Late Paleozoic icehouse
The late Paleozoic icehouse, also known as the Late Paleozoic Ice Age (LPIA) and formerly known as the Karoo ice age, was an ice age that began in the
Timeline
Interpretations of the LPIA vary, with some
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.[14] These Early Mississippian glaciations were transient and minor,[12] with them sometimes being considered discrete glaciations separate from and preceding the LPIA proper.[15] Between 335 and 330 Mya, or sometime between the middle Viséan and earliest Serpukhovian, the LPIA proper began.[16][15] The first major glacial period occurred from the Serpukhovian to the Moscovian: ice sheets expanded from a core in southern Africa and South America.[2] During the Bashkirian, a global eustatic sea level drop occurred, signifying the first major glacial maximum of the LPIA.[7] The Lhasa terrane became glaciated during this stage of the Carboniferous.[17] A relatively warm interglacial interval spanning the Kasimovian and Gzhelian, coinciding with the Alykaevo Climatic Optimum, occurred between this first major glacial period and the later second major glacial period.[18] 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.[2] This was the most intense interval of glaciation of the LPIA;[16][15] in Australia, it is known as P1.[19] An exceptionally intense cooling event occurred at 300 Ma.[20] From the late Sakmarian onward, and especially following the Artinskian Warming Event (AWE),[21] these ice sheets declined, as indicated by a negative δ18O excursion.[7] Ice sheets retreated southward across Central Africa and in the Karoo Basin. 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.[22] This massive deglaciation during the late Sakmarian and Artinskian is sometimes considered to be the end of the LPIA proper,[16] with the Artinskian-Kungurian boundary[2] and the associated Kungurian Carbon Isotopic Excursion used as the boundary demarcating the ice age's end.[23][24][25] Nonetheless, ice caps of a much lower volume and area remained in Australia. Another long regional interval also limited to Australia from the middle Kungurian to the early Capitanian, known as P3,[26] though unlike the previous glaciations, this one and the following P4 glaciation was largely limited to alpine glaciation.[27] A final regional Australian interval lasted from the middle Capitanian to the late Wuchiapingian, known as P4.[26] As with P3, P4's ice sheets were primarily high altitude glaciers.[27] This glacial period was interrupted by a rapid warming interval corresponding to a surge in activity from the Emeishan Traps and corresponding Capitanian mass extinction event.[28][29] The final alpine glaciers of the LPIA melted in what is now eastern Australia around 255 Mya, during the late Wuchiapingian.[3]
The time intervals here referred to as glacial and interglacial periods represented intervals of several million years corresponding to colder and warmer icehouse intervals, respectively, were influenced by long term variations in palaeogeography, greenhouse gas levels, and geological processes such as rates of volcanism and of silicate weathering and should not be confused with shorter term cycles of glacials and interglacials that are driven by astronomical forcing caused by Milankovitch cycles.[30]
Geologic effects
According to Eyles and Young, "Renewed Late Devonian glaciation is well documented in three large intracratonic basins in
In northern
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. Northern Victoria Land and Tasmania hosted a distinct ice sheet from the one in southern Victoria Land that flowed west-northwestward.[34]
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.[35]
Debate exists as to whether the Northern Hemisphere experienced glaciation like the Southern Hemisphere did, with most palaeoclimate models suggesting that ice sheets did exist in Northern Pangaea but that they were very negligible in volume. Diamictites from the Atkan Formation of Magadan Oblast, Russia have been interpreted as being glacigenic, although recent analyses have challenged this interpretation, suggesting that these diamictites formed during a Capitanian integrlacial interval as a result of volcanogenic debris flows associated with the formation of the Okhotsk–Taigonos Volcanic Arc.[36][37]
The tropics experienced a cyclicity between wetter and drier periods that may have been related to changes between cold glacials and warm interglacials. In the Midland Basin of Texas, increased aeolian sedimentation reflective of heightened aridity occurred during warmer intervals,[38] as it did in the Paradox Basin of Utah.[39]
Causes
Greenhouse gas reduction
The evolution of land plants with the onset of the
The
Milankovitch cycles
The LPIA, like the present
Biotic effects
The development of high-frequency, high-amplitude glacioeustasy, which resulted in sea level changes of up to 120 metres between warmer and colder intervals,
At the beginning of the LPIA, the transition from a greenhouse to an icehouse climate, in conjunction with increases in atmospheric oxygen concentrations, reduced thermal stratification and increased the vertical extent of the mixed layer, which promoted higher rates of microbial nitrification as revealed by an increase in δ15Nbulk values.[53]
The rising levels of oxygen during the late Paleozoic icehouse had major effects upon
Termination
Earth's increased planetary albedo produced by the expanding ice sheets would lead to positive feedback loops, spreading the ice sheets still further, until the process hit a limit. Falling global temperatures would eventually limit plant growth, and the rising levels of oxygen would increase the frequency of fire-storms because damp plant matter could burn. Both these effects return carbon dioxide to the atmosphere, reversing the "snowball" effect and forcing the greenhouse effect, with CO2 levels rising to 300 ppm in the following Permian period.
