Shipments of limestone on the Great Lakes totaled 3.7 million tons in September, an increase of 10.4% compared to a year ago, trade group the Lake Carriers’ Association (LCA) reports. Limestone cargos were above the month’s five-year average by 5.2%.Loadings from U.S. quarries totaled 3 million tons, an increase of 12.2% from 2020, while shipments from Canadian quarries totaled 684,234 tons, an increase of 8.3%, LCA said.Year-to-date the limestone trade stands at 21 million tons, an increase of 9.1% compared to a year ago.