TIME-AVERAGING AND STRATIGRAPHIC RESOLUTION IN DEATH ASSEMBLAGES AND HOLOCENE DEPOSITS: SYDNEY HARBOUR'S MOLLUSCAN RECORD
TIME-AVERAGING AND STRATIGRAPHIC RESOLUTION IN DEATH ASSEMBLAGES AND HOLOCENE DEPOSITS: SYDNEY HARBOUR'S MOLLUSCAN RECORD
复制标题
死亡组合和全新世沉积物的时间平均和地层分辨率：悉尼港的软体动物记录
DOI：
10.2110/palo.2015.087
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发表时间：
2016
期刊：
影响因子：
1.6
通讯作者：
Katherine E. Whitacre
中科院分区：
文献类型：
--
作者：
J. G. Domínguez;M. Kosnik;A. P. Allen;Q. Hua;DORRIT E. JACOB;D. Kaufman;Katherine E. Whitacre
摘要：时间平均已经从古生态分析中一个未被认识的变量发展成为理解沉积系统动力学和化石矿床形成的关键概念。在这里，我们使用放射性碳校准的氨基酸外消旋年龄从173 Fulvia tenuicostata壳收集悉尼港（澳大利亚新南威尔士州），以量化的时间平均在surprise和挖掘的死亡组合。提出了一种新的方法来估计总的年龄估计变异的标本集，集成的年龄估计误差与AAR校准模型和时间平均变异的年龄分布的影响。从一个单一的1.6米深的挖掘收集的Fulvia被用来量化的时间平均与埋深的变化。从六个地点的死亡聚集体中收集的Fulvia被用来量化时间平均的空间变化。随着埋藏深度的增加，中位壳龄从150年增加到4230年，时间平均从440年增加到960年。四个地点的表层贝壳组合的中位年龄为150年，平均时间为140年，两个地点的死亡组合的中位年龄更大，平均时间> 1900年。在后殖民时期的Fulvia丰富的下降可能是负责非常年轻的壳在表面死亡组合的稀有性，而当地的因素，如疏浚和其他人类活动可能是负责总的年龄估计的变化，在两个高度时间平均的表面集合。这些分析提供了一个地质年代背景下，评估殖民化以来港口的底栖生物群落的生态变化，并提供了一个重要的观点全新世化石沉积的形成。
Abstract: Time-averaging has evolved from an unrecognized variable in paleoecological analyses to a key concept in understanding the dynamics of sedimentary systems and the formation of fossil deposits. Here we used radiocarbon-calibrated amino acid racemization ages from 173 Fulvia tenuicostata shells collected from Sydney Harbour (NSW, Australia) to quantify time-averaging in surficial and excavated death assemblages. A novel approach to estimating the total age-estimate variability of a collection of specimens is presented that integrates the age-estimation error associated with the AAR calibration model and the effect of time-averaging variability on the age distribution. Fulvia collected from a single 1.6-m deep excavation were used to quantify changes in time-averaging with burial depth. Fulvia collected from surficial death assemblages at six sites were used to quantify spatial variation in time-averaging. The median shell age increased from ∼ 150 yr to ∼ 4230 yr and time-averaging from ∼ 40 yr to ∼ 960 yr with increased burial depth. While four sites contained surface shell assemblages with median ages of ∼ 150 yr and time-averaging of ∼ 40 yr, two sites had death assemblages with older median ages and time-averaging > 1900 yr. A decline in the abundance of Fulvia in the post-colonial period is likely responsible for the rarity of very young shells in the surface death assemblages, while local factors such as dredging and other human activities are likely responsible for the total age-estimate variability in the two highly time-averaged surface collections. These analyses provide a geochronological context for assessing ecological changes in the harbor's benthic communities since colonization and offer an important perspective on the formation of Holocene fossil deposits.