This image is a cross section demonstrating the two phases of deposition on the passive margin of NA. The lower part of the section is the first phase of deposition and you see it was dominantly a thick sequence of non-marine nearshore deltaic and sandy deposits. The second phase was after the strengthening of the margin, the slowing of subsidence and the deposition of nearshore, marine carbonate deposits. You can see on the left side of the slide that during the second phase we also had the deposition of the distal, fine-grained materials that had been thrust back over the passive margin. Again, Las Vegas is at the hinge line, and you can see that there was discontinuous deposition east of there, it just was not as thick as on the subsiding passive margin. This slide also raises the point that we must be careful when we interpret cross sections, at the vertical exaggeration can be deceiving. You can see below the unexaggerated section. Image courtesy of Professor Burchfiel.