Response of a late Miocene Mediterranean reef platform to high-frequency eustasy
Response of a late Miocene Mediterranean reef platform to high-frequency eustasy
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中新世晚期地中海礁台对高频海平面的响应
DOI：
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
W. Ward
中科院分区：
文献类型：
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作者：
L. Pomar;W. Ward
马略卡岛中新统上礁杂岩是一个三级沉积层序，显示了碳酸盐沉积对高频海平面旋回的响应。该珊瑚礁复合体呈现分形结构，由四阶到七阶的高频单元分层堆叠而成。构造单元是以不整合面为界的s型单元，而不是准层序。这些“sigmods”被堆叠在“sigmoids的集合”中，这些集合被堆叠在“coset”中，而这些，反过来，被堆叠在“coset的集合”中。所有这些增生单元都具有沉积层序特征，但与埃克森开发的模式和其他碳酸盐岩层序地层模式不同。这些偏离是由于与海平面波动有关的碳酸盐产量变化造成的，海平面波动决定了在没有明显下沉的情况下可容纳性的变化。这些高频序列由四个系统域组成：(1)在海平面上升旋回早期形成的低水位体系域，由向盆地方向变薄的进积礁到开陆架相组成；(2)在海平面上升期间形成的加积体系域，由厚泻湖到开陆架相组成，但没有相向陆地移动；(3)形成于海平面旋回高段的高水位体系域，由进积礁相到开陆架相组成，向盆地方向变薄，湖床变薄或不存在；(4)形成于海平面下降期的复盖体系域，由薄的下覆礁相组成，向封闭的开陆架段过渡，与台地顶部的侵蚀面相关。两个体系域之间的岩相变化可以识别出两个边界面：复叠体系域顶部的侵蚀面和复叠体系域底部的下覆面。两个表面向内合并成一个浓缩的部分。层序边界对应于海平面旋回的最低点，是向陆方向的侵蚀面，在相关的盆地内的凝聚剖面内。
The upper Miocene reef complex of Mallorca, a third-order depositional sequence, shows how carbonate deposition responds to high-frequency sea-level cycles. This reef complex displays a fractal architecture of hierarchically stacked high-frequency units from fourth to seventh order. The building blocks are sigmoidal units bounded by unconformities, not parasequences. These "sigmodds" are stacked in "sets of sigmoids," the sets are stacked in "cosets," and these, in turn, are stacked in "sets of cosets." All these accretionary units have characteristics of depositional sequences but differ from the model developed by Exxon and from other carbonate sequence-stratigraphy models. These departures result from changes in carbonate production in relation to sea-level fluctuations, which determined the changes in accommodation in the absence of significant subsidence. All these high-frequency sequences are composed of four systems tracts: (1) a lowstand systems tract formed during the early rise of a sea-level cycle and composed of progradational reef to open-shelf facies thinning toward the basin, (2) an aggrading systems tract formed during sea-level rise and composed of thick lagoon to open-shelf deposits without landward shift of facies, (3) a highstand systems tract formed during the high part of a sea-level cycle and composed of progradational reef to open-shelf facies thinning toward the basin with lagoon beds thin or absent, and (4) an offlapping systems tract formed during sea-level fall and composed of thin downlapping reef facies passing into a condensed open-shelf section, which correlates with an erosion surface on the platform top. Two bounding surfaces can be recognized by lithofacies changes between these systems tracts: the erosion surface on top of the offlapping systems tract and the downlap surface at its base. Both surfaces merge basinward into a condensed section. The sequence boundary, which corresponds to the lowest point of the sea-level cycle, is the erosion surface landward and within the correlative condensed section basinward.