Diagenesis of growth bands in fossil scleractinian corals: identification and modes of preservation
Diagenesis of growth bands in fossil scleractinian corals: identification and modes of preservation
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石珊瑚生长带的成岩作用：识别和保存模式
DOI：
10.1007/s10347-005-0064-7
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发表时间：
2005
期刊：
影响因子：
1.8
通讯作者：
K. Kroeger
中科院分区：
文献类型：
--
作者：
M. Reuter;T. Brachert;K. Kroeger
在完全重结晶的化石造礁珊瑚的光和暗带通常被解释为代表的年增长增量反映了光共生的生活方式，在古生态学意义深远的解释。在本文中，我们描述了一个完美的（文石和微观结构保留）和完全重结晶（亮晶方解石镶嵌）保存风格的晚中新世（克里特岛，希腊）沉积物中的殖民地珊瑚滨珊瑚的年度生长带。过渡性沉积阶段的连续谱分析表明，在中新世滨岩保存的生长带控制的优先溶解的高密度带与淡水成岩作用/浅埋成岩作用期间的晶簇方解石晶石胶结。海洋沉淀物（球状镁方解石）优先积累沿着tabulate dissepiments产生额外的增长节奏。块状滨珊瑚的年生长率为4.0 mm，而在分枝状滨珊瑚中，一个明显的条带是由海洋微粒状胶结物沿着间隔为1.8 mm的浓度形成的。如果作为年生长增量，这些波段代表非常低的扩展速率，然而，它们可能更确切地反映了次年度强迫函数（即，月球周期）。一个相同的方案沉淀和浓度的粒状碳酸盐沿着dissepiments和溶解控制的文件的生长带可以推断晚侏罗世microsolenids。因此，化石珊瑚的生长条带可能反映了月和年的周期。因此，在古生态学和古气候学中使用珊瑚生长带时必须小心。
Light and dark bands in fully recrystallized fossil hermatypic corals are generally interpreted to represent annual growth increments reflecting a photosymbiotic life style—an interpretation of far reaching significance in palaeoecology. In this paper we describe annual growth bands in the colonial coral Porites in a perfect (aragonite and microstructures retained) and fully recrystallized (sparry calcite mosaic) style of preservation from sediments of Late Miocene age (Crete, Greece). Analysis of a continuous spectrum of transitional preservational stages shows that in Miocene Porites preservation of the growth banding was controlled by preferential dissolution of the high-density band associated with cementation by drusy calcite spar during freshwater diagenesis/shallow burial diagenesis. Marine precipitates (pelletoidal Mg-calcite) preferentially accumulated along tabulate dissepiments producing an additional growth rhythmicity. Massive Porites had annual growth rates of ∼4.0 mm, whereas in ramose branching Porites, a conspicuous banding is formed by concentrations of marine micropelletoidal cement along dissepiments at ∼1.8 mm spacing. If taken as annual growth increments, these bands represent very low extension rates, however, they may rather reflect subannual forcing functions (i.e., lunar cycles). An identical scenario of precipitation and concentration of pelletoidal carbonate along dissepiments and dissolution-controlled documentation of growth bands can be inferred for Late Jurassic microsolenids. Therefore, growth bandings in fossil corals potentially reflect both, monthly and annual cycles. Consequently, care must be taken when using coral growth bands in palaeoecology and palaeoclimatology.