Origin of limestone/marl alterations in the upper Maastrichtian of Zumaya, Spain
Origin of limestone/marl alterations in the upper Maastrichtian of Zumaya, Spain
复制标题
西班牙祖马亚马斯特里赫特阶上部石灰岩/泥灰岩蚀变的起源
DOI：
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发表时间：
1986
期刊：
影响因子：
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通讯作者：
P. Ward
中科院分区：
文献类型：
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作者：
J. Mount;P. Ward
摘要在西班牙北方的Zumaya镇附近，上马斯特里赫特期地层由石灰岩/泥灰岩韵律和薄互层砂岩组成。泥灰岩和石灰岩主要是远洋和半远洋沉积，而砂岩是浊流的产物。泥灰岩和石灰岩体积的地层变化形成三个层次或复合旋回。一级旋回由石灰岩和泥灰岩互层组成的地层层序和几乎完全由泥灰岩组成的层序之间的20-30米的交替组成。在石灰岩/泥灰岩互层序列中，出现了由石灰岩或泥灰岩主导的5-10米交替组成的二级旋回。三级旋回由灰岩和泥灰岩逐层交替组成。这三个复合旋回是粘土-碳酸盐比值在不同岩石和时间地层尺度上变化的产物。为了确定旋回性是否是硅质岩物质或碳酸盐物质供应变化的结果，对每种岩性的体积百分比、平均层厚和地层频率进行了详细的地层测量。积差系数表明泥灰岩含量与砂岩频率呈负相关，灰岩含量与砂岩频率呈正相关。假设浊积岩沉积与石灰岩或泥灰岩沉积没有遗传关系，相关系数表明泥灰岩堆积过程中沉积速率增加。相关系数还表明，剖面中泥灰岩数量的增加是通过层增厚而不是泥灰岩层数量的增加来实现的。相反，石灰岩占主导地位的间隔是通过减少泥灰岩床厚度和增加泥灰岩和石灰岩床频率来实现的。这证实了泥灰岩为主的事件与沉积速率的增加有关的建议。从这个分析中，我们提出，硅质岩材料的流入的变化，而不是生产力或溶解的变化，导致生产的石灰岩/泥灰岩的节奏，以及在Zumaya部分看到的第一和第二阶周期。
ABSTRACT Near the town of Zumaya in northern Spain, upper Maastrichtian strata consist of limestone/marl rhythms with thin, interbedded sandstones. The marls and limestones are primarily pelagic and hemipelagic deposits, while the sandstones are the product of turbidity currents. Stratigraphic variations in the volume of marl and limestone form three hierarchical or composite cycles. The first-order cycles consist of 20-30-m alternations between stratal sequences consisting of interbedded limestone and marl, and sequences composed almost exclusively of marl. Within the interbedded limestone/marl sequences, second-order cycles occur that consist of 5-10-m alternations between limestone or marl domination. The third-order cycles consist of the bed-by-bed alternation of limestone and marl. These hree composite cycles are the product of shifts in the clay-carbonate ratio on various rock- and time-stratigraphic scales. In order to determine if the cyclicity was the result of changes in the supply of siliciclastic material or carbonate material, detailed stratigraphic measurements were made of volume percent, average bed thickness, and stratigraphic frequency for each lithology. Product-moment coefficients indicate that a negative correlation exists between percentage marl and sandstone frequency and a positive correlation exists between limestone percent and sandstone frequency. Assuming that turbidite deposition is not genetically related to limestone or marl deposition, the correlation coefficients suggest that there were increased sedimentation rates during marl accumulation. Correlation coefficients also showed that increases in amount of marl in a section occur through bed thickening rather tha the increased number of marl beds. In contrast, limestone-dominated intervals are achieved by reduction of marl-bed thickness and increases in marl and limestone bed frequency. This confirms the suggestion that marl-dominated episodes were associated with increases in the sedimentation rate. From this analysis, we propose that changes in the influx of siliciclastic material, and not changes in productivity or dissolution, led to the production of limestone/marl rhythms as well as the first- and second-order cycles seen in the Zumaya section.