The S&P 500 index on Friday has joined the ranks of market benchmarks forming that dreaded Wall Street chart pattern: the death cross.

A death cross has materialized in the S&P 500 SPX, -2.33% with the 50-day moving average at 2,759.28.02, below the 200-day moving average of 2,762.02, according to FactSet data.

A death cross is what chart watchers refer to as the point where the 50-day — a short-term trend tracker — crosses below the 200-day, which is used to define the longer-term trend. Many believe the cross marks the point where a shorter-term decline graduates to a longer-term downtrend. Read More.