41. During the Cretaceous, low-relief drainage areas are completely transgressed and the clastic supply is shut off. 42. Stratigraphically equivalent rocks on the mainland are clastic sediments with coal beds, marine to brackish fluvial units and travertines. 43. Varves form in a variety of depositional environments from seasonal variation in clastic , biological, and chemical sedimentary processes. 44. In general the Br�ches du Grand Fond Group consists of coarse grained clastic sediments composed of pre-rift lithologies. 45. Lastly, the Wara formation is created by a fluvial system exposed to bio clastic dolomite known as the wara shales. 46. The majority of the lower Triassic clastic sediments originated from a Variscan source area in northern France with minor local input. 47. The formation consists of two members : clastic , mostly feldspathic various grained sandstones, and volcano erupted-alkali lavas. 48. This alluvium is adjacent to and probably underlain by volcanic clastic rock deposited by Mount Shasta in the course of its development. 49. As the graben dropped, it immediately began to fill with clastic sediment from the surrounding hills, creating the Chumstick formation. 50. The stratigraphy of the Sauk sequence indicates shallow-water deposition, primarily consisting of well-sorted sandstones and clastic carbonates.
