Geological Survey Team's Field Trip Delayed Eight Hours by Argument Over Whether Outcrop Is Sandstone or Siltstone

A U.S. Geological Survey field mapping team lost an entire day of work Tuesday when a routine stop at a road cut along Highway 191 in Montana devolved into an eight-hour dispute over whether the exposed formation is fine-grained sandstone or coarse-grained siltstone. 'The grain size is right on the boundary,' said team leader Dr. Francesca Bedrock. 'We're talking about the difference between 62.5 and 63 microns. That's the official dividing line between silt and sand. These grains are right there. It's geological purgatory.' The team arrived at the outcrop at 8:30 AM for what was scheduled as a ten-minute observation stop. By 9:00 AM, hand lenses had been deployed. By 10:00 AM, grain size cards were being pressed against the rock face. By noon, team geologist Dr. Harold Lamination had produced a portable sieve set from the back of the field vehicle. 'I always carry sieves,' he said. 'You never know when you'll need to settle a grain size argument in the field.' The sieve analysis proved inconclusive, with results falling precisely on the silt-sand boundary. This prompted a further two-hour debate about whether the Wentworth grain size classification system itself is 'fundamentally flawed at the boundaries.' 'Wentworth published that scale in 1922,' said Dr. Lamination. 'Perhaps a hundred years of sedimentological progress has rendered the 62.5-micron cutoff obsolete.' 'You cannot just move a classification boundary because your outcrop is inconvenient,' Dr. Bedrock replied. The team eventually compromised on the description 'sandy siltstone,' which satisfied no one. Their field report for the day contains a single observation about one road cut, supported by four pages of notes. Project management has extended the mapping campaign by one week, noting that 'the rate of one outcrop per day is below our target.'