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Guevara VE, Smye AJ, Caddick MJ, Searle MP, Olsen T, Whalen L, Kylander-Clark ARC, Jercinovic MJ, Waters DJ. A modern pulse of ultrafast exhumation and diachronous crustal melting in the Nanga Parbat Massif. SCIENCE ADVANCES 2022; 8:eabm2689. [PMID: 35930636 PMCID: PMC9355356 DOI: 10.1126/sciadv.abm2689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Accepted: 04/15/2022] [Indexed: 05/26/2023]
Abstract
We combine monazite petrochronology with thermal modeling to evaluate the relative roles of crustal melting, surface denudation, and tectonics in facilitating ultrafast exhumation of the Nanga Parbat Massif in the western Himalayan syntaxis. Our results reveal diachronous melting histories between samples and a pulse of ultrafast exhumation (9 to 13 mm/year) that began ~1 Ma and was preceded by several million years of slower, but still rapid, exhumation (2 to 5 mm/year). Recent studies show that an exhumation pulse of similar timing and magnitude occurred in the eastern Himalayan syntaxis. A synchronous exhumation pulse in both Himalayan syntaxes suggests that neither erosion by rivers and/or glaciers nor a pulse of crustal melting was a primary trigger for accelerated exhumation. Rather, our results, combined with those of recent studies in the eastern syntaxis, imply that larger-scale tectonic processes impose the dominant control on the current tempo of rapid exhumation in the Himalayan syntaxes.
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Affiliation(s)
- Victor E. Guevara
- Geology Department, Amherst College, 220 South Pleasant Street, Amherst, MA 01002, USA
| | - Andrew J. Smye
- Department of Geosciences, Pennsylvania State University, 332 Deike Building, University Park, PA 16802, USA
| | - Mark J. Caddick
- Department of Geosciences, Virginia Tech, 4044 Derring Hall, 926 W. Campus Drive, Blacksburg, VA 24061, USA
| | - Michael P. Searle
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
| | - Telemak Olsen
- Geology Department, Western Washington University, 516 High Street, Bellingham, WA 98225, USA
| | - Lisa Whalen
- Department of Geosciences, Virginia Tech, 4044 Derring Hall, 926 W. Campus Drive, Blacksburg, VA 24061, USA
| | - Andrew R. C. Kylander-Clark
- Department of Earth Science, University of California, Santa Barbara, 1006 Webb Hall, Santa Barbara, CA 93106, USA
| | - Michael J. Jercinovic
- Department of Geosciences, University of Massachusetts, 627 North Pleasant Street, Amherst, MA 01003, USA
| | - David J. Waters
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
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Bailey I, Hemming S, Reilly BT, Rollinson G, Williams T, Weber ME, Raymo ME, Peck VL, Ronge TA, Brachfeld S, O'Connell S, Tauxe L, Warnock JP, Armbrecht L, Cardillo FG, Du Z, Fauth G, Garcia M, Glueder A, Guitard M, Gutjahr M, Hernández‐Almeida I, Hoem FS, Hwang J, Iizuka M, Kato Y, Kenlee B, Martos YM, Pérez LF, Seki O, Tripathi S, Zheng X. Episodes of Early Pleistocene West Antarctic Ice Sheet Retreat Recorded by Iceberg Alley Sediments. PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY 2022; 37:e2022PA004433. [PMID: 36247355 PMCID: PMC9544630 DOI: 10.1029/2022pa004433] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 05/11/2022] [Accepted: 06/08/2022] [Indexed: 06/16/2023]
Abstract
Ice loss in the Southern Hemisphere has been greatest over the past 30 years in West Antarctica. The high sensitivity of this region to climate change has motivated geologists to examine marine sedimentary records for evidence of past episodes of West Antarctic Ice Sheet (WAIS) instability. Sediments accumulating in the Scotia Sea are useful to examine for this purpose because they receive iceberg-rafted debris (IBRD) sourced from the Pacific- and Atlantic-facing sectors of West Antarctica. Here we report on the sedimentology and provenance of the oldest of three cm-scale coarse-grained layers recovered from this sea at International Ocean Discovery Program Site U1538. These layers are preserved in opal-rich sediments deposited ∼1.2 Ma during a relatively warm regional climate. Our microCT-based analysis of the layer's in-situ fabric confirms its ice-rafted origin. We further infer that it is the product of an intense but short-lived episode of IBRD deposition. Based on the petrography of its sand fraction and the Phanerozoic 40Ar/39Ar ages of hornblende and mica it contains, we conclude that the IBRD it contains was likely sourced from the Weddell Sea and/or Amundsen Sea embayment(s) of West Antarctica. We attribute the high concentrations of IBRD in these layers to "dirty" icebergs calved from the WAIS following its retreat inland from its modern grounding line. These layers also sit at the top of a ∼366-m thick Pliocene and early Pleistocene sequence that is much more dropstone-rich than its overlying sediments. We speculate this fact may reflect that WAIS mass-balance was highly dynamic during the ∼41-kyr (inter)glacial world.
