Depositional environments and diagenesis of a carbonate till from a Quaternary paleoglacier sequence in the Southern Velebit Mountain (Croatia)

• Diagenesis of carbonate tills affects the original properties of glacial sediments.
• Dissolution and formation of cements are common processes of early diagenesis.
• Dating of carbonate tills by different methods is potentially impacted by diagenesis.

Glacial sediment is an important paleoclimatological and paleoenvironmental archive. In the Mediterranean region most of the Quaternary glaciers were hosted in carbonate mountains. Diagenetical processes in carbonate sediments tend to impact preservation of glacial features and complicate the establishment of accurate chronologies. This paper presents a sedimentological study of a paleoglacier hosted in the carbonate Velebit Mountain, Croatia. Three carbonate tills were studied in order to evaluate their depositional environments and the diagenetical processes that affect them. The tills were selected from lateral moraines of different glacial stages of the paleoglacier and they are interpreted as lodgement and melt-out tills. Diagenetical processes such as cementation, dissolution and increase in organic content were enhanced by the percolation of water through the sediment and the propagation of rootlets. This research demonstrates the importance of understanding the diagenetical processes affecting carbonate tills after their sedimentation. Studies like this are an essential research stage prior to conducting geochronological and paleoclimatological interpretations based on paleoglaciers in carbonate regions.