Next GCAS Meeting Features Speaker & Geoarchaeologist Dave Rachal PhD
04/09/2025
Wednesday, April 16, 2025, 6:00 PM at 2045 Memory Lane in Silver City, New Mexico. The GCAS's next monthly IN-PERSON ONLY meeting features speaker geoarchaeologist Dave Rachal PhD of Tierra Vieja Consulting in Las Cruces NM. Dave has been involved in some YouTube interviews that discuss various aspects of geoarchaeology, site formation processes related to the formation of ancient footprints and megafauna tracks, and the peopling of the New World. This evening Dave will describe to us the issues surrounding the specific data sets that scientists are applying to the ancient human footprints recently found at White Sands National Park. Doors open at 6:00 PM with light refreshments on offer. Socializing and a brief-to-nonexistent business meeting will immediately precede Dave's presentation of: How Did The Seeds Get There? Ruppia cirrhosa Ecology, Depositional Context and Accurate Radiocarbon Dating at White Sands:
"The stratigraphic and geomorphic contexts, and ultimately the chronometric determinations, at White Sands Locality-2 (WHSA-2) are topics of controversy that stem from conflicting interpretations of the processes that deposited the Ruppia cirrhosa (Ruppia) seeds within the paleo-Lake Otero footprint site. Some studies have characterized the eastern shoreline as a stable lake margin where Ruppia plants grew in situ in shallow water. In contrast, our interpretation depicts the shoreline as an unstable, dynamic lake margin to which Ruppia seeds, impacted by the hard water effect (HWE), were transported from deep-water, offshore growth beds during storm events and deposited on the lake shore in seed balls. These unusual aggregates, known to mix seeds of wide-ranging ages, were gradually broken apart by several cycles of wave action and erosion and redeposited in layers. At WHSA-2, other researchers have claimed to focus their radiocarbon dating solely on seeds from layers and not from seed balls, ostensibly to avoid mixing issues. Yet, how do they know that the seeds they dated did not come from disaggregated seed balls? In this presentation, we will delve into both the ecology and the depositional context of Ruppia and discuss why the Ruppia seeds at paleo-Lake Otero are problematic materials for radiocarbon dating."
Dave and Tierra Vieja Consulting are featured in a series of YouTube interviews, including a discussion of the currently available data being applied to the ancient human footprints found at White Sands National Park; and a podcast by the New Mexico Department of Cultural Affairs regarding geoarchaeology, site formation processes related to footprints and megafauna tracks, and peopling of the New World. Check out Dave's videos (links are on our Events page) and bring your questions for him!
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