GEOLOGICAL AND GEOPHYSICAL INVESTIGATIONS OF THE EAST ANTARCTIC MARGIN
WORKSHOP REPORT
February 21-23, 1997
Workshop organizers
Anne Grunow
Amy Leventer
Byrd Polar Research Center
Ohio State University
Columbus, Ohio
TABLE OF CONTENTS
A workshop "Geological and geophysical investigations of the East Antarctic Margins" was held from February 21 - 23, 1997 at the Byrd Polar Research Center, Ohio State University. The focus of this workshop was to develop a cohesive plan for future earth science research along the East Antarctic margin. U.S. research along the Antarctic coast has concentrated on the areas traditionally visited by ship, such as the Antarctic Peninsula and Ross Sea regions, or areas easily accessible by aircraft from McMurdo Station. Limited access to much of the margin has resulted in data sets strongly skewed toward processes and events within and along the Ross and Weddell Sea regions and West Antarctica. A major objective of this workshop was to formalize recent discussions concerning a strong community-based interest in implementing a ship-based geologic and geophysical program along the East Antarctic margin. In particular, the workshop goal was to identify the key scientific questions which could be addressed through research cruises to the Wilkes, Enderby and Queen Maud Land areas of East Antarctica (Fig.1). In addition, during the workshop, clear science objectives which could be addressed through inland East Antarctic research programs, accessible either by ship or air-transport were discussed. Finally, given limited ship and air resources, strong consideration of specific geographic targets was emphasized.
In order to maintain a workshop focus on identification of scientific objectives, participants were divided into four sub-disciplines:
1) nearshore marine research with an emphasis on paleoclimatic studies;
2) continental shelf to oceanic crust marine research stressing questions of Mesozoic breakup and rifting geometry;
3) onshore pre-Tertiary geological research looking at Gondwana assembly and breakup events;
4) onshore Late Tertiary geological and geophysical studies, also primarily of paleoclimatic significance.
The unifying element between these disciplines was the essential need to develop a circumpolar view of Antarctic earth sciences. Implicit in this goal is cooperation of USAP efforts with other national programs, including Australia, Japan, South Africa and Russia. Accordingly, another key component of the workshop was to establish and/or further develop working relationships with Antarctic programs from those countries, with the goal of advancing mutually beneficial research programs.
Based on the workshop discussions, widespread interest in development of East Antarctic margin initiatives is clear. The workshop subgroup reports contain detailed summaries of the scientific objectives and logistical constraints. Availability of this report on the World Wide Web hopefully will facilitate continued communication among all members of the Earth Science community, including those interested investigators who were unable to attend the workshop. In the long-term, we view the workshop as a springboard toward the development of proposals by members of the U.S. scientific community. We anticipate that most of these proposals will be submitted for the June 1998 deadline.
Many countries maintain active research programs along the East Antarctic margin. Four of these countries - Australia, Japan, South Africa and Russia - were represented at the workshop. An obvious major concern is the route for USAP cooperation with the Antarctic research programs of other countries. In particular, emphasis was placed on US sensitivity to long-term objectives of non- US Antarctic programs. Two primary and non-exclusive pathways for international cooperation were outlined - scientific and logistical. The scientific objectives have been taken into consideration in the reports from individual sub-groups. Avenues for potential logistical cooperation and shared resources are outlined below, with the caveat that the discussion of shared logistics was not comprehensive, due to time and personnel limitations at the meeting.
Australia
Chris Wilson, School of Earth Sciences, The University of Melbourne, Parkville, Victoria and
Barrie McKelvey, University of New England, New South Wales
Beaver and Radok Lakes (Fig.1), two deep lakes located in the Lambert Glacial System, potentially contain a valuable paleoclimatic record. The Australian Antarctic Program has expressed an interest in coring/drilling basin. Workshop participants discussed using the Cape Roberts Drilling Program technology at Beaver and/or Radok Lakes once drilling is completed for the Cape Roberts Project. This is viewed as a positive step in terms of expanding the useful life of the available system and in terms of a USAP investment / contribution to the Australian Antarctic program. Additional considerations for Beaver and Radok Lake work include the potential for landing a wheeled aircraft and/or the use of large helicopters, potentially supplied by the Australians. A second site of interest is the Bunger Hills (110°E, 66°10'S), site of numerous lakes, raised beaches and moraines, all of which potentially contain a wealth of information regarding the Quaternary history of Antarctica (Fig.1). Compared to the Dry Valley and Vestfold Hills lakes, very little is known about those in the Bunger Hills, with only a minor amount of reconnaissance work done by the Russians and Australians. The Bunger Hills are approximately equidistant between Mirny and Casey Stations, the most likely points of access via either Twin Otter or helicopter. Again, the potential for use of Australian helicopters was discussed, as in this rough terrain, most of the work is likely to be accomplished by helicopter. Coupling this onshore work with marine geologic and geophysical work along the Wilkes Land margin was discussed.
With regard to logistic support, the potential for wheeled landings at Casey Station and sea ice landings at Davis Station were reviewed. It was noted that extremely variable weather conditions at Casey make it a less desirable choice for wheeled aircraft landings. At Davis, sea ice landings are possible and potential for an all-weather airstrip is being considered. Also during the workshop, the possibility was discussed of undertaking a combined program involving the US with the Australians and other International participants in supplying bunker oil and exchanging personnel at sea, in order to extend the number of shipping days available for the marine geoscience cruises. If two ships could rendezvous at sea then it may also be possible to extend the nature of any offshore seismic acquisition program. Similarly, if the second ship had ship-based helicopter facilities, such as those on the "Aurora Australis", then it might be possible to undertake combined onshore and offshore programs concurrently.
