Southern Victoria Land Research Articles

Depositional framework of Permian coal-bearing strata, southern Victoria Land, Antarctica

Abstract The Permian Weller Coal Measures of Antarctica are exposed in a narrow belt that extends along the edge of the Polar Plateau from the Mawson Glacier to the Mulock Glacier in southern Victoria Land. These rocks record a rapid change from glacial to postglacial conditions, with the establishment of polar peat forming conditions, during the late Paleozoic in Antarctica. The 222 m thick Weller consists of interstratified fine- to coarse-grained quartzo-feldspathic sandstone, laminated siltstone, mudstone and coal. Regional lithofacies patterns and paleocurrent orientations define a narrow elongate basin. In the lower Weller, coarse-grained sandstone sheets occur along both eastern and western basin margins. These deposits are similar to those of modern sandy braided streams. Toward the axis of the basin, this lithofacies grades into coarse-grained tabular sandstone. Lateral-accretion beds suggest that deposition of this lithofacies occurred within meandering streams. Coarse-grained basin-margin deposits interfinger with fine-grained basin-axis lithofacies of interstratified laminated siltstone and graded sandstone beds deposited from suspension and underflow currents within a lacustrine environment. In the upper Weller, braided stream deposits dominate much of the basin, grading downstream into meandering streams. Establishment of vegetation in southern Victoria Land occurred immediately following late Paleozoic deglaciation. Upward in the Weller, the distribution of plant fossils and coal seams is lithofacies dependent. Thick coals and abundant plant fossils occur in meandering stream lithofacies, while they are scarce within the lacustrine and braided stream deposits. Abrasion during transport probably contributed to the destruction of vegetable material in the braided stream environments, and to material introduced into the axial lake. Depositional patterns within the Weller Coal Measures are similar to those in the Takrouna Formation in northern Victoria Land. Similarities suggest deposition in either the same or a similar basin. Comparison of the Weller Coal Measures with Permian strata in the central Transantarctic Mountains suggest deposition in two separate basins, which are now juxtaposed across the Byrd Glacier, the sight of a possible Cenozoic strike-slip fault. Causes for the formation of the depositional basin containing the Weller Coal Measures are unknown; however, the geometry of the basin and the regional distribution of lithofacies are similar to those of rift basins and to basins excavated by glacial erosion. The ultimate cause of basin subsidence however, may be related to long-distance stress produced during late Paleozoic orogenic activity along the paleo-Pacific margin of Antarctica.

Additions and corrections to the lichen flora of the Kar Plateau, Southern Victoria Land, Antarctica

Abstract Nomenclatural corrections and species additions are provided for the published flora of the Kar Plateau, Southern Victoria Land, Antarctica. The combination Rhizoplaca priestleyi (Dodge) Seppelt is validated to accommodate Omphalodina priestleyi (Dodge) Dodge. Physcia dubia and an undetermined species of Buellia are added to the lichen flora. The lichen parasite Thelidiola caloplacae is considered referable to Muellerella. Aspicilia glacialis is confirmed for the Plateau.

Miocene and Pliocene paleoclimate of the Dry Valleys region, Southern Victoria land: a geomorphological approach

