The dilemma of gaps in carbonate stratigraphic sequences: A case history from the Jurassic of the Venetian Alps, Italy

Conference · Fri Mar 01 00:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:7262320

Zempolich, W G ^[1]

---

1. Johns Hopkins Univ., Baltimore, MD (United States)

The Lower Ammonitico Rosso (L.A.R.) of the western Venetian Alps is a thin, red nodular limestone that overlies a thick Late Triassic to Middle Jurassic (Aalenian) shallow-water platform sequence. It is thought to represent a Middle Jurassic (Bajocian) drowning event whereby the Trento Platform became a submerged plateau. The L.A.R. is problematic in that it (1) is rich in ammonites and other pelagic fauna; (2) contains stromatolites, oncolites, and shallow-water sedimentary structures; and (3) directly overlies platform sediments that contain complex brecciated fabrics filled by cement and Bajocian-age sediment. These seemingly contradictory features have generated much debate as to the sequence stratigraphy of the Trento Platform. New evidence suggests that the L.A.R. was deposited in a shallow-water environment following a period of subaerial exposure. In an east-west transect from the platform edge to platform interior, a clear transition is exhibited from high- and low-energy open-marine facies to restricted lagoonal facies. High-energy open-marine facies include well-sorted skeletal- and peloidal-rich sands possessing low-angle to planar cross stratification and thin, fairly sorted ammonite- and belemnite-rich gravels. Sands include both shallow-water and pelagic fauna; gravels commonly contain ripup clasts from underlying sediments. Low-energy open-marine facies consist of buff colored wackestones and packstones that contain ammonites, belemnites, pelagic bivalves, and peloids. With respect to paleogeography, the abrupt transition from open-marine facies at the platform edge to lagoonal facies in the platform interior indicates that thrombolites, stromatolites, and oncolites accumulated in a shallow restricted environment.

• OSTI ID: 7262320
• Report Number(s): CONF-910403-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CARBONATE ROCKS
DEPOSITION
PALEONTOLOGY
ITALY
GEOLOGIC FORMATIONS
ALPS
ARTHROPODS
GEOLOGIC HISTORY
JURASSIC PERIOD
LITHOLOGY
MOLLUSCS
STRATIGRAPHY
ANIMALS
AQUATIC ORGANISMS
DEVELOPED COUNTRIES
EUROPE
GEOLOGIC AGES
GEOLOGY
INVERTEBRATES
MESOZOIC ERA
MOUNTAINS
ROCKS
SEDIMENTARY ROCKS
580000* - Geosciences