Sand shoveled out of an Argentina river used to transport soybeans will soon reappear 1,100 kilometers (700 miles) away in the country’s booming shale fields. Tecpetrol SA, part of billionaire Paolo Rocca’s empire, has started buying sand that Belgium’s Jan de Nul hauls from banks on the Parana River to frack for natural gas in Vaca Muerta, a Maryland-sized shale formation in Patagonia. For Jan de Nul, which has been dredging the river since 1995 to make room for soy cargoes, the shale industry is emerging…