The Australian sharemarket was weaker at Thursday noon, as profit takers drive losses among materials and financial stocks.

Around midday, the benchmark S&P/ASX200 slipped 22 points or 0.5 per cent at 4639.5, after opening flat. The broader All Ordinaries index, meanwhile, shed 20.1 points or 0.4 per cent to 4682.6.

Among the sectors, materials declined 1.1 per cent, financials took off 0.7 per cent and industrials lost 0.1 per cent. Consumer shares, which posted slight gains, were the only ones in the black.

IG Markets market analyst Cameron Peacock said it was not surprising that the market had pulled back after a recent strong run.

According to him, September was normally the weakest month on the Australian market, but was still up about 5.4 per cent for the month despite today's losses.

''We've had a pretty good run,'' he said. ''It seems like only weeks ago we couldn't get past the 4500 point level and now we've broken through that resistance.

''There's some profit-taking today, but not a massive pullback.

The big four banks were all in the red, as ANZ Banking Group slipped 12 cents to $24.04, Commonwealth Bank of Australia gave back 48 cents at $53.32, National Australia Bank reversed 6 cents lower at $25.88, and Westpac Banking Corp softened 5 cents to $23.58.

Meanwhile, investment bank Macquarie Group lost 1.25 per cent to $36.30.

Bendigo and Adelaide Bank bucked the trend, rising 0.74 per cent to $9.52, after telling 1,300 investors in Great Southern to pay back their loans or risk bankruptcy.

The major miners were also negative after commodities prices took a breather overnight.

BHP Billiton was down 41 cents at $39.03, after the competition watchdog again delayed a move on the miner's proposed iron ore merger with rival Rio Tinto.

Rio Tinto was 81 cents lower at $74.49 and Fortescue Metals was 11 cents, or 2.2 per cent cheaper at $4.92.