that rotten egg smell makes me think of a volcano - maybe the rocks they found were ejected from this, in 2004?
http://earthsciencesus.blogspot.com/2008/01/volcanic-heating-is-melting-ice-caps.html
ANTARCTICA - no name volcano
June 20th, 2004
A previously unknown underwater volcano has been discovered off the coast of Antarctica, and explains mariners’ historical reports of discolored water in the area. The research vessel Lawrence M. Gould (information sheet illustrating the ship ) was returning from a study of a collapsed ice self when it passed over the volcano. Temperature probes showed evidence of geothermal heating of seawater. A lack of marine life on dark rock around the volcano indicated that lava had flowed fairly recently. The volcano is in an area known as Antarctic Sound, at the northernmost tip of Antarctica. There is no previous scientific record of active volcanoes in the region where the new peak was discovered. The volcano is located on the continental shelf, in the vicinity of a deep trough carved out by glaciers passing across the sea floor. The volcano stands 2,300 feet above the sea floor and extends to within roughly 900 feet of the ocean surface.
Very interesting, could be a topic, hmm, maybe worth a search.
Semi-related sidebar:
In an article in the now-defunct “Strange” magazine, Vincent Gaddis recounted how a vessel charted and landed on an island in the southern Pacific (if memory serves, it was east of Africa), one of three smallish islands in a group. They landed to either hunt or butcher something (whales, seals, I forget) and didn’t think much of it.
There’s nothing there today.
Apparently the boulders sticking up were merely carried along in big icebergs, or some islands have subsequently sunk. S’cool.