DOI: 10.1016/j.palaeo.2013.08.017
论文题名: Microstructure variability in freshwater microbialites, Pavilion Lake, Canada
作者: Omelon C.R. ; Brady A.L. ; Slater G.F. ; Laval B. ; Lim D.S.S. ; Southam G.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2013
卷: 392 起始页码: 62
结束页码: 70
语种: 英语
英文关键词: Bacteria
; Biosignature
; Calcite
; Carbonate precipitation
; Electron microscopy
; Freshwater microbialite
; Synchrotron micro-X-ray fluorescence spectroscopy
英文摘要: Calcite microbialites in Pavilion Lake, British Columbia, exhibit a diverse range in macro-morphology, biomass abundance, porosity, and mineral content. To evaluate the role of microorganisms in their formation, samples collected from a range of depths were examined by scanning electron microscopy (SEM) and synchrotron radiation-based micro-X-ray fluorescence (μ-XRF) spectroscopy to characterize both their outer surfaces as well as internal structures. Observed trends in both surface colonization as well as microbialite framework with increasing lake depth include decreasing microbial abundance on outer surfaces as well as increasing ratios of carbonate:biomass in the microbialites. Microscopic investigations of the interiors show bacteria and algae entrapped within calcite, with this calcite exhibiting micropores and casts similar in size and shape to microorganisms. Based on these observations, it is hypothesized that microbialite development in Pavilion Lake initiates calcite precipitation in phototrophic microbial mats, i.e., combined phototrophy and heterotrophy, followed by heterotrophic oxidation of organic matter leading to eventual carbonate infilling of the microbial-mineral matrix. In addition, an observed shift from cyanobacteria to algae with increasing lake depth suggests variability in contemporary conditions controlling microbialite growth and diagenesis. High photosynthetic growth rates at shallower depths result in significant porosity and friability due to biomass accumulation outpacing carbonate precipitation. At intermediate depths, lower light levels and slower growth rates of phototrophs lead to a greater proportion of the microbialite matrix being in-filled by carbonate. Carbonates precipitate initially within the bacteria-EPS matrix, with abundant uncalcified algae maintaining microbialite porosity. In the deepest waters, the presence of only sparse algal colonization as well as fine-grained, laminated metal-rich sediments covering microbialites suggests that present-day insolation levels are too low to support the development of photosynthetic microbial mats. As a consequence, heterotrophic carbonate precipitation has progressively in-filled these microbialite interiors to create lithified calcite fabrics that exhibit minimal porosity but preserve the casts of microorganisms as biosignatures. While the origin of microbialites in Pavilion Lake remains unknown, current observations provide valuable information in evaluating how environmental conditions influence microbialite growth in a freshwater, lacustrine environment. © 2013. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/69528
Appears in Collections: 过去全球变化的重建
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作者单位: Department of Earth Sciences, Western University, 1151 Richmond Street North, London, ON N6A 5B7, Canada; School of Geography and Earth Sciences, McMaster University, General Science Building, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada; Department of Civil Engineering, University of British Columbia, Civil and Mechanical Engineering Building, Vancouver, BC V6T 1Z4, Canada; NASA Ames Research Center, Mail-Stop 245-3, Bldg N245, P.O. Box 1, Moffett Field, CA 94035-1000, United States
Recommended Citation:
Omelon C.R.,Brady A.L.,Slater G.F.,et al. Microstructure variability in freshwater microbialites, Pavilion Lake, Canada[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2013-01-01,392