RT Journal Article
T1 Ammonites, taphonomic cycles and stratigraphiccycles in carbonate epicontinental platforms
A1 Fernández López, Sixto Rafael
AB Some variations of the taphonomic features and the distribution of thesuccessive recorded associations of ammonites in the carbonate epicontinentalplatforms enable to distinguish elementary taphonomic sequences,taphosequences, taphorecords, taphocycles, megataphosequences and supertaphocyclesresulting from relative sea-level changes. The identificationof such taphonomic cycles is of utmost importance in interpreting thestratigraphic cycles of Mesozoic epicontinental platforms, when no evidenceof coastal onlap is preserved but fossiliferous sediments of outerplatform are widely developed.Five environmental cycles of deepening/shallowing were developedin the Castilian, Aragonese and Tortosa platforms during the Middle Jurassic:four cycles of median deepening (early Aalenian, middle Aalenianearly Bajocian, Bathonian and Callovian) and one cycle of advanced deepening(late Bajocian). Ammonite taphorecords of the Opalinum Biozonerepresent the last terms of a shallowing upwards megataphosequence which began in the late Toarcian. The maximum deepening and the maximumrelative sea-level rise were reached during the Niortense Biochron(late Bajocian). Sediments of the Polygyralis Subchronozone belongs to asecond-order peak transgression. Foremost shallowing episodes duringthe Middle Jurassic, representing peak regression of second order, correspondto middle Aalenian (Murchisonae Biochron) and late Callovian(Lamberti Biochron). Murchisonae and Lamberti biochrons conform twosecond-order peak regressions. Recorded associations of ammonites comprísedbetween these two biochrons represent a supertaphocycle of secondorder in the Iberian Basin. Sediments of the Middle Jurassic comprisedbetween these two stratigraphic discontinuities, from the middleAalenian until the upper Callovian, also represent a stratigraphic supercycleof second order in the Iberian Basin.
PB Universidad Complutense de Madrid. Departamento de Estratigrafía
SN 0378-102X
YR 1997
FD 1997
LK https://hdl.handle.net/20.500.14352/58524
UL https://hdl.handle.net/20.500.14352/58524
LA eng
DS Docta Complutense
RD 25 abr 2025