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Lithosphere Removal in the Sierra Nevada de Santa Marta, Colombia
  • David Ernesto Quiroga,
  • Claire A. Currie,
  • Jillian Pearse
David Ernesto Quiroga
University of Alberta

Corresponding Author:dquiroga@ualberta.ca

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Claire A. Currie
University of Alberta
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Jillian Pearse
Universidad de Los Andes
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The Sierra Nevada de Santa Marta (SNSM) in northwestern Colombia is one of the
world’s highest coastal mountains, with an elevation above 5.7 km. Gravity measurements
show that the SNSM has a high Bouguer anomaly (>+130 mGal), indicating that the
mountain lacks a crustal root. In this work, we test the hypothesis that these observa-
tions can be explained by gravitational removal of the dense lower lithosphere. We use
2D numerical models to examine the dynamics of lithosphere removal and its effect on
surface elevation, gravity and heat flow. The models consist of continental lithosphere
that includes a pre-thickened crustal region, representing the SNSM. In our preferred model,
the dense mantle lithosphere instability and crustal root are gravitationally unstable and
undergo removal as local drips within ∼10 Ma from the onset of foundering. This cre-
ates an area of thinned crust (∼38 km) underlain by a buoyant sublithospheric mantle
where melting and low seismic velocities are predicted. Subsequent non-isostatic forces
maintain a topography of 3.3 km with a Bouguer gravity anomaly of +103 mGal. Pa-
rameter tests show that a strong lower-crustal rheology provides greater support for the
high topography and that a weak mantle lithosphere rheology produces faster removal.
The models demonstrate that local lithosphere dynamics can explain the first-order ob-
servations in the SNSM. We propose that lithosphere removal could have occurred at 40-
50 Ma, possibly inducing anomalous short-lived Eocene magmatism, or more recently
(∼2 Ma), explaining the localized low seismic velocity zone below the SNSM.