What is Lower Cretaceous?
The '''Lower Cretaceous''' is the first [[geology|geological]] [[Epoch (geology)|epoch]] in the [[Cretaceous]]. It began 145 [[million]] years ago, and ended 100.5 million years ago. Lasting for about 46 million years, this is the longest stage in the [[Phanerozoic]] [[eon]]. It is longer than some of the geological periods in the [[Phanerozoic]]. The Lower Cretaceous is best displayed in [[England]], where it is composed of two series of rocks. Between the two is a major rise in [[sea level]]. *Lower, the ''Wealden Beds'', laid down in [[freshwater]] or [[brackish]] conditions. [[Sand]]s came from the flood plain of a huge [[tropical]] braided [[river]]. [[Clay]]s came from a [[coast]]al [[lagoon]]al plain. *Upper, the ''Greensands'', an olive-green [[sandstone]] deposited in the sea; and the ''Gault Clay'', a formation of stiff blue clay deposited in a calm, fairly deep water [[Ocean|marine]] [[environment]]. It overlays the Lower Greensand formation. [[File:KentGeologyWealdenDomeSimple.svg|thumb|center|500px|A simplified geological diagram of the Wealden Dome as relating to [[Kent]].]] The two parts of the Cretaceous represent the [[sea level]] where the divisions were first defined. In the Lower Cretaceous, the sea level was much lower than in the [[Upper Cretaceous]]. In the Wealden, Southern England was a huge [[tropical]] [[river delta]]; in the Greensand the same areas were just off[[shore]]. However, in the Upper Cretaceous the deposits were made in deeper water, on what was then the [[continental shelf]]. Sea level then stood at its highest level in the [[Mesozoic]]. == References == {{Reflist}} {{Geologic History}} {{DEFAULTSORT:Cretaceous, Lower}} [[Category:Cretaceous]]