The Dry Valleys region is a hyper-arid, cold polar desert. Modern climate varies systematically with increasing elevation and distance from the coast. We distinguish three microclimate zones on the basis of varying precipitation, wind direction, relative humidity, temperature, and soil-moisture content. Zone 1 represents coastal, Zone 2 intermediate, and Zone 3 far-western areas of the Dry Valleys region. Soil-moisture content and relative humidity are the key parameters that control the areal distribution of solifluction terraces, gelifluction lobes, polygonal ground, scree slopes, and soil development in Zones 1, 2 and 3. The coastal Zone 1 shows active solifluction terraces, gelifluction lobes, levees, streams, debris flows, mudflows, and subxerous soils. The intermediate Zone 2 contains little evidence for modern downslope movement; here active gelifluction lobes, debris flows, and streams are largely restricted to north-facing slopes with high moisture content. The inland Zone 3 lacks evidence for significant modern downslope movement. There are no active solifluction terraces, stream channels, debris flows, or levees in Zone 3. Instead, Zone 3 shows Miocene- and Pliocene-age sand wedges, avalanche cones, and desert pavements. The mid-Miocene landsurface of Zone 3 is preserved to a remarkable degree. The antiquity and longevity of paleoforms in Zone 3 can be readily demonstrated by the topographic position of dated ashfall deposits. Our chronology comes from laser-fusion 40Ar/ 39Ar analyses of in-situ ashfall deposits that rest at, or just below, the ground surface in Zones 2 and 3 ( Marchant et al., 1993a,b,c, 1995). The lack of gelifluction lobes, solifluction terraces, rills, levees, and stream channels on in-situ Miocene- and Pliocene-age deposits in Zone 3 indicates that here mean-annual air temperature, soil moisture content, and relative humidity did not reach levels that now occur in Zones 1 and 2. The present mean-annual air temperature and relative humidity of Zones 1 and 2 are about −17 °C/ 75% and −27 °C/ 45%, respectively. The implication is that climatic wanning of the magnitude necessary for East Antarctic Ice Sheet deglaciation predicted by some glaciological models (e.g., about 20 °C above present values according to Huybrechts, 1993) and growth of vascular vegetation in the Transantarctic Mountains (e.g., Webb and Harwood, 1993) could not have occurred during Pliocene time. In addition, the preservation of Miocene-age ashfall deposits, avalanche cones, and delicate desert pavements strongly suggest that no wet-based, erosive glaciers advanced into the far western Dry Valleys region above 1200 m elevation during late Pliocene time. Overall, our paleoclimate record from the Dry Valleys region implies an enduring East Antarctic Ice Sheet since Middle Miocene time. This makes it difficult to ascribe large-scale Pliocene sea-level fluctuations to ice-volume variations on the East Antarctic craton.

Evidence for regional climate change in the recent evolution of a high latitude pro-glacial lake

Lake Wilson, a perennially ice-capped, deep (>100 m) lake at 80°S in southern Victoria Land was investigated in January 1993. Water chemistry and physical structure showed three distinct layers; an upper c. 35 m mixed layer of low salinity, moderately turbid water; a less turbid mid layer, 20 m thick of slightly higher salinity and supersaturated with oxygen; and a deep 20 m brackish layer (conductivity c. 4000 μS cm−1) with anoxic conditions in the lower 5 m. Extreme supersaturation of N2O (up to 400 times air saturation) together with high nitrate concentration (4000 mg m−3) was recorded in the deep layer. Phytoplankton biomass and photosynthetic activity was confined to the upper mixed layer and the band of supersaturated dissolved oxygen located at 40–55 m appears to represent a relict layer from when the lake level was lower. The evidence from a comparison of profiles between 1975 and 1993 suggests that Lake Wilson has risen 25 m since 1975, synchronous with a period of lake level rise in the McMurdo Dry Valleys lakes to the north at 77°S. Geochemical diffusion models indicate that Lake Wilson had evaporated to a smaller brine lake about 1000 yrs BP, which also fits the pattern shown by the McMurdo Dry Valleys lakes. Climate changes influencing lake levels have thus covered a wide area of southern Victoria Land.

Late Cenozoic Antarctic paleoclimate reconstructed from volcanic ashes in the Dry Valleys region of southern Victoria Land

