Not so sure about this being the start of a spike below 4000. Looks to me that the AUD/USD is forming a bearish ascending triangle with the apex at 70c on about 30th October and at the moment is simply retesting the sloping side of this triangle.
The apex being in about a week's time co-incides roughly with when I personally expect a break up or down on the sharemarkets (Unlike some of the date gurus on the XJO thread, I don't have a specific date). As its ascending, this IMO is more likely to break down to a 60c spike low than break up - therefore also is suggesting to me a spike low on the sharemarkets perhaps next Thursday/Friday is probable.