Aretz et al_2011.pdf - ORBi - Université de Liège

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Kölner Forum Geol. Paläont., 19 (2011)
M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.)
Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, Liège, August 19-29, 2011
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An exotic Late Albian coral fauna from the Prebetic Platform (Betic
External Zone, South Spain)
Hannes LÖSER 1 , José Manuel CASTRO 2 & Luis NIETO 2
1 Universidad Nacional Autónoma de México, Instituto de Geología, Estación Regional del Noroeste, Col.
Los Arcos, L.D.Colosio s/n, 83200 Hermosillo, Sonora, Mexico; loeser@paleotax.de
2 Departamento de Geología, Universidad de Jaén, Facultad de Ciencias Experimentales, Edificio B-3,
Campus de Las Lagunillas, 23071 Jaén, Spain
After the disappearance of the Late Triassic coral reefs, the development of extensive reefs started again
in the Middle Jurassic and lasted into the Latest Jurassic. Reef formation ceased with the beginning of the
Cretaceous, primarily caused by a falling sea level. Not only was reef formation inhibited, but coral
diversity was also affected by the sea level low-stand. Reef formation did not recover in the Cretaceous due
to a high Calcium/Magnesium proportion in the seawater, but diversity increased again with the
transgression of the Early Hauterivian and reached its highest value in the Early Aptian. The Oceanic
Anoxic Event 1a of the Early Aptian had an immediate effect on coral faunas. The number of faunas
decreased at the beginning of the Late Aptian and this decrease continued until the Late Albian. Whereas
Barremian to Early Aptian coral faunas are geographically widely distributed, those of the Late Aptian are
mainly restricted to the Iberian Peninsula, the Western Pacific and the Western Atlantic. Caused by OAE 1b
in the Early Albian, only a few faunas of shallow marine corals are known from the central Tethys
(northern Spain, southern France) during this time span. Early Albian faunas are known from North
America, which was less affected by anoxic events. In the Western Atlantic, coral faunas existed throughout
the Albian, but from the Middle Albian on, they were poor in species. In the Western Pacific, shallow
marine corals are not found at all from the Albian on because of the absence of carbonate sedimentation
probably caused by changes in ocean currents and temperature decreases. The diversity of coral faunas
recovered in the Early Cenomanian, being initially more common in Boreal regions than in the Tethys and
Western Atlantic.
A recently discovered Late Albian coral fauna in the Sierra de La Llorençá (Alicante, Spain), belonging
to the easternmost part of the Betic Cordillera, is therefore of important interest because it provides links
between the Early and Late Cretaceous corals. The La Llorençá fauna is the first central Tethys shallow
marine coral fauna of the Late Albian described in detail. It encompasses 35 species in 28 genera of the
suborders Amphiastraeina, Faviina, Fungiina, Heterocoeniina, Microsoleniina, Rhipidogyrina, and
Stylinina. The fauna counts with three new genera of the families Heterocoeniidae and Lasmogyridae, and
seven new species. The faunal composition shows both Early Cretaceous elements (Aulastraea,
Aulastraeopora, Complexastrea, Diplogyra, Metaulastrea, Tiarasmilia), as well as elements known only from the
Late Albian/Early Cenomanian of the Boreal and central Tethys (Confusaforma, Eocomoseris,
Parnassomeandra). The fauna contains the last known indication of the genera Aulastrea, Metaulastrea and
Mitrodendron whose last occurrence was previously known as being Aptian. This finding extends the
range of the Amphiastraeina suborder until the Late Albian. One new genus is known from the Aptian to
Albian worldwide, but the other two new genera are known only from the Aptian to Albian of the Iberian
Peninsula and Southern France. The Late Albian fauna is a true link between corals from the Early and Late
Cretaceous, and it comes with a high number of new and short-lived taxa. The outcrop area was probably
in an isolated geographic position less affected by OAE 1c, which allowed carbonate production and coral
growth.
Preliminary list of species: Acrosmilia fraterculus, Actinacis magna, Astraeofungia nagaoi, Astraeofungia sp.,
Aulastraea n. sp., Aulastraeopora harrisi, Brachyseris sp., "Columastrea" sp., Complexastrea dollfusi, Complexastrea
sp., Confusaforma n. sp., Cryptocoenia aguilerai, C. almerai, C. párvula, Dimorpharaea aff. williamsonensis,
Dimorphastrea hiraigaensis, D. regularis, Diplogyra sp., Diplogyra vivesi, Eocomoseris raueni, Eugyra affinis,
Heterocoenia sp., Metaulastrea n. sp., Microsolena haldonensis, Mitrodendron n. sp., Paraacanthogyra n. sp.,
Parnassomeandra sp. 1, Parnassomeandra sp. 2, "Pseudopistophyllum" quinqueseptatum, Polyphylloseris
polymorpha, Stelidioseris cf. hourcqi, Thecosmilia rutogensis, Tiarasmilia casteri, n. gen. n. sp. 1, n. gen. n. sp. 2
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