Research Article| July 01, 2006 The age and origin of the Labyrinth, western Dry Valleys, Antarctica: Evidence for extensive middle Miocene subglacial floods and freshwater discharge to the Southern Ocean Adam R. Lewis; Adam R. Lewis 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar David R. Marchant; David R. Marchant 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar Douglas E. Kowalewski; Douglas E. Kowalewski 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar Suzanne L. Baldwin; Suzanne L. Baldwin 2Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA Search for other works by this author on: GSW Google Scholar Laura E. Webb Laura E. Webb 2Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Adam R. Lewis 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA David R. Marchant 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Douglas E. Kowalewski 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Suzanne L. Baldwin 2Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA Laura E. Webb 2Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA Publisher: Geological Society of America Received: 08 Aug 2005 Revision Received: 26 Jan 2006 Accepted: 02 Feb 2006 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 The Geological Society of America, Inc. Geology (2006) 34 (7): 513–516. https://doi.org/10.1130/G22145.1 Article history Received: 08 Aug 2005 Revision Received: 26 Jan 2006 Accepted: 02 Feb 2006 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Adam R. Lewis, David R. Marchant, Douglas E. Kowalewski, Suzanne L. Baldwin, Laura E. Webb; The age and origin of the Labyrinth, western Dry Valleys, Antarctica: Evidence for extensive middle Miocene subglacial floods and freshwater discharge to the Southern Ocean. Geology 2006;; 34 (7): 513–516. doi: https://doi.org/10.1130/G22145.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A 50+-km-long network of bedrock channels and scoured terrain occupies the ice-free portion of a major trough that crosses the Transantarctic Mountains in southern Victoria Land. The channels, collectively termed the Labyrinth, emerge from beneath the margin of the East Antarctic Ice Sheet (Wright Upper Glacier) and are incised into a 300-m-thick sill of Ferrar Dolerite at the head of Wright Valley. Upper- and intermediate-elevation erosion surfaces of the Labyrinth exhibit striations and molding characteristic of glacial erosion. Channels and canyons on the lower surface are as much as 600 m wide and 250 m deep, have longitudinal profiles with many reverse gradients, and contain potholes >35 m deep at tributary junctions. These characteristics are most consistent with incision from fast-flowing subglacial meltwater; estimated discharge is on the order of 1.6–2.2 × 106 m3s−1. Our 40Ar/39Ar analyses of volcanic tephra from the Labyrinth show that the channels are relict, that major channel incision predates 12.4 Ma, and that the last major subglacial flood occurred sometime between 14.4 Ma and 12.4 Ma. The most plausible origin for the Labyrinth is erosion associated with episodic drainage of subglacial lakes in East Antarctica. One compelling possibility is that discharge of large volumes of subglacial meltwater to the Southern Ocean, and to the Ross Sea in particular, may have coincided with, and contributed to, oscillations in regional and/or global climate during the middle Miocene. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Research Article| June 01, 2002 Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica D.R. Marchant; D.R. Marchant 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar A.R. Lewis; A.R. Lewis 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar W.M. Phillips; W.M. Phillips 2Department of Geography, University of Edinburgh, Edinburgh EH8 9XP, UK Search for other works by this author on: GSW Google Scholar E.J. Moore; E.J. Moore 3Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar R.A. Souchez; R.A. Souchez 4Départment des Sciences de la Terre et de l'Environment, CP 160/03, Université Libre de Bruxelles, B-1050 Bruxelles, Belgium Search for other works by this author on: GSW Google Scholar G.H. Denton; G.H. Denton 5Department of Geological Sciences and Institute for Quaternary Studies, University of Maine, Orono, Maine 04469, USA Search for other works by this author on: GSW Google Scholar D.E. Sugden; D.E. Sugden 6Department of Geography, University of Edinburgh, Edinburgh EH8 9XP, UK Search for other works by this author on: GSW Google Scholar N. Potter, Jr.; N. Potter, Jr. 7Department of Geology, Dickinson College, Carlisle, Pennsylvania 17013, USA Search for other works by this author on: GSW Google Scholar G.P. Landis G.P. Landis 8U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2002) 114 (6): 718–730. https://doi.org/10.1130/0016-7606(2002)114<0718:FOPGAS>2.0.CO;2 Article history received: 19 Apr 2001 rev-recd: 09 Jan 2002 accepted: 23 Jan 2002 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation D.R. Marchant, A.R. Lewis, W.M. Phillips, E.J. Moore, R.A. Souchez, G.H. Denton, D.E. Sugden, N. Potter, G.P. Landis; Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica. GSA