Environmental significance of microbialites in reef environments during the last deglaciation
Environmental significance of microbialites in reef environments during the last deglaciation
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DOI：
10.1016/j.sedgeo.2005.12.018
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发表时间：
2006-03-15
影响因子：
2.8
通讯作者：
Lericolais, G
中科院分区：
文献类型：
--
作者：
Camoin, G;Cabioch, G;Lericolais, G
在塔希提岛和马克萨斯群岛现代前礁斜坡上，在水深80至130之间疏浚的礁岩中原位发现的微生物岩产生的年龄范围为17,100 - 2900 - 4410 - 2250年BP，这表明它们在最后一次冰消期海平面上升过程中发挥了重要作用。微生物岩发育于浅水和深水沉积环境，描绘了珊瑚礁带的不同区域（礁顶、上礁坡、深礁前坡），反映了微生物岩发育的对比情景，水背景和“斜坡微生物岩”，形成于1020英寸以上的环境中，向下延伸超过100米。礁微生物岩对应于珊瑚群落的死亡部分，或更常见的是相关结壳生物（红藻和有孔虫）的死亡部分，从而形成表面结壳。斜坡微生物岩通常形成生物演替的最后阶段，表明一个加深的序列，浅水珊瑚和相关的结壳生物体被替换为更深的水组合的红藻和有孔虫微生物岩生长之前。磷酸铁锰结壳的沉积和微生物岩上的钙长石泥晶灰岩的沉积是一个向上加深的层序。末次冰消期以来生物礁层序中微生物岩的广泛发育是一个环境退化时期的特征，这一时期海平面迅速上升，气候突变。报告的生物演替反映了水质的变化，特别是营养物质的增加。在浅水环境中，间隙沃茨中碱度和营养盐有效性的增加与地表通量和陆地地下水渗漏有关，而斜坡环境在末次冰消期海平面上升期间暴露于富含营养盐的深层沃茨的持续上涌。珊瑚和覆盖斜坡微生物岩之间的年龄差异在1600到8400年之间。根据对珊瑚和微生物岩的高精度U系列年龄测量，这表明珊瑚藻框架的发展和斜坡微生物岩结壳的生长之间经过了一段很长的时间（几千年）。微生物岩不能被认为是大约14,000年前导致现在90-110米深度范围内珊瑚礁框架消亡的溺水事件的一部分，但实际上更年轻。(c)2006 Elsevier B. V.保留所有权利。
In situ microbialites occurring in reef rocks dredged between 80 and 130 in water depth on the modern fore-reef slopes of Tahiti and the Marquesas islands yield ages ranging from 17,100 2900 to 4410 2250 years BP, suggesting that they played a prominent role during the last deglacial sea level rise.Microbialites developed in both shallow and deep water depositional environments where they characterize various zones of the reef tracts (reef crests, upper reef slopes, deep fore-reef slopes), reflecting contrasting scenarios of microbialite development involving ''reefal microbialites'' in shallow-water settings and ''slope microbialites'' that formed in environments deeper than 1020 in and extending down to more than 100 m.Reefal microbialites correspond to a late stage of encrustation of the dead parts of coral colonies, or more commonly, of related encrusting organisms (red algae and foraminifers), thus forming surface crusts. Slope microbialites generally form the ultimate stage of a biological succession indicating a deepening sequence, whereby shallow water corals and associated encrusting organisms are replaced by deeper water assemblages of red algae and foraminifers before microbialite growth. The precipitation of phosphatic-iron-manganese crusts and the deposition of planktonic micritic limestones on the microbialites characterize a deepening-upward sequence.The widespread development of microbialites in reef sequences from the Last Deglaciation characterizes a period of environmental degradation consequential oil the rapid sea-level rise and abrupt climatic changes of that time. The reported biological succession reflects changes in water quality, and especially an increase in nutrients. In shallow-water settings, increased alkalinity and nutrient availability in interstitial waters were related to surface fluxes and terrestrial groundwater seepage while slope environments were exposed to continuous upwelling of nutrient-rich deeper waters during the last deglacial sea level rise.The age differences between corals and overlying slope microbialites range from 1600 to 8400 years, based on high-precision U-series age measurements of both corals and microbialites, and indicates that a significant time (several thousand years) elapsed between the development of the coralgal frameworks and the growth of slope microbialite crusts. Microbialites cannot be considered as part of the drowning event some 14,000 years ago that resulted in the demise of reef frameworks in the 90-110 m present depth range, but are Substantially younger. (c) 2006 Elsevier B.V. All rights reserved.