Informace o publikaci

Multi-proxy study of shallow platform carbonates at the Devonian/Carboniferous boundary (Ertoucun and Nanbiancun, South China): a diachronous detrital event



Rok publikování 2013
Druh Konferenční abstrakty
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Popis The Nanbiancun section is exposed in a small hill located close to the Nanbiancun village, about 4 km north-west of Guilin city. Based on the evolution of conodont Siphonodella praesulcata – S. sulcata community, the D/C boundary is placed between beds 55 and 56 in the top of Rongxian Formation. The Ertoucun section is located 7 km south of Guilin in the carbonate platform while the Nanbiancun section is on the marginal slope of the Guilin Platform. In Ertoucun, the upper part of the Famennian (Ertoucun Formation, 0 to 23 m) consists mainly of medium-bedded limestones. The lowermost part of the section (0 to ~11 m) comprises algal wackestones with abundant unilocular and multilocular (quasiendothyrid) foraminifers, peloids, bacterial lumps, ostracods and, in places, fenestral fabric. Peloid-foraminiferal wackestones to packstones with brachiopods, crinoids and algae occur higher up the section (11 to 23 m). A thin layer of shale is observed on the topmost part of the Famennian. The overlying basal Carboniferous Yinggoudong Formation (23 to 31.5 m) consists of thin bedded and/or nodular foraminifer-algal wackestones to packstones with peloids, ostracods, crinoids and brachiopods. Low-field magnetic susceptibility (XLF) measurements reveals: 1) fluctuating, weak and sometimes negative MS values during the Famennian, 2) increasing positive XLF values before the D/C boundary, staying positive up to the basal Carboniferous and 3) decreasing upwards to very weak and negative XLF values. A similar pattern at large-scale is observed in the Nanbiancun section but the GRS peaks and positive XLF values are present in the basal Carboniferous suggesting a clear diachronous detrital signal recorded between the inner platform and marginal slope settings. Sea-level fluctuations and 3rd order systems tracts should probably explain these differences between sections located in the same basin.
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