Late Paleozoic Ice Age

Late Paleozoic Ice Age
Name	Late Paleozoic Ice Age
Period	Carboniferous–Permian
Start	~335 Ma
End	~260 Ma
Major glaciations	Late Paleozoic glaciation
Regions	Gondwana, Pangaea
Notable fossils	Glossopteris, Mesosaurus

Late Paleozoic Ice Age The Late Paleozoic Ice Age was a prolonged interval of major glaciation spanning much of the Carboniferous and Permian periods during the Paleozoic Era. This episode involved repeated glacial and interglacial cycles that affected the supercontinent Gondwana and contributed to continental rearrangements associated with Pangaea, with widespread impacts recorded in paleoclimate proxies, sedimentary basins, and fossil assemblages.

Overview and Timing

The onset of the interval is generally placed in the late Mississippian to early Pennsylvanian, roughly coinciding with stages such as the Tournaisian, Visean, and Serpukhovian, and extended into the Permian stages including the Cisuralian and Guadalupian. High-resolution chronostratigraphy links glacial peaks to marine isotope events and to assembly episodes of Pangaea during the collisions of Gondwana with Laurussia and terranes like Avalonia and Armorica. Key regional time markers include the Karoo Supergroup, the Glennie Formation, and the Glossopteris flora beds used in Gondwanan correlation.

Causes and Climate Mechanisms

Explanations invoke tectonics, atmospheric composition, ocean circulation, and orbital forcing. Continental assembly during the Variscan Orogeny and Alleghanian orogeny altered paleogeography and promoted high-latitude ice growth on Gondwana, while uplift associated with the Appalachian Mountains and Hercynian orogeny enhanced silicate weathering. A decline in atmospheric CO2—linked to extensive burial of organic carbon in coal measures such as the Pennsylvanian coal swamps—is tied to cooling, alongside perturbations from episodes related to Large Igneous Provinces and basalt emplacements like the Siberian Traps precursor events. Changes in ocean gateways affecting the Panthalassa basin and Milankovitch-scale eccentricity and obliquity cycles are inferred from cyclic glacial deposits and cyclothems correlated to stratotypes like the Gzhelian and Asselian.

Extent and Glacial Features

Glaciation was concentrated on the southern high-latitude margins of Gondwana, with ice centers inferred across modern-day Antarctica, South Africa, South America, India, and Australia. Glacial deposits include diamictites, tillites, striated pavements, and dropstones preserved in the Karoo Basin, the Permo-Carboniferous glaciogenic succession of Brazil, and the Glacial Till of the Dwyka Group in South Africa. Sea-level oscillations produced glacioeustatic signatures recorded in cyclothem sequences from the Midcontinent, Donets Basin, and Rotliegend facies. Moraines, varves, and glacial pavements provide geomorphological evidence analogous to features documented in the Transantarctic Mountains and inferred from palaeomagnetic reconstructions tied to the Gondwanan glaciation.

Biological and Ecological Impacts

The interval saw major biotic turnover among plants and animals. The proliferation of lycophytes, sphenopsids, and coal-forming forests such as those preserving Lepidodendron contrasts with declines and regional extirpations of warm-temperate taxa during glacial maxima. Marine faunas adapted via shifts in brachiopod, crinoid, and ammonoid distributions documented in the Paleozoic marine faunal succession, while freshwater taxa like Mesosaurus and seed-fern assemblages including Glossopteris indicate altered paleohydrology. Repeated habitat fragmentation contributed to events like the Carboniferous rainforest collapse and influenced early tetrapod diversification recorded in localities such as Joggins and Mazon Creek, and correlated to faunal turnovers seen in the Permian–Triassic boundary precursors.

Stratigraphy and Geological Evidence

Stratigraphic records combine glaciogenic units, cyclothems, sequence stratigraphy, and isotope geochemistry. Carbon isotope excursions (δ13C), oxygen isotope trends (δ18O), and strontium isotope ratios in marine carbonates provide chemostratigraphic ties between Gondwanan tills and Laurasian sedimentary basins. Key stratotypes include the Karoo Supergroup in southern Africa, the Permo-Carboniferous stratigraphy of Argentina and India, and the Midcontinent Cyclothem sequences of North America. Paleomagnetic data from paleolatitude studies and palynological assemblages such as spores and pollen (e.g., Microspora and Triletes) aid correlation across basins used in International Commission on Stratigraphy frameworks.

Termination and Post-glacial Effects

The waning of glaciation in the late Permian correlates with continental reorganization, climatic warming, and shifts in atmospheric composition prior to the Permian–Triassic extinction event. Deglaciation influenced sea-level rise, redistribution of sedimentary regimes, and the reestablishment of extensive arid belts across parts of Pangaea, facilitating the spread of gymnosperms like Conifers and the expansion of Red Beds such as the Rotliegend. Long-term legacies include redistribution of mineral deposits in basins like the Karoo Basin, altered ocean chemistry that set the stage for later crises, and biogeographic patterns preserved in Gondwanan and Laurasian fossil records.

Category:Glaciology Category:Paleozoic glaciations