South Africa
Mike Watkeys, Dept. Of Geology and Applied Geology, University of Natal, Durban
Two research vessels, the SA Agulhas and SS Outerique, both with ice-strengthened hulls, are used by the South African program to resupply SANAE, service weather stations at Marion and Gough Islands, and for scientific research. Cooperative research programs might make use of these ships, with the consideration that logistical needs of the South African Base must be met first. Accordingly, marine geological and geophysical projects would most likely be limited to the routing between South Africa and the South African base.
A new base is under construction ~160 km inland and only 2 hours from the second largest glacial system in Antarctica. This base will be able to accommodate 80 people in mid-summer. Vehicles available at the base will include Puma helicopters "J" series with de-icers, Oryx helicopters ("super-Pumas"), skidoos and other larger tracked vehicles. Dr. Watkeys expressed an interest in acquiring refraction and reflection seismic data across the Jutulstraaumen Glacier.
Japan
Takemi Ishihara, Geological Survey of Japan
Dr. Ishihara presented a detailed review of the availability of seismic lines taken by the Japanese Program. In particular, a large volume of lines have been run along the Wilkes Land margin. Both marine subgroups expresses a strong interest in continued research along this part of the East Antarctic margin, and view the seismic lines as an important resource.
Russia
German Leitchenkov, VNIIOkeangeologia, St. Petersburg, Russia
Dr. Leitchenkov presented a wide variety of geophysical data, including gravity, magnetic, and seismics, collected by the Russians. Extensive multichannel marine seismic work from the Prydz Bay and Queen Maud Land margin are available. Airborne geophysical surveys have provided excellent magnetic anomaly maps of the central sector of the East Antarctic margin, as well as from the Larson and Weddell Seas. Dr. Leitchenkov also pointed out the excellent cooperation already in existence among the Russians, Japanese and Australians.
United States
Potential contributions of the United States Antarctic Program to international initiatives range widely. Dr. Webb explored the possibilities for shelf drilling, emphasizing the potential to recover a full range of sediments, from glacial to interglacial, and proximal to distal glacial settings. "Piggybacking" across a basin may permit the acquisition of a complete stratigraphic section. The pros and cons of several shallow drilling systems were presented.
In addition, the US may be able to contribute to international programs through wider use of its airborne geophysical program. Dr. Jezek presented the SOAR facility via Twin Otter as an excellent tool to acquire magnetic and gravity data over wide regions, and also the possibility of doing ice radar work.
Summarized below are the scientific goals, logistics requirements and recommendations made by each of the four working groups.
"Nearshore Marine Research" Group Quaternary Investigations
CONTRIBUTORS
J. Anderson, R. Askin, P. Bart, L. Bartek, P. Berkman, L. Burckle, L. DeSantis, E. Domack, C. Escutia, P. Harris, L. Krissek, A. Leventer, P. O'Brien, R. Powell, P. Quilty, R. Scherer, S. Shipp, J. Stravers, P. Webb
BACKGROUND
The Antarctic Ice Sheet is central to the global ocean and atmospheric systems, and to global sea level; the sedimentary record around the continent should record the changes in these linked systems. Understanding the connections will help assess future impact of changes in the Antarctic Ice Sheet system.
Much of the margin of the East Antarctic Ice Sheet has yet to be investigated in great detail, thus much of the history of Antarctic Ice Sheet activity remains obscure. Understanding past activity and predicting future activity of the East Antarctic Ice Sheet and the entire Antarctic Ice Sheet hinges on detailed, high-resolution seismic and sedimentologic investigations. Critical questions remain, such as:
In addition, several other questions may be addressed through nearshore marine studies, including:
Little is known of the East Antarctic continental margin setting in the Late Quaternary. Detailed investigations of the West Antarctic margin, and sparse studies along the East Antarctic margin suggest significant differences in the two systems. The base of the West Antarctic Ice Sheet is grounded below sea level; the East Antarctic Ice Sheet is a terrestrial ice sheet. The volume of the West Antarctic Ice Sheet is 3 M km3; the water equivalent of 6 m of global sea-level rise. The East Antarctic Ice Sheet holds almost an order of magnitude more ice volume at 26 M km3, or the water equivalent of 60 m of global sea-level rise (Denton et al., 1995). Large ice streams drain ice from the West Antarctic Ice Sheet system; the East Antarctic Ice Sheet margin is characterized by relatively few large ice streams/outlet glaciers, numerous small ice streams/outlet glaciers, and large regions of divergent flow (Drewry, 1983). Partially as a result of its basement setting and drainage by ice streams, the profile of the West Antarctic Ice Sheet is lower than the East Antarctic Ice Sheet, and the West Antarctic Ice Sheet is considered potentially unstable. The East Antarctic Ice Sheet is considered to reflect an equilibrium profile and be stable. The continental shelf of West Antarctica is broad in many regions, reflecting progradation of shelf sediment (e.g., Ross and Weddell regions). The East Antarctic continental shelf is narrow, with the exception of regions associated with major ice streams/outlet glaciers (e.g., Prydz Bay/Amery region). The West Antarctic Ice Sheet is underlain by extensive sedimentary basins. A smaller percentage of the East Antarctic Ice Sheet is believed to be underlain by sedimentary basins (Drewry, 1983).
Specific priorities of investigation of the East Antarctic margin are outlined in the following discussion. It should be noted that the objectives parallel the objectives of the SCAR-GLOCHANT Initiative on the Late Quaternary Evolution of the Antarctic Ice Margin (ANTIME).
Primary Objective: Characterize the Late Quaternary setting of the East Antarctic Margin (shelf, slope, and rise).
To achieve this objective several key tasks need to be completed, as outlined below.
1) Determine the character of Late Quaternary glacial advances.
