Diversity, composition and structure of Late Eocene shelf-edge coral associations (Nago Limestone, Northern Italy) |
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Authors: | Dr Francesca R Bosellini |
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Institution: | (1) Dipartimento di Scienze della Terra, Universitàdi Modena, Via Università 4, 41100 Modena, Italy |
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Abstract: | Summary During the Late Eocene, shelf-edge patch reefs developed on the western margin of the Lessini Shelf. The coral fauna, studied
in the Nago Limestone type locality, is described and interpreted for the first time, and provides further data for better
understanding of the generally poorly known Eocene reef communities.
Facies analysis was carried out across the shallowing upward succession that characterizes the well exposed type-section of
the Nago Limestone. Four distinct facies are identified and a detailed qualitative-quantitative investigation has been applied
to the coral-bearing facies in particular, in order to describe and quantify the distribution and palaeoecological zonation
of corals.
By a comparison of sedimentological and palaeoecological data, it is possible to reconstruct a depositional model of the Nago
Limestone at its type locality. In particular, the palaeoecological study clearly reveals that corals change with depth in
taxonomic composition, in percentage and proportion within the framework and in growth form, allowing the definition of a
relative depth coral zonation.
Three coral associations are recognized from the base to the top of the shallowing upward sequence. These differ from each
other in the relative abundance of main reefbuilders, in the growth form exhibited by corals in growth position and in the
density of the reef framework. These variations are interpreted as responses to major environmental controls which prevailed
during the deposition of the different facies (mainly light intensity and hydrodynamic energy).
The coral speciesActinacis rollei
Reuss is the most abundant and ubiquitous coral of the Nago Limestone. Its adaptation to low-light levels is described here for
the first time, confirming the high plasticity of this important Paleogene reef-builder.
The results of the present study are finally compared with data from other Middle-Late Eocene European reef sites and some
common features are inferred. |
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Keywords: | Scleractinian corals Facies Palaeoecology Reefs Nago limestone Lessini shelf Northern Italy Late eocene (Priabonian) |
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