Bulletin 2002;; 114 (6): 718–730. doi: https://doi.org/10.1130/0016-7606(2002)114<0718:FOPGAS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract A thin glacial diamicton, informally termed Granite drift, occupies the floor of central Beacon Valley in southern Victoria Land, Antarctica. This drift is <1.0 m thick and rests with sharp planar contacts on stagnant glacier ice reportedly of Miocene age, older than 8.1 Ma. The age of the ice is based on 40Ar/39Ar analyses of presumed in situ ash-fall deposits that occur within Granite drift. At odds with the great age of this ice are high-centered polygons that cut Granite drift. If polygon development has reworked and retransported ash-fall deposits, then they are untenable as chronostratigraphic markers and cannot be used to place a minimum age on the underlying glacier ice.Our results show that the surface of Granite drift is stable at polygon centers and that enclosed ash-fall deposits can be used to define the age of underlying glacier ice. In our model for patterned-ground development, active regions lie only above polygon troughs, where enhanced sublimation of underlying ice outlines high-centered polygons. The rate of sublimation is influenced by the development of porous gravel-and-cobble lag deposits that form above thermal-contraction cracks in the underlying ice. A negative feedback associated with the development of secondary-ice lenses at the base of polygon troughs prevents runaway ice loss. Secondary-ice lenses contrast markedly with glacial ice by lying on a δD versus δ18O slope of 5 rather than a precipitation slope of 8 and by possessing a strongly negative deuterium excess. The latter indicates that secondary-ice lenses likely formed by melting, downward percolation, and subsequent refreezing of snow trapped preferentially in deep polygon troughs.The internal stratigraphy of Granite drift is related to the formation of surface polygons and surrounding troughs. The drift is composed of two facies: A nonweathered, matrix-supported diamicton that contains >25% striated clasts in the >16 mm fraction and a weathered, clast-supported diamicton with varnished and wind-faceted gravels and cobbles. The weathered facies is a coarse-grained lag of Granite drift that occurs at the base of polygon troughs and in lenses within the nonweathered facies. The concentration of cosmogenic 3He in dolerite cobbles from two profiles through the nonweathered drift facies exhibits steadily decreasing values and shows the drift to have formed by sublimation of underlying ice. These profile patterns and the 3He surface-exposure ages of 1.18 ± 0.08 Ma and 0.18 ± 0.01 Ma atop these profiles indicate that churning of clasts by cryoturbation has not occurred at these sites in at least the past 105 and 106 yr. Although Granite drift is stable at polygon centers, low-frequency slump events occur at the margin of active polygons. Slumping, together with weathering of surface clasts, creates the large range of cosmogenic-nuclide surface-exposure ages observed for Granite drift. Maximum rates of sublimation near active thermal-contraction cracks, calculated by using the two 3He depth profiles, range from 5 m/m.y. to 90 m/m.y. Sublimation rates are likely highest immediately following major slump events and decrease thereafter to values well below our maximum estimates. Nevertheless, these rates are orders of magnitude lower than those computed on theoretical grounds. During eruptions of the nearby McMurdo Group volcanic centers, ash-fall debris collects at the surface of Granite drift, either in open thermal-contraction cracks or in deep troughs that lie above contraction cracks; these deposits subsequently lower passively as the underlying glacier ice sublimes. The fact that some regions of Granite drift have escaped modification by patterned ground for at least 8.1 Ma indicates long-term geomorphic stability of individual polygons. Once established, polygon toughs likely persist for as long as 105–106 yr. Our model of patterned-ground formation, which applies to the hyperarid, cold-desert, polar climate of Antarctica, may also apply to similar-sized polygons on Mars that occur over buried ice in Utopia Planitia. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Research Article| November 01, 2007 Major middle Miocene global climate change: Evidence from East Antarctica and the Transantarctic Mountains A.R. Lewis; A.R. Lewis 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar D.R. Marchant; D.R. Marchant 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar A.C. Ashworth; A.C. Ashworth 2Department of Geosciences, North Dakota State University, Fargo, North Dakota 58105, USA Search for other works by this author on: GSW Google Scholar S.R. Hemming; S.R. Hemming 3Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA Search for other works by this author on: GSW Google Scholar M.L. Machlus M.L. Machlus 3Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2007) 119 (11-12): 1449–1461. https://doi.org/10.1130/0016-7606(2007)119[1449:MMMGCC]2.0.CO;2 Article history received: 26 Oct 2006 rev-recd: 26 Mar 2007 accepted: 08 