Taphonomy of Marsh Foraminiferal Assemblages: Implications for Rates and Mechanisms of Holocene Sea-Level Rise

9614155马丁/皮祖托在过去的十年里，应用地球科学已经从强调资源开发转向了资源保护和管理。为了让古生物学充分参与这一“范式转变”，主要强调信息损失和地层无序的挖掘学科学必须转而强调可以从化石记录中恢复什么。必须使用数据来重建地层信号，以便评估自然干扰与人为干扰。对分流滤器的准确理解对未来古生物学和其他传统地球科学领域在环境问题上的应用具有重要意义。沼泽为应用割草学提供了肥沃的试验田。沼泽环境极易受到自然和人为干扰，因此它们是利用历史(前人类)记录区分自然和人为变化的理想选择。沼泽还表现出接近或超过深海岩心的特殊的时间分辨率(低信号衰减)，这使它们成为挖掘模型的理想选择。然而，用于分析海平面上升的自然和人为原因的沼泽有孔虫组合的差异化保存在很大程度上被忽视了。然而，差异保存本身可以模拟实际没有发生过的海平面变化。我们建议建立描述特拉华州海岸易接近的全新世潮间带沼泽相有孔虫组合的壳体输入、保存和时间分辨率的挖掘-年龄-环境模型。然后，我们将测试我们的正向模型(Taphonomic Filters)，使用它们重建用于产生过滤器的相同输入。我们将进一步测试我们的模型，用它们重建保存在附近地点的振荡器中的最后~2ka的古环境，并评估其对区分自然和人为海平面上升的意义。我们将使用多种技术来约束沉积参数和基于这些参数的重建。测试的投入和衰减率(“半衰期”)影响有孔虫组合的丰度、保存、重新加工的概率和时间分辨率，将通过对选定的沼泽地点进行季节性采样来确定。混合层厚度(M)、沉降率(V)和生物扰动系数(D)将使用X射线和放射性示踪剂(7Be、137Cs、210Pb、14C)进行估算。使用人工保守的(非腐烂的)“脉冲”玻璃珠层(类似于类似深海研究中的微玻璃陨石层和火山灰层)的现场实验将独立于放射性示踪剂评估沉积参数。时间分辨率将通过对珠层和其他数据的分散(衰减或涂抹)应用包括图形相关在内的几种定量方法来检查。在试验生产和沉积中，花粉剖面将控制可能的人为变化(森林砍伐和径流造成的富营养化)。除了古生物学和地层学在环境科学中的作用，我们的研究还涉及一些关键的(古)环境问题，如：1)全新世海平面上升的幅度和速率的计算，它们与所提出的因果气候现象的速率和机制的相关性，以及对自然和人为海平面变化的区分；2)全新世的古环境分辨率低于现有的气候指标，如海洋氧同位素曲线；3)从全新世海侵的角度研究湿地的自然演变及其管理；4)准确理解地层剖面的完整性、时间平均和时间分辨率，最终关系到化石记录中的生物灭绝模式和生物多样性动态记录等深刻的古生物学问题。例如，对这些问题的回答对于理解过去(因此也是当前)的生物多样性危机至关重要，但它们依赖于非常高的时间分辨率。其他建模工作主要集中在深海组合和稳定同位素上，但由于3月组合固有的高时间分辨率，我们的研究为将定量的挖掘学模型应用于地层更复杂的陆架和斜坡环境提供了一个很好的起点，在那里形成了大部分化石记录。

9614155 Martin/Pizzuto Over the last decade, the applied Earth Sciences have moved from an emphasis on resource exploitation to one of resource conservation and management. In order for paleontology to fully participate in this "paradigm shift", the science of taphonomy, which has largely stressed information loss and stratigraphic disorder, must instead accentuate what can be regained from the fossil record. Data must be used to reconstruct stratigraphic signals in order to evaluate natural versus anthropogenic disturbances. Precise understanding of taphonomic filters bears strongly on the future application of paleontology and other traditional fields of the Earth sciences to environmental problems. Marshes provide a fertile proving ground for applied taphonomy. Marsh environments are extremely susceptible to natural and anthropogenic disturbance, so they are ideal for distinguishing between natural and anthropogenic change using historical (pre-anthropogenic) records. Marshes also display exceptional temporal resolution (low signal attenuation) that approaches or surpasses that of deep-sea cores, and which makes them ideal for taphonomic modeling. Nevertheless, differential preservation of marsh foraminiferal assemblages, which have been used to analyze natural and anthropogenic causes of sea-level rise, has been largely ignored. By itself, though, differential preservation can mimic sea-level change when none has actually occurred. We propose to construct taphonomic-age-environment models that describe shell input, preservation, and temporal resolution of foraminiferal assemblages in easily accessible intertidal Holocene marsh facies of the Delaware coast. We will then test our forward models (taphonomic filters) by using them to reconstruct the same inputs used to produce the filters. We will further test our models by using them to reconstruct paleoenvironments of the last ~2 ka preserved in vibracores taken from nearby sites, and assess the implications for distinguishin g natural versus anthropogenic sea-level rise. We will use multiple techniques to constrain sedimentary parameters and the reconstructions based on them. Inputs and decay rates of tests ("half-lives"), which affect the abundance, preservation, probability of reworking, and temporal resolution of foraminiferal assemblages, will be determined by seasonal sampling of selected marsh sites. Mixed layer thickness (m), sedimentation rate (v), and the bioturbation coefficient (D) will be estimated using x-rays and radiotracers (7Be, 137Cs, 210Pb, 14C). Field experiments involving artificial conservative (non-decaying) "impulse" layers of glass beads (analogous to microtektite and volcanic ash layers of similar deep-sea studies) will assess sedimentary parameters independently of radiotracers. Temporal resolution will be examined by applying several quantitative approaches, including graphic correlation, to dispersion (attenuation or smearing) of bead layers and other datums. Pollens profiles will control for possible anthropogenic changes (eutrophication due to deforestation and runoff) in test production and sedimentation. Besides the implications for the role of paleontology and stratigraphy in the environmental sciences, our investigation also bears on a number of critical (paleo) environmental issues, such as: 1) Calculation of the magnitude and rates of Holocene sea-level rise, their correlation with rates and mechanisms of proposed causal climatic phenomena, and distinguishing between natural and anthropogenic sea-level change; 2) Paleoenvironmental resolution in the Holocene below that of available climate proxies such as the marine oxygen isotope curve; 3) The natural evolution of wetlands and their management in light of the Holocene transgression; 4) Precise understanding of taphonomic filters an the integrity, time-averaging, and temporal resolution of stratigraphic sections, all of which ultimately bear on such profound paleobiological questions as patterns of extinction and the record of biodiversity dynamics in the fossil record. Answers to these questions are crucial to understanding, for example, past (and therefore current) biodiversity crises, but they are dependent upon very high temporal resolution. Other modeling efforts have concentrated on deep-sea assemblages and stable isotopes, but because of the intrinsically high temporal resolution of march assemblages, our study serves as an excellent starting point for applying quantitative taphonomic models to more stratigraphically-complex shelf and slope settings where much of the fossil record has formed.