Paleocology of Peruvian Mollusks Intended for the Studies ofAncient El Ninos

对南美上升流沿海生态系统的模拟必须考虑古代厄尔尼诺事件(全新世中期和早期、更新世和第三纪)的影响。这类事件可能在平均发生频率和/或强度上有所不同，也可能完全不存在。记录古代厄尔尼诺现象具有极其重要的意义，因为这类事件可能在以下方面发挥作用：(1)安第斯山脉和沿海海洋文明的文化发展；(2)第四纪沿海动物群的生物地理发展；(3)远洋生态系统的演变。已公布的古代厄尔尼诺事件的地质支持未能同时满足两个必要的标准：(1)与厄尔尼诺相关的离散事件的证据；(2)南美洲西海岸海洋变暖的证据。建议通过对秘鲁沿海广泛的软体动物记录应用生长增量和地球化学分析来满足这两个标准。1982-1983年厄尔尼诺事件以双壳类贝壳生长的形态、同位素和痕量元素模式编码，我们将应用这些技术研究秘鲁海岸从以下来源获得的古代软体动物：(1)后哥伦布时代的垃圾场，(2)前哥伦布时代的贝壳幼虫，(3)海侵陆架贝壳滞后，(4)海平面上升，(5)海相沉积岩。这将提供从历史时代到上新世的时间跨度。

Modelling of the South American upwelling coastal ecosystem must consider the impact of ancient El Nino events (Middle and Early Holocene, Pleistocene, and Tertiary). Such events may have varied in average frequency of occurrence and/or strength, or may have been absent altogether. Documentation of ancient El Ninos is of paramount significance because of the role such events may have played in (1) the cultural development of Andean and coastal maritime civilizations, (2) the biogeographic development of Quaternary littoral faunas, and (3) the evolution of the pelagic ecosystem. The published geological support for ancient El Nino events fails to simultaneously satisfy two requisite criteria: (1) evidence of discrete El Nino-associated events and (2) evidence of oceanic warming along the west coast of South America. It is proposed to satisfy both criteria by application of growth increment and geochemical analyses to the extensive molluscan record of coastal Peru. The 1982-1983 El Nino event was encoded in morphologic, isotopic, and trace elemental patterns of bivalve shell growth and we will apply these techniques to the study of ancient mollusks obtained form the following sources along the coast of Peru: (1) post-Columbian dump sites, (2) pre-Columbian shell middens, (3) transgressive shelf shell lags, (4) raised marine terraces, and (5) marine sedimentary rocks. This will provide a temporal span from historical times back to the Pliocene.