Abstract
Both modern and palaeo-ice streams experience shutdown, which has critical implications for their mass balance and influence on relative sea level. Reconstructions of palaeo-ice streams have mainly focused on their phase of active flow and thus less is understood of their shutdown and style of deglaciation. Mapping of streamlined subglacial bedforms (SSBs), including drumlins and mega-scale glacial lineations, in northeast Iceland reveals cross-cutting flow-sets of palaeo-ice streams within the Iceland Ice Sheet (IIS) during and following the last glacial maximum (LGM). Here we map geometrical ridges (linear and reticular) within the Bakkaflói and Þistilfjörður flow-sets and combine the morphological data with sedimentological analyses to increase our understanding of the dynamics of the IIS during deglaciation in northeast Iceland. We interpret the ridges as crevasse-squeeze ridges (CSRs), based on their interconnected network, primary orientation transverse and/or oblique to former ice flow and internal composition of homogenous subglacial till. In both areas, the CSRs are superimposed on the SSBs, indicating that they post-date the SSBs and signify the waning stage of ice streaming associated with the readvance of the IIS during the Younger Dryas period. The preservation of the CSRs suggests ice stagnation following the readvance and ice-stream shutdown. The morphological difference of the CSRs between the flow-sets is taken to indicate different kinematic setting within the ice streams; the linear CSRs in Bakkaflói formed further upstream where extensional forces parallel to ice flow were dominant, whereas the reticular CSRs in Þistilfjörður are more indicative of transverse and longitudinal forces near the terminal zone. Future research reconstructing past ice-sheet behaviour and ice-stream dynamics would benefit from high-resolution bathymetric data from the adjoining shelf as well as enhanced geochronological constraints.
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Earth Surface Processes and Landforms |
| Vol/bind | 48 |
| Udgave nummer | 12 |
| Sider (fra-til) | 2412-2430 |
| Antal sider | 19 |
| ISSN | 0197-9337 |
| DOI | |
| Status | Udgivet - 2023 |
Bibliografisk note
Funding Information:This project has been supported through grants from the University of Iceland Research Fund (to ÓI), the Icelandic research fund (NA), the Energy Research Fund of Landsvirkjun (to NA and ÍÖB) and the Icelandic Road and Coastal Administration (to ÍÖB). All our colleagues and graduate students are thanked for great company during fieldwork, constructive discussions and helpful feedback during the project. Daniel Ben‐Yehoshua is especially thanked for droning the area in Þistilfjörður at the early stage of the project. Thanks are also due to Ólafur B. Vigfússon, farmer at Syðra‐Áland, for guidance in the field and giving us the permission to excavate the ridges in Álandstunga in Þistilfjörður and the Icelandic Road and Coastal Administration for excavate the ridge in Bakkaflói. We would like to thank the two anonymous reviewers for their constructive comments that improved the manuscript.
Publisher Copyright:
© 2023 John Wiley & Sons Ltd.