Research Article| February 01, 1996 Late Cenozoic Antarctic paleoclimate reconstructed from volcanic ashes in the Dry Valleys region of southern Victoria Land David R. Marchant; David R. Marchant 1Institute for Quaternary Studies, University of Maine, Orono, Maine 04469 Search for other works by this author on: GSW Google Scholar George H. Denton; George H. Denton 2Department of Geological Sciences and Institute for Quaternary Studies, University of Maine, Orono, Maine 04469 Search for other works by this author on: GSW Google Scholar Carl C. Swisher, III; Carl C. Swisher, III 3Berkeley Geochronology Center, Berkeley, California 94709 Search for other works by this author on: GSW Google Scholar Noel Potter, Jr Noel Potter, Jr 4Department of Geology, Dickinson College, Carlisle, Pennsylvania 17013 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1996) 108 (2): 181–194. https://doi.org/10.1130/0016-7606(1996)108<0181:LCAPRF>2.3.CO;2 Article history 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 David R. Marchant, George H. Denton, Carl C. Swisher, Noel Potter; Late Cenozoic Antarctic paleoclimate reconstructed from volcanic ashes in the Dry Valleys region of southern Victoria Land. GSA Bulletin 1996;; 108 (2): 181–194. doi: https://doi.org/10.1130/0016-7606(1996)108<0181:LCAPRF>2.3.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 report the discovery of numerous in situ Miocene and Pliocene airfall volcanic ashes that occur within the hyperarid Dry Valleys region of the Transantarctic Mountains in southern Victoria Land, Antarctica. Ashes that occur above 1000 m elevation rest at the ground surface, covered only by a thin ventifact pavement 1 to 2 cm thick. The ash deposits are loose and unconsolidated and show no signs of chemical weathering. Laser-fusion 40Ar/39Ar analyses of volcanic crystals and glass shards indicate that the ashes range from 4.33 Ma to 15.15 Ma in age. The Arena Valley ash (4.33 ± 0.07 Ma) rests on the surface of a well-developed desert pavement and ultraxerous soil profile at 1410 m elevation. Lack of geomorphic evidence of liquid water on surficial sediments coeval and older than the Arena Valley ash, together with the pristine condition of volcanic crystals and lack of authigenic clay formation, indicates a cold desert at and since 4.33 Ma. The Beacon Valley ash (10.66 ± 0.29 Ma), the Koenig Valley ash (13.65 ± 0.06 Ma), and the Nibelungen Valley ash (15.15 ± 0.02 Ma) fill the upper half of relict sand-wedge troughs that form only in cold-desert conditions. The lack of authigenic clay-sized minerals in these ash deposits, along with preservation of sharp lateral contacts with surrounding sand-and-gravel deposits, suggests that frozen conditions (without rain or well-developed active layers during summer months) have persisted in Beacon, Koenig, and Nibelungen Valleys since ash deposition. Ash-avalanche deposits that rest on rectilinear slopes contain matrix ash dated to 7.42 ± 0.31 Ma in upper Arena Valley and 11.28 ± 0.05 Ma in lower Arena Valley. Little slope development has occurred since emplacement of these ash-avalanche deposits. Such slope stability is consistent with cold-desert conditions well below 0 °C. Taken together, these ash deposits point to persistent polar conditions similar to the present at elevations above 1000 m in the western Dry Valleys region during at least the last 15.0 m.y. This conclusion contradicts the view that, during part of the Pliocene epoch, East Antarctica was largely free of glacier ice and that scrub vegetation (Nothofagus, Southern Beech) survived along the Transantarctic Mountain front in the Dry Valleys region and to at least lat 86°S (Webb and Harwood, 1993). Instead, it supports marine and geomorphological evidence that calls for a stable Antarctic cryosphere, much the same as today, since middle Miocene time. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Jurassic titaniferous ironstone in a Devonian host: Pivot Coal Measures expunged

The Devonian, Pivot Coal Measures in southern Victoria Land are non-carbonaceous. The sequence contains bedding parallel, titaniferous ironstones up to 50 cm thick, but no coal or carbonaceous shale, the unit is consequently renamed Pivot Member of the Arena Sandstone. The more Fe-Ti oxide-rich (up to 40 modal %) beds appear black and coal-like with conchoidal fracture and closely spaced cleat-like fractures. The coal-like beds grade laterally and vertically into less altered sedimentary rocks in which fine bedding-parallel concentrations of Fe-Ti oxide pick-out parting surfaces on ripples and other sedimentary structures. Thin section petrography shows that the Fe-Ti oxide is replacive, and outcrop relationships show that the replacement was related to dolerite intrusion 200 million years after the sedimentary host was deposited. Replacement of muscovite, biotite and chlorite by Fe-Ti-oxide occurred at 179 ± 3 Ma, at pressures of 0.3–0.4 kbar and at temperatures as low as 380°C.

Implications for Gondwana of new Ordovician paleomagnetic data from igneous rocks in southern Victoria Land, East Antarctica

New paleomagnetic data presented here from the southern Victoria Land (SVL) region of East Antarctica further refine the Gondwana early Paleozoic apparent polar wander path. The results are based on paleomagnetic analyses of Early to Middle Ordovician granitoids and dike swarms from which a new SVL pole (23°E, 3.5°S, A95 = 5.9°) was calculated. The new SVL paleomagnetic pole agrees with less well‐determined Ordovician poles from other parts of East Antarctica indicating little or no translation/rotation across the East Antarctic craton since the Middle Ordovician. A new Gondwana ∼475 Ma mean pole (11°E 36°N, A95 = 7°, N = 4 studies, in African coordinates) has been calculated from African, Australian, and Antarctic Early and early Middle Ordovician paleomagnetic poles. Age reassignment of the Antarctic Sør Rondane paleopole (Zijderveld, 1968) places it into the Cambrian period and when combined with other Gondwana Cambrian poles results in a new Gondwana ∼515 Ma pole (7°E, 22°N, A95 = 9.5°, N = 7 studies, in African coordinates). The new Gondwana ∼515 Ma and ∼475 Ma poles, when compared with poles of similar age from Laurentia, allow paleogeographic reconstructions to be made that are in keeping with models predicting that Iapetus Ocean basin opening and closure may have been related first to rifting and then collision of Laurentia with Gondwana. The paleomagnetic data also suggest that most of West Gondwana moved toward lower latitudes between the Middle/Late Cambrian and the late Early Ordovician which may be reflected in the fossil record.

