Upper Jurassic

Subdivision of the Jurassic system according to the IUGS, as of July 2012.

The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago (Ma), which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name “Malm” indicates rocks of Late Jurassic age. In the past, this name was also used to indicate the unit of geological time, but this usage is now discouraged to make a clear distinction between lithostratigraphic and geochronologic/chronostratigraphic units.

Subdivisions

The Late Jurassic is divided into three ages, which correspond with the three (faunal) stages of Upper Jurassic rock:
  • Tithonian     (150.8 ± 4.0 – 145.5 ± 4.0 Ma)
  • Kimmeridgian     (155.7 ± 4.0 – 150.8 ± 4.0 Ma)
  • Oxfordian     (161.2 ± 4.0 – 155.7 ± 4.0 Ma)

Paleogeography

During the Late Jurassic epoch, Pangaea broke up into two supercontinents, Laurasia to the north, and Gondwana to the south. The result of this break-up was the spawning of the Atlantic Ocean. However, at this time, the Atlantic Ocean was relatively narrow.

Note : The above story is based on materials provided by Wikipedia

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