lias). Lias and Black Jura are defined purely lithologically or with the methods of lithostratigraphy, the boundaries are also determined purely by changes in the rock features. Schwarzer Jura and North German Lias essentially correspond in time to the Unterjura series, but only roughly. The deposits of the Black Jura and the North German Lias only set in after the Triassic / Jura border and regionally end before the Lower / Middle Jura border. There are also gaps between the layers between the individual formations of the North German Lias and the Black Jura. North German Lias and Black Jura are essentially characterized by dark clay stones and clay marls, which are now divided into numerous formations. The names in the North German Jura are only provisional and not yet final.

Chronostratigraphic subdivision of the Lower Jurassic

The watercolor Duria Antiquior ("Ancient Dorset"), painted by Henry Thomas de la Beche in 1830, depicting the Lias Sea of Dorset in southern England is the earliest attempt at reconstructing a prehistoric habitat with its fossil organisms ( paleoecology ).

The Lower Jura is divided into the following international levels:

Fauns

A common fossil from the Lower Jurassic is the oyster-like clam Gryphaea . The black posidonia schist with its well-known fossil deposit near Holzmaden in Baden-Württemberg is dated to the Toarcium stage of the Lower Jurassic series.

Individual proof

  1. ↑ Eckhard Mönnig: The Jura of Northern Germany in the Stratigraphic Table of Germany 2002. Newsletters on Stratigraphy, 41 (1-3): 253-261, Stuttgart 2005

literature

Flap from Gryphaea
  • Friedrich August Quenstedt: The Jura. Laupp Publishing House, Tübingen 1856–57.
  • Gert Bloos, Gerd Dietl & Günter Schweigert: The Jura of Southern Germany in the Stratigraphic Table of Germany 2002. Newsletters on Stratigraphy, 41 (1-3): 263-277, Stuttgart 2005 ISSN  0078-0421
  • Felix Gradstein, Jim Ogg, Jim & Alan Smith: A Geologic timescale. Cambridge University Press 2005 ISBN 978-0-521-78673-7
  • Eckhard Mönnig: The Jura of Northern Germany in the Stratigraphic Table of Germany 2002. Newsletters on Stratigraphy, 41 (1-3): 253-261, Stuttgart 2005 ISSN  0078-0421

Web links

Commons : Unterjura  - collection of images, videos and audio files