U-series ages and morphology of a Quaternary large-volume travertine deposit at Mesa del Oro, NM: Implications for paleohydrology, paleoclimate, and neotectonic proceses

—This paper describes a large-volume travertine deposit that formed at the northeastern end of Mesa del Oro, a basalt mesa located at the southwestern edge of the Colorado Plateau and along the Jemez lineament. The travertine deposit forms two topographically elevated platforms that cover an area of 27 km 2 , are up to 63 m thick, and have a calculated volume of 0.7 km 3 . We report six new dates for the Mesa del Oro accumulation and show that travertine formation occurred in two main intervals, 360-250 ka and 760-560 ka. The intervals overlap with episodes of basaltic volcanism in the area. The northern platform was deposited along a fissure ridge and an associated marsh as shown by both travertine morphology and facies. Large-volume travertine formation requires both high CO 2 influx and significant groundwater discharge. The high CO 2 influx is interpreted to be related to the episodic volcanic activity that produced over-pressuring of the CO 2 /groundwa- ter system with magmatic gasses. Intervals of high groundwater discharge are attributed to high head in a confined aquifer achieved through increased recharge and thus, episodes of travertine formation at Mesa del Oro are interpreted to record wet paleoclimate periods.