(Reuters) - Australian corporate earnings have been a "positive surprise" amid investor euphoria over estimate-beating margins, but historical trends suggest results could take a turn as the earnings season approaches its end, Macquarie analysts said.

Companies have posted better-than-expected margins, often supported by lower tax and interest costs, with most of them outperforming market view so far this season than in February, Macquarie said in a note.

The upbeat earnings have prompted investors to add back to their portfolio, especially after reducing their equity exposure in the recent correction at the start of the month, the analysts noted.

Cyclical retailers were the stand-outs last week. Shares of JB Hi-Fi ( JBHIF ) posted their best weekly gain in more than four years after the consumer electronics retailer announced a special dividend last week and an estimate-beating annual results.

Top telco Telstra ( TTRAF ) also came as a positive surprise after it raised its earnings forecast.

Investors appeared to shrug off the drop in profit from leading Australian banks, and instead focused on the positives such as Commonwealth Bank of Australia's ( CBAUF ) lower provision for bad loans and National Australia Bank's ( NAUBF ) steady margin.

Still, the biggest disappointment came from Origin Energy ( OGFGF ), whose shares crashed on a warning that profit in its electricity generation business is likely to drop.

The cycle is slowing and the key uncertainty is how much it improves in reaction to rate cuts by the U.S. Federal Reserve and the Reserve Bank of Australia, analysts said, adding that results' upbeat momentum tend to deteriorate towards the end, especially in the final week.

"While the high share of beats is positive, we would caution against extrapolating this trend to the rest of reporting season."

A bulk of the earnings season still lies ahead, with iron ore majors BHP and Fortescue, energy giants Woodside and Santos and supermarktes Woolworths and Coles reporting in the coming weeks.