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Affiliation(s)
- Ian Bailey
- Camborne School of MinesUniversity of ExeterPenryn CampusCornwallUK
| | - Sidney Hemming
- Lamont‐Doherty Earth ObservatoryColumbia UniversityPalisadesNYUSA
| | - Brendan T. Reilly
- Scripps Institution of OceanographyUniversity of California San DiegoLa JollaCAUSA
| | - Gavyn Rollinson
- Camborne School of MinesUniversity of ExeterPenryn CampusCornwallUK
| | - Trevor Williams
- International Ocean Discovery ProgramTexas AM UniversityCollege StationTXUSA
| | - Michael E. Weber
- Department of Geochemistry and PetrologyInstitute for GeosciencesUniversity of BonnBonnGermany
| | - Maureen E. Raymo
- Lamont‐Doherty Earth ObservatoryColumbia UniversityPalisadesNYUSA
| | | | - Thomas A. Ronge
- Alfred‐Wegener‐Institut Helmholtz‐Zentrum für Polar‐und MeeresforschungBremerhavenGermany
| | | | - Suzanne O'Connell
- Department of Earth and Environmental SciencesWesleyan UniversityMiddletownCTUSA
| | - Lisa Tauxe
- Scripps Institution of OceanographyUniversity of California San DiegoLa JollaCAUSA
| | | | - Linda Armbrecht
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaBattery PointTASAustralia
| | - Fabricio G. Cardillo
- Departmento OceanografiaServicio de Hidrografia NavalMinisterio de DefensaBuenos AiresArgentina
| | - Zhiheng Du
- State Key Laboratory of Cryospheric ScienceNorthwest Institute of Eco‐Environment and ResourcesLanzhouChina
| | - Gerson Fauth
- Geology ProgramUniversity of Vale do Rio dos SinosSão LeopoldoBrazil
| | - Marga Garcia
- Andalusian Institute of Earth Science (CSIC‐UGR)GranadaSpain
- Cádiz Oceanographic Centre (IEO‐CSIC)CádizSpain
| | - Anna Glueder
- College of Earth, Ocean, and Atmospheric SciencesOregon State UniversityCorvallisORUSA
| | - Michelle Guitard
- College of Marine ScienceUniversity of South FloridaSt. PetersburgFLUSA
| | - Marcus Gutjahr
- GEOMARHelmholtz Centre for Ocean ResearchUniversity of KielKielGermany
| | | | - Frida S. Hoem
- Department of Earth Science, Marine Palynology and PaleoceanographyUtrecht UniversityUtrechtThe Netherlands
| | - Ji‐Hwan Hwang
- Earth Environmental SciencesKorea Basic Science InstituteChungbuk CheongjuRepublic of Korea
| | | | - Yuji Kato
- Faculty of Life and Environmental SciencesUniversity of TsukubaTsukubaJapan
| | - Bridget Kenlee
- Department of Earth SciencesUniversity of California RiversideRiversideCAUSA
| | - Yasmina M. Martos
- NASA Goddard Space Flight CenterPlanetary Magnetospheres LaboratoryGreenbeltMDUSA
- Department of AstronomyUniversity of MarylandCollege ParkMDUSA
| | - Lara F. Pérez
- British Antarctic SurveyCambridgeUK
- Department of Marine GeologyGeological Survey of Denmark and GreenlandAarhus University CityAarhusDenmark
| | - Osamu Seki
- Institute of Low Temperature ScienceHokkaido UniversitySapporoJapan
| | - Shubham Tripathi
- Marine Stable Isotope LabNational Centre for Polar and Ocean ResearchMinistry of Earth SciencesVasco Da GamaIndia
| | - Xufeng Zheng
- South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhouChina
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Yan Y, Brook EJ, Kurbatov AV, Severinghaus JP, Higgins JA. Ice core evidence for atmospheric oxygen decline since the Mid-Pleistocene transition. SCIENCE ADVANCES 2021; 7:eabj9341. [PMID: 34910502 PMCID: PMC8673763 DOI: 10.1126/sciadv.abj9341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 11/03/2021] [Indexed: 06/14/2023]
Abstract
The history of atmospheric oxygen (PO2) and the processes that act to regulate it remain enigmatic because of difficulties in quantitative reconstructions using indirect proxies. Here, we extend the ice-core record of PO2 using 1.5-million-year-old (Ma) discontinuous ice samples drilled from Allan Hills Blue Ice Area, East Antarctica. No statistically significant difference exists in PO2 between samples at 1.5 Ma and 810 thousand years (ka), suggesting that the Late-Pleistocene imbalance in O2 sources and sinks began around the time of the transition from 40- to 100-ka glacial cycles in the Mid-Pleistocene between ~1.2 Ma and 700 ka. The absence of a coeval secular increase in atmospheric CO2 over the past ~1 Ma requires negative feedback mechanisms such as Pco2-dependent silicate weathering. Fast processes must also act to suppress the immediate Pco2 increase because of the imbalance in O2 sinks over sources beginning in the Mid-Pleistocene.
