Milankovitch cycles. Lacustrine strata in the Newark basin, such as this part of the Passaic Formation from the NBCP Rutgers core, show cyclical changes in color and depth rank. The basic cycle of a lake-level rise, highstand, and lake-level fall--the Van Houten cycle--is grouped into a series of longer compound cycles. There are about 5 Van Houten cycles in the short-modulating cycle, and 20 Van Houten cycles in the McLaughlin cycle. Note that the character of the Van Houten cycle changes within the compound cycle. In the short modulating cycle, the lowest Van Houten cycle has a thick black shale, whereas the second cycle has a much thinner black shale. The third cycle lacks black and gray shale, and the fourth and fifth cycles do not show any appreciable color changes (although the rock typically becomes less massive). Modified from Olsen et al. (1996).