 Marine sediments younger than about 9 million years are not preserved in the Carrizo Plain National Monument area, but they occur throughout the Kettleman Hills region (about north of the park).The Pliocene-age Etchegoin Formation contains marine fossils to about 4 million years old.Fossils of the Etchegoin Formation are supporting evidence that the Coast Ranges and the Temblor Range are young, having been uplifted mostly during the Pleistocene Epoch (or Quaternary Period) in the past several million years.