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Quaternary laminar calcretes with bee nests: evidences of small-scale climatic fluctuations, Eastern Canary Islands, Spain

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Alonso-Zarza, Ana María and Silva Barroso, Pablo Gabriel (2002) Quaternary laminar calcretes with bee nests: evidences of small-scale climatic fluctuations, Eastern Canary Islands, Spain. Palaeogeography, palaeoclimatology, palaeoecology, 178 . pp. 119-135. ISSN 0031-0182

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Official URL: http://www.journals.elsevier.com/palaeogeography-palaeoclimatology-palaeoecology/



Abstract

Thick laminar calcrete profiles are common on the surface of the eastern Canary Islands of Lanzarote and
Fuerteventura. This paper reports the study of one profile from Lanzarote (Macher profile) and one from
Fuerteventura (Tef|¨a profile). These profiles are about 2 m thick. The Macher profile is developed on basaltic host rocks
and consists of two main horizons: a lower horizon in which white veins of laminated micrite penetrate cracks, and an
upper laminar horizon. The Tef|¨a profile is cumulative and consists, from base to top, of massive, laminar, and massive
and laminar-brecciated horizons. Highlighted in the study of these profiles are the presence of ooids, the complex
structure of the laminar horizons, and the occurrence of fossil bee nests (Celliforma). Ooids consist of a nucleus of clay,
micrite and etched grains coated with envelopes of micrite and clay (mainly palygorskite). Organic films favoured both
the precipitation of carbonate and the adhesion of clays when the ooids formed in the soil. The laminar horizons consist
of a centimetre-scale alternation of massive micrite with varied amounts of ooids and detrital grains with laminated
micrite. This alternation indicates the small-scale periods of sedimentation, erosion and soil formation in the upper part
of a relatively stable surface. These small-scale alternations may reflect climatic vegetation changes in which arid
periods are represented by micrite with ooids, while laminated micrite reflects a better-developed vegetation of the wet
periods. Celliforma occur as ovoid larval cells with more or less rounded bases and a flat top. The cells are about 3 cm
long and 1.5 cm in diameter. Their wall is about 5 mm thick, and is commonly laminated. Celliforma is interpreted as
fossil nests of solitary bees. Their presence in the laminar horizon is evidence for the existence of a vegetation cover
containing angiosperms.


Item Type:Article
Uncontrolled Keywords:Laminar calcretes; Trace fossils; Palaeoclimate fluctuations; Quaternary; Canary Islands; Celliforma
Subjects:Sciences > Geology > Petrology
ID Code:25272
Deposited On:06 May 2014 12:16
Last Modified:06 May 2014 13:07

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