A Fort Carson training exercise set to start this weekend in southern Colorado at the Piñon Canyon Maneuver Site has put the state office charged with historic preservation at odds the Army officials, following what the state called an “unjustified threat” to end their working relationship.  Fort Carson said discussions to end the relationship were a necessary tool to adhere to strict timelines to ensure a planned monthlong training at Piñon Canyon Maneuver Site northeast of Trinidad could take place. During the training, soldiers will test a new communications system that could be rolled out across the whole Army. For the first time at Piñon Canyon, soldiers will fire test artillery shells that are expected to damage two historic sheep ranching sites and three archeological sites, including a area where scattered stone tools have been found. The sites are just a handful of the 6,000 archeological sites across the Piñon Canyon training area.…