1a) Determine the extent and timing of Late Quaternary glacial advances.
Investigations to date yield a variety of models for the extent of Antarctic ice sheets during glacial periods tied to oxygen isotope stages 2, 4, and 6. In addition, a variety of ice volume reconstructions exist, leading to contradictory models of sea-level contribution of the Antarctic Ice Sheet. Finally, onshore studies indicate higher-than-present ice elevations in coastal regions of East and West Antarctica, though the timing of these elevations remains obscure. Further study along the East Antarctic margin will help constrain past ice sheet volume models, determine the magnitude and timing of East Antarctic Ice Sheet contribution to global sea level, correlate fluctuations in West Antarctic Ice Sheet and the Northern Hemisphere, and constrain models of Antarctic Ice Sheet response to future climatic and sea-level changes.
1b) Characterize Antarctic Ice Sheet retreat from the last glacial maximum.
Sedimentary and ice-core records, primarily from the Northern Hemisphere, contain evidence of rapid, episodic glacial, oceanographic, and atmospheric events (surges in ice streams/outlet glaciers, Heinrich events, rapid atmospheric and oceanic temperature shifts). Antarctic research suggests that ice streams/outlet glaciers may respond rapidly to internal and perhaps external forcings, including sea-level rise, bed deformation, ice shelf collapse, however observational data are limited. These data are key to understanding the driving processes for rapid climate change, on a global scale. In addressing the questions posed above, we hope to determine the magnitude and timing of East Antarctic Ice Sheet contributions to global sea level and correlate East Antarctic Ice Sheet fluctuations with environmental changes (sea level, bed conditions, ocean circulation, climate changes).
2) Characterize the behavior of the ice sheet system during glacial and interglacial periods, with objectives of understanding the differences in behavior and record of convergent and divergent ice flow systems and how components of different ice systems (sheet, stream, shelf, sea ice) changed through time.
Little documentation exists of ice sheet behavior or processes at margins having divergent flow. The East Antarctic Ice Sheet margin is characterized by divergent flow punctuated by regions of convergent ice flow and so is an excellent region to compare and contrast the flow regimes. In addition, models and investigations suggest a link between convergent ice flow over deforming substrate and rapid streaming ice. The East Antarctic Ice Sheet may be in contact with crystalline basement for a significant portion of its base; sedimentary basins also occur in the subglacial environment. For this reason, the East Antarctic margin is an ideal setting to identify key controlling factors on ice sheet behavior and design constraints on models of future ice sheet activity based on environmental setting. Finally, research suggests rapid responses of ice streams/outlet glaciers to environmental changes; in particular, Holocene fluctuations have been observed in climate-sensitive regions. This is of particular significance given global warming scenarios.
3) Characterize the sedimentology, stratigraphy, and marine ecosystems of the East Antarctic Ice Sheet during the Late Quaternary.
Little is known of the sedimentary processes on the East Antarctic Ice Sheet margin. A process study using ROV technology has been conducted at an outlet glacier-floating glacier tongue system in the Ross Sea area; more of these studies at different ice flow and ice margin types are needed. Documentation of modern processes at different types of ice-sheet margins is critical to developing models to interpret older successions. The continental shelf sedimentary record, based on investigations of the West Antarctic continental shelf, is anticipated to be characterized by stacked glacial sequences bound by glacial erosional unconformities. Sections of the record will be missing. Although the "deep-sea" record is probably more continuous, it is only a proxy record of glacial activity, while the shelf record may be related more directly to changes in the ice sheet. Correlation of the two records should permit reconstruction of the glacial history of the East Antarctic Ice Sheet.
4) Determine the character of climate change during the Holocene.
Investigations to date from both the Antarctic Peninsula and Ross Sea demonstrate both millennial-scale and century-scale variability in primary production and sea ice extent on the continental margin during the Holocene. The periodicity of variability correlates with Holocene records from other parts of the world, suggesting a common external forcing mechanism. Similar periodicities in radiocarbon distribution suggest the possible role of solar variability in driving some changes in Holocene climate. Furthermore, the latest Holocene records (marine sediments, ice core, historical data, changes in biota) appear to demonstrate a response to global warming. We suggest the development of a high resolution record of Holocene climate change for the East Antarctic margin. These data will be used to understand the relationship between century- to millennial-scale response to climate change in Antarctica and the rest of the world and to evaluate the response of the East Antarctic margin to global warming.
5) Additional key questions
The Mesozoic rifting history of the East Antarctic margin largely has been inferred using data from conjugate margins and ocean basins. Little direct evidence has been obtained from the Antarctic margin itself. This is particularly a problem along the margin from 040°E to 090°E, where magnetic anomalies are poorly developed and the Kerguelen Plateau complicates the picture. Recent discovery of a synrift basin containing Callovian to Aptian palynofloras on the MacRobertson Shelf suggests that the rifting of India from this part of Antarctica may have taken place later than its rifting from western Australia (O'Brien et al, 1995). The new data imply a more complex history of Gondwana breakup than previously thought. This is not explored in further detail here, as it is the focus of later discussion.
Glacial sediments found on the continental shelf are derived in part from rocks within subglacial basins. Inasmuch as provenance can be used to determine subglacial geology, surveys across nearshore and offshore regions adjacent to subglacial basins will be extremely useful in assessing the stratigraphy and lithofacies of these currently unknown regions via a careful examination of erratic clasts and palynology within glacial sediments.
