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Jurassic Period


Abstract

This page describes the Jurassic Period, including stratigraphy, paleogeography, and famous lagerstätten, followed by a sketched outline of some of the major evolutionary events.

Keywords: Jurassic, Jurassic biota, fossil record, evolution

Introduction

 
 

Related Topics


Further Reading

  • The Concise Geologic Time Scale (Ogg et al. 2008)

    Other Web Sites

     
     

    Stratigraphy

    Historical Development

    Lower (Triassic–Jurassic) Boundary

    “The end-Triassic mass extinction terminated many groups of marine life, including the conodonts, whose distinctive phosphatic jaw elements constitute a primary zonation for much of the Paleozoic and Triassic, and the majority of ammonoids. Indeed, in the few regions with continuous deposition there is an interval devoid of either typical latest-Triassic taxa (e.g., conodonts or Choristoceras ammonoids) or earliest-Jurassic forms (e.g., Psiloceras ammonites). A sea-level fall produced extended gaps in many shallow-marine sections; therefore, the boundary between upper Triassic and the overlying lower Jurassic was commonly a sequence boundary and hiatus” (Gradstein et al. 2012, p. 733, and references therein).

    The GSSP for the base of the Jurassic is set at 5.80 m above the base of the Tiefengraben Member of the Kendelbach Formation, corresponding to the local lowest occurrence of the ammonite Psiloceras spelae subsp. tirolicum, in the Kuhjoch section, Northern Calcareous Alps, Austria. Other useful markers include the FAD of Cerebropollenites thiergartii (a pollen grain), Praegubkinella turgescens (a foraminifer), and Cytherelloidea buisensis (an ostracod) (see Gradstein et al. 2012).

    Upper (Jurassic–Cretaceous) Boundary

    As yet there is no ratified GSSP for the base of the Berriasian Stage (= the base of the Cretaceous System) although, by common usage, it lies near the first appearance datum (FAD) of the ammonite, Berriasella jacobi. Unfortunately, this ammonite is largely confined to the Mediterranean realm, so the datum is not much use internationally.

    Chronology

    Paleogeography

    Major Tectonic Events

    Land and Sea

    Paleogeographic reconstruction for the Jurassic
    Paleogeographic reconstruction for the Jurassic from Christopher Scotese’s excellent ‘Paleomap Project’.

    Climate

    Paleontology

    General Characteristics

    Major Taxa

    Mammals

    “The Jurassic period is an important stage in early mammalian evolution, as it saw the first diversification of this group, leading to the stem lineages of monotremes and modern therian mammals. However, the fossil record of Jurassic mammals is extremely poor, particularly in the southern continents. Jurassic mammals from Gondwanaland are so far only known from Tanzania and Madagascar, and from trackway evidence from Argentina” (Rauhut et al. 2002, p. 165).

    Throughout the early Mesozoic they remained small, becoming more abundant, larger, and more diverse in the Cretaceous, which may have been a time of explosive radiation of Tribosphenida – early relatives of marsupials and placentals (Rougier 2002).

    Major Biotic Events

    “The Jurassic period is an important stage in early mammalian evolution, as it saw the first diversification of this group, leading to the stem lineages of monotremes and modern therian mammals. However, the fossil record of Jurassic mammals is extremely poor, particularly in the southern continents. Jurassic mammals from Gondwanaland are so far only known from Tanzania and Madagascar, and from trackway evidence from Argentina” (Rauhut et al. 2002, p. 165).

    Lagerstätten

    Posidonia/Holzmaden Shale: Early Jurassic; Holzmaden, approx. 30 km east of Stuttgart, Germany; fossil reptiles – noteably ichthyosaurs, crustaceans, cephalopods; Selden & Nudds 2012, Hauff & Hauff 1981

    Stonefield Slates: Middle Jurassic; Stonefield, Oxfordshire, England; bed of sandy slate 30-45 cm thick; surface occurrences exhausted and the underground mine is now closed; most important for a large number of small mammal jaws and teeth representing three orders: Multituberculata, Triconodonta and Pantotheria; also pterosaurs, crocodilians, invertebrates and a possible dicotyledonous angiosperm

    Christian Malford: Middle Jurassic; England; soft-body preservation of squids; Allison 1988

    Solnhofen Limestone: Late Jurassic (Lower Titonian); Altmuhl Valley, Bavaria, Germany; fine-grained lagoonal sediments; most famous for the Archeopteryx and Compsognathus fossils found there, though these two together amount to only nine out the many thousands of specimens known from the Solnhofen; Barthel et al. 1990, Viohl 1985.

    Morrison Formation: Late Jurassic; North American states of Wyoming and Colorado

    Purbeck Beds: Late Jurassic; England, esp. near Drulston Bay; essentially modern, temperate insect fauna including dragonflies, locusts, grasshoppers, butterflies, ants and aphids; elsewhere (”Beckel’s Mammal Pit”) numerous mammal species representing five orders and having similarities with those of the contemporaneous Morrison Formation of Wyoming and Colorado

    Extinctions

    New Zealand Occurrences

    For most of the Paleozoic and Mesozoic, the rocks which would become the basement rocks of the Zealandia continent formed part of the Pacific margin of Gondwana, flanking Australia and Antarctica (Edbrooke 2017; Strogen et al. 2017). During this time, the Zealandia basement developed mainly by subduction-driven, episodic accretion.

    “In an initial period of growth, from Cambrian to Carboniferous time, the oldest sedimentary rocks known in mainland New Zealand were deposited and acreted…. Intrusion of granitic rocks occurred intermittently but mainly during Late Devonian and Early Carboniferous time” (Edbrooke 2017, p. 31).

    References

    Allison, P.A. 1988: Phosphatised soft bodied squid from the Jurassic Oxford Clay. Lethaia 21: 403-410.

    Barthel, W.; Morris, S.C.; Swinburne, N.C. 1990: Solnhofen, 2nd ed. Cambridge University Press.

    Edbrooke, S.W. 2017: The geological map of New Zealand. GNS Science Geological Map 2: 1-183.

    Gradstein, F.M.; Ogg, J.G.; Schmitz, M.D.; Ogg, G.M. 2012: The Geologic Time Scale 2012. Elsevier 1-2.

    Hauff, B.; Hauff, R.B. 1981: Das Holzmadenbuch. Self published: 1-136.

    Ogg, J.G.; Ogg, G.; Gradstein, F.M. 2008: The Concise Geologic Time Scale. Cambridge University Press: 1-177.

    Rauhut, O.W.M.; Martin, T.; Ortiz-Jaureguizar, E.; Puerta, P. 2002: A Jurassic mammal from South America. Nature 416: 165-168. Nature.

    Rougier, G.W. 2002: Mesozoic Mammals. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001571].

    Selden, P.; Nudds, J. 2012: Evolution of Fossil Ecosystems (2nd Edition). Academic Press: 1-288.

    Strogen, D.P.; Seebeck, H.; Nicol, A.; King, P.R. 2017: Two-phase Cretaceous–Paleocene rifting in the Taranaki Basin region, New Zealand; implications for Gondwana breakup. Journal of the Geological Society, London 174: 929-946.

    Viohl, G. 1985: Geology of the Solnhofen Lithographic Limestone and the habitat of Archeopteryx. In Hecht, M.K.; Ostrom, J.H.; Viohl, G.; Wellnhofer, P. (ed.) 1985: The beginnings of birds. Eichstatt. Freude des Jura-Museums Eichstätt, Willibaldsburg: 31-44.


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