Time-scale uncertainty of abrupt events in the geologic record arising from unsteady sedimentation
Time-scale uncertainty of abrupt events in the geologic record arising from unsteady sedimentation
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DOI：
10.1130/g35783.1
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发表时间：
2014-10-01
期刊：
影响因子：
5.8
通讯作者：
Sexton, Philip F.
中科院分区：
文献类型：
--
作者：
Kemp, David B.;Sexton, Philip F.
确定地层记录中突变事件的时间尺度是高分辨率古气候分析的主要目标。这一奋进中的一个重大障碍是突然的，即，千禧年和亚千禧年，由于在事件规模上通常缺乏高精度的年龄控制，深时事件很少能在时间上精确地约束。相反，突发事件的持续时间通常经由年龄控制点之间的时间的线性划分来估计（例如，使用天文周期或辐射测定日期定义），包括事件并跨越更长的时间间隔。这种方法的缺点是，沉积是一个不稳定的过程，并不随时间线性进行。在这里，一个数值模型，参数化的地质数据，是用来量化的理论时间尺度的不确定性，导致不稳定的沉积。这项工作表明，假设千年事件的持续时间估计通过线性分区的方法可能是显着的错误，即使在完整的，天文校准和unbioturbated继承最适合于研究突然的古气候变化。在这项研究中建立的不确定性在很大程度上是一个函数的精确的统计特性的沉积过程中，属性是难以约束的经验，特别是在短时间跨度。然而，这项研究说明了如何不稳定沉积设置一个重要的限制，可达到的时间分辨率的地层记录，从而影响准确地定义的速率和持续时间的快速事件在地球历史上。
Defining the time scale of abrupt events in the stratigraphic record is a primary goal of high-resolution paleoclimate analysis. A significant hurdle in this endeavor is that abrupt, i.e., millennial and submillennial, events in deep time can rarely be temporally constrained accurately owing to the typical absence of high-precision age control at the scale of the events. Instead, the duration of abrupt events is commonly estimated via the linear partitioning of time between age control points (e.g., defined using astronomical cycles or radiometric dates) that bracket the event and span longer time intervals. The flaw with this approach is that sedimentation is an unsteady process and does not proceed linearly with time. Here a numerical model, parameterized by geologic data, is used to quantify theoretical time-scale uncertainties that result from unsteady sedimentation. This work demonstrates that the duration of assumed millennial events estimated via a linear partitioning approach may be significantly in error, even in complete, astronomically calibrated and unbioturbated successions best suited to the study of abrupt paleoclimate change. The uncertainties established in this study are largely a function of the precise statistical properties of the sedimentation process, properties that are difficult to constrain empirically, particularly over short time spans. Nevertheless, this study illustrates how unsteady sedimentation sets an important limit on the attainable temporal resolution of the stratigraphic record, with consequent implications for defining accurately the rates and durations of rapid events in Earth history.