DOI: 10.1016/j.palaeo.2012.10.018
论文题名: Evaluation of the effect of diagenetic cements on element/Ca ratios in aragonitic Early Miocene (~16Ma) Caribbean corals: Implications for 'deep-time' palaeo-environmental reconstructions
作者: Griffiths N. ; Müller W. ; Johnson K.G. ; Aguilera O.A.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2013
卷: 369 起始页码: 185
结束页码: 200
语种: 英语
英文关键词: 'Deep-time' palaeo-proxies
; Corals
; Diagenetic cements
; Element/Ca ratios
; LA-ICPMS
; Miocene
; Runoff
; Seasonality
; SST anomalies
英文摘要: Early Miocene corals (Siderastrea conferta and Montastraea limbata) from the Paraguaná Peninsula, Venezuela and a modern coral (S. radians) from Bermuda were examined in order to quantitatively assess the effect of skeletal preservation on element/Ca proxies used for palaeo-environmental reconstructions. The biostratigraphic age (Burdigalian) of the corals was confirmed via Sr isotope stratigraphy to 16.5 ± 0.4. Ma. Light and scanning electron microscopy revealed the presence of aragonite and calcite cements in both fossil and modern corals, but brucite cements were found only in the modern coral. Cement distribution is very heterogeneous, resulting in zones of excellent preservation juxtaposed with less well preserved regions in both modern and fossil coral. Oil-filled pore spaces were noted in the fossil specimens. Targeted LA-ICPMS depth profile analyses showed significant differences in Sr/Ca, Mg/Ca, B/Ca, Ba/Ca and U/Ca in aragonite and calcite cements compared to primary skeletal aragonite. Increased Sr/Ca and decreased Mg/Ca ratios were found in aragonite cements compared to skeletal aragonite, whereas in calcite cements these trends were reversed. B/Ca ratios were lower in both aragonite and calcite cements compared to primary aragonite. Estimates of the effect of 1% contamination by aragonite cements on coral Sr/Ca, Mg/Ca, B/Ca and U/Ca palaeo-sea-surface-temperature reconstructions for the fossil corals produced anomalies of - 1.2. °C, - 0.2. °C, + 0.3. °C and - 0.1. °C respectively. Similar percentage calcite cement contamination produced temperature anomalies of + 1.7. °C, + 2.7. °C, + 0.3. °C and - 0.1. °C. Because of both highly elevated and depleted Ba/Ca signatures in aragonite and calcite cements respectively, care has to be exercised when reconstructing past flood or upwelling events from fossil corals. When using targeted spatially-resolved analysis, well-preserved early Miocene corals may overall yield reliable 'deep-time' palaeo-proxy information in much the same way as commonly utilised Holo/Pleistocene corals. © 2012. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/69885
Appears in Collections: 过去全球变化的重建
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作者单位: Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, United Kingdom; Department of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, United Kingdom; Coordenação de Ciências da Terra e Ecologia, Av. Perimetral, 1901, Belém, Brazil
Recommended Citation:
Griffiths N.,Müller W.,Johnson K.G.,et al. Evaluation of the effect of diagenetic cements on element/Ca ratios in aragonitic Early Miocene (~16Ma) Caribbean corals: Implications for 'deep-time' palaeo-environmental reconstructions[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2013-01-01,369