--> ABSTRACT: Late Triassic Milankovitch Cycle Record of a Hungarian Marine Carbonate Platform Compared with Record from Italian Alps and United States Rift Basins, by A. Balog, J. F. Read, J. Haas; #91020 (1995).

Datapages, Inc.Print this page

Late Triassic Milankovitch Cycle Record of a Hungarian Marine Carbonate Platform Compared with Record from Italian Alps and United States Rift Basins

A. Balog, J. F. Read, J. Haas

Triassic lake fills, eastern United States, record high frequency climate change dominated by roughly 20, 109 and 413 k.y. Milankovitch cycles (Olsen, 1986). Given the clear evidence for Milankovitch climate forcing in the Triassic, we examined the large Late Triassic carbonate platform in Hangars. A combination of 2 km total of detailed logs of cores and outcrops provided the data base. Cycles (1 to 5 m) consist of variably developed transgressive laminites, subtidal carbonates, and regressive tidal flat laminites capped by disconformities or paleosols. Individual cycles have durations suggesting precessional forcing. Spectral analysis based on water depth rank shows well defined wavelengths of 2 to 2.5 m, a weak obliquity? peak around 4.5 m, and eccentricity peaks aroun 10 to 11 m (100 k.y. roughly) and 40 m (400 k.y.?); these also are evident in the wireline logs. The spectra and weak cycle bundling on Fischer plots of 3 to 4 precessional cycles per ~100 k.y. bundle and about 10 to 15 cycles per 400 k.y. bundle are consistent with missing eustatic beats from the cyclic record. This bundling contrasts with the well developed 5:1 bundling in parts of the marine Middle Triassic Latemar platform (Goldhammer, et al, 1990). This suggests that the large Hungarian platform shoaled to sea level during each marine flooding event (precessional beats), of which roughly 75% actually flooded the platform. Thus, this large platform, which probably is representative of most large platforms developed under greenhouse climatic conditions, only records about 3/4 of the Milankovitch climatic signal in contrast to lakes, which may contain a more complete record.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995