Both shallow banks and deep troughs are found in close proximity across the entire East Antarctic shelf. As a result, two distinct benthic systems, one highly disturbed due to iceberg turbation and one of deep undisturbed character, are situated next to one another. In addition, these benthic systems of the East Antarctic margin are coupled with coastal processes. Recent observations in Vincennes Bay suggest a dense community of benthic invertebrates within deep basins and sediments. The source of carbon for these systems is unknown although particulates of macroalgae swept off adjacent banks and coastal shallows may be an important source. In other deep regions of the Antarctic, benthic communities are sparse and carbon flux is dominated by vertical settling and lateral advection of phytoplankton detritus. The relative role of these two carbon sources should be investigated by a cooperative team of sediment geochemists and marine biologists.
The bank and trough topography of the East Antarctic margin is simpler to study than that of the Ross Sea, because East Antarctic systems are relatively small. In addition, in the Ross Sea, the banks are divorced from the coast by the deep Drygalski trough that parallels the Victoria land coast. Thus, the East Antarctic bank and trough topography is more easily surveyed in the context of similar coastal environments.
Cenozoic floras and faunas are very poorly known from Antarctica. In particular, the Paleogene transition from non-glacial to glacial conditions poorly understood. The rise of groups which now dominate the Antarctic environment such as euphausiids and the disappearance of other groups now absent, requires exploration for Cenozoic section around the Antarctic margin, which may be accomplished through study of submarine outcrop material. Submarine outcrops on the MacRobertson Shelf have yielded well preserved Paleocene to Eocene palynofloras, woody material and marine microfaunas suggesting other parts of the margin may contain the records necessary to understand the evolution of the Antarctic biota (Harris and O'Brien, 1996). The stratigraphic context of Cenozoic marine microfaunas and palynofloras can be established with seismic reflection data and swath mapping. A ship with these capacities (as the Palmer) would be able to make major advances in understanding this field of research and provide a framework where shallow drilling would provide a comprehensive data bases for understanding the longer-term history of the Antarctic margin.
MARGIN TARGET SITES
1) Investigation of the Wilkes Land Margin
Logistically, the Wilkes Land margin appears to be the most accessible coast for an operation run by the U.S. With the exception of the Prydz Bay/Amery Ice Shelf system, nearshore Wilkes Land has been the most extensively studied portion of the East Antarctic margin (e.g., Barnes, 1987; Domack et al., 1991; Eittreim et al., 1995; Escutia et al., 1996). This offers the advantage of having background information around which to design a detailed regional study. Several seismic investigations have been conducted on the margin, but the majority of these are farther offshore and have not focused on the high-resolution shelf record.
The Wilkes Land margin is characterized by coastal zones of divergent ice flow punctuated by regions of convergent ice that flows into floating glacier tongues (e.g., Mertz, Ninnis, and Dibble ice tongues) (Drewry, 1983). Ice shelves occupy only a limited portion of the coast. The Wilkes Subglacial Basin, suggested to be a sedimentary basin, underlies the East Antarctic Ice Sheet in this region (Drewry, 1983). This basin figures prominently in models of an unstable Pliocene ice sheet at which time the basin is believed to periodically have been void of ice and filled by an inland sea. The Wilkes Subglacial Basin lies below present sea level and may represent an unstable portion of the East Antarctic Ice Sheet. Flow through the Wilkes Subglacial basin represents drainage of a significant portion of the East Antarctic Ice Sheet. Investigations suggest that during the last glacial maximum, the ice sheet advanced to the continental shelf edge in the troughs and supplied sediment to the trough-mouth fans. Either no ice, or slow moving ice occupied the inter-trough regions (Domack et al., 1991; Eittreim et al., 1995).
Finally, deep inner shelf basins, like those along the George V Coast, are characterized by high sediment accumulation rates and sequences which are often well-laminated (non-bioturbated).
The Wilkes Land margin thus offers an ideal location to:
2) Investigation of the Queen Maud Land Region
Queen Maud Land is one of the least studied regions of the East Antarctic Ice Sheet, barring detailed investigations in Lutzow-Holm Bay. Several seismic investigations have been conducted on the margin, but the majority of these are farther offshore and have not focused on the high-resolution shelf record.
The Queen Maud Land margin is characterized by a narrow continental shelf. Mountains lie adjacent to the margin, buttressing some of the highest ice elevations and thickest ice of the East Antarctic Ice Sheet (Drewry, 1983). The second largest outlet glacier in Antarctica drains through the mountains and flows to the Queen Maud Land shelf. Divergent flow characterizes ice at the coast (Drewry, 1983). Coastal islands serve as pinning points for numerous ice shelves. The ice flowing to the Queen Maud margin is inferred to cross crystalline basement; few sedimentary basins occur in this region.
The Queen Maud Land margin thus offers an ideal location to:
3) Investigation of the Amery Ice Shelf/Prydz Bay Region
Investigation of the Amery margin of the East Antarctic Ice Sheet is underway, primarily by the Australian Geological Survey Organization and researchers at the CRC. Research objectives parallel the objectives outlined in this document. The Amery system, flowing within the confines of sediment-filled Lambert Graben, drains almost 25% of the East Antarctic Ice Sheet. Nearshore deep basins will be important to the acquisition of extended high-resolution shelf records of margin sedimentation and paleoclimatic history. Correlation of results of investigations from the Amery, Wilkes Land and Queen Maud Land margins will be vital to understanding the past, present, and future activity of the East Antarctic Ice Sheet.
Logistical Considerations for Exploration of the EAIS Margin:
Plan of Attack for EAIS Margin Target Sites
"Continental Shelf to Oceanic Crust Marine Research"
CONTRIBUTORS
Mike Coffin, Alan Cooper, Carlota Escutia, Takemi Ishihara, German Leitchenkov, Ralph von Frese
MAIN SCIENTIFIC CONCERNS
What is the deep structure of the continental margin?
