RT Journal Article
T1 Megarhizoliths in Pleistocene aeolian deposits from Gran Canaria (Spain): Ichnological and palaeoenvironmental significance
A1 Alonso Zarza, Ana María
A1 Genise, J.F.
A1 Cabrera, M.C.
A1 Mangas, J.
A1 Martín Pérez, Andrea
A1 Valdeolmillos Rodríguez, Ana
A1 Dorado Valiño, M.
AB The Pleistocene dune field of Tufia, located on the east of Gran Canaria (Spain), contains differentstratigraphic levels of indurated pillar-like structures that are interpreted as megarhizoliths. Themegarhizoliths occur at the top of different aeolian sets and reach 31.5 cm in diameter and over 1 m inheight. These scattered, free-standing, vertical, cylindrical-to-slightly conical columns usually appear ashollow cylinders, displaying elliptical cross-sections aligned with the prevailing wind. On the leeward side ofsome specimens the external wall shows a tail of rock matrix resembling a sort of “wind shadow”. These tailsand other remains of the associated rock matrix show a texture composed of long, horizontal, parallelcylinders orientated with the wind.Internally the most complete structures show five concentrically arranged zones: Zone (a), is a central porecorresponding to the cavity originally occupied by the root; Zones (b) and (c), which include alveolar andlaminated carbonate textures indicating that carbonate precipitation was mostly induced by the roots andtheir associated microorganisms; and Zones (d) and (e), consisting mostly of aeolian sands. In (d) the sandgrains show thin micritic coatings whereas in (e) vadose aragonite cements can be seen on the grain surfacesuggesting a less biogenic influence in their formation. The degree of cementation and the time of theprecipitation of carbonate around the roots controlled the preservation of these zones. Thus, in some cases,Zones b, c and/or d are not preserved. Cylinders are up to 30× the diameter of the root that nucleated them.The presence of the megarhizoliths at the top of the aeolianite beds indicates that aeolian sedimentationhalted several times, allowing soil formation and plant colonisation during slightly more humid periods. Theoccurrence of megarhizoliths is further proof of the alternation of arid and slightly more humid climates inthe north Atlantic during the last glacial period. It is also noted that they may be misinterpreted as animaltrace fossils or tree trunk casts, resulting in incorrect ichnological or palaeoenvironmental interpretations.
PB Elsevier
SN 0031-0182
YR 2008
FD 2008-07-31
LK https://hdl.handle.net/20.500.14352/49301
UL https://hdl.handle.net/20.500.14352/49301
LA eng
DS Docta Complutense
RD 21 abr 2025