May 2007 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation A.R. Lewis, D.R. Marchant, A.C. Ashworth, S.R. Hemming, M.L. Machlus; Major middle Miocene global climate change: Evidence from East Antarctica and the Transantarctic Mountains. GSA Bulletin 2007;; 119 (11-12): 1449–1461. doi: https://doi.org/10.1130/0016-7606(2007)119[1449:MMMGCC]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract We present a glacial record from the western Olympus Range, East Antarctica, that documents a permanent shift in the thermal regime of local glaciers, from wet- to cold-based regimes, more than 13.94 m.y. ago. This glacial record provides the first terrestrial evidence linking middle Miocene global climate cooling to a permanent reorganization of the Antarctic cryosphere and to subsequent growth of the polar East Antarctic Ice Sheet. The composite stratigraphic record constructed from field mapping and analyses of 281 soil excavations shows a classic wet-based till (Circe till, including an extensive melt-out facies), overlain by a weathered colluvial deposit (Electra colluvium), and then a series of stacked tills deposited from cold-based ice (Dido drift). Chronologic control comes from 40Ar/39Ar analyses of concentrated ash-fall deposits interbedded within glacial deposits. The shift from wet- to cold-based glaciation reflects a drop in mean annual temperature of 25–30 °C and is shown to precede one or more major episodes of ice-sheet expansion across the region, the youngest of which occurred between 13.62 and 12.44 Ma. One implication is that atmospheric cooling, following a relatively warm mid-Miocene climatic optimum ca. 17 to 15 Ma, may have led to, and thus triggered, maximum ice-sheet overriding. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Research Article| November 01, 2007 Major middle Miocene global climate change: Evidence from East Antarctica and the Transantarctic Mountains A.R. Lewis; A.R. Lewis 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar D.R. Marchant; D.R. Marchant 1Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar A.C. Ashworth; A.C. Ashworth 2Department of Geosciences, North Dakota State University, Fargo, North Dakota 58105, USA Search for other works by this author on: GSW Google Scholar S.R. Hemming; S.R. Hemming 3Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA Search for other works by this author on: GSW Google Scholar M.L. Machlus M.L. Machlus 3Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2007) 119 (11-12): 1449–1461. https://doi.org/10.1130/0016-7606(2007)119[1449:MMMGCC]2.0.CO;2 Article history received: 26 Oct 2006 rev-recd: 26 Mar 2007 accepted: 08 May 2007 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation A.R. Lewis, D.R. Marchant, A.C. Ashworth, S.R. Hemming, M.L. Machlus; Major middle Miocene global climate change: Evidence from East Antarctica and the Transantarctic Mountains. GSA Bulletin 2007;; 119 (11-12): 1449–1461. doi: https://doi.org/10.1130/0016-7606(2007)119[1449:MMMGCC]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract We present a glacial record from the western Olympus Range, East Antarctica, that documents a permanent shift in the thermal regime of local glaciers, from wet- to cold-based regimes, more than 13.94 m.y. ago. This glacial record provides the first terrestrial evidence linking middle Miocene global climate cooling to a permanent reorganization of the Antarctic cryosphere and to subsequent growth of the polar East Antarctic Ice Sheet. The composite stratigraphic record constructed from field mapping and analyses of 281 soil excavations shows a classic wet-based till (Circe till, including an extensive melt-out facies), overlain by a weathered colluvial deposit (Electra colluvium), and then a series of stacked tills deposited from cold-based ice (Dido drift). Chronologic control comes from 40Ar/39Ar analyses of concentrated ash-fall deposits interbedded within glacial deposits. The shift from wet- to cold-based glaciation reflects a drop in mean annual temperature of 25–30 °C and is shown to precede one or more major episodes of ice-sheet expansion across the region, the youngest of which occurred between 13.62 and 12.44 Ma. One implication is that atmospheric cooling, following a relatively warm mid-Miocene climatic optimum ca. 17 to 15 Ma, may have led to, and thus triggered, maximum ice-sheet overriding. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Summary A cold-based, debris-covered alpine glacier in Mullins Valley, a tributary to upper Beacon Valley, contains ancient glacier ice. Four independent dating techniques confirm that the glacier age ranges from ~10 ka near the valley head, to >8 Ma at its diffuse terminus in central Beacon Valley (where it abuts opposing buried ice that originated from Taylor Glacier; e.g., Sugden et al., 1995). The dating methods include 1) cosmogenic-nuclide analyses of boulders from a sublimation till that caps the ice; 2) numerical ice-flow modeling of the glacier system; 3) 40 Ar/ 39 Ar analyses of in-situ ash fall from relict polygon troughs at the till surface; and, 4) modern horizontal ice-flow velocities as determined from synthetic aperture radar interferometry (InSar, from Rignot et al., 2002). Multi-channel seismic surveys demonstrate that the ancient ice is ~45 to ~100 m thick in Mullins Valley and ~150 m thick in upper Beacon Valley. Citation: Marchant, D.R., Phillips, W.M., Schaefer, J.M., Fastook, J.L., Shean, D.E., Head, J.W., Kowalewski, D.E. and A.R. Lewis (2007), Estab-lishing a chronology for the world’s oldest glacier ice.
