Facies architecture of an isolated carbonate platform: tracing the cycles of the Latemàr (Middle Triassic, northern Italy)

Abstract

The 720-m-thick succession of the Middle Triassic Latema Ár 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 re¯ect a syndepositional palaeorelief. Based on tracing of lagoonal¯ooding 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 decimetrethick 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 re¯ect 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 re¯ects two third-order sequences during the late Anisian to early middle Ladinian.

Geometry and chronology of growth and drowning of Middle Triassic carbonate platforms (Cernera and Bivera/Clapsavon) in the Southern Alps (northern Italy)

“…1a, b) have attracted the attention of generations of geologists in the past decades (among the more recent publications, e.g., Bosellini & Rossi 1974;Gaetani et al 1981;Bosellini 1984;Bosellini & Stefani 1991;Goldhammer et al 1993;Brack et al 1996;Egenhoff et al 1999;Maurer 1999Maurer , 2000Emmerich et al 2005). These platforms typically consist of narrow cores surrounded by thick packages of foreslope deposits terminating within thin intervals of starved basinal sediments.…”

Geostatistical modelling of cyclic and rhythmic facies architectures

“…Because the space domain is considered here, we use the term rhythmicity rather than periodicity. Rhythmic stacking of facies cycles has been observed in many shallow-marine carbonate successions (Goldhammer et al 1993;Egenhoff et al 1999;Lindsay et al 2006). This aspect is also shown by the red facies in Fig.…”

Cyclostratigraphy concepts, definitions, and applications

“…Comparison and intercalibration with independent radio-isotopic dating methods is fundamentally important. For example, new radiometric age dating recently challenged the up to then widely accepted cyclostratigraphical interpretation of the Middle Triassic Latemar platform in Italy (e. g., Goldhammer et al 1987, Hinnov & Goldhammer 1991, Brack et al 1996, Egenhoff et al 1999, Zühlke 2004. At the Tortonian GSSP at Monte dei Corvi (Italy), however, new 40 Ar/ 39 Ar ages essentially confirm the cyclostratigraphic dating (Kuiper et al 2005).…”