Mid-Holocene erosive episodes in tufa deposits from Trabaque Canyon, central Spain, as a result of abrupt arid climate transitions

Abstract

During the Holocene a series of tufa sediments were deposited from a karstic spring along the Trabaque Canyon, central Spain. A long-term lowering of the water table caused the location of the spring to be displaced from the upper sector of the canyon during the early Holocene to the lower sector in the late Holocene. This progressive shift was in response to decreased precipitation in the region. The depositional environments and their geomorphologic relationships were characterized. Thus, five morphosedimentary units (MSUs) were identified within the Holocene tufa deposits. Erosive episodes were recognized between MSUs and, as most of the MSUs partially overlap, the older ones are perched in relation to the younger ones. The chronology of the MSUs is based on 14C dates, and stable isotopes and total organic carbon content provided environmental information during the period of tufa sedimentation. The successive dissection episodes in the Trabaque Canyon tufa deposits took place during transitioning climate conditions from the relatively wet early Holocene to the more arid late Holocene. During this transitional period in the mid-Holocene, wet phases alternated with more arid conditions, causing the largest hydrological regime gradients in the Holocene. Thus, the four erosive episodes causing tufa dissection in Trabaque during the Holocene are interpreted as the result of abrupt transitional periods towards arid conditions.