Shallowing-upward sequences in Purbeckian peritidal carbonates (lowermost Cretaceous, Swiss and French Jura Mountains)

摘要: Purbeckian carbonates in the Swiss and French Jura (Goldberg Formation, lower Berriasian) comprise shallow-subtidal, intertidal, supratidal, low-energy, high-energy, marine, brackish, freshwater, hypersaline facies. These facies are arranged small (0–2–1.5 m thick) sequences which display a dominant shallowing-upward component, form fundamental units of highly structured sedimentary record. Six types small-scale can be recognized. A: intertidal to supratidal overprinting shallow lagoonal facies; B: algal-marsh sequence with frequent dolomitization; C: sabkha sequence, often associated collapse breccia; D: tidal-flat desiccation features; E: lacustrine sequence; F: terrestrial subtidal or Episodic event deposits such as tempestites superimposed] Thin transgressive beds rework elements underlying frequently found at base sequences. Green marls black pebbles common top indicate long subaerial exposure. The incomplete, may absent, their upper part eroded. Lateral changes common, is due very partly emergent platform where various depositional environments were juxtaposed. However, many boundaries well developed correlated over large parts study area. The generated by climatically controlled sea-level changes. Autocyclic processes occurred locally, but overprinted drops affecting entire platform. most probably related 20 000-year cycle precession equinoxes. Larger usually well-developed emersion surfaces attributed 100 000 400 eccentricity cycles Earth's orbit. Identification correlation makes it possible set up framework isochronous (which cut across boundaries), thus interpret detail palaeogeographic, sedimentological diagenetic evolution peritidal carbonate environments.