Stock and U.S. Treasury ETFs often move in opposite directions, but that hasn’t been the case this week.

For example, SPDR S&P 500 (NYSEArca: SPY) and iShares Barclays 20+ Year Treasury Bond Fund (NYSEArca: TLT) were both in the green on Thursday afternoon, which is a bit unusual the past few years during and after the credit crisis.

In Tuesday’s deep stock sell-off, the Treasury ETF also lost ground.

The correlation between SPY and TLT this week has some technical analysts scratching their heads because they usually move in separate directions. They’re not sure which asset class is telling the truth: stocks or bonds.

From a technical perspective, the Treasury fund TLT is facing some key resistance lines: the 50-day simple moving average and a falling trend line.

iShares Barclays 20+ Year Treasury Bond Fund

Full disclosure: Tom Lydon’s clients own TLT and SPY.