ACCOMPLISHMENT-BASED RENEWAL: Spatial, Temporal and Environmental Resolution of Shelly Assemblages

基于成就的更新：雪莱组合的空间、时间和环境分辨率

• 批准号: 9805165
• 负责人: Karl Flessa
• 金额: $ 24.41万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 2002-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9805165&HistoricalAwards=false
• 关键词: ACCOMPLISHMENT; BASED; RENEWAL; Spatial; Temporal

9805165FlessaWork will continue on assessing the quality of the biotic and environmental information that can be preserved in the fossil record. Research will focus on a field area that has proven an especially productive "natural laboratory": the northern Gulf of California. Paleoecological and geochemical approaches will be developed to: (1) Estimate changes in productivity. Changes in productivity will be estimated through the analysis of changes in growth rates and carbon isotope composition in bivalve mollusk shells. Shells dated from before the diminution of the Colorado River's flow (in about 1935) are expected to reflect the higher productivity of the northern Gulf of California that resulted from the river's input of nutrients. Such techniques may be applicable to other areas and to pre-Holocene coastal environments. (2) Establish guidelines for restoration of habitats altered by human activity. Diminution of the River's flow has altered the Delta's salinity, sediments, and fauna. The living shelly fauna will be compared to the shelly remains to document the faunal changes. One species, the bivalve Mulinia coloradoensis is now confined to a relict population in the River's mouth, whereas it formerly occurred in great abundance throughout the Delta. Analysis of oxygen isotopes from dated shells of this species may indicate the minimum influx of river water needed to restore populations of this and its associated species. This technique may be of use in other coastal habitats altered by human activity. (3) Reconstruct the paleohydrology of the Colorado River. Oxygen isotope variation will be used to document the variation in the discharge of the Colorado River during the past 2,000 years. Use of stable isotopes from dated Mulinia coloradoensis shells will permit an independent estimate of river discharge in close proximity to the river's mouth, where other species are rare. Techniques developed for estimating the Colorado's paleohydrology may be used in other settings to provide proxy estimates of virgin river flow during the late Holocene.

9805165 fleessawork将继续评估化石记录中可保存的生物和环境信息的质量。研究将集中在一个已被证明是特别多产的“自然实验室”的地区：加利福尼亚湾北部。将发展古生态和地球化学方法，以便：(1)估计生产力的变化。生产力的变化将通过分析双壳类软体动物壳的生长速率和碳同位素组成的变化来估计。在科罗拉多河流量减少之前（大约1935年）的贝壳被认为反映了加利福尼亚湾北部更高的生产力，这是由于河流的营养输入造成的。这些技术可能适用于其他地区和全新世以前的沿海环境。(2)为恢复受人类活动改变的生境制定准则。河流流量的减少改变了三角洲的盐度、沉积物和动物群。活的shelly动物群将与shelly遗骸进行比较，以记录动物群的变化。其中一种，双壳类的科罗拉多Mulinia coladoensis现在只局限于河口的一个残馀种群，而它以前在整个三角洲都大量存在。对这一物种过时贝壳的氧同位素分析可能表明，恢复这一物种及其伴生物种种群所需的最小河水流入。这项技术可用于其他因人类活动而改变的沿海生境。(3)重建科罗拉多河的古水文。氧同位素变化将被用来记录科罗拉多河在过去2000年的流量变化。利用从年代久远的科罗拉多木螺壳中提取的稳定同位素，可以对河口附近的河流流量进行独立估计，而其他物种在河口附近非常罕见。为估算科罗拉多河的古水文而开发的技术可用于其他环境，以提供全新世晚期原始河流流量的代理估算。