In this post we will be looking at the Jurassic Period, Etymology and history, Geology of Jurassic Period and the climate of the Jurassic.<\/p>\r\n\r\n\r\n\r\n
INTRODUCTION<\/strong><\/p>\r\n\r\n\r\n\r\n The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified. The start of the Jurassic was marked by the major Triassic\u2013Jurassic extinction event, associated with the eruption of the Central Atlantic Magmatic Province. The beginning of the Toarcian Stage started around 183 million years ago and is marked by the Toarcian Oceanic Anoxic Event, a global episode of oceanic anoxia, ocean acidification, and elevated temperatures associated with extinctions, likely caused by the eruption of the Karoo-Ferrar large igneous provinces. The end of the Jurassic, however, has no clear boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north and Gondwana to the south. The climate of the Jurassic was warmer than the present, and there were no ice caps. Forests grew close to the poles, with large arid expanses in the lower latitudes. On land, the fauna transitioned from the Triassic fauna, dominated jointly by dinosauromorph and pseudosuchian archosaurs, to one dominated by dinosaurs alone. The first birds appeared during the Jurassic, evolving from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards and the evolution of therian mammals. Crocodylomorphs made the transition from a terrestrial to an aquatic life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates. The first sharks, rays and crabs also first appeared during the period.<\/p>\r\n\r\n\r\n\r\n The Jurassic Period<\/strong><\/p>\r\n\r\n\r\n\r\n Great plant-eating dinosaurs roaming the earth, feeding on lush ferns and palm-like cycads and bennettitaleans \u2026 smaller but vicious carnivores stalking the great herbivores \u2026 oceans full of fish, squid, and coiled ammonites, plus great ichthyosaurs and long-necked plesiosaurs \u2026 vertebrates taking to the air, like the pterosaurs and the first birds. This was the Jurassic Period, 199.6 to 145.5 million years ago* \u2014 a 54-million-year chunk of the Mesozoic Era. Today, the name “Jurassic” conjures up images of the phenomenally successful book and movie, Jurassic Park. It is quite true that the dinosaurs dominated the land fauna \u2014 although many of the dinosaurs featured in Jurassic Park, such as Triceratops and Tyrannosaurus rex, did not evolve until after the Jurassic was over. The largest dinosaurs of the time \u2014 in fact, the largest land animals of all time \u2014 were the gigantic sauropods, such as the famous Diplodocus (top right, above), Brachiosaurus and Apatosaurus. Other herbivorous dinosaurs of the Jurassic included the plated stegosaurs. Predatory dinosaurs of the Jurassic included fearsome carnosaurs such as Allosaurus, small, fast coelurosaurs, and ceratosaurs such as Dilophosaurus. The Jurassic also saw the origination of the first birds, including the well-known Archaeopteryx, probably from coelurosaurian ancestors. But there was more to life than dinosaurs! In the seas, the fishlike ichthyosaurs (top left, above) were at their height, sharing the oceans with the plesiosaurs, giant marine crocodiles, and modern-looking sharks and rays. Also prominent in the seas were cephalopods \u2014 relatives of the squids, nautilus, and octopi of today. Jurassic cephalopods included the ammonites, with their coiled external shells (upper left), and the belemnites, close relatives of modern squid but with heavy, calcified, bullet-shaped, partially internal shells. Among the plankton in the oceans, the dinoflagellates became numerous and diverse, as did the coccolithophorids (microscopic single-celled algae with an outer covering of calcareous plates). Land plants abounded in the Jurassic, but floras were different from what we see today. Although Jurassic dinosaurs are sometimes drawn with palm trees, there were no palms or any other flowering plants \u2014 at least as we know them today \u2014 in the Jurassic. Instead, ferns, ginkgoes, bennettitaleans or “cycadeoids,” and true cycads \u2014 like the living cycad pictured above, lower left \u2014 flourished in the Jurassic. Conifers were also present, including close relatives of living redwoods, cypresses, pines, and yews. Creeping about in this foliage, no bigger than rats, were a number of early mammals.<\/p>\r\n\r\n\r\n\r\n Etymology and history<\/strong><\/p>\r\n\r\n\r\n\r\n The chronostratigraphic term “Jurassic” is linked to the Jura Mountains, a forested mountain range that mainly follows the France\u2013Switzerland border. The name “Jura” is derived from the Celtic root *jor via Gaulish *iuris “wooded mountain”, which was borrowed into Latin as a name of a place and evolved into Juria and finally Jura. During a tour of the region in 1795, German naturalist Alexander von Humboldt recognized carbonate deposits within the Jura Mountains as geologically distinct from the Triassic aged Muschelkalk of Southern Germany, but he erroneously concluded that they were older. He then named them Jura-Kalkstein (‘Jura limestone’) in 1799. In 1829, the French naturalist Alexandre Brongniart published a book entitled Description of the Terrains that Constitute the Crust of the Earth or Essay on the Structure of the Known Lands of the Earth. In this book, Brongniart used the phrase terrains jurassiques when correlating the “Jura-Kalkstein” of Humboldt with similarly aged oolitic limestones in Britain, thus coining and publishing the term “Jurassic”. The German geologist Leopold von Buch in 1839 established the three-fold division of the Jurassic, originally named from oldest to the youngest: the Black Jurassic, Brown Jurassic, and White Jurassic. The term “Lias” had previously been used for strata of equivalent age to the Black Jurassic in England by William Conybeare and William Phillips in 1822. The French palaeontologist Alcide d’Orbigny in papers between 1842 and 1852 divided the Jurassic into ten stages based on ammonite and other fossil assemblages in England and France, of which seven are still used, but none has retained its original definition. The German geologist and palaeontologist Friedrich August von Quenstedt in 1858 divided the three series of von Buch in the Swabian Jura into six subdivisions defined by ammonites and other fossils. The German palaeontologist Albert Oppel in his studies between 1856 and 1858 altered d’Orbigny’s original scheme and further subdivided the stages into biostratigraphic zones, based primarily on ammonites. Most of the modern stages of the Jurassic were formalized at the Colloque du Jurassique \u00e0 Luxembourg in 1962.