At 12.00pm (AEST), the benchmark S&P/ASX200 was down 67.3 points, or 1.54 per cent, at 4310.2, while the broader All Ordinaries had fallen 64.7 points, or 1.47 per cent, to 4326.7.
Burrell Stockbroking adviser Daniel Manley said there was no influence drive the market up.
"The futures feed for the US tonight is currently down about 30 points ... There is nothing to drive our market any higher at this point,'' he said.
"There was a bit of a scratchy report from Rio Tinto yesterday which is probably a bit of a drag on the rest of the resources.''
Mr Manley said that oil prices were driving up the energy stocks and that Woodside Petroleum had been a standout performer after announcing its plans for expansion in its profit report yesterday.
The major banks were down.
NAB was 89 cents lower, by 3.31 per cent, at $25.97, ANZ lost 48 cents or 2.45 per cent to $19.14, Commonwealth Bank was down 63 cents at $44.35, and Westpac fell 73 cents or 3.13 to $22.58.
Miners were also in the red.
BHP Billiton was 20 cents lower at $36.93, while Rio Tinto was down 2.19 per cent at $56.76.
In the energy sector, Woodside Petroleum rose 2 cents to $47.55, Santos added 33 cents or 2.25 to $14.98, and Oil Search was steady at $5.70.
On the Sydney Futures Exchange, the September share price index contract was 42 points lower at 4279 on 20,613 contracts.
Resources push shares lower at noonWall St. seeks to extend rally