Lichens and mosses from the Kar Plateau, Southern Victoria Land, Antarctica

Abstract The Kar Plateau, southern Victoria Land, Antarctica, is an ice-free area of about 4 km2, at 600 m altitude, and covered with a frost-shattered felsenmeer. Mosses occur sporadically at low density on debris islands (one species) and in sheltered rock crevices (four species). Lichens (22 species) also occur throughout but with one area (0.1 km2) of exceptional richness. The plateau is a floristically rich locality for the latitude (near 77°S). The new combination Rhizoplaca priestleyi (Dodge) Seppelt is made to accommodate Omphalodina priestleyi (Dodge) Dodge following earlier transfer of Omphalodina to Rhizoplaca. Phytogeography of the species in Antarctica is briefly discussed.

A case study of a midtropospheric subsynoptic-scale cyclone that developed over the Ross Sea and Ross Ice Shelf of Antarctica

Satellite imagery, synoptic-scale analyses and automatic weather station data were used to study a subsynoptic-scale cyclone that developed over the Ross Sea and Ross Ice Shelf areas of Antarctica. A pre-existing subsynoptic-scale midtropospheric cyclone descended from southern Victoria Land into the semi-permanent baroclinic environment over the south-western corner of the Ross Sea. The subsynoptic-scale cyclone then developed into a frontal system travelling south-eastward over the Ross Ice Shelf and decayed five days later over Marie Byrd Land. It is concluded that stretching of the subsynoptic-scale low, while descending over 2000 m from the high plateau down to sea level, increased its cyclonic vorticity via conservation of potential vorticity. This, along with a cold katabatic outbreak into the northern part of the circulation, provided the mechanisms for its initial development. Subsequently, cold boundary-layer air over the Ross Ice Shelf spiralled into the subsynoptic-scale cyclone supporting its further development. An upper-level synoptic-scale cyclone that approached the area provided the upper-level support for its ESE displacement and development.

Petrogenesis of carbonate-bearing nepheline syenites and carbonatites from Southern Victoria Land, Antarctica: origin of carbon and the effects of calcite-graphite equilibrium

Chemically-evolved carbonate-bearing nepheline syenites are intruded into basement metasediments of the Koettlitz Group on Dismal and Radian Ridges in the Pipecleaner Glacier region of Southern Victoria Land, Antarctica. Whole rock XRF data from the Dismal Nepheline Syenite defines a broad trend which is consistent with the removal of a cumulate fraction of approximate composition 70% hedenbergite, 15% nepheline, 10% titanite and 5% apatite. Stable isotope, major and trace element and mineralogical characteristics of the syenites are very similar to those of cross-cutting calcite-rich dykes indicating derivation from closely-related source magmas. The general association of carbonatites and nepheline syenites with extensional environments, suggests that the Dismal and Radian Ridge nepheline syenites and carbonatite dykes indicate a period of early Paleozoic (531 Ma) rifting or intrusion into localised tensional structures in an overall compressional regime. Assimilation of marble by the syenite magmas is evidenced by abundant rafts and xenoliths within the Dismal Nepheline Syenite, however, carbon and oxygen isotopic ratios from syenite and carbonatite calcites are distinctly lighter than values from the marble country rock indicating a magmatic source. Graphite and calcite commonly occur as aggregates in the Dismal Nepheline Syenite suggesting equilibrium between these two carbon-bearing phases. Isotopic fractionation between calcite and graphite, via the equilibrium: C + O 2 = CO 2 has resulted in enrichment of the 13C isotope in calcites from the Dismal Nepheline Syenite.

