NEXT MEETING: 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. 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....[O]ur interpretation depicts the shoreline as an unstable, dynamic lake margin to which Ruppia seeds...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....[W]e 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." Check out Dave's and Tierra Vieja Consulting's YouTube videos (links are on our Events page) and bring your questions for him!

NEXT FIELD TRIP: Sunday, April 6, through Tuesday, April 8, 2025: Lyman Lake State Park/Springerville/Casa Malpais AZ. Sunday-Monday, explore Lyman Lake's petroglyphs & archaeological site on your own or with a group. On Tuesday 4/8, we have guided tour of Casa Malpais archaeological site. Reservations are required for ONLY the guided tour to the Casa Malpais site but we must give them a final tally no later than March 23, 2025, so please let trip co-leader Torie Grass ([email protected]) or Eduardo Argüello ([email protected]) know to put you on the list. More details available in newsletter and on Events page of this website, and in the blog posts below. As usual for any GCAS field trip, wear sturdy shoes and pack sun protection & water. See you there!

Navajo Culture On Mars!
MAREC Progress Report - Phase III

Meet D-Stretch: the Archaeologist's Friend

Picto 3 - natural Picto 3 - StretchSome avocational archaeologists have already learned of the fascinating technology of D-Stretch, aka decorrelation stretch, a digital imaging tool that was originally developed to enhance (i.e., "stretch") the color differences in aerial photographs. Today, this technology has become more widely used and user-friendly to boot. It is now an essential tool to analyze rock art images, especially ones too faint for the naked eye to see.

Picto 4- Stretch Picto 4- naturalThe two pairs of images you see on this page were taken by the GCAS's own Marglyph, alias Margaret Berrier. She has kindly given us permission to post them here so that we can all see how significant the D-Stretch enhancement can be. The left-most photos are her examples of natural, "naked eye" photos of rock art; and the brightly colored photos next to them reveal the same image in D-Stretch.

For many more images of rock art in D-Stretch as well as technical data, start at the D-Stretch home page itself.

In its most professional format, D-Stretch is a plugin to the Javascript program, ImageJ, that must be installed before D-Stretch can be used. Some of our more tech-savvy readers may be inclined to select this alternative. However, for the more casual of us avocational archaeologists who do not necessarily need high functionality, there's an app for that. Our GCAS President, the straightforward Kyle Meredith, opted for the straightforward app and reports: "...I looked up the app on Google Play for my android phone and ordered it. I think the price was $19.99. SO EASY!" Kyle adds that use of the D-Stretch app has a bit of a learning curve but it promises to be big fun for anyone interested in photographing and enhancing rock art in the field. Like all of us GCAS members who've spent a year itching for resumption of field trips.

If Joe Bob Briggs were into rock art, he'd say check it out.

/s/ webmaster

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