Facies architecture of an isolated carbonate platform: tracing the cycles of the Latemàr (Middle Triassic, northern Italy) |
| |
Authors: | Sven O. Egenhoff,Arndt Peterhä nsel,Thilo Bechstä dt,Rainer Zü hlke,& Jü rgen Grö tsch |
| |
Affiliation: | Geologisch–Paläontologisches Institut der Universität, INF 234, D-69120 Heidelberg, Germany,;Geologisch–Paläontologisches Institut der Universität, INF 234, D-69120 Heidelberg, Germany (E-mail:;), Geologisch–Paläontologisches Institut der Universität, INF 234, D-69120 Heidelberg, Germany (E-mail:;), Shell Research and Technical Services, Volmerlaan 8, 2288 GD Rijswijk, The Netherlands |
| |
Abstract: | The 720-m-thick succession of the Middle Triassic Latemàr Massif (Dolomites, Italy) was used to reconstruct the lagoonal facies architecture of a small atoll-like carbonate platform. Facies analysis of the lagoonal sediments yields a bathymetric interpretation of the lateral facies variations, which reflect a syndepositional palaeorelief. Based on tracing of lagoonal flooding surfaces, the metre-scale shallowing-upward cycles are interpreted to be of allocyclic origin. Short-term sea-level changes led to subaerial exposure of wide parts of the marginal zone, resulting in the development of a tepee belt of varying width. Occasional emergence of the entire lagoon produced lagoon-wide decimetre-thick red exposure horizons. The supratidal tepee belt in the backreef area represented the zone of maximum elevation, which circumscribed the sub- to peritidal lagoonal interior during most of the platform's development. This tepee rim, the subtidal reef and a sub- to peritidal transition zone in between stabilized the platform margin. The asymmetric width of facies belts within individual metre-scale cycles was caused by redistribution processes that reflect palaeowinds and storm paths from the present-day south and west. The overall succession shows stratigraphic changes on a scale of tens of metres from a basal subtidal unit, overlain by three tepee-rich intervals, separated by tepee-poor units composed of subtidal to peritidal facies. This stacking pattern reflects two third-order sequences during the late Anisian to early middle Ladinian. |
| |
Keywords: | Carbonate platform depositional palaeorelief lateral facies changes supratidal tepee belt windward/leeward effects |
|
|