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Provenance of Last Glacial Maximum Till from the Ross Embayment, Antarctica

Provenance of Last Glacial Maximum Till from the Ross Embayment, Antarctica. Jason Lederer, Kathy Licht, and Jeff Swope Geology Department Indiana University – Purdue University, Indianapolis. Nathaniel B. Palmer. Contributors : H. Engelhardt – California Institute of Technology

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Provenance of Last Glacial Maximum Till from the Ross Embayment, Antarctica

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  1. Provenance of Last Glacial Maximum Till from the Ross Embayment, Antarctica Jason Lederer, Kathy Licht, and Jeff Swope Geology Department Indiana University – Purdue University, Indianapolis Nathaniel B. Palmer • Contributors: • H. Engelhardt – California Institute of Technology • J. Bockheim – University of Wisconsin – Madison • G. Faure – The Ohio State University • T. Janecek – Florida State University, Antarctic Research Facility

  2. EAIS and WAIS balanced WAIS-dominated 180o 180o Denton and Hughes, 2000 The Problem What was the contribution of the EAIS and WAIS to the expansion of the LGM Ross Ice Sheet? • Answering this question will provide important information for modeling

  3. Project Objective and Hypotheses • Determine influence of the East Antarctic Ice Sheet (EAIS) and West Antarctic Ice Sheet (WAIS) on the expansion of the Ross Ice Sheet • East and West Antarctic source terranes have distinct petrologic signatures • Source terrane signature can be identified in Ross Sea till

  4. Ice Stream A Nimrod Glacier Ice Stream D RISP Ice Stream E Nimrod Group McMurdo Volcanic Group Beacon Group Basement Complex – metasedimentary rocks Ferrar Group Granite Harbour Intrusives Drygalski Ice Tongue Byrd Group Beardmore Group Ross Embayment Regional Geology East Antarctica • PreCambrian to mid - Paleozoic • Felsic igneous & mafic igneous rocks (Granite, dolerite, gabbro, basalt) • Clastic and chemical sedimentary (i.e. Beacon Group) • Metamorphic rocks(Marble, quartzite, schist, gneiss) West Antarctica • 30 My rift basin • Volcanic and sedimentary strata • Basalt • Unlithified sediment shed from TAM Marie Byrd Land

  5. Previous studies • Anderson et al., 1992 noted E-W variability in sand, pebble and heavy mineral composition • Balshaw (1981) identified E-W variations in clay mineralogy • Tulaczyk et al. (1998) characterized sub-ice stream till with clay mineralogy, sand petrography and particle size analysis. • Better core coverage, especially in CRS and ERS • Have till samples from source areas Taken from Anderson et al., 1992

  6. Analytical Methods • Separated 500 – 2000 µm (sand) fraction from 2.5-3.0 g of till • Prepared a resin mount and followed standard thin-section making procedures • Counted 300+ grains using Indiana point counting method (several samples <300 grains)

  7. Beardmore Glacier Whillans Ice Stream Ice Stream C Mt. Achernar RISP Ice Stream D Byrd Glacier Darwin Glacier Allan Hills NBP9308-01 NBP9407-63 NBP9501-10 NBP9902-04 NBP9501-11 NBP9407-39 NBP9501-12 NBP9902-16 NBP9501-17 NBP9902-17 NBP9501-20 NBP9902-05 NBP9501-21 NBP9902-08 NBP9501-23 NBP9401-39 NBP9501-24 NBP9501-07 Sampling Locations West Antarctica East Antarctica Ross Ice Shelf Ross Sea S RADARSAT 180o

  8. Strategy Step 1: Determine EA and WA source terrane signatures • Examine 500 – 2000 µm sand fraction of till from: • East Antarctic (EA) outlet glaciers • West Antarctic (WA) ice streams

  9. East and West Antarctic Source Terranes b. SAL 227 a. East Antarctica = 9 samples West Antarctica = 4 samples

  10. EAST ANTARCTICA Quartz Mafic igneous lithic fragments Sedimentary lithic fragments Regionally high carbonate abundance WEST ANTARCTICA Quartz,feldspar Felsic igneous Some metamorphic lithic fragments Extrusive igneous fragments Absence of mafic igneous fragments Source Terrane Signatures

  11. Strategy Step 2: Examine till from Ross Sea and beneath Ross Ice Shelf and correlate with source terrane • Use division between Eastern Ross Sea, Western Ross Sea, Central Ross Sea

  12. Ross Sea SAL 192 Western Ross Sea = 14 samples Eastern Ross Sea = 6 samples Central Ross Sea = 11 samples RISP = 2 samples