This study describes 16 well-dated, terrestrial glacial sedimentary cycles deposited during astronomically paced climate cycles from the termination of the Miocene Climatic Optimum (MCO) through the middle Miocene Climate Transition (MMCT) (15.1−13.8 Ma) in the Friis Hills, Transantarctic Mountains, Antarctica. Three locations were continuously cored (79% recovery) to a maximum depth of 50.48 m through a succession of interbedded till sheets and fossil-bearing, fluvio-lacustrine sediments. A composite chronostratigraphic framework is presented for the cores based on the previous mapping, a seismic refraction survey that defines basin geometry, and a new, integrated age model based on paleomagnetic stratigraphy that is constrained by radioisotopic 40Ar/39Ar numeric ages on two newly identified silicic tephra. The paleoecologic and sedimentologic characteristics of organic-rich lithologies are relatively consistent up-section, which implies that successively younger interglacial deposits during the MMCT represented broadly similar environmental and climatic conditions. During these interglacials, the Friis Hills hinterland was likely ice-free. Major disconformities in the section suggest a transition to colder climates, and after ca. 14.6 Ma, thicker, more extensive and erosive ice cover occurred across the Friis Hills during glacial episodes. Diamictites in the upper three cycles suggest that climate cooled and became drier after ca. 14.2 Ma. However, cyclical retreat of the ice and a return to warm climate conditions during interglacials continued through ca. 13.9 Ma. These direct records reflect a highly variable East Antarctic Ice Sheet margin but show that the ice margin became progressively more extensive during successive glacial intervals, which is consistent with a cooling trend toward more glacial values in the far-field benthic foraminifera δ18O proxy ice volume and temperature record. Age constraints show that glacial-interglacial variability at the terrestrial margin of the East Antarctic Ice Sheet was primarily paced by astronomical precession (∼23 k.y.) through the onset of the MMCT (15−14.7 Ma). Precession-driven cycles are modulated by short-period (∼100 k.y.) eccentricity cycles. Intervals of maximum eccentricity (high seasonality) coincide with sedimentary cycles comprising thin diamictites and relatively thick interglacial sandstone and mudstone units. Intervals of minimum eccentricity (low seasonality) coincide with sedimentary cycles comprising thick diamictites and relatively thin interglacial sedimentary deposits. Major disconformities in the Friis Hills succession that span more than ∼100 k.y. reflect episodes of expansion of erosive ice across, and well beyond, the Transantarctic Mountains and coincide with nodes in eccentricity (∼400 k.y.). These relationships suggest that during relatively warm intervals in the middle Miocene, the East Antarctic Ice Sheet expanded and contracted over 100 k.y. cycles, while its margins continued to fluctuate at higher (∼23 k.y.) frequency. After 14.5 Ma, obliquity is the dominant frequency in δ18O records, marking a period during which large regions of the Antarctic Ice Sheet grounded in marine environments.
'/%3e%3cuse xlink:href='%23a' transform='rotate(72 0 0)'/%3e%3cuse xlink:href='%23a' transform='rotate(-72 0 0)'/%3e%3cuse xlink:href='%23a' transform='scale(-1 1) rotate(72)'/%3e%3c/g%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h1200v600H0z'/%3e%3cpath stroke='%23FFF' stroke-width='60' d='m0 0 600 300M0 300 600 0' clip-path='url(%23b)'/%3e%3cpath stroke='%23C8102E' stroke-width='40' d='m0 0 600 300M0 300 600 0' clip-path='url(%23c)'/%3e%3cpath stroke='%23FFF' stroke-width='100' d='M300 0v300M0 150h600' clip-path='url(%23b)'/%3e%3cpath stroke='%23C8102E' stroke-width='60' d='M300 0v300M0 150h600' clip-path='url(%23b)'/%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='matrix(45.4 0 0 45.4 900 120)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='matrix(30 0 0 30 900 120)'/%3e%3cg transform='rotate(82 900 240)'%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='rotate(-82 519.022 -457.666) scale(40.4)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='rotate(-82 519.022 -457.666) scale(25)'/%3e%3c/g%3e%3cg transform='rotate(82 900 240)'%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='rotate(-82 668.57 -327.666) scale(45.4)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='rotate(-82 668.57 -327.666) scale(30)'/%3e%3c/g%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='matrix(50.4 0 0 50.4 900 480)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='matrix(35 0 0 35 900 480)'/%3e%3c/svg%3e)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)