Paleoecology of Pennsylvanian phylloid algal buildups in south Guizhou, China
Paleoecology of Pennsylvanian phylloid algal buildups in south Guizhou, China
复制标题
DOI：
10.1007/s10347-007-0122-4
复制
发表时间：
2007-09
期刊：
影响因子：
1.8
通讯作者：
Gong Enpu;E. Samankassou;G. Chang-qing;Zhang Yongli;Sun Baoliang
中科院分区：
文献类型：
--
作者：
Gong Enpu;E. Samankassou;G. Chang-qing;Zhang Yongli;Sun Baoliang
在贵州南部，宾夕法尼亚叶状藻礁分布广泛且暴露良好。在这里，我们报告了2至8米厚度和30-50米横向延伸的珊瑚礁。藻类是主要的组成部分，其生长形式多种多样，但通常是cyathiform（杯状）和leaf- shaped（波状板状）。藻礁相以边界岩为主。藻体形成致密的地毯式结构，其框架孔隙中充满海相胶结物和球囊泥晶。肾盂基质致密，部分呈层状或凝块，表面不规则，常与重力对抗。贵州的藻礁不同于迄今为止报道的生物多样性高的例子，如藻类与珊瑚（其中一些是藻体的两倍大）和许多大型腕足动物的共生。这与之前的观点形成对比，即叶状藻类“草甸”主导了实际的海底，不包括其他生物群。此外，普遍存在的海洋水泥（高达50%），包括葡萄状水泥也值得注意。藻礁在台地边缘发育，这种沉积环境类似于爪哇、澳大利亚和巴哈马附近的现代哈利米德蒙德，也类似于加拿大北极群岛报道的时间相当的例子。尽管营养物似乎在海藻类礁的生长中起着决定性作用，但本文报道的藻类礁似乎是在低营养物水平的条件下生长的。总体而言，贵州的藻礁挑战了以往关于生长形式、多样性模式和沉积环境的观点，并增加了这些部分令人困惑的生物成因结构的光谱。
Pennsylvanian phylloid algal reefs are widespread and well exposed in south Guizhou, China. Here we report on reefs ranging from 2 to 8 m thickness and 30–50 m lateral extension. Algae, the main components, display a wide spectrum of growth forms, but are commonly cyathiform (cup-shaped) and leaf-like (undulate plates). The algal reef facies is dominated by boundstone. Algal thalli form a dense carpet whose framework pores are filled with marine cement and peloidal micrite. The peloidal matrix is dense, partly laminated or clotted with irregular surfaces and often gravity defying. Algal reefs in Guizhou differ from examples reported to date by the high biodiversity of organisms other than phylloids: e.g., the intergrowth of algae with corals (some of which are twice the size of algal thalli) and numerous large brachiopods. This contrasts to previous views that phylloid algal “meadows” dominated the actual seafloor, excluding other biota. Also, the pervasive marine cements (up to 50%) including botryoidal cement are noteworthy. Algal reefs developed at platform margins, a depositional environment similar to that of modernHalimedamounds in Java, Australia and off Bahamas, and to that of time-equivalent examples reported from the Canadian Arctic Archipelago. Whereas nutrients appear decisive in the growth ofHalimedareefs, algal reefs reported herein seemingly grew under conditions of low nutrient levels. Overall, algal reefs in Guizhou challenge previous views on growth forms, diversity patterns, and depositional environments and add to the spectrum of these partly puzzling biogenic structures.