Miocene Phosphogenesis and Depositional History of the Florida Platform: Implications for Changes in the Carbon Isotopic Composition of Seawater

佛罗里达中新世山楂群的初步研究 平台表明，磷酸化主要发生在 中新世早期至中中新世早期。 磷酸化的时间 似乎是同步的全球积极偏移的 海水碳同位素组成（δ 13C）。 初步 对佛罗里达东北部的山楂的研究表明， 这些沉积物富含磷块岩、白云石、二氧化硅， 其他矿物质表明强烈的上升流，但含有 少量有机碳或黄铁矿。 同位素光的埋藏 富有机质沉积碳，大陆边缘 中新世早期美国东南部的层序可能导致 全球海水中的Δ C增加。 多 改造和表生风化作用 中新世中期， 有机碳和成岩黄铁矿。 快速氧化 埋藏的有机碳导致海水的δ C 返回到其偏移前的值。 我们将测试这个 假设通过确定的机制和时机， 磷酸化，沉积物氧化的时间， 佛罗里达地台上的这些事件与全球 海平面的变化和三角洲C和三角洲O的变化 中新世的海水 该研究计划依赖于 综合地震层序地层学、沉积学、 矿物学和结构，元素和同位素组成， 磷块岩及其伴生矿物。 Sr同位素 山楂剖面的地层学将与 中新世δ C、δ O和Sr同位素地层学 西南太平洋的沉积物（DSDP Site 588）。

Previous studies of the Miocene Hawthorn Group of the Florida Platform indicate that phosphogenesis occurred primarily during the early to early middle Miocene. The timing of Phosphogenesis appears to be synchronous with a global positive excursion of the carbon isotopic composition (delta13C) of seawater. Preliminary examination of the Hawthorn in northeastern Florida shows that these sediments are rich in phosphorite, dolomite, silica and other minerals indicative of intense upwelling, but contain little organic carbon or pyrite. Burial of isotopically light carbon by deposition of organic-rich, continental margin sequences in the SE U.S. during the early Miocene likely resulted in a global increase in the delta C of seawater. Multiple reworking and supergene weathering from subaerial exposure after the middle middle Miocene oxidized and removed most of the organic carbon and diagenetic pyrite. Rapid oxidation of the buried organic carbon resulted in the delta C of seawater returning to its pre-excursion value. We will test this hypothesis by determining the mechanism and timing of phosphogenesis, the timing of sediment oxidation, and the relationship of these events on the Florida Platform to global sea-level changes and variations in the delta C and delta O of seawater during the Miocene. The research program relies on integrating the seismic sequence stratigraphy, sediment mineralogy and texture, and elemental and isotopic composition of the phosphorite and associate minerals. The Sr isotope stratigraphy of the Hawthorn sections will be compared to the delta C, delta O, and Sr isotope stratigraphy of the Miocene sediments from the southwest Pacific (DSDP Site 588).