Strontium isotope stratigraphy for Late Cretaceous time: Direct numerical calibration of the Sr isotope curve based on the US Western Interior
Strontium isotope stratigraphy for Late Cretaceous time: Direct numerical calibration of the Sr isotope curve based on the US Western Interior
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DOI：
10.1016/0031-0182(94)90024-8
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发表时间：
1994-03
期刊：
影响因子：
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通讯作者：
J. McArthur;W. Kennedy;M. Chen;M. Thirlwall;A. Gale
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文献类型：
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作者：
J. McArthur;W. Kennedy;M. Chen;M. Thirlwall;A. Gale
美国西部内陆海道上白垩统碳酸盐巨化石中Sr的87 Sr/86 Sr比值提供了一条晚白垩世（Cenomanian-Early Maastrichtian）的Sr同位素曲线。该曲线是校准生物地层学对最精细的菊石分带已知的时间间隔，和校准数字与39 Ar/40 Ar年龄的20个菊石序列。Marine 87 Sr/86 Sr从中赛诺曼晚期的0.70743下降到晚白垩世晚期Turonian（89 Ma）的最低值0.70730。从最小值开始，87 Sr/86 Sr通过中坎帕尼亚期的一个小周期（最小值在77 Ma，最大值在78-80 Ma）增加，在坎帕尼亚期/马斯特里赫特期边界达到0.70772。此后，87 Sr/86 Sr在最晚的早马斯特里赫特期经过一个很短的时间增加到我们在最早的晚马斯特里赫特期取样的极限。事件子提供用于关联的全局事件标记。对于我们的曲线所覆盖的大部分时期，用我们的2s.d.测量精度为±18 × 10−6。我们的87 Sr/86 Sr数据显示，没有证据表明已受到淡水流入美国西部内陆航道从河流，包括那些排水塞维尔造山带。
The87Sr/86Sr of Sr in macrofossil carbonate from Upper Cretaceous strata deposited in the Western Interior Seaway, USA, provides a Sr-isotope curve for Late Cretaceous time (Cenomanian-Early Maastrichtian). The curve is calibrated biostratigraphically against the most refined ammonite zonation known for the interval, and calibrated numerically with39Ar/40Ar dates for 20 bentonites within the sequence. Marine87Sr/86Sr decreased from 0.70743 in the late Middle Cenomanian to a Late Cretaceous minimum of 0.70730 in the Late Turonian (89 Ma). From the minimum,87Sr/86Sr increased through a Middle Campanian inflexion (minimum at 77 Ma, maximum at 78–80 Ma) to reach 0.70772 at the Campanian/Maastrichtian boundary. Thereafter87Sr/86Sr increased through a very short inflexion in the latest Early Maastrichtian to the limit of our sampling in the earliest Late Maastrichtian. The inflexions provide global event markers for correlation. For most of the period covered by our curve resolution in dating and correlation of ⩽0.8 Ma should be achievable with our 2 s.d. precision in measurement of ±18 × 10−6. Our87Sr/86Sr data show no evidence of having been affected by influxes of freshwater into the US Western Interior Seaway from rivers, including those that drained the Sevier Orogenic Belt.