Under-pressure mining and energy stocks bounced in spectacular fashion this week and the multi-digit gains on otherwise bad company news had a lot to do with the US dollar, Pengana Global Resources Fund senior fund manager Tim Schroeders said.

The strength of the US dollar was one of the strongest convictions the market had until now. But it fell spectacularly this week, enduring its worst two days of selling since the global financial crisis on softer-than-expected US economic data, which also pushed US dollar-traded commodity prices higher.

There were also comments from two US Federal Reserve officials who acknowledged tightening financial conditions, leaving the market to all but rule out interest rate rises in 2016.

"Lo and behold what we've seen is the rug has been pulled from beneath the market and it has had some fairly interesting consequences," Mr Schroeders said.

Take the share price performance of BHP Billiton spinoff South32, which jumped 16 per cent on Thursday after announcing jobs cuts and a $US1.7 billion ($2.4 billion) write-down. Royal Dutch Shell, meantime, announced 10,000 job cuts overnight and an 80 per cent full-year profit slump, but its shares climbed almost 5 per cent in London.

"The same news two or three weeks ago would have sent those stocks down in the order of 10 or 15 per cent. It is a glass half-empty, glass half-full environment," Mr Schroeders said.

Safe place to work from

The conventional wisdom since the decline of the mining boom was that China was slowing, so resources earnings and consequently their share prices would trend lower.That had been a safe place for investors to work from, Mr Schroeders said.

"The [US dollar fall] calls into question the unquestioned assumptions around the way the world is panning out."

Romano Sala Tenna, a Perth-based portfolio manager at Katana Asset Management, said the volatility particularly in the past two weeks had differed from previous bouts, because it was moves in both directions.

"In my view it's typical of a market that is really at a potential turning point," he said.

The mining and energy stocks were caught between short sellers who are cashing in on their bets on falling share prices, and those who are seeing "profound value" and buying with a view that the share prices must rise from here.

On Thursday, Australia's two biggest miners, BHP Billiton and Rio Tinto, had their best day on the index since 2009. BHP's shares lifted 8.3 per cent and Rio Tinto added 8.9 per cent. It came the same day the S&P/ASX 200 marked its best day of 2016, rebounding a day after its worst day of 2016.

Credit ratings cut

In the same week, some of the world's biggest resources and energy companies had their credit ratings cut by Standard & Poor's, while others reported huge profit falls. BP reported a fourth-quarter earnings fall of 91 per cent.

S&P cut BHP from an A+ rating to A, a move that its biggest investors said was the death knell for its progressive dividend policy. Chevron was cut from AA to AA-, while Exxon Mobil kept its AAA rating but was put on credit watch negative.

On Thursday night Swiss-based mining behemoth Glencore was the latest to be hit, falling from BBB to BBB-, just one level above "junk" status.

But the latest credit rating cut came on a day when London-based miners staged their biggest one-day rebound since the global financial crisis, helped by solid gains in metals, including zinc, copper and lead.

Anglo American shares rose 20 per cent and Glencore rallied 16 per cent.

Mr Schroeders said the credit downgrades might have been the line in the sand some investors needed.

"The inevitability of the cut to BHP's dividend has been a painful and drawn-out process, to be frank," he said.

Hesitant to call a bottom

ANZ Banking Group economists are hesitant to call a bottom to the commodity price rout, despite much of the negative risk already having been priced in.

"Given the sustained sell-off experienced in many commodities, this may have simply been a matter of short covering," the bank said.

"In coming months we continue to view oil and iron ore markets as the commodities most susceptible to further weakness. Both have ongoing supply-side issues, although iron ore has the added complication of a structural decline in demand."

Mr Schroeders said investors had largely given up on the prospect of energy and resources share prices finding a bottom for now.

"Anyone that's been investing on the basis of faith that share prices can't get lower are probably severely damaged emotionally and financially at the moment," he said.

What happened next was anyone's guess, he said.

"This is not an event where we can look back and go, 'Here's what happened in the 1950s or 1960s'. No one has lived through this."