The Spotlight #10

The paper featured in this “The Spotlight” post is entitled “Glacial outburst flood in the marginal zone of the Wartanian Glaciation: An example from Adamów, central Poland”, led by Małgorzata Frydrych. Link to the paper.

The research

The authors investigated extensive sediment exposures, attesting to glacial lake-outburst flood episodes, at Adamów, south central Poland (Figure 1). The studied site lies at the margins of the area occupied by ice sheets during the Wartanian (MIS 6) glaciation. The goal of the study is to characterize the deposition environments and their evolution through time; the investigated outcrops lie in a sandur plain nearby the terminal moraines of the Wartanian glaciation.

Two subsequent flooding episodes were recognized, thanks to grain size, structural and paleohydraulic analyses. A detailed sedimentologic interpretation allowed to reconstruct different deposition environments, including buried erosional channels and gravel dunes (Figure 2). Moreover, the sequence is locally deformed; this fact is interpreted as evidence of liquefaction phenomena, caused by the fast accumulation of flood deposits.

Figure 1: A) Location of the study area (blue star) in central Poland, at the margins of the maximum extent of the Wartanian ice sheets. B) Aerial view of the studied site.

Figure 2: Field photo - erosional channel visible in the eastern wall of the outcrop; older sediments of unit A1 and glacial flood sediments of unit A3.

 

The local environmental evolution and the processes that shaped the landscape are summarized in Figure 3. The older deposits identified in the outcrops can be interpreted as subaqueous sediments settled in a proglacial lake with an intense supply of rock material (Unit A1). After the filling of the proglacial lake, an outwash plain developed and the related deposits attest to high flow energy conditions (Unit A2). Then, two phases of outburst flood deposits are present (Unit A3) and represent the channel fill created by the quick flow of water from the depth of the ice sheet lobe.

Figure 3: Sketch showing the formation stages of the proximal outwash fan in the studied site.

 

Why should we care?

This study documents the impact of glacial lake-outburst floods in a marginal zone and foreland of past ice sheets; such impact is much more intense than previously thought and the study site provides an additional case history, beside those already known.

Understanding the dynamics and evolution of past glacial lake-outburst floods is relevant for similar environments worldwide, since glacial lake-outburst floods leave a significant imprint on the landscape and may affect the drainage network at a regional scale. The importance of a proper reconstruction of past glacial lake-outburst floods is particularly true in light of the sudden environmental changes that similar zones are experiencing nowadays and will face in the near future.

 

The Author

Małgorzata Frydrych works as an assistant professor at the University of Lodz, Faculty of Geographical Sciences, Department of Physical Geography in Poland. She finished her Ph.D. in 2020. She is an active member of the INQUA Peribaltic Working Group. Her main research interests are focused on glacial geomorphology especially eskers, subglacial processes and glacial floods, Quaternary geology and sedimentology.

Contacts: email, RGate page