<\/p>\r\n\r\n\r\n\r\n Geology <\/strong>of Jurassic Period<\/strong><\/p>\r\n\r\n\r\n\r\n The Jurassic Period is divided into three\u00a0epochs: Early, Middle, and Late. Similarly, in\u00a0stratigraphy, the Jurassic is divided into the\u00a0Lower Jurassic,\u00a0Middle Jurassic, and\u00a0Upper Jurassic\u00a0series. Geologists divide the rocks of the Jurassic into a\u00a0stratigraphic\u00a0set of units called\u00a0stages, each formed during corresponding time intervals called ages. Stages can be defined globally or regionally. For global stratigraphic correlation, the\u00a0International Commission on Stratigraphy\u00a0(ICS) ratify global stages based on a\u00a0Global Boundary Stratotype Section and Point\u00a0(GSSP) from a single\u00a0formation\u00a0(a\u00a0stratotype) identifying the lower boundary of the stage.[3]<\/sup>\u00a0The ages of the Jurassic from youngest to oldest are as follows:[6]<\/sup><\/p>\r\n\r\n\r\n\r\n Series\/epoch\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 stage\/age\u00a0\u00a0\u00a0\u00a0\u00a0 lower boundary<\/p>\r\n\r\n\r\n\r\n Early cretaceous\u00a0\u00a0\u00a0\u00a0 berriasian\u00a0\u00a0\u00a0\u00a0 ~145 mya<\/p>\r\n\r\n\r\n\r\n Upper\/late jurassic tithonian\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 152.1 \u00b10.9 mya<\/p>\r\n\r\n\r\n\r\n Kimmeridgian\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 157.3 \u00b11.0 mya<\/p>\r\n\r\n\r\n\r\n Oxfordian\u00a0\u00a0\u00a0\u00a0\u00a0 163.5 \u00b11.0 mya<\/p>\r\n\r\n\r\n\r\n Middle jurassic\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 callovian\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 166.1 \u00b11.2 mya<\/p>\r\n\r\n\r\n\r\n Bathonian\u00a0\u00a0\u00a0\u00a0 168.3 \u00b11.3 mya<\/p>\r\n\r\n\r\n\r\n Bajocian\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 170.3 \u00b11.4 mya<\/p>\r\n\r\n\r\n\r\n Aalenian\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 174.1 \u00b11.0 mya<\/p>\r\n\r\n\r\n\r\n Lower\/early jurassic\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 toarcian\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 182.7 \u00b10.7 mya<\/p>\r\n\r\n\r\n\r\n Pliensbachian\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 190.8 \u00b11.0 mya<\/p>\r\n\r\n\r\n\r\n Sinemurian\u00a0 199.3 \u00b10.3 mya<\/p>\r\n\r\n\r\n\r\n Hettangian\u00a0\u00a0 201.3 \u00b10.2 mya<\/p>\r\n\r\n\r\n\r\n The climate of the Jurassic<\/strong><\/p>\r\n\r\n\r\n\r\n The climate of the Jurassic was generally warmer than that of present, by around 5 \u00b0C to 10 \u00b0C, with atmospheric carbon dioxide likely four times higher. Intermittent “cold snap” intervals are known to have occurred during this time period, however, interrupting the otherwise warm greenhouse climate. Forests likely grew near the poles, where they experienced warm summers and cold, sometimes snowy winters; there were unlikely to have been ice sheets given the high summer temperatures that prevented the accumulation of snow, though there may have been mountain glaciers. Dropstones and glendonites in northeastern Siberia during the Early to Middle Jurassic indicate cold winters. The ocean depths were likely 8 \u00b0C warmer than present, and coral reefs grew 10\u00b0 of latitude further north and south. The Intertropical Convergence Zone likely existed over the oceans, resulting in large areas of desert and scrubland in the lower latitudes between 40\u00b0 N and S of the equator. Tropical rainforest and tundra biomes are likely to have been rare or absent. The Jurassic also witnessed the decline of the Pangaean megamonsoon that had characterised the preceding Permian and Triassic periods. The beginning of the Jurassic was likely marked by a thermal spike corresponding to the Triassic\u2013Jurassic extinction and eruption of the Central Atlantic magmatic province. The first part of the Jurassic was marked by the Early Jurassic Cool Interval between 199 and 183 million years ago. It has been proposed that glaciation was present in the Northern Hemisphere during the late Pliensbachian. There was a spike in global temperatures of around 4\u20138 \u00b0C during the early part of the Toarcian corresponding to the Toarcian Oceanic Anoxic Event and the eruption of the Karoo-Ferrar large igneous provinces in southern Gondwana, with the warm interval extending to the end of the Toarcian around 174 million years ago. The end of the Jurassic was marked by the Tithonian\u2013early Barremian Cool Interval, beginning 150 million years ago and continuing into the Early Cretaceous.<\/p>\r\n","protected":false},"excerpt":{"rendered":" In this post we will be looking at the Jurassic Period, Etymology and history, Geology of Jurassic Period and the climate of the Jurassic. INTRODUCTION The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[32],"tags":[],"class_list":["post-8489","post","type-post","status-publish","format-standard","hentry","category-life"],"acf":[],"yoast_head":"\n