RT Journal Article
T1 Fan-surface dynamics and biogenic calcrete development:Interactions during ultimate phases of fan evolution in thesemiarid SE Spain (Murcia)
A1 Alonso Zarza, Ana María
A1 Silva Barroso, Pablo Gabriel
A1 Goy Goy, José Luis
A1 Zazo Cardeña, Caridad
AB Pleistocene alluvial fan surfaces of the Campo de Cartagena–Mar Menor Basin, Murcia, SE Spain. are capped by thickmature calcretes. Calcrete profiles consist mainly of six different horizons: prismatic, chalky, nodular, massive, laminar andcoated-gravels. Petrographic study of the calcretes has shown the occurrence of features such as alveolar septal structures,calcified filaments, coated grains, spherulites, calcified root cells and calcispheres that indicate the biogenic origin of thecalcretes, mainly induced by plant root related microbial activity. The calcretes studied were formed initially in the soil andrepresented the K horizon. Development of the calcrete profiles took place in six main stages and was driven by multiplephases of soil formation, erosion and reworking. The relationships between these processes caused the formation of differentcalcrete profiles in proximal and distal fan areas. In the distal areas, which are controlled by limited distal fan aggradation,episodic sediment input, buried previously developed calcretes and generated new space for calcrete growth by plantsgrowing in the overlying unconsolidated materials. This allowed the renewal of calcrete formation and it led to thedevelopment of complex composite profiles which are thicker than in proximal areas, where surface stabilisation andrordissection enabled calcrete reworking and brecciation. These processes of erosion, sedimentation, reworking and renewedcalcrete formation initiated by vegetation were repeated through time. They explain the complex macro- and microstructuresof these calcretes and indicate that calcrete development, even reaching mature stages, can start before the fan surface iscompletely abandoned, but it requires episodic sedimentation. Eventually, distal fan aggradation and continuous calcretedevelopment throughout the entire fan surface, led to the ultimate fan surface induration, controlling subsequent landscapeevolution. So, fan surface calcretes cannot be envisaged as simple top-surface carbonate accumulations, but as complexfeedback systems in which pedogenic, biogenic and sedimentary processes interact in response to the evolving fan-surfacedynamics during the terminal phases of fan development in semiarid environments. q1998 Elsevier Science B.V. All rightsreserved.
PB Elsevier Science B.V., Amsterdam
SN 0169-555X
YR 1998
FD 1998
LK https://hdl.handle.net/20.500.14352/59019
UL https://hdl.handle.net/20.500.14352/59019
LA eng
DS Docta Complutense
RD 4 abr 2025