A 2500-yr late holocenemulti-proxy record of vegetation and hydrologic changes from a cave guano-clay sequence in SW Romania

We provide sedimentological, geochemical, mineral magnetic, stable carbon isotope, charcoal, and pollen-based evidence froma guano/clay sequence in Gaura cuMuscă Cave (SWRomania), fromwhichwe deduced that from ~1230 BC to ~AD 1240 climate oscillated betweenwet and dry. From ~1230 BC to AD 1000 the climate was wetter than the present, prompting flooding of the cave, preventing bats fromroosting, and resulting in a slowrate of clay accumulation. The second half of the MedievalWarm Period (MWP) was generally drier; the cave experienced occasional flash flooding in between which maternity bat roosts established in the cave. One extremely wet event occurred around AD 1170, when Fe/Mn and Ti/Zr ratios show the highest values coincident with a substantial increase of sediment load in the underground stream. The mineral magnetic characteristics for the second part of the MWP indicate the partial input of surface-sourced sediments reflecting agricultural development and forest clearance in the area. Pollen and microcharcoal studies confirm that the overall vegetation cover and human land use have not changed much in this region since the medieval times

Guano-Derived δ\u3csup\u3e13\u3c/sup\u3eC-Based Paleo-Hydroclimate Record from Gaura cu Musca Cave, SW Romania

The δ13C values of 23 unevenly spaced guano samples from a 17-cm long clay sediment profile in Gaura cu Muscă Cave (GM), in SW Romania, made it possible to preliminarily characterize the Medieval Warm Period summer hydroclimate regime. The beginning of the sequence (AD 990) was rather wet for more than a century, before becoming progressively drier. After a brief, yet distinct wet period around AD 1170, drier conditions, with a possible shift from C3 to a mixed C3-dominated/C4 type vegetation (2 ‰ lower δ13C values), prevailed for almost half a century before the climate became colder and wetter at the onset of the Little Ice Age, when bats left the cave. The guano-inferred wet and dry intervals from the GM Cave are mirrored by changes in the color and amount of clay accumulated in the cave. They also agree well with reconstructions based on pollen and charcoal from peat bogs and δ13C and δ18O on speleothems from other Romanian sites. Overall, these results indicate that the δ13C of bat guano can provide a sensitive record of the short-term coupling between local/regional climate and the plant–insect–bat–guano system