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Forkner, Robert1
(1) The University of Texas at Austin, Austin, TX

ABSTRACT: Stratigraphic Packaging and Syndepositional Extensional Tectonism: A Preliminary study of the Dolomia Principale, the Dolomites, N. Italy

The Norian (late Triassic) Dolomia Principale (DP) is a broad peritidal carbonate complex that nucleated atop several mid-Triassic carbonate platforms in the Dolomites of northern Italy. Early studies by Bosellini and Hardie (1985) recognized a record of glacio-eustatic cyclicity throughout the DP. Doglioni, (1992); Bertotti et al., (1993); and Cozzi, (2000) recognized the effects of syndepositional rifting in the DP, including intraformational marginal, slope, and basinal facies within the DP complex. Preliminary results of this study indicate that syndepositional extension modified the stratigraphic packaging within the DP and served as a accommodation-generating mechanism upon which an allocyclic record is superimposed. Evidence for synsedimentary extension in the DP can be observed at several scales, and includes centimeter scale fractures with fill from overlying beds, sealed meter-scale normal faults, and lateral variability in complete vertical section thickness. A comparison of complete DP sections along a west-to-east transect indicates that the DP more than doubles in thickness over a few tens of kilometers. Measured sections from the bases of the Sella, Tofane and Monte Cristallo show subtle variability in facies as well as measurable differences in cycle thickness. Fischer plots generated from measured sections indicate that cycles thicken from west to east rather than increase in number, likely a result of sedimentation keeping up with differential subsidence. The results of synsedimentary extension and subsidence can be readily observed in the subsurface in most passive margins. As in many passive margins, it is likely that the synsedimentary extension in the DP is the direct result of extensional normal faulting in the upper crust and detachment on underlying evaporite.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.