SHRIMP zircon age control of Gondwanan sequences in Late Carboniferous and Early Permian Australia

Abstract

Australia during the Late Carboniferous formed part of the Gondwana supercontinent and was close to the South Pole. Resulting continental glacigene deposits and cold water marine sequences in the Southern New England Orogen cannot be correlated biostratigraphically with Late Carboniferous successions in the northern hemisphere because they contain a low diversity biota endemic to Gondwana. Magnetostratigraphic correlation via the Permian-Carboniferous reversed magnetic superchron is presently uncertain. Sensitive high-resolution ion microprobe (SHRIMP) zircon dating of volcanics horizons in the sedimentary sequence of the Southern New England Orogen is now establishing relationships between the Gondwanan faunas and warm-climate European equivalents. In Continental sediments, correlation of the major Gondwanan glaciation of Late Carboniferous Australia is revised from Stephanian to early Namurian-Westphalian in age, a timing that matches that of the Hoyada Verde glaciation in Argentina. A major hiatus of > 15 Ma between Carboniferous rocks of the Southern New England Orogen and Permian rocks of the Sydney Basin of eastern Australia probably reflects the first deformational movements within the accretionary prism of the orogen. Nothorhacopteris , traditionally a Late Carboniferous indicator in Australia, now ranges from late Viséan to Westphalian, and an ‘enriched’ assemblage, previously correlated with the top of the Nothorhacopteris flora, is confined to the late Viséan to early Namurian. Palynofloras assigned to the Spelaeotriletes ybertii/Diatomozonotriletes birkheadensis Zones (Namurian-early Westphalian), are now confined to the Namurian, and a mid to late Westphalian age is indicated for a more diverse palynoflora identified as uppermost D. birkheadensis Zone (? = Asperispora reticulatispinosus Zone). In the cold climate marine sequence, the Levipustula levis brachiopod Zone appears to be confined to the early Namurian, and so partly corresponds in age to the continental glaciation.

Response of Late Carboniferous and Early Permian Plant Communities to Climate Change

“…These provinces may have changed compositionally over time within the Carboniferous as indicated by mid-Carboniferous floras on Gondwana that were referred to as the Paracas flora (Alleman & Pfefferkorn 1988, Pfefferkorn & Alleman 1989, Iannuzzi et al 1998. The tropical coal belt appears to have developed during the Namurian A (Pendleian), during the late Early Carboniferous (Raymond 1996), probably in response to the onset of glaciation (Roberts et al 1995). Raymond (1996) argued that glaciation increased global biogeographic differentiation by establishing and maintaining an ever-wet, ever-warm equatorial climate and by steepening the equator-to-pole temperature and rainfall gradient.…”

High-precision U-Pb CA-TIMS calibration of Middle Permian to Lower Triassic sequences, mass extinction and extreme climate-change in eastern Australian Gondwana

“…Highprecision dating of multiple volcanic tuffs in these sequences now provides a robust highresolution temporal framework that can be globally correlated and can thus provide vital constraints on the nature of biotic crises, climate change and other geological events. We here present twenty-eight new high-precision U-Pb zircon CA-TIMS dates for P-T air-fall tuffs in the Sydney and Bowen Basins of eastern Australian Gondwana that provide vital undertake an innovative program of tuff dating to address this problem (Roberts et al, 1995a(Roberts et al, , 1995b(Roberts et al, , 1996. The results from these studies were controversial as they contradicted previously assigned ages based on biostratigraphy and in some cases indicated that rocks regarded as Permian were in fact Triassic (Draper et al, 1997).…”

A new Pennsylvanian Oriocrassatellinae from Brazil and the distribution of the genusOriocrassatellain space and time

“…2009);33, Newell (1958); 34, Dickins et al (1989), Archbold et al (1996); 35, Archbold et al (1996); 36, Wanner (1940), Archbold et al (1996). Ages for glacial periods: in Argentina, according to González (1981González ( , 1990González ( , 2002 and González & Díaz-Saravia (2007); in Australia, to Roberts et al (1995), Dickins (1996) and Fielding et al (2008a, b); in Brazil, to Holz et al (2008); in India, to Veevers & Tewari (1995) and Maejima et al (2001). Ages for Biozones in Argentina and Australia from Kelly et al (2001); for Marginirugus barringtonensis, Roberts et al (1976 Oriocrassatella sp.…”

“…This warming eliminated the climatic barrier that interrupted the faunal interchange during the "Middle" Carboniferous glacial period and favored larval dispersion following a South to The Late Pennsylvanian time elapsed without records of Oriocrassatella (and the Gondwana fauna), except for occurrences in Argentina (see Fig. 1[6-8]), may be related to the generalized marine regressions in Gondwana (see Roberts et al 1995;Dickins 1996). In addition, the pattern of occurrences described above for the Late Pennsylvanian may be a result of taphonomic bias and/or incomplete sampling.…”