Scientific Targets:
a. Transect across Wilkes Land margin: Wilkes Basin to Ocean Basin
The emphasis would be on the thickness of crust and sediments in the Wilkes Basin; the magmatic nature of COB; the origin of the Hakurei seamount; the nature of oceanic crust near major fracture zones; and the strength of continental lithosphere.
b. Transect across north end of Transantarctic Mountains (TAM) on Wilkes Land Margin
The emphasis would be on creating a 3-D model of TAM structure; neotectonic activity in and adjacent to TAM; the uplift history of the TAM.
c. Transect across Prydz Bay margin: Prydz Bay to Kerguelen Plateau
The emphasis would be on rift-basin structure, volcanism in rifted areas and COB, the nature of the crust under Kerguelen Plateau, the geometry of rifting, presence of transverse faults, mechanisms of rifting, onshore geology and metamorphic belts.
d. Transect across Enderby Land Margin
The emphasis would be on oceanic fractures, the geometry of rifting, the oldest magnetic anomalies, onshore geology with positive gravity anomaly region, and neotectonics(?) inferred from isostatic anomalies.
e. Transect across western Queen Maud Land margin
The emphasis would be on the oceanic crust, transform boundary, COB in relation to the Explora wedge and the geometry of rifting.
f. Regional geophysical lines across E. Antarctic continental margin to 4000-4500m contour
The emphasis would be on delineating the oldest identifiable magnetic anomalies, and likely magmatic bodies (especially those associated with the COB). The goal is to establish the relationship of volcanics to extensive flood basalts seen around Gondwana (and beneath parts of the Antarctic margin), and establishing the age of breakup.
Logistics Requirements:
a. Crustal onshore-to-offshore transects require onshore: seismic stations, seismic shots, gravity, magnetic & ice-thickness measurements; andoffshore: MCS, gravity, magnetic profiles, Ocean bottom seismometers, and large-volume (70 liter) airgun arrays.
b. Crustal transects will likely require multinational cooperation, as many such co-op projects have already been done in the Ross Sea and Antarctic Peninsula regions by U.S., Germany, Italy, Japan, Russia and others.
Potential Proposals:
a. There is potentially widespread U.S. interest in the transects, and there is general interest by Japan, Russia, Italy and Germany in some of the desired transects. Russia plans to work along the E. Antarctic margin for at least the coming 5 years, and would be a potential collaborator.
b. About 30 days of ship time would be required for the offshore survey, in addition to any ship time that would be required to support the land operation.
c. A proposal has been submitted to study flood basalt volcanism along the East Antarctic margin (Coffin et al.) and its relation to Mesozoic volcanism elsewhere in Antarctica and surrounding regions. Two 50-day geophysical cruises (MCS, sonobuoy, gravity, magnetics, Sea Beam) using the Palmer across the Enderby and Wilkes Land margins, and a 60-day ODP leg are proposed for the work.
2. What is the geometry and timing of Gondwana breakup along East Antarctica?
Scientific Target:
Enderby Land and eastern Queen Maud Land
The emphasis would be on: i) collecting magnetic and gravity data in order to identify magnetic-anomalies and determine the age of the crust and extension direction; ii) gravimetric resolution of fracture zones for geometry of spreading; iii) early spreading of East Antarctica / Greater India / Madagascar / Sri Lanka; iv) identifying locations of COBs from enhanced satellite gravity data; v) understanding the detailed geometry of post-breakup (and some basement-breakup) structures from swath bathymetry
Logistics:
Regional geophysical cruises would be needed with seismic-reflection, gravity, and magnetic data collection capability, to map broad regions of the continental margin and adjacent ocean basins. Note that ice-breaking capabilities are not critical to the success of this science mission.
Potential Proposals:
a. Similar studies are proposed or have recently been conducted (but results not published) by Russia, Japan, Australia and Germany. There is likely to be future interest from these countries and Italy (Wilkes Land region).
b. A proposal(s) has been submitted (Coffin et al.) to study the timing and direction of breakup and initial sea-floor spreading among East Antarctica, Greater India, Madagascar and Sri Lanka in the Enderby Land region. A UNOLS vessel or the RV NB Palmer is proposed for a SCS, gravity, magnetic, SeaBeam cruise of 50-day duration with six scientists.
3. What is the crustal framework of sedimentary basins of continental margin?
Scientific Target:
Obtain MCS data from segments of the margin that now have no MCS data to delineate basins (e.g., western Wilkes Land, Enderby Land, and parts of Queen Maud Land). The emphasis will be on the geometry of basin strata, faulting, and basement structures; the relationship of basin structures to onshore features, oceanic structures and conjugate margins
Logistics:
The work would involve geophysical (seismic reflection/refraction, gravity, magnetics and sonobuoy), detailed bathymetry (SeaBeam), and coring and dredging operations. An ice-breaker would be required to collect data in regions which are up to 80% ice-covered and in critical nearshore regions where massive glacial troughs have deeply eroded the sedimentary section, allowing sampling access to older sedimentary strata. Onboard digital data processing of seismic data would be required to ascertain the best sampling localities and line positions.
Potential Proposals:
Similar work is currently being done, or has recently been done, in Enderby Land and Prydz Bay by the Russians and Australians. The Italians have proposed a cruise for the 1998 - 1999 season off the Wilkes Land margin.
4. Assess the glacial history and paleoenvironments including:
Targets:
a. Establish ANTOSTRAT type regional-working-group in regions of Wilkes Land and Prydz Bay where ODP drilling is proposed. The emphasis will be on the initial time of glaciation; styles and environments of glaciation; ice-sediment depositional processes; timing of glacial/inter-glacial cycles; origins of outer shelf prograding sequences; canyon-depositional processes; links from shelf-to-basin deposition (i.e., from prograding sequences to drift deposits)
b. Poorly surveyed areas of the E. Antarctic margin are important targets because they may contain prograding glacial deposits where present ice-flow directions focus toward the continental shelf. And, areas where lobate bathymetric contours at the continental-shelf edge where prograding deltas can be inferred. The emphasis will be on identification and 3-D geometry of glacial(?) sedimentary sequences; coring/drilling transects of dipping sequences eroded at seafloor, to get age progression, lithology and paleoenvironments of the sequences; other objectives are same as above.