Once these factors brought a halt and a small reversal in the spread of ice sheets, the lower planetary albedo resulting from the fall in size of the glaciated areas would have been enough for warmer summers and winters and thus limit the depth of snowfields in areas from which the glaciers expanded. 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). With a smaller area for deposition of carbon, more carbon dioxide was returned to the atmosphere, further warming the planet. Over the course of the Early and Middle Permian, glacial periods became progressively shorter while warm interglacials became longer, gradually transitioning the world from an icehouse to a greenhouse as the Permian progressed.[54] Obliquity nodes that triggered glacial expansion and increased tropical precipitation before 285.1 Mya became linked to intervals of marine anoxia and increased terrestrial aridification after this point, a turning point signifying the icehouse-greenhouse transition.[55] Increased lacustrine methane emissions acted as a positive feedback enhancing warming.[56] The LPIA finally ended for good around 255 Ma.[3]
See also
- History of Earth
- Quaternary glaciation – the current ice age
- Timeline of glaciation
References
- S2CID 228838061. Retrieved 29 November 2022.
- ^ S2CID 226643402.
- ^ S2CID 218953074. Retrieved 17 September 2022.
- ^ ISSN 0084-6597."The late Paleozoic icehouse was the longest-lived ice age of the Phanerozoic, and its demise constitutes the only recorded turnover to a greenhouse state."
- . Retrieved 27 August 2022.
- ISBN 978-0-8137-2441-6. Retrieved 14 September 2022.
- ^ S2CID 224922824. Retrieved 29 September 2022.
- S2CID 198421412. Retrieved 21 October 2022.
- S2CID 210782726.
- S2CID 251819987. Retrieved 29 November 2022.
- ISSN 0895-9811. Retrieved 26 September 2023.
- ^ S2CID 226194983. Retrieved 29 September 2022.
- . Retrieved 20 October 2022.
- . Retrieved 14 November 2023.
- ^ ISSN 0012-8252. Retrieved 26 September 2023.
- ^ S2CID 244235424.
- ISSN 0921-8181. Retrieved 26 September 2023.
- S2CID 248504537.
- ^ ISSN 0031-0182. Retrieved 26 September 2023.
- . Retrieved 26 September 2023.
- S2CID 245892961. Retrieved 30 October 2022.
- . Retrieved 20 October 2022.
- PMID 31719563.
- . Retrieved 10 October 2022.
- S2CID 134157257. Retrieved 29 November 2022.
- ^ S2CID 245312062. Retrieved 2 October 2022.
- ^ . Retrieved 2 December 2022.
- S2CID 252526238. Retrieved 2 December 2022.
- ^ . Retrieved 7 October 2022.
- ISBN 978-0521548038.
- ISBN 978-94-017-8026-1.
- S2CID 247160660. Retrieved 24 August 2022.
- doi:10.1130/B35905.1. Retrieved 28 September 2022.
- S2CID 214119448. Retrieved 5 November 2022.
- .
- .
- . Retrieved 2 November 2023.
- ISSN 1342-937X. Retrieved 14 November 2023.
- PMID 10500106.
- ^ S2CID 55701037.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - S2CID 225046506. Retrieved 5 October 2022.
- . Retrieved 2 November 2023.
- ^ . Retrieved 5 November 2022.
- doi:10.1038/ngeo2931. Retrieved 14 September 2022.
- . Retrieved 24 November 2022.
- .
- S2CID 216338756.
- . Retrieved 5 November 2022.
- . Retrieved 4 September 2022.
- S2CID 130097035. Retrieved 4 September 2022.
- S2CID 42512923. Retrieved 24 November 2022.
- . Retrieved 14 November 2023.
- S2CID 146718511. Retrieved 27 August 2022.
- S2CID 248353840. Retrieved 17 October 2022.
- ISSN 2041-1723. Retrieved 7 January 2024.
Bibliography
- PMID 11050154.