Mineralogy of the Dismal Nepheline Syenite, Southern Victoria Land, Antarctica

The mineralogy of the Dismal Nepheline Syenite indicates crystallisation from a pulse of chemically evolved, anhydrous, alkaline magma concordantly intruded into Koettlitz Group metasediments. In the main intrusion, orthomagmatic phases exhibit only minor mineralogical variation with typical compositions being hedenbergite (mg # 0.050-0.080), nepheline (Ne 76Ks 19Qtz 5), alkali-feldspar (Or 79 − 86 for orthoclase host and Ab 85 −98 for albite lamallae) and carbonate ( > 95 mol.% CaCO 3, < 1.6 mol.% SrCO 3). The Fe 2+-rich nature of the hedenbergite indicates that the orthomagmatic assemblage formed under low ƒ O 2 conditions as a result of internal buffering of the oxygen and CO 2 fugacities, during crystallisation, by the graphite-CO 2 equilibrium. Subsolidus coronas composed of hastingsite (mg # 0.015-0.070) + andradite-rich garnet (And 25 − 72Gross 22 − 61Ti-And 2 −15Alm 2 −9Spess ⩽ 2) + albite (Ab ⩾ 98) have formed at the expense of hedenbergite and nepheline. This corona assemblage indicates an increase in the ƒ H 2O and relative ƒ O 2 of the system, as a result of gradual equilibration with hydrous fluids from the surrounding Koettlitz Group metasediments. Cross-cutting fine-grained and pegmatitic dykes containing diopside (mg # 0.6-0.7), ferroan pargasite (mg # ∼ 0.4) and oligoclase (An 22 − 23) are thought to have been fed by a less-evolved parental source magma than that from which the Dismal Nepheline Syenite was derived.

Cenozoic transtension along the Transantarctic Mountains‐West Antarctic rift boundary, southern Victoria Land, Antarctica

Brittle fault arrays mapped along the structural boundary between the Transantarctic Mountains and the West Antarctic rift system are oriented obliquely to the axis of the mountains and offshore rift basins. The north to northwest trending regional rift boundary is thus not controlled by continuous rift border faults. Instead, the rift margin trend must be imposed by inherited lithospheric weaknesses along the ancestral East Antarctic craton margin. Fault kinematic solutions indicate that a dextral transtensional regime characterized the rift boundary in the Cenozoic and that dominantly transcurrent motion occurred during the most recent faulting episode. The Transantarctic Mountains are considered to be a rift‐flank uplift, yet no substantial isostatic uplift is expected in a transtensional setting, and the mechanism of large‐magnitude Cenozoic uplift of the mountains remains problematical. Regional deformation patterns in Victoria Land and the Ross Sea can be explained by a transtensional model and are not compatible with large‐magnitude crustal stretching within the West Antarctic rift system in the Cenozoic. The crustal thinning across the rift system more likely took place in the Mesozoic, when major West Antarctic crustal block motions occurred. The Cenozoic intracontinental deformation can be related to plate interaction resulting from the global Eocene plate reorganization, prior to the final separation between Antarctica and a narrow salient of the southeastern Australian margin. Displacement magnitude was probably minor, and thus early Tertiary east–west Antarctic motion is unlikely to account for discrepancies in global plate motion circuits.

A preliminary comparison of two perennially ice-covered lakes in Antarctica: Analogs of past Martian lacustrine environments

Perennially ice-covered lakes in the Antarctic have been suggested as analogs to lakes which may have existed on the surface of Mars 3.5 billion years ago. During the 1991–1992 austral summer, a joint Russian/American research effort was directed at studies of ice-covered lakes in the Bunger Hills Oasis, Antarctica (66° S, 100° E). The primary objective of the expedition was to investigate this ice-free area for features analogous to ancient martian environments that may have been capable of supporting life and to compare the ice-covered lakes of the Bunger Hills with those in the McMurdo Dry Valleys of southern Victoria Land (77° S, 166°E) as part of the continuing studies of Antarctic-Mars analogs.

