Antarctica ice cap and Australia from Google Earth.
This research examines the structural geology of Antarctica by structural enhancement of the ice-cap seen in Landsat. Comparison with basement geology show the basement structures project through the ice cap to the surface.
This is my second paper onthe geology of Antarctica and there are 40 papers of background reading on my research and methods freely available on my website; Geotreks.com — https://www.geotreks.com.au/. There is also my LinkedIn post page https://www.linkedin.com/in/bob-watchorn-97b95624/detail/recent-activity/posts/ and my public lectures – August 2013 Perth AusIMM branch https://www.youtube.com/watch?v=l0HdKnHomeA, April 2019 AusIMM https://ausimm.com/news/bob-watchorn-tech-talk/ and October 2019 AusIMM https://www.geotreks.com.au/work/giant-ring-structures/ausimm-innovation/
Plan showing the surface topography, ice streams and ice divides in the Antarctic ice cap (Goodge 2007).
Landsat image from Google Earth shows the ice cover of Antarctica.
The small black areas around the edge of the ice-cap represent the exposed geology and shows how difficult it is to map the geology of Antarctica
This paper is looking at the ice-cap to see if structures transmitted through the 1-4 km thick ic-cap to the surface can be recognised. Can continent wide structures be seen? If they are present then how do these structures propagate?
One needs excellent methods of looking beneath the ice cover to gain structural detail. One such method on the Gambertsev Mountains uses Radar. The next section shows structures actively propagating through the central East Antarctic ice-cap above the Gambertsev Mountains
Radar cross section through the Gambertsev Mountains showing the ice cap structures (Bell et al. 2011).
Enhanced and interpreted Radar cross section through the Gambertsev Mountains showing the ice cap structures.
This figure shows value of the extra detail obtained from even good quality geophysical data of all types. It shows that the ice flows like a slow river over the basement mountains. This is not evident in the published radar traverse. , Unless one can structurally enhance the lithosphere and crust then these structures are invisible. That none of these deep structures are reported (like the above non-reporting of the above turbulent ice structures) is perhaps due to the lack of a good enhancement method
Antarctica ice cap comparative thickness. Cross-sectional profile of the Antarctic ice sheet based on BEDMAP bed topography (Lythe et al).
Basement structures should be seen in the ice-cap as it is a very thin layer. It seems thick in the close up images normally shown but the thickness of 0 – 4 km is only 1400th of the diameter of the Antarctic continent. This is equivalent to a film only 0.7 millimetre thick over a disc of 1metre diameter (see lower inset).
Enhanced Landsat image showing detailed structures in the Antarctic ice cap
Enhanced Landsat image showing detailed structures and ice divides in the Antarctic ice cap.
The ice divides and streams are much more complicated in my figure than the published figure. Is my figure reflecting the true ice topography? If it is then this is a good fast way of mapping the ice surface in much greater detail.
Enhanced Landsat image showing detailed structures and ice rings in the Antarctic ice cap.
Rings seen are similar in size to those seen on surface geographical, topographical, and geological data in Australia, North America China and Scandinavia/Russia.
The giant structures in these continents are observed more clearly when there is minimal human disturbance, the surface has been scoured by ice or there is a thin surface veneer of cover as in deserts allowing preferential alteration or vegetation along fracture patterns.
Enhanced Landsat image showing linear, ring and arcuate structures in the Antarctic ice cap.
This enhancement is a structural exercise. Several large structures show. The method emphasises abrupt changes in topography and ice colour.
Enhanced Landsat image showing linear structures in the Antarctic ice cap.
This figure shows the major linear structures transacting Antarctica. Some of these linears, particularly the right hand side vertical linear appears to line up with the dislocation of eastern Antarctica.
Enhanced Landsat image showing ring and arcuate structures in the Antarctic ice cap.
The top left ring lines up with a semicircular range of mountains on the south west of the Antarctic craton. North is towards Australia, see arrow. The lower central, upward facing, arc lines up with the Trans Antarctic Mountains seen in the topography. The two north facing arcs (5000 km diameter) line up with arcs in the craton at 250 km depth which were outlined using seismic tomography (later paper).
Antarctica ice cap ring and arcuate structures projected onto Antarctica geography.
They show the top left ring lines up with the semicircular range of mountains.The bottom, upward facing, arc lines up with the Trans-Antarctic Mountains seen in the topography
Antarctica ice-cap linear structures datasets projected onto the geology plan of Antarctica.
Are the basement geological structures transmitted through the ice to the surface?
Linear set A follows (but offset 300 km to the left) the large structure extending from the rift that bisects continental Antarctica. This structure correlates with the shift in the coast outline and suggests this is the most recent active structure. This structure correlates with the EW structures in Australia, which are also considered the most recent structures. These structures have a spacing of about 300 km out to the left of the plan and the far left structure cuts off the continent.
Linear set B form in the same WNW direction as the Kalgoorlie Shark Bay set in Australia. They are associated with the direction of the rift at the top centre and with the chains of islands in the bottom centre of the plan (D dark grey).
Linear Set C follows the cut off between the Precambrian and younger rocks and the cut off of the continent in the lower left and the chain of islands in the bottom centre of the plan.
The strongest influence of these basement structures appear to be in the zigzag pattern (D dark grey) of the Archipelago in the bottom of the plan. This is a similar structural situation to the influence of the Main Australian craton structures upon the Tasmanides of Eastern Australia. The earlier structures influence the broad mountain building geology up the Eastern Australian seaboard.
The third section of this paper detailing the structure of the lithosphere below Antarctica will be completed soon.
For a detailed paper on the ice cap structural geology open up the attached paper. If you like it share it.
aaExploration of Antarctica using Landsat of the ice cap.pdf