117-1 From Lake to Raised Bog: Multi–Proxy Reconstruction of Holocene Environmental Change in the Juodymas Peatland

Abstract:

Peatlands are sensitive recorders of past environmental and hydrological change, yet their developmental trajectories remain understudied in many regions of Eastern Europe. This study presents a multi–proxy reconstruction of Holocene environmental change based on a 6.9 meter sediment core from the Juodymas peatland (NE Lithuania). Our aim was to reconstruct the development of the peatland from a postglacial lake through minerotrophic fen and transitional mire stages to an ombrotrophic raised bog, integrating lithological, geochemical, and decomposition–based indicators.   

We combined sediment lithology, loss-on-ignition (LOI), granulometry, pH, magnetic susceptibility (MS), energy-dispersive X–ray (EDX) elemental composition, and peat decomposition degree with AMS radiocarbon dating. The obtained age–depth model shows that sedimentation began ca. 10,000–12,000 calibrated years BP in a shallow lacustrine environment, characterized by low organic content, fine mineral matter, and low decomposition. Around 8,500 cal BP, the basin transitioned into a fen as organic accumulation increased and mineral influx declined. Decomposition values exceeded 50%, indicating sustained minerotrophic, waterlogged, and reducing conditions. Between 5,500 and 4,500 cal BP, the peatland underwent a transitional mire stage distinguished by declining peat decomposition values, which fell below 50%, reflecting improved preservation of organic matter and a gradual reduction in groundwater influence. By approximately 4,500 cal BP, proxies collectively record the onset of ombrotrophication: pH decreased, MS stabilized at very low values, and elemental profiles (especially Ca, Na, Mg vs. S, Fe) shifted, reflecting the establishment of predominantly rain–fed conditions. The uppermost sediments show slight mineral enrichment, suggesting possible recent changes in the hydrological regime or external environmental influence, without evidence of major drainage.

Together, these proxies reveal a coherent environmental sequence from lake to fen, transitional mire, and raised bog, consistent with regional postglacial hydrological and climatic trends. The study demonstrates the value of integrating peat decomposition degree with geochemical and lithological indicators for reconstructing long–term peatland dynamics. Juodymas peatland represents a largely intact raised bog, highlighting its importance as an archive of Holocene environmental history and its relevance for peatland conservation. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 5, 2026

doi: 10.1130/abs/2026AM-18390

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