Figure 2. The K-Pg boundary recovered from the Bass River borehole in New Jersey. The New Egypt Formation is below the boundary, and the Hornerstown Formation is above. Note the high iridium concentration, presence of shocked minerals, and clay clasts. No in situ mosasaur fossils are known above the boundary/contact of these two units. From www-odp.tamu.edu/publications/174AXSIR/leg_sum/sum_f9.htm.
Figure 3: The K-Pg section in Maastricht. The Meersen Member of the Maastricht Formation (lower, light tan rocks) is capped by characteristic elevated iridium levels, shocked quartz (concentrated in small shrimp burrows), and distinct clay layers (grey) resulting from the impact of a large meteor or comet. No in situ mosasaur fossils are known above this layer. Photo by Marcus Ross.