Refined porosities of the AND-1B core reflecting the glacial history in the McMurdo region
During austral summer 2006/07 the ANDRILL program successfully drilled the 1285 meters long AND-1B sediment core from beneath the McMurdo Ice Shelf covering the last 12 Ma. One of the major goals is to better constrain the past Ross Ice Shelf/ice sheet history. High-resolution measurements of whole-...
| Main Authors: | , |
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| Format: | Conference Object |
| Language: | unknown |
| Published: |
2008
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| Subjects: | |
| Online Access: | https://epic.awi.de/id/eprint/19450/ https://hdl.handle.net/10013/epic.31236 |
| Summary: | During austral summer 2006/07 the ANDRILL program successfully drilled the 1285 meters long AND-1B sediment core from beneath the McMurdo Ice Shelf covering the last 12 Ma. One of the major goals is to better constrain the past Ross Ice Shelf/ice sheet history. High-resolution measurements of whole-core wet-bulk densities (WBD) were collected at the drill site laboratory using a Multi-Sensor Core Logger. WBD can be applied to calculate fractional porosity if the grain density (GD) is known. GD values of about 1,200 discrete samples were determined through pycnometer measurements, ranging from 2.15 to 2.9 g/ccm. A mathematical relationship was established between WBD and GD in order to calculate porosity from the entire WBD data. The overall down-core trend of the porosity holds information about the compaction history of the deposited sediments. Removing this trend allows for detailed studies of the residual porosities in terms of regional environmental change related to ice shelf/ice sheet dynamics, in particular overconsolidation through ice-loading. The down-core compaction-trend anaysis is based on density changes for shales and siltstones. Overconsolidation is mainly found in diamictite units and here significantly more pronounced in the upper 200m indicative of intensive ice-sheet grounding during the last 2 Ma. |
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