DOI: 10.1016/j.palaeo.2014.01.002
论文题名: Anatomy of a mass extinction: Sedimentological and taphonomic evidence for drought-induced die-offs at the Permo-Triassic boundary in the main Karoo Basin, South Africa
作者: Smith R.M.H. ; Botha-Brink J.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2014
卷: 396 起始页码: 99
结束页码: 118
语种: 英语
英文关键词: Drought
; Fluvial facies
; Karoo Basin
; Permo-Triassic mass extinction
; Therapsids
; Vertebrate taphonomy
英文摘要: The southern part of the Karoo Basin of South Africa contains a near complete stratigraphic record of the Permo-Triassic boundary (PTB). Isotope- and magneto-stratigraphy confirm that these predominantly fluvial strata are approximately the same age as zircon-dated marine PTB sections (252. Mya). By August 2013, our team had found 579 in situ vertebrate fossils, mostly of the clade Therapsida, in PTB exposures at three widely separated locations in the southern Karoo Basin. Biostratigraphic ranges of the various taxa found in each of the sections reveal three separate phases of die-off within the same roughly 75 metre-thick stratigraphic interval displaying the same sequence of sedimentary facies interpreted as indicative of climatic drying, increased seasonality and the onset of an unpredictable monsoon-type rainfall regime. The three phases of an inferred ecologically-stepped mass extinction are: Phase 1 (45. m-30. m below PTB datum) brought on by lowered watertables, which led to loss of shallow rooting groundcover in the more elevated proximal floodplain areas and the disappearance of the smaller groundcover-grazing herbivorous dicynodonts and their attendant small carnivores. Phase 2 (20-0. m below PTB datum), is the main extinction that occurs in massive maroon/grey mudrock culminating in an event bed of laminated reddish-brown siltstone/mudstone couplets. This facies reflects progressively unreliable rainfall leading to vegetation loss in proximal and distal floodplain areas. The larger tree-browsing herbivores and their attendant carnivores are confined to watercourses before finally disappearing. Phase 3 (25-30. m above PTB datum) occurs in massive maroon siltstone facies with evidence of climatic aridity including the accumulation of mummified carcasses buried by windblown dust. All of the surviving Permian taxa disappear within 30. m of the PTB.Temporal resolution based on accretion rates and pedogenic maturity of each stratigraphic section reveals that Phase 1 and Phase 2 die-offs lasted 21. 000 and 33. 000. years separated by a short period of 7000. years where no disappearances are recorded and this was followed by 50. 000. years of stasis for the final extinction phase, lasting only 8000. years, that removed all the Permian survivor taxa,. We propose that the recorded disappearances are real (rather than preferential preservation failure) and that they represent drought-induced die-offs moving progressively up the food chain as the terrestrial ecosystem collapsed; the latter mostly likely caused by volcanogenic greenhouse gas emissions and rapid global warming. © 2014 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/69461
Appears in Collections: 过去全球变化的重建
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作者单位: Iziko South African Museum, PO Box 61, Cape Town 8000, South Africa; Department of Geological Sciences, University of Cape Town, Rondebosch, 7701 Cape Town, South Africa; National Museum, PO Box 266, Bloemfontein 9300, South Africa; Department of Zoology and Entomology, University of the Free State, Bloemfontein 9300, South Africa; Centre of Excellence in Palaeosciences, Hosted by the University of the Witwatersrand, Private Bag 3, Wits, 2050, South Africa
Recommended Citation:
Smith R.M.H.,Botha-Brink J.. Anatomy of a mass extinction: Sedimentological and taphonomic evidence for drought-induced die-offs at the Permo-Triassic boundary in the main Karoo Basin, South Africa[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2014-01-01,396