Ediacaran lichens—a reply to Waggoner

It is pleasing to see Waggoner take seriously my heretical reinterpretation of Ediacaran fossils, even to the extent of agreeing that some Precambrian fossils from Namibia and China may indeed have been lichens. I also agree that more needs to be done. My paper outlined several potential lines of inquiry additional to isotaphonomy, including studies of Vendobiont size, morphology, microstructure, paleoenvironments, and biostratigraphy. For the near future my contributions to this question include reevaluation of the putative Witwatersrand lichens mentioned in my paper, together with new lichenlike fossils from the 2.2 Ga Waterval Onder paleosol of South Africa. There also arose a recent opportunity to restudy the compaction of the Devonian lycopsid Haplostigma in quartz sandstone from West Beacon, southern Victoria Land, Antarctica. The lichen hypothesis opens up a variety of new tests for evaluating the biological meaning of Ediacaran fossils. The limitations of sample size of Vendobionta and the dissimilar matrix of the jellyfish Essexella in my study were made painfully obvious in my paper, but are not fatal to my conclusions. I collected the fossil Vendobionta myself, and this made a critical difference because I could see that all but one found in float were raised impressions. This form of preservation is unknown in fossil logs and unexplained by Waggoner's ingenious mechanism of compactional deformation of associated shaly beds. I would like to hear more about his idea of lateral injection of clay from slab and thin section studies of specimens preserved in part and counterpart. My Vendobiont specimens appear quite typical compared with those of museum collections, which generally do not have recorded ori-

Constraints on age, erosion, and uplift of Neogene glacial deposits in the Transantarctic Mountains determined from in situ cosmogenic 10Be and 26Al

Research Article| December 01, 1995 Constraints on age, erosion, and uplift of Neogene glacial deposits in the Transantarctic Mountains determined from in situ cosmogenic 10Be and 26Al Edward J. Brook; Edward J. Brook 1Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02540 Search for other works by this author on: GSW Google Scholar Erik T. Brown; Erik T. Brown 2Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Bâtiment 108, 91405, Campus Orsay, France Search for other works by this author on: GSW Google Scholar Mark D. Kurz; Mark D. Kurz 1Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02540 Search for other works by this author on: GSW Google Scholar Robert P. Ackert, Jr; Robert P. Ackert, Jr 1Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02540 Search for other works by this author on: GSW Google Scholar Grant M. Raisbeck; Grant M. Raisbeck 2Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Bâtiment 108, 91405, Campus Orsay, France Search for other works by this author on: GSW Google Scholar Françoise Yiou Françoise Yiou 2Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Bâtiment 108, 91405, Campus Orsay, France Search for other works by this author on: GSW Google Scholar Geology (1995) 23 (12): 1063–1066. https://doi.org/10.1130/0091-7613(1995)023<1063:COAEAU>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Edward J. Brook, Erik T. Brown, Mark D. Kurz, Robert P. Ackert, Grant M. Raisbeck, Françoise Yiou; Constraints on age, erosion, and uplift of Neogene glacial deposits in the Transantarctic Mountains determined from in situ cosmogenic 10Be and 26Al. Geology 1995;; 23 (12): 1063–1066. doi: https://doi.org/10.1130/0091-7613(1995)023<1063:COAEAU>2.3.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 SocietyGeology Search Advanced Search Abstract 10Be and 26Al data from sandstone boulders in three Neogene glacial deposits in the McMurdo Sound–Dry Valleys region of southern Victoria Land, Antarctica, indicate minimum exposure ages of (Approx.)3 Ma and maximum long-term erosion rates of (Approx.)5–12 cm/m.y., supporting the suggestion that polar desert conditions have persisted in the Dry Valleys since at least late Pliocene time. Variation of cosmogenic nuclide production rate with altitude also allows constraints on past uplift rates. Model calculations employing 10Be data indicate little or no uplift in the Dry Valleys region in the past 3 m.y., precluding rapid (≈1 km/m.y.) late Pliocene uplift previously suggested for some parts of the Transantarctic Mountains. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Sediment oxygen profiles in a super-oxygenated antarctic lake.

Perennially ice-covered lakes are found in the McMurdo Dry Valleys of southern Victoria Land, Antarctica. In contrast to temperate lakes that have diurnal photic periods, antarctic (and arctic) lakes have a yearly photic period. An unusual feature of the antarctic lakes is the occurrence of O2 at supersaturated levels in certain portions of the water column. Here we report the first sediment O2 profiles obtained using a microelectrode from a perennially ice-covered antarctic lake. Sediment cores collected in January and October 1987 from Lake Hoare in Taylor Valley show oxygenation down to 15, and in some cases, 25 cm. The oxygenation of sediments several centimeters below the sediment-water interface is atypical for lake sediments and may be characteristic of perennially ice-covered lakes. There is a significant difference between the observed January and October sediment O2 profiles. Several explanations may account for the difference, including seasonality. A time-dependent model is presented which tests the feasibility of a seasonal cycle resulting from the long photoperiod and benthic primary production in sediments overlain by a highly oxygenated water column.

