--> ABSTRACT: Recent Carbonate Sedimentation on Balearic Platform: Model for Temperate-Climate Carbonate Shelves, by J. Fornos, A. Rodriguez-Perea, C. Massuti, L. Pomar, J. Acosta, P. Herranz, and J. L. Sanz; #91022 (1989)

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Recent Carbonate Sedimentation on Balearic Platform: Model for Temperate-Climate Carbonate Shelves

J. Fornos, A. Rodriguez-Perea, C. Massuti, L. Pomar, J. Acosta, P. Herranz, J. L. Sanz

Existing models for carbonate sedimentation on continental platforms are derived from the study of modern carbonate platforms in tropical climates. The Balearic platform in the western Mediterranean provides a new model for carbonate sedimentation in a temperate, semiarid climate. On most of the continental shelf around the Balearic Islands, modern sediments are exclusively bioclastic carbonates.

Shoreline carbonate sediments are bioclastic sands and muds accumulating in beach-dune systems without significant tidal influence (there are no astronomical tides in the western Mediterranean). From the upper shoreface to 35 m deep, the sandy bottom is extensively colonized by sea grass (Posidonia oceanica), the rhizomes and roots of which form a rigid entrapment that retains the sediment derived from calcareous organisms living within the sea grass and from calcareous epiphytes living on the stems and leaves. Archeological dating establishes a rate of vertical accretion in this zone of 103 Bubnoff units (1 Bubnoff unit = 1 mm/1,000 years).

Between depths of 40 and 60 m, carbonate sands are composed predominantly of red-algal fragments. Intensely bioturbated wave ripples occur in environments dominated by laminar red algae (Lithothamnium and Phymatolithon).

Below depths of 60 m, coarse sediment produced by rhodolitic and ramose red algae is deposited in areas of tens to hundreds of meters in size. Biogenic buildups up to 2 m high occur in sandy areas as well as in deeper muddy areas. At the same depth in open-platform zones, the bottom topography is characterized by large hummocks several hundred meters across.

From the horizontal distribution of facies, it is possible to construct the probable vertical sequence of lithofacies which would characterize carbonates accumulating on a temperate-climate carbonate shelf. Many of these lithofacies are recognized in upper Miocene limestones on the Balearic Islands.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.