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>Carbonate Sedimentation Rates Today and in the Past: Holocene of Florida Bay, Bahamas, and Bermuda vs. Upper Jurassic and Lower Cretaceous of the Jura Mountains (Switzerland and France)
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Carbonate Sedimentation Rates Today and in the Past: Holocene of Florida Bay, Bahamas, and Bermuda vs. Upper Jurassic and Lower Cretaceous of the Jura Mountains (Switzerland and France)
Lagoonal to intertidal sediments from the Holocene in Florida Bay, on the Bahamas, and in Bermuda are compared to similar facies in the Kimmeridgian and Berriasian of the Swiss and French Jura Mountains. Dating by 14C permits the estimation of sediment accumulation rates in the Holocene. In the ancient outcrops, the timing is given by cyclostratigraphic analysis. Elementary depositional sequences formed in tune with the 20-ka precession cycle, although much of this time may have been spent in non-deposition and/or erosion. After decompaction of the ancient sequences, their accumulation rates can be evaluated. It is suggested that the studied Holocene sediments accumulated over the past 6000 years with rates of 0.3 to 3 mm/a, whereas the Kimmeridgian and Berriasian facies show somewhat lower rates of 0.07 to 0.6 mm/a. This difference may be due to methodological errors, but also to variable carbonate production. In shallow carbonate systems, much of the sediment produced may be redistributed over the platform or exported. Furthermore, basin morphology and currents can strongly influence facies and thickness of the accumulated sediment. Finally, the accumulated sediment may suffer further erosion before it is preserved in the sedimentary record. Consequently, when estimating sedimentation rates in ancient sequences, it is important to do this with the highest time resolution possible, and only after having decompacted the sediment and evaluated the time lost in hiatuses or condensed intervals.
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机译：比较了佛罗里达湾，巴哈马群岛和百慕大的全新世的泻湖至潮间带沉积物，并将其与瑞士和法国侏罗山的基米底亚纪和贝里亚斯时期的类似相进行了比较。通过14C进行约会可以估算全新世的沉积物积累速率。在古代露头中，时间是通过旋回地层学分析给出的。基本的沉积序列与20 ka的岁差周期一致，尽管大部分时间可能都花在了非沉积和/或侵蚀上。对古代序列进行解压缩后，可以评估其累积速率。建议研究的全新世沉积物在过去的6000年中以0.3至3 mm / a的速率积累，而基米底尔纪和贝里亚斯相的沉积率较低，为0.07至0.6 mm / a。这种差异可能是由于方法学上的错误，也可能是由于碳酸盐的产量不同。在浅碳酸盐系统中，产生的大部分沉积物可能会重新分布在平台上或输出。此外，盆地的形态和水流可以强烈影响沉积物的相和厚度。最后，积累的沉积物在保存到沉积记录中之前可能会遭受进一步的侵蚀。因此，在估算古代序列的沉积速率时，重要的是要以尽可能高的时间分辨率来完成此操作，并且只有在对沉积物进行压实之后，并评估在中断或压缩间隔中损失的时间。
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