Facies architecture and sequence-stratigraphic features of the Tumbiana Formation in the Pilbara Craton, northwestern Australia: Implications for depositional environments of oxygenic stromatolites during the Late Archean
Facies architecture and sequence-stratigraphic features of the Tumbiana Formation in the Pilbara Craton, northwestern Australia: Implications for depositional environments of oxygenic stromatolites during the Late Archean
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DOI：
10.1016/j.precamres.2005.05.008
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发表时间：
2005-08
影响因子：
3.8
通讯作者：
R. Sakurai;Makoto Ito;Y. Ueno;K. Kitajima;S. Maruyama
中科院分区：
文献类型：
--
作者：
R. Sakurai;Makoto Ito;Y. Ueno;K. Kitajima;S. Maruyama
Tumbiana Formation（Tumbiana Formation）2.7Ga）是澳大利亚西北部皮尔巴拉地区晚太古代地壳伸展的产物。该地层的特征是叠层石碳酸盐的夹层，并提供了光合生物进化的视角，这些生物被解释为负责早期地球表面环境的氧化。在这里，我们调查了叠层石碳酸盐岩的沉积环境，以更好地了解环境，这可能控制了产氧光合作用的大规模发展。在对陆上露头进行三维分析的基础上，研究了皮尔巴拉盆地北方南缘Redmont地区Tumbiana组的岩相和层序地层特征。Tumbiana组厚达170米，不整合地覆盖在早太古代至中太古代基底岩石之上，并不整合地被Maddina组覆盖，Maddina组由镁铁质凝灰质沉积物和玄武岩熔岩组成。Tumbiana组下部以平面和槽状交叉分层砾岩为特征，解释为从北方丘陵地脱落的冲积扇存款，主要发育于低水位晚期和海侵早期基底岩石的局部凹陷中。中部的基底由上覆砾岩和/或角砾岩的海侵侵蚀面确定，这些砾岩和角砾岩向上延伸至镁铁质凝灰质泥岩和砂岩，其间夹有增生的火山岩、角砾岩和玄武岩枕状熔岩。泥岩通常是层状的，砂岩包含水流和波浪纹纹层、平行纹层、丘状交错层理和槽状交错层理。一般来说，中部表现出一个整体的细化和粗化向上的模式，并解释为指示海进和海退陆棚到海岸岩相序列。特别是，中部的最上层以具有人字形结构和干燥裂缝的砂岩层为特征，并被解释为指示在后期高位和/或随后的下降阶段期间发育的潮间带存款。一般来说，地层的中部向北方近端区域增厚，并最终使基底岩石的地形不规则性变平。上部的特点是叠层石碳酸盐岩，与小泥岩和波和电流波纹砂岩，并没有表现出明显的横向变化的厚度和垂直岩相组织。上部基底以海侵滞留存款为特征。随后的海侵超过潮间沉积的中上部被解释为已经开发了一个新的容纳空间的叠层石的垂直堆叠与不同的外部形状从细长的小圆顶和圆柱型与干燥裂缝层状和大圆顶型。这些变化可能是由于古水深度的增加，可能是从潮间带到潮下带环境。总之，叠层石在上Tumbiana组在Redmont地区被解释为已开发在沿海和浅海环境中的相对海平面的上升，而不是在短暂的盐湖，如以前的研究所提出的。然而，本研究的结果并不一定否定先前提出的解释，但表明Tumbiana组的沉积环境从北到南的空间变化。
The Tumbiana Formation (ca. 2.7Ga) is a succession developed in response to Late Archean crustal extension in the Pilbara Craton, northwestern Australia. The formation is characterized by intercalations of stromatolitic carbonates and provides a perspective of the evolution of photosynthetic organisms, which are interpreted to have been responsible for the oxygenation of earth surface environments in early Earth. Here we investigated the depositional setting of the stromatolitic carbonates for the better understand of the environments, which may have controlled the massive development of oxygenic photosynthesis. We studied lithofacies and sequence-stratigraphic features of the Tumbiana Formation in the Redmont area, a southern margin of the northern Pilbara Craton, on the basis of three-dimensional analyses of onshore outcrops. The Tumbiana Formation, as much as 170m thick, unconformably overlies the Early to Middle Archean basement rocks and is unconformably overlain by the Maddina Formation that consists of mafic tuffaceous sediments and basalt lavas. The lower part of the Tumbiana Formation is characterized by planar- and trough cross-stratified conglomerates, which are interpreted to be an alluvial-fan deposit shed from the northern hinterlands and developed mainly in local depressions of the basement rocks during late lowstand and early transgressive stages. The base of the middle part is defined by a transgressive surface of erosion overlain by conglomerates and/or breccias that pass upward to mafic tuffaceous mudstones and sandstones intercalated with accretionary lapillis, breccias, and basalt pillow lavas. Mudstones are commonly laminated and sandstones contain current- and wave ripple-lamination, parallel lamination, hummocky cross-stratification, and trough cross-stratification. In general, the middle part exhibits an overall fining- and coarsening-upward pattern and is interpreted to indicate transgressive and regressive shelf-to-coastal lithofacies successions. In particular, the uppermost horizon of the middle part is characterized by sandstone beds with herringbone structures and desiccation cracks, and is interpreted to indicate an intertidal deposit developed during late highstand and/or following falling stages. The middle part of the formation, in general, thickens to the northern proximal area and eventually flattened out the topographic irregularity of the basement rocks. The upper part is characterized by stromatolitic carbonates, associated with minor mudstones and wave- and current-rippled sandstones, and does not exhibit distinct lateral variation in thickness and vertical lithofacies organization. The base of the upper part is characterized by a transgressive lag deposit. The ensuing transgression over the intertidal deposits of the uppermost middle part is interpreted to have developed a new accommodation space for the vertical stacking of stromatolites with different external shapes from elongated small-domal- and columnar-types associated with desiccation cracks to stratiform- and large domal-types. These changes may have responded to the increase in paleowater depth possibly from intertidal to subtidal environments. In conclusion, stromatolites in the upper Tumbiana Formation in the Redmont area are interpreted to have developed in coastal and shallow marine environments in response to the rise in relative sea level rather than in ephemeral saline lakes as proposed by previous studies. However, the outcome of the present research does not necessarily deny the previously proposed interpretation but suggests spatial variations in depositional environments of the Tumbiana Formation from the north to …