Rhodoliths, uniformitarianism, and Darwin: Pleistocene and Recent carbonate deposits in the Cape Verde and Canary archipelagos

Johnson, Markes E.; Baarli, B. Gudveig; Cachão, Mário; Silva, Carlos Marques da; Ledesma-Vázquez, Jorge; Mayoral, Eduardo; Ramalho, Ricardo S.; Santos, Ana

doi:10.1016/j.palaeo.2012.02.019

Cited by 41 publications

(21 citation statements)

References 30 publications

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“…Johnson et al . (2012) re-examined the limestone deposits and found that Darwin correctly interpreted the lower parts of the sequence as a former beach. Darwin (1844, p. 35) recorded: ‘I suppose the shells in the former beach are the same as now exists.’ A small coastal quarry is located on Pontas das Bicudas, south of Signal Post Hill.…”

Section: Introductionmentioning

confidence: 99%

What Darwin did not see: Pleistocene fossil assemblages on a high-energy coast at Ponta das Bicudas, Santiago, Cape Verde Islands

et al. 2012

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Two distinct Pleistocene assemblages from SE Santiago Island are comparable to modern analogues elsewhere in the Cape Verde Islands. A low-diversity Siderastrea radians assemblage lived atop basalt knobs surrounded by sand on a slope below a cliff. A Millepora alcicornis-Megabalanus azoricus assemblage occupied the cliff. The latter was a typical rocky-shore assemblage from a high-energy setting below the tidal zone. Bioerosion structures in basalt produced by Circolites kotoncensis and Gastrochaenolites isp. also occur there. Despite extensive studies on local limestone deposits in 1832 and 1836, lack of exposure prevented Darwin from seeing these fossils.

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Section: Introductionmentioning

confidence: 99%

What Darwin did not see: Pleistocene fossil assemblages on a high-energy coast at Ponta das Bicudas, Santiago, Cape Verde Islands

et al. 2012

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“…A few, such as Spongites fruticulosus and Phymatolithon calcareum, have been living in the Mediterranean region for more than 25 Ma. Similar assemblages are present in Macaronesia, in the Miocene (Johnson et al 2012), and younger limestone deposits enriched by rhodoliths and rhodolith-derived sediments are also known from the late Pleistocene (Amen et al 2005). However their taxonomy in some areas are limited and need evaluation of species and genera present in the area.…”

Section: Introductionmentioning

confidence: 75%

Rhodolith forming coralline algae in the Upper Miocene of Santa Maria Island (Azores, NE Atlantic): a critical evaluation

et al. 2014

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The Late Miocene Malbusca outcrop is located in the southeastern coast of Santa Maria Island (Azores, NE Atlantic), interspersed in volcanic formations. At ~20 meters above present sea level, a prominent discontinuous layer of rhodoliths seizes with an extension of ~250 meters. This paper presents the first taxonomic record of fossil rhodolith forming coralline algae for the Miocene of the Azores. The preserved taxonomic features used were the following: (1) arrangement of basal filaments, (2) epithallial cells (when observable), (3) presence of cell fusions, (4) conceptacle type, (5) number of cells layers which conceptacle chamber floors are situated below the surrounding thallus surface and (6) for the sporangial pores, the orientation of the filaments around the conceptacle pores. Based on these characters, six taxa were identified encompassing three Corallinaceae (Lithophyllum prototypum, Lithophyllum sp., Spongites sp. and Hydrolithon sp.) and one Hapalidaceae (Phymatolithon calcareum and cf. Phymatolithon sp.). An unidentified coaxial thallus was also present, the coaxial construction ascribing the specimens to the genus Mesophyllum or Neogoniolithon. Taxonomic accounts for the identified taxa are described, illustrated and an identification key is provided. The report of L. prototypum represents the first Miocene record and the preservation of the specimens is very good. Miocene coralline algae seem very consistent among deposits but some species are relevant for particular areas, like in the Azores.

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“…However, specimens belong to placolith robust taxa with scarce presence of typical deep ocean genera such as the Sphenolithus and Discoaster , perhaps a reflection of deposition in a shelf environment. The associations found across the entire sedimentary sequence at Corgo do Barrinho are compatible with those found in similar Miocene to Pliocene coastal transitions from submarine to subaerial volcanic sequences on other volcanic islands such as Porto Santo (Madeira Archipelago) [ Cachão et al ., ], Santiago and São Nicolau from Cape Verde Archipelago [ Johnson et al ., ].…”

Section: Resultsmentioning

confidence: 99%

The emergence of volcanic oceanic islands on a slow‐moving plate: The example of Madeira Island, NE Atlantic

Ramalho

Silveira

Fonseca

et al. 2015

Geochem Geophys Geosyst

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The transition from seamount to oceanic island typically involves surtseyan volcanism. However, the geological record at many islands in the NE Atlantic-all located within the slow-moving Nubian plate-does not exhibit evidence for an emergent surtseyan phase but rather an erosive unconformity between the submarine basement and the overlying subaerial shield sequences. This suggests that the transition between seamount and island may frequently occur by a relative fall of sea level through uplift, eustatic changes, or a combination of both, and may not involve summit volcanism. In this study, we explore the consequences for island evolutionary models using Madeira Island (Portugal) as a case study. We have examined the geologic record at Madeira using a combination of detailed fieldwork, biostratigraphy, and 40 Ar= 39 Ar geochronology in order to document the mode, timing, and duration of edifice emergence above sea level. Our study confirms that Madeira's subaerial shield volcano was built upon the eroded remains of an uplifted seamount, with shallow marine sediments found between the two eruptive sequences and presently located at 320-430 m above sea level. This study reveals that Madeira emerged around 7.0-5.6 Ma essentially through an uplift process and before volcanic activity resumed to form the subaerial shield volcano. Basal intrusions are a likely uplift mechanism, and their emplacement is possibly enhanced by the slow motion of the Nubian plate relative to the source of partial melting. Alternating uplift and subsidence episodes suggest that island edifice growth may be governed by competing dominantly volcanic and dominantly intrusive processes.

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Rhodoliths, uniformitarianism, and Darwin: Pleistocene and Recent carbonate deposits in the Cape Verde and Canary archipelagos

Cited by 41 publications

References 30 publications

What Darwin did not see: Pleistocene fossil assemblages on a high-energy coast at Ponta das Bicudas, Santiago, Cape Verde Islands

What Darwin did not see: Pleistocene fossil assemblages on a high-energy coast at Ponta das Bicudas, Santiago, Cape Verde Islands

Rhodolith forming coralline algae in the Upper Miocene of Santa Maria Island (Azores, NE Atlantic): a critical evaluation

The emergence of volcanic oceanic islands on a slow‐moving plate: The example of Madeira Island, NE Atlantic

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