‘Holocene history of the eastern side of Novaya Zemlya from glaciomarine sediment records in the Tsivol’ki Fjord’: Comments

Abstract

Rusakov et al. (2022) present a multiproxy-based reconstruction of the Holocene history of Tsivol’ki Fjord located on the Kara Sea coast of the northern Novaya Zemlya. A considerable portion of the palaeoreconstructions is derived from the data on macro- and microfossils. As an author of these data (although not acknowledged in the paper), I point to several mistakes in the data presentation, argue for a different palaeoenvironmental interpretation of certain fossil assemblages and add new data for the topmost part of the sediment core. Additionally, information on ice- and iceberg-rafted debris (IRD) counts is presented that provides evidence for past variations in the glacier front position and iceberg calving. Altogether, this considerably changes the palaeoenvironmental reconstructions of the Holocene history of Tsivol’ki Fjord as drawn by Rusakov et al. (2022). The revised environmental interpretation is as follows: microfossil data give evidence for a distal position of the glacier front from the studied core site in the outer fjord and a persistent exchange with open sea waters throughout the whole time period since 10.6 cal. ka BP. After the relatively warm Early–Middle Holocene, cooling started that resulted in the offshore glacier advance manifested by the rise in sedimentation rates and strong meltwater influence that were the reason for the drop in the total abundance of microfossils and IRD during 3.6 to 4.6 cal. ka BP. Between 3.6 and 0.9 cal. ka BP, the highest relative abundance of the glacier-distal benthic foraminiferal species Islandiella norcrossi/helenae, the growing total abundance and diversity of microfossils, the decrease in sedimentation rates and the rising IRD content imply the gradual retreat of the glacier front after the short progradation event. The last millennium is characterized by the highest total abundance and diversity of microfossils, low sedimentation rates and benthic foraminiferal assemblages gradually becoming similar to the Early–Middle Holocene ones.

The lead author of Rusakov et al. (2022) article was invited by Boreas to reply to these comments but we received no response.