Geomorphology of Cape York and Solander Point, Examining Opportunity's destination at Endeavour Crater Options

[Stu]

Everyone, say hello to Cape York... in colour...



Larger version on my blog: http://roadtoendeavour.wordpress.com/2010/...-york-in-colour

[algorimancer]

Great stereo, Stu (much better than the one I improvised). The more I look at this, the more I think "beach". Consider that, if Endeavour were flooded, with the water extending beyond the current rim (so that Cape York was an island), the big open deep water would be to the east of Cape York, and consequently the major wave action would be from that direction. All along the east side of Cape York is what appears to be a longshore bar, which might be expected from that wave action. This feature is largely lacking to the west. It makes sense that, as the water declined, water which accumulated behind the bar would channelize and flow through gaps. While the Wedge seems most prominent, I also see signs of channels to the south of it (immediately below the apparent small crater in the "bar", and a smaller channel at the northern "point" of Cape York. I see signs of channels feeding into these 3 outlets which are traceable southwards beyond half the length of the Cape.

Here's a portion Wikipedia's description of beach geology:

"There are several conspicuous parts to a beach, all of which relate to the processes that form and shape it. The part mostly above water (depending upon tide), and more or less actively influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline. The berm has a crest (top) and a face — the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, and further seaward one or more longshore bars: slightly raised, underwater embankments formed where the waves first start to break.

The sand deposit may extend well inland from the berm crest, where there may be evidence of one or more older crests (the storm beach) resulting from very large storm waves and beyond the influence of the normal waves. At some point the influence of the waves (even storm waves) on the material comprising the beach stops, and if the particles are small enough (sand size or smaller) , winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune."

[ngunn]

beach geology

I was using the word 'beach' in a very lazy way as shorthand for 'shoreline feature'. I realise that in a geomorphology thread that's inappropriate and I apologise for the sloppiness. What we may call the Cape York terrace (though it can actually be traced around much of the Endeavour rim) has to be a hard formation to have resisted erosion in the way it apparently has. The result of some sort of concretion process happening at the lake margin maybe, rather than loose material emplaced by wave action. Another possibility is that it marks the stable stand of an old water table from a time when the whole of Endeavour was filled with porous sediments.

I also have been looking for signs of an outflow, but maybe in the wrong place. I thought the lowest gaps in the rim lay in the general direction of Iazu. There are some channel-like features there that appear to begin a short distance outside the crater and flow away from it.