Logistics:
a. The marine data required are high resolution seismic reflection (SCS and MCS), SeaBeam (with backscatter), and high resolution bathymetry (3.5 khz), gravity and piston cores, shallow drilling and ODP drilling.
b. The RV NB Palmer will be required to work in regions which are up to 80% ice-covered where sedimentary units are exposed on the ice-covered inner and middle shelf.
Potential Proposals:
none noted to date
"Bedrock Geology Science Objectives in East Antarctica"
CONTRIBUTORS
Jim Collinson, David Elliot, Tom Fleming, Anne Grunow, Sam Mukasa, Mike Watkeys, Chris Wilson, Terry Wilson
MAIN SCIENTIFIC QUESTIONS
1. When was the Supercontinent Assembled and when did it Disperse?
The East Antarctic craton contains a critical record to test models for the timing and kinematics of assembly and dispersal of the Rodinia and Gondwana supercontinents. Key points to be addressed include:
2. What processes were associated with Mesozoic-Cenozoic Breakup processes; what Neotectonics processes are occurring in Antarctica?
The margins of East Antarctica and the interior rift-related basins record the progressive fragmentation of the Gondwana supercontinent. The presence of large-scale subglacial basins and uplifted regions as well as Neogene regional uplift patterns suggest there may be neotectonic deformation in East Antarctica (in addition to the better-known active volcanism and rifting in West Antarctica). Key issues of interest include:
LOGISTICS:
SHIP-BASED INITIATIVES:
1. WILKES LAND (~90 to ~130 degrees East)
Science target:
Gondwana Assembly and the Pan African event:
Cooperative Considerations:
Logistic points:
2. ENDERBY LAND - DRONNING MAUD LAND REGION
Sverdrupfjella-Sor Rondane-western Enderby Land is key sector
Science Problems:
Gondwana Assembly and the Pan African event
Gondwana Breakup Record
Cooperative Considerations:
Logistics Considerations:
3. OATES COAST: Commonwealth Bay - George V - Oates Coast - NVL
Science Problems:
Gondwana assembly and the Pan African event
Breakup record:
Cooperative Considerations:
Logistic points:
LAND-BASED INITIATIVES:
1. PRINCE CHARLES MOUNTAINS
Scientific Problems:
Breakup Record:
Cooperative Considerations:
Logistic points:
2. QUEEN MAUD LAND:
Scientific Problems:
Breakup Record:
Gondwana Assembly and the Pan African event
Cooperative Considerations:
Logistic Points
BEDROCK GEOLOGY PLAN
The personnel involved in the following plan would generally be in groups of 4 to 6 people, divided between US, Australian and South African scientists. All three countries would be involved in the following field years. It is estimated that 4 to 6 weeks of field time/yr (and ship time) is required for the following plan. The ship time can be easily meshed with the ship based objectives on the nearshore Tertiary group if helicopters can be on the ship. We anticipate that small field parties would be established at certain locations for 1 to 2 weeks and then moved by helicopter or twin otter to another location. Some isolated locations may involve day trips by helo or Twin otter rather than establishing a camp. The field camps should have either 4-wheel bikes or snow-mobiles available for local transport.
1999-2000 Wilkes Land Coast - (ship-based season) This links together the #1 objective of the Marine Tertiary group with the #3 priority of the Bedrock geology group. This work can be accomplished by: helo's on the ship during year 1 while the ship is doing marine geophysics along the margin; work to the west can be accomplished using long range S76 Helo's from Casey station for onshore studies. Australian program may have 2 ships that year and has already tentatively set aside 28 days of ship time for marine geophysics.
2000-2001 Prince Charles Mountains - (land- based season) This links together the onshore Tertiary geology #1 objective with the Bedrock geology #1 land-based objective. This work can be accomplished by: helo's from Davis Station deploying personnel to PCM's; LC-130's from McMurdo landing in the Prince Charles Mountains and using US or Australian helo's; using Australian 4 wheelers for travel. This work could be combined with drilling in the Radok Lake area. Also, the SOAR platform could be used for aerogeophysical studies of the Lambert Glacier area for geological and glaciological purposes.
2001-2002 Enderby Land - (ship-based season) This links the #2 objective of the marine Tertiary group with the #2 objectives of the onshore Tertiary and Bedrock geology groups. This work would need helo's on the ship to reach key onshore locations. Potentially use Japanese logistics and South African logistics in this sector.
2002-2003 Queen Maud Land - (land-based season) This links the #2 objective of the onshore Tertiary group with the #2 land-based bedrock geology objective. Work can be accomplished by a coordinated program with the South Africans. South African helicopters might be used to move field parties. US Twin Otters may also be able to transport parties to different locations.