  13. EASTERN ROSS SEA Quartz, feldspar, mica Felsic igneous fragments Small quantities of extrusive igneous fragments Absence of mafic igneous fragments WESTERN ROSS SEA Quartz, feldspar, pyroxene Felsic igneous fragments (compositionally different from Eastern Ross Sea) Extrusive volcanic fragments (more substantial that Eastern Ross Sea) Mafic igneous fragments Sedimentary lithic fragments Eastern and Western Ross Sea Signature

  14. Central Ross Sea Signature Mix of WRS and ERS • Quartz, feldspar, mica • Felsic igneous fragments • Extrusive igneous fragments • Sedimentary lithic fragments • Mafic igneous fragments (though small) • Some carbonate (marble, twinned calcite) • Oolitic limestone Sample from Central Ross Sea 100x Sample from Whillans Ice Stream 400x

  15. Source Terranes and Ross Sea a. b. East Antarctica Western Ross Sea West Antarctica Eastern Ross Sea Central Ross Sea RISP

  16. ? ? ? ? ? Flow Lines WA Ice Stream A Beardmore Glacier Whillans Ice Stream Mt. Achernar EA Ice Stream C Nimrod Glacier Holyoake Range Ice Stream D Byrd Glacier RISP Darwin Glacier Ice Stream E Ross Ice Shelf Hatherton Glacier ? Marie Byrd Land 9902 - 17 McMurdo Island 9407 - 39 9902 - 04 9501 - 17 Victoria Land 80 - 193 9407 - 63 Allan Hills 9501 - 12 9401 - 01 9902 - 05 9505 - 11 9902 - 08 9501 - 30 9501 - 24 David Glacier 9501 - 35 EL - 32 S 9501 - 07 ERS Dryglaski Ice Tongue 9501 - 39 CRS WRS Coulman Island

  17. Conclusions • East and West Antarctic source terranes are distinct • There is E-W variability in the Ross Sea till composition • Can identify East and West Antarctic signatures in Ross Sea samples, though Ross Sea samples more mature • Central Ross Sea and RISP till are a mix of East and West Antarctic till • Data suggest an even contribution from the EAIS and WAIS to the expansion of the Ross Ice Sheet

  18. Ice Stream A EA WA WA Beardmore Glacier Whillians Ice Stream Mt. Achernar EA Ice Stream C Nimrod Glacier Holyoake Range Ice Stream D Byrd Glacier Ross Ice Shelf Darwin Glacier Ice Stream E Ice Stream F Hatherton Glacier Marie Byrd Land McMurdo Island Victoria Land Allan Hills ERS CRS WRS David Glacier S Dryglaski Ice Tongue Coulman Island

  19. Function 2 Function 3 Function 2 Function 1 Function 2 Function 1: felsic igneous fragments Intermediate igneous fragments extrusive volcanic fragments opaqaue minerals calcite potassium feldspar plagioclase mudstone fragments sandstone fragments claystone fragments Function 2: metamorphic igneous fragments mafic igneous fragments biotite iron ore quartz olivine chlorite Function 1: intermediate igneous fragments metamorphic fragments extrusive volcanic fragments limestone fragments sandstone/siltstone fragments claystone fragments pyroxene potassium feldspar biotite chlorite Function 2: mudstone fragments mafic fragments felsic fragments olivine iron ore calcite quartz Function 3: opaque minerals muscovite Function 1 DiscriminantAnalysis – Are the clusters correctly assigned? EA (1) EA + RS (3) EA WA RS 2b 2a 2d 2c

  20. Where did the oolitic limestone come from? • Did not see it in any East Antarctic samples • Rare occurrences in Antarctica • Only reported in occurrence in Ross Embayment drainage is in the Holyoake Range near Nimrod Glacier • Did not analyze samples from that region.

  21. Sample Locations Cluster Darwin 1 Upper Beardmore Hatherton Ice Stream C Ice Stream C Whillans Ice Stream A Whillans Ice Stream NBP9501 - 17 DF80 - 193 DF80 - 193 NBP9501 - 11 NBP9501 - 17 NBP9501 - 17 B NBP9501 - 17 RISP RISP NBP9501 - 24 2 NBP9501 - 12 NBP9501 - 07 NBP9902 - 08 NBP9902 - 17 NBP9902 - 04 C NBP9902 - 04 NBP9907 - 63 NBP9902 - 16 NBP9902 - 05 Hatherton/Darwin NBP9501 - 35 EL32 - 13 NBP9501 - 35 NBP9501 - 30 D EL32 - 13 EL32 - 13 DF80 - 193 EL32 - 13 Upper Beardmore Central Beardmore NBP9401 - 01 Darwin Terminus DF80 - 193 NBP9501 - 11 3 NBP9501 - 17 NBP9401 - 01 Mt. Achernar Allan Hills Cluster Analysis of Ross Sea Samples

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