Taphonomic Tiering: Preservational Constraints on Micro- and Macrofauna

埋藏学分层：微型和大型动物群的保护限制

• 批准号: 9628221
• 负责人: Sally Walker
• 金额: $ 14万
• 依托单位: University of Georgia Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-01 至 2000-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9628221&HistoricalAwards=false
• 关键词: Taphonomic; Tiering; Preservational; Constraints; Micro

Walker 9628221 Preservation and destruction of marine carbonate systems (e.g., hardgrounds, shells, reefs, foraminiferan tests) has figured prominently in the paleontological and sedimentological literature from the preservation of shelly hardparts thorough time to destruction by various physical and biological processes. This area of research , carbonate production and destruction, is gaining more momentum in ecological and environmental fields, and in conjunction with paleontologists, will provide information on global carbon budgets both in modern environments and for the past. A review of the pertinent literature in experimental field taphonomy from benthic marine systems focusing on two important carbonate producers (mollusca and foraminifera), revealed that most taphonomic work on these important organisms primarily concerns the processes that affect preservation at the sediment/water interface, and rarely are processes examined which happen below the sediment-water interface and deeper, within the sediments. At this interface and within the sediments, skeletal hardparts are presumably degraded and recycled or preserved. Little is known about the rate of degradation on micro- and macroorganisms that inhabit these sediments. This proposal directly addresses the need for experimental work and a reevaluation of the previously estimated carbonate retention rates of skeletal hardparts in shallow, siliciclastic settings. This proposed research provides methods to address retention rates at varying depths within the sediments for molluscan shells, calcareous and agglutinated foraminifera and crustacean exoskeletons. Additionally, little is known about how these hardparts are preserved or degraded in varying geochemical milieus. Emphasizing experimental field work and porewater geochemistry, this proposed 3-year study will evaluate skeletal retention rates and preservational signatures of molluscan shells, crustacean exoskeletons, and tests of both calcareous and agglutinated foramin ifera within the "taphonomically active zone" or TAZ, of selected depositional settings of coastal Georgia. Taphonomic gradients will be examined in conjunction with porewater analyses from the sediment surface to a depth of one meter to assess preservation stratification or "taphonomic tiering." Goals of this proposed research are 1) document taphonomic gradients of skeletal preservation with increasing burial depths in the sediments, across different siliciclastic environments within coastal and estuarine settings. Importantly, we will study how the different geomicrobial zones (using porewater chemistry analyses) within the sediments affect preservation of skeletal hardparts; 2) assess taphonomic characteristics across salinity gradients at different localities and depths within the sediments; 3) assess scale dependency, with regard to size, of taphonomic rates of degradation or preservation between foraminiferans and molluscs; 4) determine the effects of shell/test microstructure and mineralogy on preservation at different burial depths in these depositional settings; and 5) test our modern findings with a subfossil deposit to determine if geomicrobial signatures are retained on shells or forams in subfossil and fossil estuarine environments in light of the modern studies. Experimental data on invertebrate and protist retention rates would greatly enhance paleoecological studies on associations from comparable settings preserved in the rock record.

步行者9628221 海洋碳酸盐系统的保存和破坏（例如，硬地、贝壳、珊瑚礁、有孔虫测试）在古生物学和沉积学文献中占有突出地位，从贝壳硬部分的保存到各种物理和生物过程的破坏。 这一研究领域，碳酸盐的生产和破坏，在生态和环境领域正在获得更多的动力，并与古生物学家一起，将提供现代环境和过去全球碳预算的信息。 一个有关文献的审查，在实验现场埋藏从海底海洋系统的重点是两个重要的碳酸盐生产者（软体动物和有孔虫），揭示了大多数埋藏这些重要的生物的工作主要涉及的过程，影响保存在沉积物/水界面，很少被检查的过程发生在沉积物-水界面以下和更深的沉积物内。 在这个界面和沉积物内，骨骼硬部件可能会降解和回收或保存。 对栖息在这些沉积物中的微生物和大型生物的降解速度知之甚少。 该提案直接解决了实验工作的需要，并重新评估了之前估计的浅层硅质碎屑环境中骨骼硬部的碳酸盐保留率。 这项拟议的研究提供了方法，以解决保留率在不同深度的沉积物内的软体动物壳，钙质和凝集有孔虫和甲壳类动物外骨骼。 此外，很少有人知道这些硬部件是如何保存或降解在不同的地球化学环境。 强调实验性实地工作和孔隙水地球化学，这项拟议的3年研究将评估骨骼保留率和软体动物壳，甲壳类动物外骨骼，并在“taphonomically活跃区”或TAZ，选定的沉积设置沿海格鲁吉亚的钙质和凝集有孔虫的测试和识别标志。 将结合从沉积物表面到一米深度的孔隙水分析来检查埋藏梯度，以评估保存分层或“埋藏分层”。" 本研究的目标是：1）记录在海岸和河口环境中不同的硅质沉积环境中，随着沉积物埋藏深度的增加，骨骼保存的埋藏梯度。 重要的是，我们将研究不同的地质微生物区（利用孔隙水化学分析）影响骨骼硬部的保存; 2）评估沉积物内不同地点和深度的盐度梯度的埋藏特征; 3）评估有孔虫和软体动物之间埋藏退化或保存速率的尺度依赖性; 4）确定这些沉积环境中不同埋藏深度下贝壳/测试微结构和矿物学对保存的影响; 5）根据现代研究，用亚化石存款测试我们的现代发现，以确定亚化石和化石河口环境中的贝壳或有孔虫上是否保留了地质微生物特征。 无脊椎动物和原生动物保留率的实验数据将大大提高古生态学研究的协会从岩石记录中保存的可比设置。