"Land-based Teriary and Quaternary Records"
CONTRIBUTORS
Allan Ashworth, Charles Hart, David Harwood, Barrie McKelvey, Peter Webb, Gary Wilson
MAIN SCIENTIFIC QUESTIONS
Land-based Tertiary and Quaternary records are aimed at a wide variety of large-scale questions including:
1. Ice Sheet history / dynamics 2. Paleogeography 3. Sea level history 4. Paleoclimates 5. Biogeography and evolution 6. Sub glacial basin reconstruction 7. Regional tectonic history 8. East versus West Antarctic ice sheet response to change in climate
SCIENCE OBJECTIVES IN ORDER OF PRIORITIZATION
1. Southern Prince Charles Mountains - Pagodroma Group
Tertiary basin studies of the Pagodroma Group are aimed at answering paleoclimatic and paleogeographic questions. Known deposits of the Pagodroma Group include: Mt. Johnson Formation, Kar Bolsol Formation, Battye Glacier Formation and the Bardin Bluffs Formation. We suggest drilling of selected sections as a first step toward reconstructing conditions under which Pagodroma Group sediments were deposited. Additional general reconnaissance work in the Southern Prince Charles Mountains is suggested also. This work, as outlined below, would mesh well with proposed objectives in Beaver and Radok Lakes outlined below.
2. Beaver Lake and Radok Lake - marine-terrestrial connections
Beaver and Radok Lakes are of great interest, primarily because of the potential for sedimentary records which archive the Quaternary climate history of Antarctica. Comparison of these records to those from the marine system will aid in our understanding of the relative impact of local, regional, and global scale processes of climate change in the high southern latitudes. In order to efficiently retrieve and interpret lacustrine sediments from these deep lakes, we suggest the following sub-projects:
3. Dronning Maud Land - Tertiary - Quaternary outcrops
Outcrops of Tertiary to Quaternary age have been mapped previously by Japanese geologists, specifically in the following regions - Sor Rondane, Enderby Land, Lutzow-Holm Bay, and Coates Land. We propose to build upon this work, with the following objectives:
4. Wilkes Land coast reconnaissance - distal limits of Wilkes / Aurora basins
Several questions can be addressed through reconnaissance work along the Wilkes Land Coast. Both terrestrial and uplifted marine sections will be targeted, including studies of filled cirques and fjords, polygonal ground, low relief areas at high elevation, and coastal records and beaches. The following briefly summarizes the scientific goals:
5. Circum-Antarctic Coastal Deposits
Primary interest in circum-Antarctic coastal deposits is to develop a better understanding of the Late Quaternary history of Antarctica. This includes studies focused on paleoenvironmental reconstructions and sea level history. Studies will be based on both exposures of late Quaternary deposits and lake sediments. Techniques to be applied include development of detailed chronologies based on radiocarbon and amino acid racemization methods, paleoecological reconstructions based on faunal and floral data and geochemical methods, such as stable isotope and trace element studies. The following briefly summarizes the scientific goals:
The working group reports provide strong scientific rationale for development of geological and geophysical projects along the East Antarctic margin. These onshore and offshore research possibilities range from investigation of Proterozoic tectonic events, eg. the assembly and dispersal of Rodinia and Gondwana supercontinents, to high resolution reconstructions of Holocene paleoclimate. Clearly, the need for both ship-based and land-based research has been expressed and justified. Given the breadth and volume of research proposed here, a single season of research would only scratch the surface. For this reason, despite general prioritization of logistics objectives, working groups opted to outline potential sequences of projects into three to four field seasons. In addition, prioritization by general research site, based on a combination of scientific, logistical and international collaborative reasons, is summarized below.
Research Priorities
| GROUP 1
NEARSHORE MARINE RESEARCH |
GROUP 2
CONT.SHELF- OCEANIC CRUST MARINE RESEARCH |
GROUP 3
BEDROCK GEOLOGY |
GROUP 4
ONSHORE TERTIARU RESEARCH |
|
|
1 |
Wilkes Land | Wilkes Land | Prince Charles Mts. | |
|
2 |
Queen Maud Land | Prince Charles Mts. | Beaver/Radok Lakes | |
|
3 |
Amery Ice Shelf/ Prydz Bay | Enderby Land | Dronning Maud Land | |
|
4 |
Wilkes Land | Queen Maud Land |
We emphasize that creative use of the USAP logistics platforms will enhance our ability to complete both offshore and onshore work. We suggest a combination of ship and aircraft efforts including the possibilities of:
In particular, we promote combined LC-130, Twin otter and Helicopter support at remote locations, especially within the context of shared support from international partners. This support may be in the form of large helicopters, enhanced air strips, or refueling assistance.
With regard to the suggested drilling programs on Beaver and Radok Lakes, modification and use of the Cape Roberts Drilling Platform is recommended. We also emphasize the need for development of a ship-board drilling rig which could be used aboard multiple platforms, such as the sea ice, from the research ships, and on sediment or rock. Ideally, conversion between the different platforms would be fairly simple and rapid, such that drilling could occur from more than a single site per season. Another important consideration is the ease of transport of the drilling system such that delivery to the field site may be possible via air support. This necessitates a compact, portable system.
Finally, we underscore the need for international cooperation and collaboration. This is necessary not only to recognize the international programs already in place, but also to maximize our scientific potential. For example, it is clear that the Australian Antarctic Program already has far-reaching scientific programs in the Prydz Bay - Amery Oasis - Prince Charles Mountains region. Existing international collaborations must be noted, particularly in the case of work on the Pagodroma Group. Extension of the collaborative framework of Cape Roberts Project to drilling work in the Amery Oasis should emphasize not only the use of the drilling platform, but also the model of international cooperation exemplified by the Cape Roberts project.
We thank Dr. Scott Borg and the Office of Polar Programs for supporting this workshop, and Ms. Lynn Everett and for all of her help in workshop organization.
Alonso, B., Anderson, J.B., Diaz, J.I. and Bartek, L.R., 1992, Pliocene-Pleistocene seismic stratigraphy of the Ross Sea: evidence for multiple ice sheet grounding episodes, in Antarctic research Series, v. 57, p. 93-103.
