A TEMPLATE FOR SOUTHWESTERN UNITED STATES LATE HOLOCENE PALEOCLIMATE FROM STALAGMITE HC-1

The subtle changes in climate throughout the Holocene are often challenging to define. Stalagmites in semi-arid regions from slightly evaporative cave zones host multiple climate proxies that have varying degrees of sensitivity to these subtle changes. Of the many stalagmites studied, one exhibits sensitivity to climate change that defines important shifts in climate during the Late Holocene. We present a paleoclimate record from stalagmite HC-1 as a template for the southwestern United States Late Holocene climate history. Stalagmite HC-1 from Hidden Cave, Guadalupe Mountains, New Mexico, hosts multiple climate proxies that include stalagmite growth (annual banding and hiatuses), mineral assemblage (calcite and aragonite), transmitted-light grayscale, and δ²³⁴U, δ¹³C, and δ¹⁸O time-series constructed from >30 uranium-series dates. Similar to many other Holocene columnar stalagmites from Guadalupe Mountains caves, growth of stalagmite HC-1 began 3400 yr BP. The sensitivity of this stalagmite defines the increased variability and aridity coincident with the Pueblo Period as numerous aragonite layers and growth hiatuses from 1300 to 350 yr BP. This period is in distinct contrast with the continuous calcite-only growth from 3400 to 1300 yr BP, and 350 to 120 yr BP. Increased variability and aridity return from 120 yr BP to the stalagmite top at ~50 yr BP. The top layer is an aragonite hiatus layer, indicating that the stalagmite was broken by early visitation to the cave during or soon after a drought. Our stalagmite HC-1 record suggests the following eastern-half of southwestern United States Late Holocene climate divisions: Transitional Late Holocene (4200 to 3400 yr BP; a transition from overall slightly drier conditions in the Middle Holocene to wetter conditions in the Late Holocene), Pluvial Late Holocene (3400 to 1300 yr BP; a period representing most abundant stalagmite growth and overall wetter, less variable conditions), Pueblo Late Holocene (1300 to 350 yr BP; marked by numerous aragonite layers and growth hiatuses representing overall drier and more variable conditions), and Neopluvial Late Holocene (350 to the present; a brief period of wetter conditions that become progressively drier toward the present).