Late Paleozoic icehouse
Interpretations of the LPIA vary, with some researchers arguing it represented one continuous glacial event and others concluding that as many as twenty-five separate ice sheets across Gondwana developed, waxed, and waned independently and diachronously over the course of the Carboniferous and Permian,[5][6][7] with the distribution of ice centres shifting as Gondwana drifted and its position relative to the South Pole changed.
[10] The first glacial episodes of the LPIA occurred during the late Famennian[4][11] and the Tournaisian,[12][13] with δ15N evidence showing that the transition from greenhouse to icehouse was a stepwise process and not an immediate change.
[17] The first major glacial period occurred from the Serpukhovian to the Moscovian: ice sheets expanded from a core in southern Africa and South America.
[20] The second glacial period occurred from the late Gzhelian across the Carboniferous-Permian boundary to the early Sakmarian; ice sheets expanded from a core in Australia and India.
A regional glaciation spanning the latest Sakmarian and the Artinskian, known as P2, occurred in Australia amidst this global pulse of net warming and deglaciation.
[35] In southern Victoria Land, Antarctica, the Metschel Tillite, made up of reworked Devonian Beacon Supergroup sedimentary strata along with Cambrian and Ordovician granitoids and some Neoproterozoic metamorphic rocks, preserves glacial sediments indicating the presence of major ice sheets.
[36] The Sydney Basin of eastern Australia lay at a palaeolatitude of around 60°S to 70°S during the Early and Middle Permian, and its sedimentary successions preserve at least four phases of glaciation throughout this time.
[45] The reduction of carbon dioxide levels in the atmosphere would be enough to begin the process of changing polar climates, leading to cooler summers which could not melt the previous winter's snow accumulations.
[21] The tectonic assembly of the continents of Euramerica and Gondwana into Pangaea, in the Hercynian-Alleghany Orogeny, made a major continental land mass within the Antarctic region and an increase in carbon sequestration via silicate weathering, which led to progressive cooling of summers, and the snowfields accumulating in winters, which caused mountainous alpine glaciers to grow, and then spread out of highland areas.
[46] Modelling evidence points to tectonically induced carbon dioxide removal via silicate weathering to have been sufficient to generate the ice age.
The uplift, driven by mantle dynamics rather than by crustal tectonic processes, is evidenced by the increase in temperature of the southwestern Gondwanan crust as shown by changing compositions of granites formed at this time.
[51] Evidence from the Middle Permian Lucaogou Formation of Xinjiang, China indicates that the climate of the time was particularly sensitive to the 1.2 million year long-period modulation cycle of obliquity.
These were produced by the repeated alterations of marine and nonmarine environments resulting from glacioeustatic rises and falls of sea levels linked to Milankovitch cycles.
[53] The development of high-frequency, high-amplitude glacioeustasy, which resulted in sea level changes of up to 120 metres between warmer and colder intervals,[32] during the beginning of the LPIA, combined with the increased geographic separation of marine ecoregions and decrease in ocean circulation it caused in conjunction with closure of the Rheic Ocean, has been hypothesised to have been the cause of the Carboniferous-Earliest Permian Biodiversification Event.
The herbivorous stocky-bodied and armoured millipede-like Arthropleura was 1.8 metres (5.9 ft) long, and the semiterrestrial Hibbertopterid eurypterids were perhaps as large, and some scorpions reached 50 or 70 centimetres (20 or 28 in).
Rising sea levels produced by global warming drowned the large areas of flatland where previously anoxic swamps assisted in burial and removal of carbon (as coal).
