Collaborative Research: The Extension of a Dendrochronological Sequence to northern Mexico

Paula Turkon、Sturt Manning和Carol Griggs博士将与墨西哥的同事沿着进行研究，利用树木年轮和AMS放射性碳数据的组合，为北方中美洲考古遗址提供高分辨率的绝对树木年轮年表。 该项目在地理和年代学上扩展了他们的初步研究，目标是将现有的中美洲西北部的Epiclassic年表连接起来，该年表结束于公元8世纪，从同一地区的活树和残树中提取的区域广泛的、年代久远的年表。树木年代学的结果将为在这些地区工作的考古学家提供精确的年代测定，因为这些地区没有书面的年代学数据来源。它还将为气候重建研究奠定基础，这些研究今后将有助于澄清气候变化幅度与人类反应之间的长期关系。为了促进来自墨西哥和美国多个机构的考古学家、树木年代学家、研究生和本科生之间的密切合作，该项目的使命是鼓励树木考古学的应用，目前这还不是墨西哥考古实地工作或分析的一部分。中美洲考古学家长期以来一直承认需要精确的测年方法来了解文化变迁，特别是在中美洲文化核心以北的地区。然而，尽管在美国西南部北部的考古遗址的树木年轮年代测定方面取得了巨大的成功，并且最近在墨西哥开发了涵盖过去1300年的长期树木年轮年表，但在中美洲几乎没有树木考古学。这个NSF资助的项目的第一阶段展示了从公元5世纪到8世纪中美洲西北部考古树木年轮样本的可用性，可测量性和生长模式的相似性（“可交叉性”）在第二阶段，研究人员将把考古样本从后古典和历史遗址位于中美洲北方更广泛的地理区域。由于新的考古学木材收藏同样来自一个没有完善的主年表的时期，所以从西班牙语前遗址产生的树木年轮序列最初将通过“放射性碳摆动匹配”来固定在时间上。" 该方法将特定树木年轮的放射性碳年代的已知相对序列与放射性碳校准曲线拟合，以实现精确的拟合，从而以最小的误差放置日历。 最终，我们打算创建一个连续的树木年轮记录，从现在回到古典时期，使用考古和历史收藏，以及现有的考古年代年表。 由此产生的数据不仅将填补我们对北方中美洲年表知识的重大空白，而且有助于解决更广泛的问题，如中美洲文化核心的文化影响的速度，时间和方向性。由于树木考古学的方法是累积和迭代的，年表将获得长度，样本深度和鲁棒性，并将成为越来越有用的考古学家在更广泛的地理区域和时间periods.This奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Drs. Paula Turkon, Sturt Manning, and Carol Griggs, along with colleagues from Mexico, will conduct research to provide a high-resolution absolute tree-ring chronology for Northern Mesoamerican archaeological sites using a combination of tree-ring and AMS radiocarbon data. This project extends their preliminary research both geographically and chronologically, with the goal of linking the existing Epiclassic chronology from Northwestern Mesoamerica that ends in the 8th century A.D., to the regionally extensive, calendar-dated chronologies from living and relic trees in the same region. The dendrochronological results will offer dating precision to archaeologists working in these regions for time periods that do not have written sources of chronological data. It will also establish the foundation for climate reconstruction studies that, in the future, will help clarify the long-term relationships between the magnitude of climatic change and human response. In fostering close collaboration between archaeologists, dendrochronologists, graduate, and undergraduate students from multiple institutions throughout Mexico and the United States, this project's mission is to encourage the application of dendroarchaeology [=archaeological dendrochronology], currently not part of archaeological fieldwork or analysis in Mexico. Mesoamerican archaeologists have long acknowledged the need for precise dating methods in order to understand cultural change, particularly in the region north of the core of Mesoamerican culture. Yet despite tremendous success in the development of tree-ring dating of archaeological sites just north in the American Southwest, and the more recent development of long tree-ring chronologies in Mexico that cover the past 1300 years, dendroarchaeology has been virtually absent in Mesoamerica. The first stage of this NSF funded project demonstrated the availability, measurability, and similarities in growth patterns ("crossdatability") of archaeological tree-ring samples in Northwestern Mesoamerica from the 5th to 8th centuries A.D. In this second stage, the researchers will incorporate archaeological samples from Postclassic and historic sites located in a broader geographic region in northern Mesoamerica. Because the new archaeological collections of wood will likewise be from a time period for which there are no well-established master chronologies, the tree-ring sequences produced from the prehispanic sites will be initially anchored in time by "radiocarbon wiggle-matching." This method fits a known relative sequence of radiocarbon dates from specific tree-rings against the radiocarbon calibration curve to achieve a precise fit and thus calendar placement with minimal error. Ultimately, we intend to create a continuous tree-ring record from the present back to the Classic period, using both the archaeological and historic collections, as well as existing calendar-dated chronologies. The resulting data will not only fill a significant gap in our knowledge of the chronology of Northern Mesoamerica, but help address broader questions such as the rate, timing, and directionality of cultural influences with the Mesoamerican cultural core. Since dendroarchaeological methods are cumulative and iterative, the chronologies will gain in length, sample depth, and robustness, and will become increasingly useful to archaeologists working in broader geographic regions and time periods.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.