in the early cambrian, there was little tectonic activity in virginia and sediments were deposited along the continental margin. the deposition of sand, silt, and other clastic materials was gradually replaced by the deposition of limy sediments in the warm tropical waters of the iapetus ocean. if we were to look at the layers of rock dating back to this time period, we would expect to   a)limestone layered over sandstone and shale. b)sandstone and shale layered over limestone. c)limestone intruding into sandstone and shale layers. d)three layers from top down, sandstone, shale, limestone.