PERMIAN PERIOD  (280-250 Ma)

Name: Murchison (1842) recognized faunal assemblages above the Carboniferous but below typical Triassic in Perm province of Russia; named this intervening strata Permian

Climate: continued icehouse conditions but glaciers wane early in Period associated with increasingly arid climates; lots of redbeds, desert dune deposits and immense amounts of evaporites; coal swamps gradually drying out; shift to upland vegetation

Global Tectonics: Later rumblings of Alleghenian Orogeny;  fluids through rocks and remagnetisation

Pangea nearly assembled; final phases involve  Tien Shan which assembles parts of China-Mongolia and Uralian Orogeny in which Asia is attached to Baltica, completing "Laurasia"

Continents now in bi-lobed array Laurasia  in north and Gondwanaland in south with wedge-shaped Tethys seaway in between

Also begiing of development and collision of Sonomia island arc/microcontinent of western Laurentia; beginnings of Sonomia Orogeny

Sequence Stratigraphy:  all part of the prolonged regressive phase pf Absaroka Supersequence;

Sea is now withdrawn from most of North America but remnant remains in southwest; carbonate sediments of Kaibab Limestone in Arizona;  Kaibab forms rim and plaeau at top of Gran d Canyon;

Phosphoria Formation a major minable source of phsphate due to upwellings and productivitty along  then west side of Laurentia

 Ouachita-Marathon basin; and in west Texas

Famous area of west Texas Panhandle is the Delaware Basin (Delaware-Midland basins separated by a central platform; on the platform developed the famous West Texas reef complex; great sponge-algal reefs developed and prograded basin ward into Delaware dysoxic basin; Carlsbad evaporites accumulated to north in lagoonal/back reef settings
 

Vast salt deposits in Siberia and i n Urals; major salt mines; salt helped lubricate great thrusts of the Ural Mountains
 

Permian life:

Marine: more of same :

Sponge algal reefs

Fusulinids prolific rapidly evolving

Brachiopods include some bizarre forms such as richthofenids (coral-like reef builders)

Terrestrial:  drying of coal swamps led to increase in upland, seed-bearing plants such ass first true conifers

Insects radiate; many modern orders appear

Amphibians still somewhat common

Retiles rapidly diversifying; include:

Stem-reptiles; and pareiosaurs

First lizard-like forms; earliest archosaurs

Reptiles include abundant mammal-like reptiles, including Pelycosaurs and Therapsids;
 

Perm-Triassic extinctions; very severe (over 90% of species wiped out

All          Most
 Trilobites         Ammonoids

Blastoids;          Crinoids

Fusulinids         sea urchins

Productid brachiopods     bryozoans

Facts about PT Extinction

Two phases (at least) :
Guadalupian  (major 70% species  extinct; lots of fusulinids ;  associated with ice-lid dropstones in Siberia)

Terminal Permian extinction (80% of what was left after Guadalupian) largest of all major extinction

a) very sudden
b) tropical taxa hardest hit
c) spike of 12C enrichment
d) 100m sea level drop in last two million years of Permian
e) brief interval of widespread anoxia
f) shift of dry-adapted Dicroidium flora toward equator
g) largest food basalts in earth history : Siberian traps
h) maximum Pangea configuration

Causes of extinction:

decreased provinciality

harsh seasonal, continental climate

greenhouse gasses frm volcanoes

sea level regression

anoxia- hypoxia

CO2 burp

PT extinction marks major decline of Paleozoic fauna, shift to dominance of Modern fauna. excellent event to mark end of Paleozoic Era, beginning of Mesozoic