Lithologic features of near-surface layers of the Quaternary cover as a key to understanding of environmental constraints for the Quaternary ground squirrel species

ABSTRACT

Here, we propose the modern soil map as a source for creating spatial context for agent-based modelling of the historical expansion and dispersal of ground squirrel species. On the basis of this soil map, we produced a lithologic map of the near-surface layers of the Quaternary cover. Units of this new lithologic map (i.e. certain kinds of substrate) were assessed in context of preferability by certain ground squirrel species. Then, these (basic) preference rates were modified for the case of valley slopes (positive impact of valley slopes) and for the case of loess-and-soil accumulation (also positive impact). The hypothesis of the positive impact of loess and soil accumulation is supported by following facts: range shrinking of Spermophilus species in the Holocene; stability of the range boundary between Spermophilus pygmaeus and Spermophilus suslicus in the Middle and Late Pleistocene and the ability of the Pleistocene ecosystems to support high animal biomass even during cold epochs.

KEYWORDS:

• Ground squirrels
• substrate preferences
• Quaternary
• lithologic composition of the uppermost part of the Quaternary deposits

Acknowledgements

This work was supported by the State Geological Survey of Ukraine: [Grant Number 686] and the International Union of Quaternary research, Commission ‘Humans and Biosphere’: [Grant Number 1606]. Authors thank the reviewers G. Zazula and N. Gerasimenko for providing constructive comments and help in improving the contents of this paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. Sites of the Swiderian culture, which are known in the north of Ukraine (Zaliznyak 2010) as well as in Poland and Baltic areas at the end of the Pleistocene, on the contrary, were commonly associated with dunes and would appear to be an exception. However, the Swiderian economy, although belongs to the final Palaeolithic, bears marks of some Mesolithic traits (like fishing) and was, so to say, a step in human adaptation to the Holocene-like ecosystems (not occasionally, Swirerian people are believed to be inhabitants of tundra [not tundra-steppe] ecosystems). So, this is the exception that confirms the rule.

2. Difficulties of palaeoecological interpretation of fossil burrows are easier to show on an example. Let us take one of well-documented cases, the krotovina locality Arapovychy in Ukraine. This small mammal fauna was collected from the Briansk soil. Among rodents, there were identified marmots, ground squirrels, jerboas and voles. Krotovinas did not visualise because of the insignificant difference in colour between the soil and the overlying loess (Markova 1982). Still, it is obvious that burrows in this burrow horizon differ in age: voles’ burrows cannot penetrate in soil deeper than first centimetres, while ground squirrels’ ones are approximately, a meter deep (the ground squirrel species considered in this paper are meant), marmots’ – up to 3.5 m, jerboas’ – up to 1.1 m (summer burrows) or 2.5 m (winter burrows). In such a way, voles in this locality must be contemporary to the Briansk soil, while larger rodents are younger and correspond to the overlying loess (Late Weichselian), and the marmot can be Holocene in age.

Additional information

Funding

This work was supported by the State Geological Survey of Ukraine: Grant Number [686] and the International Union of Quaternary research, Commission ‘Humans and Biosphere’: Grant Number [1606].