Jurassic conchostracans from Carapace Nunatak, southern Victoria Land, Antarctica

Fossiliferous horizons of the Ferrar Group at Carapace Nunatak of southern Victoria Land have yielded the richest and most diverse freshwater Jurassic biota hitherto recorded from Antarctica. Fossil conchostracans are the most important in terms of number of individuals and distributional area. Scanning electron microscopy is used to establish a new genus and species (Carapacestheria balli), and Cyzicus (Lioestheria) disgregaris Tasch is attributed to Carapacestheria disgregaris (Tasch) emend. The conchostracan fauna of the Ferrar Group, characterized by Carapacestheria, is probably of early Middle Jurassic age.

Quaternary changes in level of the upper Taylor Glacier, Antarctica: implications for paleoclimate and East Antarctic Ice Sheet dynamics

Glacial drifts perched alongside outlet glaciers that drain through the Transantarctic Mountains constrain inland polar plateau ice elevations. The Taylor Glacier, which heads in the Taylor Dome (a peripheral dome of the East Antarctic Ice Sheet), drains East Antarctic ice into the Dry Valleys sector of Transantarctic Mountains and terminates in central Taylor Valley, about 24 km west of the Ross Sea. Five gravel‐rich drifts (including 39 distinct moraine ridges) fringe a lateral lobe of the Taylor Glacier in the lower Arena Valley, Quartermain Mountains, southern Victoria Land. 3He and 10Be exposure age dating (from Brook et al. 1992), together with Arena Valley stratigraphy and soil morphologic data, provide chronologic control for these drifts and constrain maximum Quaternary thickening of the inland Taylor ice dome to less than 160 m. These minor Quaternary expansions of Taylor Glacier were out‐of‐phase with outlet glaciers that pass through the Transantarctic Mountains and terminate in the Ross Sea north and south of the Dry Valleys region. Textural analyses suggest that drift deposition occurred from cold‐based ice, even though Taylor Glacier advances most likely occurred during global interglaciations. The thermal regime of former Taylor Glacier ice lobes, the character of geomorphic features superimposed on individual drifts, the chemical composition of soils developed on Taylor drifts, and the stability of in situ moraine ridges on steep valley walls suggest that the present cold‐desert climate in Arena Valley has persisted for at least the last 2.2 Ma.

New records of Devonian plants from southern Victoria Land, Antarctica

AbstractAn assemblage of fossil plants is here recorded from the Middle Devonian Beacon Heights Orthoquartzite and overlying Aztec Siltstone (Taylor Group), of the Cook Mountains and Skelton Névé regions, southern Victoria Land, Antarctica. The Beacon Heights Orthoquartzite exposed in the southern Cook Mountains yielded specimens of the lycopods Haplostigma lineare, Malanzania sp., and Archaeosigillaria sp. cf. A. caespitosa. The Aztec Siltstone flora contains Praeramunculus alternatiramus and H. lineare.

Abandoned penguin rookeries as Holocene paleoclimatic indicators in Antarctica

Penguins are sensitive indicators of the Antarctic climate and of the environmental parameters that limit their presence and distribution. Paleoenvironmental data, obtained from the study of abandoned penguin rookeries ( Pygoscelis adeliae ) along the Victoria Land coast in Antarctica, indicate 14C date of 11-13 ka for the oldest abandoned rookery and supply new information about the timing of glacier retreat in southern Victoria Land after the last glacial maximum. The continuous presence of the Adelie penguins is documented from 7 ka. According to our data, the limiting factors that control the presence of penguins along the coast of Victoria Land changed during the Holocene. Whereas several colonies were occupied for very long periods, other sites were used for more or less extended periods and then abandoned. The greatest diffusion of rookeries occurred between 3 and 4 ka, a period of particularly favorable environmental conditions that has never been repeated. It was followed by a sudden decrease in the number of penguin rookeries shortly after 3 ka. This event has been attributed to an increase of the sea-ice extension and may have been correlated to a worldwide phase of climate change near the Subboreal-Subatlantic boundary. A minor phase of penguin reoccupation occurred locally in the eighth to fourteenth centuries (A.D.). Because the presence and number of penguins reflect the state of health of the Antarctic marine ecosystem, it is important to evaluate the variations in their distribution in the past, in the absence of human-induced changes.