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- 157 to 167
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- National Science Foundation
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Calendar-dated tree-ring sequences offer an unparalleled resource for high-resolution paleoenvironmental reconstruction. Where such records exist for a few limited geographic regions over the last 8,000 to 12,000 years, they have proved invaluable for creating precise and accurate timelines for past human and environmental interactions. To expand such records across new geographic territory or extend data for certain regions further backward in time, new applications must be developed to secure “floating” (not yet absolutely dated) tree-ring sequences, which cannot be assigned single-calendar year dates by standard dendrochronological techniques. This study develops two approaches to this problem for a critical floating tree-ring chronology from the East Mediterranean Bronze–Iron Age. The chronology is more closely fixed in time using annually resolved patterns of 14 C, modulated by cosmic radiation, between 1700 and 1480 BC. This placement is then tested using an anticorrelation between calendar-dated tree-ring growth responses to climatically effective volcanism in North American bristlecone pine and the Mediterranean trees. Examination of the newly dated Mediterranean tree-ring sequence between 1630 and 1500 BC using X-ray fluorescence revealed an unusual calcium anomaly around 1560 BC. While requiring further replication and analysis, this anomaly merits exploration as a potential marker for the eruption of Thera.
Radiocarbon offsets and old world chronology as relevant to Mesopotamia, Egypt, Anatolia and Thera (Santorini)
The new IntCal20 radiocarbon record continues decades of successful practice by employing one calibration curve as an approximation for different regions across the hemisphere. Here we investigate three radiocarbon time-series of archaeological and historical importance from the Mediterranean-Anatolian region, which indicate, or may include, offsets from IntCal20 (~0–2214C years). While modest, these differences are critical for our precise understanding of historical and environmental events across the Mediterranean Basin and Near East. Offsets towards older radiocarbon ages in Mediterranean-Anatolian wood can be explained by a divergence between high-resolution radiocarbon dates from the recent generation of accelerator mass spectrometry (AMS) versus dates from previous technologies, such as low-level gas proportional counting (LLGPC) and liquid scintillation spectrometry (LSS). However, another reason is likely differing growing season lengths and timings, which would affect the seasonal cycle of atmospheric radiocarbon concentrations recorded in different geographic zones. Understanding and correcting these offsets is key to the well-defined calendar placement of a Middle Bronze Age tree-ring chronology. This in turn resolves long-standing debate over Mesopotamian chronology in the earlier second millennium BCE. Last but not least, accurate dating is needed for any further assessment of the societal and environmental impact of the Thera/Santorini volcanic eruption.
New Bayesian radiocarbon models for Early Bronze IV Tell Abu en-Ni‘aj and Middle Bronze Age Tell el-Hayyat, Jordan.Jull, A.J.T. (Ed.)ABSTRACT. We present two new Bayesian 14C models using IntCal20 that incorporate 17 new calibrated AMS ages for Early Bronze IV Tell Abu en-Ni‘aj and Middle Bronze Age Tell el-Hayyat, located in the northern Jordan Valley, Jordan. These freshly augmented suites of carbonized seed dates now include 25 AMS dates from Tell Abu en-Ni‘aj and 31 AMS dates from Tell el-Hayyat. The modeled founding date for Tell Abu en-Ni‘aj strengthens an emerging high chronology for Early Bronze IV starting by 2500 cal BC, while the end of its habitation by 2200 cal BC may exemplify a regional pattern of increasingly pervasive abandonment among late Early Bronze IV settlements in the Southern Levant. In turn, our modeled date for the Early Bronze IV/Middle Bronze Age transition at Tell el-Hayyat around 1900 cal BC pushes this interface about a century later than surmised traditionally, and its abandonment in Middle Bronze III marks an unexpectedly early end date before 1600 cal BC. These inferences, which coordinate Bayesian AMS models and typological ceramic sequences for Tell Abu en-Ni‘aj and Tell el-Hayyat, contribute to an ongoing revision of Early and Middle Bronze Age Levantine chronologies and uncoupling of their attendant interpretive links between the Southernmore »
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