Coralline red algae are common in Oligocene and Miocene marine shallow-water carbonate and siliciclastic rocks and deep-water re-deposited sediments containing particles removed from the platforms. Corallines are mostly reported in reef-related carbonates but are also the main components in shallow-water heterozoan carbonates from temperate regions. The known distribution of Oligocene coralline assemblages does not suggest any palaeobiogeographical differentiation. In contrast, for the Miocene, the occurrence of taxa still living today with restricted geographic distribution supports an actualistic approach and the rough differentiation of palaeobiogeographic regions as follows: (a) a tropical region (characterised by thick Hydrolithon plants and Aethesolithon); (b) a subtropical Mediterranean (with common Spongites and Neogoniolithon species); and (c) a temperate region with shallow-water assemblages dominated by Lithophyllum. In a few examples from the northern margin of the western Tethys, the correlation of Oligocene carbonate-facies and algal assemblages indicates a dominance of Lithothamnion species in the shallower environments, while Mesophyllum is most abundant in deeper platform settings. The taxonomic composition of Miocene coralline assemblages and growth forms changed with depth, having patterns similar to those in the algal associations in present-day marine platforms. Mastophoroids and lithophylloids (Aethesolithon, Hydrolithon, Neogoniolithon, Spongites, and Lithophyllum species) characterise the shallower assemblages, whereas the melobesioids Lithothamnion and Mesophyllum and the sporolithacean Sporolithon are dominant in deeper-water settings. The common algal nodules (rhodoliths) comprised thick plants of few species in the shallowest palaeoenvironments, while in deeper platform areas they are composed of more diverse algal assemblages, with thin encrusting and protuberant-branching growth forms.
Palaeoenviromental significance of Oligocene-Miocene coralline red algae ‒ a review
BASSI, Davide;
2010
Abstract
Coralline red algae are common in Oligocene and Miocene marine shallow-water carbonate and siliciclastic rocks and deep-water re-deposited sediments containing particles removed from the platforms. Corallines are mostly reported in reef-related carbonates but are also the main components in shallow-water heterozoan carbonates from temperate regions. The known distribution of Oligocene coralline assemblages does not suggest any palaeobiogeographical differentiation. In contrast, for the Miocene, the occurrence of taxa still living today with restricted geographic distribution supports an actualistic approach and the rough differentiation of palaeobiogeographic regions as follows: (a) a tropical region (characterised by thick Hydrolithon plants and Aethesolithon); (b) a subtropical Mediterranean (with common Spongites and Neogoniolithon species); and (c) a temperate region with shallow-water assemblages dominated by Lithophyllum. In a few examples from the northern margin of the western Tethys, the correlation of Oligocene carbonate-facies and algal assemblages indicates a dominance of Lithothamnion species in the shallower environments, while Mesophyllum is most abundant in deeper platform settings. The taxonomic composition of Miocene coralline assemblages and growth forms changed with depth, having patterns similar to those in the algal associations in present-day marine platforms. Mastophoroids and lithophylloids (Aethesolithon, Hydrolithon, Neogoniolithon, Spongites, and Lithophyllum species) characterise the shallower assemblages, whereas the melobesioids Lithothamnion and Mesophyllum and the sporolithacean Sporolithon are dominant in deeper-water settings. The common algal nodules (rhodoliths) comprised thick plants of few species in the shallowest palaeoenvironments, while in deeper platform areas they are composed of more diverse algal assemblages, with thin encrusting and protuberant-branching growth forms.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
