Carbon isotope composition as indicator for climatic changes during the middle and late Holocene in a peat bog from Maramureş Mountains (Romania)

Abstract

The main goal of this study was to use stable carbon isotopic composition of bulk peat sampled in Tăul Mare-Bardău peat bog, Maramureş Mountains, as a tool to provide paleoclimatic information over the middle and late Holocene in this region. A peat core of 3.60 m was sampled for δ13C analysis, and bulk peat samples were analyzed by isotope ratio mass spectrometry (IRMS) method. δ13C values reveal a maximum variation of 4.69‰ along a 3.6-m-long peat core. We examined the vertical variation of δ13C bulk peat and concluded that several factors could contribute to up core trends of δ13C. Four intervals of climatic variability could be related with variations of δ13C values between ~6800 cal. yr BP and present: two wet periods (around 2800 and 545 cal. yr BP) and two dry periods (6760 and 1430 cal. yr BP). We concluded that variability in the δ13C of bulk peat profile could be influenced most heavily by the water availability, which in turn is related to the amount of precipitation at the time. Four intervals of δ13C variations of the peat sequence between 225 and 25 cm can be related with generally accepted intervals of climatic variability that have occurred within the last 2000–2500 years (‘Roman Warm Period’ (RWP), ‘Dark Age Cold Period’ (DACP), ‘Medieval Warm Period’ (MWP) and ‘Little Ice Age’ (LIA)). The climate was probably of warm–cold alternations, as revealed in our peat core by δ13C variations between 2800 cal. yr BP and present. The δ13C values of the peat profile showed two positive signals at 40 and 225 cm depth and two negative signals at 105 and 350 cm depth. We suggest that these could also represent a change in vegetation at the time.