Application of carbon isotope stratigraphy to dating the Baltic Silurian rocks
Application of carbon isotope stratigraphy to dating the Baltic Silurian rocks
复制标题
碳同位素地层学在波罗的海志留纪岩石定年中的应用
作者：
D. Kaljo;T. Martma
碳同位素漂移作为地层对比工具的潜力已经被早期的一些研究证明，但部分模糊的生物地层定义阻碍了它们的使用。在波罗的海志留纪建立了6个正碳同位素偏移（前4个在东波罗的海）：早Aeronian偏移（峰值δ13C值达到+3.7‰）；早期特利基亚偏移（+2.7‰）；沈木淀早期偏移（+5.2‰）；荷马中晚期双峰偏移（+4.6‰）；显生宙偏移最显著的是晚戈尔斯特偏移（+1.1‰，在哥特兰）和中期卢德福尔偏移（最大值在东波罗的海+8.2‰，在斯堪尼亚+11.2‰）。本文讨论并完善了温洛克和勒德洛三次短途（舍伍德纪早期、中晚荷马纪和勒德福德纪中期）的生物地层定年，尽管存在一些小问题，但它们可以成功地作为地质对比和年代地层标志的工具。以中卢德福期移位为标志，认为哥特兰的Hamra-Sundre段上部与爱沙尼亚的Kuressaare期下部相对应。
Abstract The potential of carbon isotope excursions as a stratigraphic correlation tool has been proved by several earlier studies, but partly indistinct biostratigraphic definition hinders their usage. Six positive carbon isotope excursions have been established in the Baltic Silurian (values of the first four in the East Baltic): the early Aeronian excursion (peak δ13C values reach +3.7‰); the early Telychian excursion (+2.7‰); the early Sheinwoodian excursion (+5.2‰); the middle to late Homerian double-peaked excursion (+4.6‰); the late Gorstian excursion (+1.1‰, in Gotland) and the middle Ludfordian excursion—the most prominent shift in the Phanerozoic (maximum values reach in the East Baltic +8.2‰, in Scania +11.2‰).The biostratigraphic dating of three Wenlock and Ludlow excursions (the early Sheinwoodian, mid to late Homerian and mid-Ludfordian) is discussed and refined in the paper and despite minor problems, these could successfully serve as a tool for geological correlation and as chronostratigraphic markers. Using the mid-Ludfordian shift as a marker, it is suggested that the upper part of the Hamra-Sundre interval on Gotland correlate with the lower part of the Kuressaare Stage in Estonia.