RT Journal Article
T1 Quaternary laminar calcretes with bee nests: evidences ofsmall-scale climatic fluctuations, Eastern Canary Islands,Spain
A1 Alonso Zarza, Ana María
A1 Silva Barroso, Pablo Gabriel
AB Thick laminar calcrete profiles are common on the surface of the eastern Canary Islands of Lanzarote andFuerteventura. This paper reports the study of one profile from Lanzarote (Macher profile) and one fromFuerteventura (Tef|¨a profile). These profiles are about 2 m thick. The Macher profile is developed on basaltic host rocksand consists of two main horizons: a lower horizon in which white veins of laminated micrite penetrate cracks, and anupper laminar horizon. The Tef|¨a profile is cumulative and consists, from base to top, of massive, laminar, and massiveand laminar-brecciated horizons. Highlighted in the study of these profiles are the presence of ooids, the complexstructure 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 boththe precipitation of carbonate and the adhesion of clays when the ooids formed in the soil. The laminar horizons consistof a centimetre-scale alternation of massive micrite with varied amounts of ooids and detrital grains with laminatedmicrite. This alternation indicates the small-scale periods of sedimentation, erosion and soil formation in the upper partof a relatively stable surface. These small-scale alternations may reflect climatic vegetation changes in which aridperiods are represented by micrite with ooids, while laminated micrite reflects a better-developed vegetation of the wetperiods. Celliforma occur as ovoid larval cells with more or less rounded bases and a flat top. The cells are about 3 cmlong and 1.5 cm in diameter. Their wall is about 5 mm thick, and is commonly laminated. Celliforma is interpreted asfossil nests of solitary bees. Their presence in the laminar horizon is evidence for the existence of a vegetation covercontaining angiosperms.
PB Elsevier
SN 0031-0182
YR 2002
FD 2002
LK https://hdl.handle.net/20.500.14352/59026
UL https://hdl.handle.net/20.500.14352/59026
LA eng
DS Docta Complutense
RD 21 abr 2025