Barnes, P.W., 1987, Morphologic studies of the Wilkes Land continental shelf, Antarctica--glacial and iceberg effects: in S. L. Eittreim and M. A. Hampton, The Antarctic Continental Margin: Geology and Geophysics of Offshore Wilkes Land, Circum-Pacific Council for Energy and Mineral Resources, Houston, p. 175-194.
Barnes, P.W., and Lien, R., 1988, Icebergs rework shelf sediments to 500 m off Antarctica. Geology, 16, 1130-1133.
Barron, J.E. and Larsen, B., 1991, Proceedings of the Ocean Drilling Program Scientific Results, 119, College Station, TX, 1003 pp.
Denton, G.H., Prentice, M.L., and Burckle, L.H., 1991, Cainozoic history of the Antarctic Ice Sheet, in Tingey, R.J., ed., The Geology of Antarctica, Chapter 10, Clarendon Press, Oxford, p. 365-433.
Domack, E.W., 1982, Sedimentology of glacial and glacial-marine deposits on the George V - Adelie continental shelf, East Antarctica, Boreas, 11, 79-97.
Domack, E.W., 1987, Preliminary stratigraphy of a portion of the Wilkes Land continental shelf: evidence of till provenance, in Eittreim, S.L. and Hampton, M.A. (eds.), The Antarctic Continental Margin: Geology and Geophysics of Offshore Wilkes Land. Circum-Pacific Council for Energy and Mineral Resources, v. 5A, Houston Texas, pp. 195-204.
Domack, E.W. and Anderson, J.B., 1983, Marine Geology of the George V continental margin: combined results of Deep Freeze 1979 and the 1911-1914 Australasian expedition, in: Jago, J.B. (ed.), Fourth International Symposium on Antarctic earth Sciences, Adelaide, Australia, pp. 402-406.
Domack, E.W., Fairchild, W.W., and Anderson, J.B., 1980, Lower Cretaceous sediment from the East Antarctic continental shelf, Nature, 287, 625-626.
Domack, E.W., Jull, A.T.J., and Donahue, D.J., 1991, Holocene chronology for the unconsolidated sediments at Hole 740A: Prydz Bay, East Antarctica, Proceedings of the Ocean Drilling Program Scientific Results, 119, College Station, TX, pp. 747-750.
Domack, E.W., Jull, A.T.J., and Nakao, S., 1991, Advances of East Antarctic outlet glaciers during the hypsithermal: implications for the volume state of the Antarctic ice sheet under global warming, Geology, 19, 1059-1062.
Domack, E.W., Jull, A.T.J., Anderson, J.B., and Linick, T.W., Mid-Holocene ice-sheet recession from the Wilkes Land continental shelf, East Antarctica: in Thomson, R.A., Crame, J.A., and Thomson, J.W., editors, Geological Evolution of Antarctica, Cambridge University Press, Cambridge, p. 693-698.
Domack, E.W., Jull, A.T.J., Anderson, J.B., and Linick, T.W., 1989, Application of tandem accelerator mass-spectrometer dating to late Pleistocene Holocene sediments of the East Antarctic continental shelf, Quaternary Research, 31, 277-287.
Drewry, D.J., editor, 1983, Antarctica: Glaciological and Geophysical Folio: Scott Polar Research Institute, University of Cambridge.
Dunbar, R.B., Anderson, J.B., Domack, E.W., and Jacobs, S.S., 1985, Oceanographic influences on sedimentation along the Antarctic continental shelf, in Jacobs, S.S. (ed.), Oceanography of the Antarctic Continental Shelf, Antarctic Research Series, 291-312.
Eittreim, S.L., Cooper, A.K., and Wannesson, J., 1995, Seismic stratigraphic evidence of ice-sheet advances on the Wilkes Land margin of Antarctica: Sed. Geol., v. 96, p. 131-156.
Escutia, C., Eittreim, S.L., and Cooper, A.K., 1995, Cenozoic glaciomarine sequences on the Wilkes and Continental Rise, Antarctica (abstract): VII International Symposium on Antarctic Earth Sciences, 10-15 September 1995, Siena, Italy.
Fitzsimons, S.J. and Domack, E.W., 1993, Evidence for the early Holocene deglaciation of the Vestfold Hills, East Antarctica, The Polar Record, 29, 237-240.
Harris, P.T., O'Brien, P.E., Sedwick, P. and Truswell, E.M., 1996, Late Quaternary history of sedimentation on the MacRobertson shelf, East Antarctica: problems with 14C dating of marine sediment cores, Papers and Proceedings of Royal Society Tasmania, 130, 47-53.
Harris, P.T. and O'Brien, P.E., 1996, Geomorphology of the continental shelf adjacent to MacRobertson Land, East Antarctica: a scalped shelf, Geo-Marine Letters, 16, 287-296.
Johnson, G.L., Vanney, J.R. and Hayes, D., 1982, The Antarctic continental shelf, in Craddock (ed.), Antarctic Geoscience, Madison, University of Wisconsin Press, 995-1002.
O'Brien, P.E. and Harris, P.T., 1996, Patterns of glacial erosion and deposition in Prydz and the past behavior of the Lambert Glacier, Papers & Proc. Royal Society Tasmania, 130, 79-85.
O'Brien, P.E. and Leitchenkov, G., in press, Deglaciation of Prydz Bay, East Antarctica, based on echo sounder and topographic features, Antarctic Research Series.
Quilty, P., 1985, Distribution of foraminiferids in sediments of Prydz Bay and MacRobertson shelf, South Australian Department of Mines and Energy Special Publication, 5, 329-340.
Quilty, P., 1996, The Pliocene environment of Antarctica, Papers and Proceedings Royal Society Tasmania, 130, 1 -8.
Stagg, H.M.J., 1985, The structure and origin of Prydz bay and MacRobertson Shelf, East Antarctica, Tectonophysics, 114, 315-340.
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