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Affiliation(s)
- Yuzhen Yan
- Department of Geosciences, Princeton University, Princeton, NJ, USA
- Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA
| | - Edward J. Brook
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | | | | | - John A. Higgins
- Department of Geosciences, Princeton University, Princeton, NJ, USA
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Cowan EA, Zellers SD, Müller J, Walczak MH, Worthington LL, Caissie BE, Clary WA, Jaeger JM, Gulick SPS, Pratt JW, Mix AC, Fallon SJ. Sediment controls dynamic behavior of a Cordilleran Ice Stream at the Last Glacial Maximum. Nat Commun 2020; 11:1826. [PMID: 32286283 PMCID: PMC7156478 DOI: 10.1038/s41467-020-15579-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Accepted: 03/17/2020] [Indexed: 11/14/2022] Open
Abstract
The uncertain response of marine terminating outlet glaciers to climate change at time scales beyond short-term observation limits models of future sea level rise. At temperate tidewater margins, abundant subglacial meltwater forms morainal banks (marine shoals) or ice-contact deltas that reduce water depth, stabilizing grounding lines and slowing or reversing glacial retreat. Here we present a radiocarbon-dated record from Integrated Ocean Drilling Program (IODP) Site U1421 that tracks the terminus of the largest Alaskan Cordilleran Ice Sheet outlet glacier during Last Glacial Maximum climate transitions. Sedimentation rates, ice-rafted debris, and microfossil and biogeochemical proxies, show repeated abrupt collapses and slow advances typical of the tidewater glacier cycle observed in modern systems. When global sea level rise exceeded the local rate of bank building, the cycle of readvances stopped leading to irreversible retreat. These results support theory that suggests sediment dynamics can control tidewater terminus position on an open shelf under temperate conditions delaying climate-driven retreat. Tidewater glaciers in fjords can advance/retreat independent of climate due to stabilization by sediments at their termini. We show that an Alaskan paleo-ice stream behaved similarly on an open shelf, suggesting that increased sediment flux may delay catastrophic retreat of outlet glaciers in a warming world.
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Affiliation(s)
- Ellen A Cowan
- Department of Geological and Environmental Sciences, Appalachian State University, Box 32067, Boone, NC, 28608, USA.
| | - Sarah D Zellers
- School of Geoscience, Physics, and Safety, University of Central Missouri, Warrensburg, MO, 64093, USA
| | - Juliane Müller
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, 27568, Bremerhaven, Germany.,Center for Marine Environmental Sciences, University of Bremen/MARUM, 28359, Bremen, Germany
| | - Maureen H Walczak
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, 97331, USA
| | - Lindsay L Worthington
- Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Beth E Caissie
- Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA, 50011, USA
| | - Wesley A Clary
- Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, 87131, USA
| | - John M Jaeger
- Department of Geological Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - Sean P S Gulick
- Institute for Geophysics & Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, 78758, USA
| | - Jacob W Pratt
- Department of Geological and Environmental Sciences, Appalachian State University, Box 32067, Boone, NC, 28608, USA
| | - Alan C Mix
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, 97331, USA
| | - Stewart J Fallon
- Research School of Earth Science, The Australian National University, Canberra, ACT, 2601, Australia
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5
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Ice sheets as a missing source of silica to the polar oceans. Nat Commun 2017; 8:14198. [PMID: 28120824 PMCID: PMC5288494 DOI: 10.1038/ncomms14198] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 12/07/2016] [Indexed: 11/15/2022] Open
Abstract
Ice sheets play a more important role in the global silicon cycle than previously appreciated. Input of dissolved and amorphous particulate silica into natural waters stimulates the growth of diatoms. Here we measure dissolved and amorphous silica in Greenland Ice Sheet meltwaters and icebergs, demonstrating the potential for high ice sheet export. Our dissolved and amorphous silica flux is 0.20 (0.06–0.79) Tmol year−1, ∼50% of the input from Arctic rivers. Amorphous silica comprises >95% of this flux and is highly soluble in sea water, as indicated by a significant increase in dissolved silica across a fjord salinity gradient. Retreating palaeo ice sheets were therefore likely responsible for high dissolved and amorphous silica fluxes into the ocean during the last deglaciation, reaching values of ∼5.5 Tmol year−1, similar to the estimated export from palaeo rivers. These elevated silica fluxes may explain high diatom productivity observed during the last glacial–interglacial period. Glacial runoff often has relatively low dissolved silica concentrations and therefore ice sheets have been thought insignificant in the global silicon cycle. Here, the authors show that ice sheets likely play an important role in the production and export of dissolved and dissolvable amorphous silica downstream.
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