Collaborative Research: Chronology of Epi-Classic Northwestern Mesoamerica

《外经》是中美洲史前最动荡的时期之一。主要是由于不精确的时间控制，它也是最不被理解的之一。在美国国家科学基金会的支持下，伊萨卡学院的保拉·图尔肯博士和康奈尔大学的斯特特·曼宁博士将使用“树状年代学-14C摆动匹配”方法开发出比以前可能的更高分辨率的年表。虽然该项目仅局限于中美洲的西北边界，但该地区与其他地区之间的紧密联系将使该项目能够提前确定整个中美洲文化变迁的年代。中美洲文化区最显著的向北扩展发生在古典晚期至公元古典时期。解释中美洲人民大规模迁入北部的理论包括中美洲核心地区的政治解体、这一干旱地区的气候变化以及剥削活动和贸易网络的发展。尽管近年来我们对这一地区的了解有了很大的进步，但文化影响的时间和方向性的指示依赖于14C年代，误差为±50-90年。该项目将同时解决年代学问题，并通过对马尔帕索山谷最北端地区之一的EPI-经典考古遗址的现有考古木材收藏采用“树状年代学-14C摆动匹配”方法，为检验气候变化理论奠定基础。摆动匹配法将具有已知年轮数量的树木年轮片段的14C日期拟合到14C校准曲线上，产生的日期比单独使用放射性碳测年要精确得多。对马尔帕索山谷考古木材的初步研究表明，即使是短的、不太理想的样本，也可以提高测年精度，从100年的范围到低至16年的范围。该项目是目前在中美洲应用树状年代学研究考古木材的唯一尝试。编制与西北边疆被占的时间相对应的精确年代的树木年轮年表还将能够外推可用水的变化，这可以在未来的项目中为解决气候变化理论奠定基础，作为对边疆相对于中美洲其他地区的短暂占领的解释。该项目将为墨西哥和美国的考古学家和树状年代学家提供一个论坛，为伊萨卡学院和康奈尔大学的本科生提供培训场所，并为墨西哥学生和研究人员提供培训机会，以探索考古树状年代学在中美洲的应用。研究人员在墨西哥的研讨会和大学讨论树轮年代测定和项目结果的优点的正式报告将扩大对现有项目和收藏品中合适材料的呼吁，并鼓励收集用于树轮分析的木材/木炭。这些数据将通过同行评议的期刊、会议报告、公开讲座传播，并在开放获取的数据库中提供。

The Epi-Classic is one of the most turbulent periods in Mesoamerican prehistory. Primarily due to imprecise chronological control, it is also one of the least understood. With National Science Foundation support, Dr. Paula Turkon (Ithaca College) and Dr. Sturt Manning (Cornell University) will use the "dendrochronology-14C wiggle-match" method to develop a much higher-resolution chronology than previously possible. Though narrowly focused on the northwestern frontier of Mesoamerica, the strong connections between this and other regions will allow this project to advance the dating of prehispanic cultural changes throughout MesoamericaThe most significant northward expansion of the Mesoamerican culture area occurred during the Late Classic to Epi-Classic Period. Theories to explain this mass movement of Mesoamerican peoples and their lifestyles into the north include political disintegration in the Mesoamerican core, climate change in this arid region, and the development of exploitive activities and trade networks. Though our understanding of this region has greatly advanced in recent years, indications of the timing and directionality of cultural influences rely on 14C dates with errors of ± 50-90 years. This project will simultaneously address the chronology issue, and set the stage to examine the climate change theory, by employing the "dendrochronology-14C wiggle-matching" method on existing collections of archaeological wood from Epi-Classic archaeological sites in the Malpaso Valley, one of the northernmost regions on the frontier. The wiggle-match method fits 14C dates from tree-ring segments with a known number of rings onto the 14C calibration curve, producing substantially more precise dates than radiocarbon dating alone. Preliminary work on archaeological wood from the Malpaso Valley demonstrates that even short, less-than-ideal samples, can refine dating precision from a 100 calendar year range to as low as a 16 year range.This project represents the only current attempt to apply dendrochronological work on archaeological wood in Mesoamerica. The development of precisely-dated, tree-ring chronologies for the period that corresponds to the prehispanic occupation of the northwestern frontier will also allow extrapolation of variation in water availability that can, in a future project, set the stage to address the climate change theory as an explanation for the frontier's short-lived occupation relative to other regions of Mesoamerica. This project will provide a forum for Mexican and U.S. archaeologists and dendrochronologists, a venue to train undergraduate students at Ithaca College and Cornell University, as well as provide training opportunities for Mexican students and researchers to explore the application of archaeological dendrochronology in Mesoamerica. Formal presentations by the researchers to discuss the merits of tree-ring dating and project results at workshops and universities in Mexico will both extend the call for suitable materials from existing projects and collections, and encourage the collection of wood/charcoal for tree-ring analysis. The data will be disseminated through peer-reviewed journals, conference presentations, public lectures, and be made available in open-access databases.