World Congres on Geology & Earth Science

1. Acknowledgements
This work has been supported by the Ministry of Science and Innovation of Spain (project CGL2013-44076-P and CGL2016-78380-P). We also wish to acknowledge
the help and assistance to: Junta de Castilla y León, Sierra de Gredos Natural Park (JCYL) and Local Administration of Candelario Village. Valentí Turu acknowledges
grant ATC013 -and- 2015/2016 from the Government of Andorra.Location of field work carried out in the ND
Infill sequence
Surface geology
Fracture network
Chronology, stratigraphy and geometry of ND
INDIRECT GEOPHYSICAL METHODS
SR Seismic Refraction profiles (5)
MRS Magnetic Resonance Sounding (2)
VES Vertical Electrical Sounding (9)
ERT Electrical Resistence Tomography profiles (9)
DIRECT METHODS
DPSH Dynamic Probing Super Heavy (1)
S Handheld auger drilling (3)
AMS 14
C
m e t h o d o l o g y
S2
S1 PM
S0
Sampling in 2009 and Panoramic view of the Navamuño depression. S0, S1 and S2 correspond
to the situation of drillings. The white line represents the crest of the left lateral moraine (CML)
of the Cuerpo de Hombre paleoglacier
The Navamuño depression (ND), located
in the high sector of the Cuerpo de
Hombre valley (Sierra de Béjar), was partly
occupied by a glacier during the Late
Pleistocene. The basin is a ~ 14 Ha pseu-
doendorheic depression with water
ponds lying over a granite bedrock. This
wetland is included in the Natura 2000 Eu-
ropean protection network, located in the
Sierra de Béjar (Iberian Central System),
western Spain.
ND is limited by fault lineaments and the
left lateral moraine of the Cuerpo de
Hombre paleoglacier. The basin is an elon-
gated trapezoid and is associated with the
Puerto de Navamuño fault, a NNE-SSW
trending Variscan strike-slip fault. The
bottom of the depression is a seasonal
flood-plain with peatlanddevelopment,
currently dissected by fluvial channels.
I n t r o d u c t i o n
This poster presents the results obtained in these works:
* Turu et al., 2018: Late glacial and post-glacial deposits of the Navamuño peatbog (Iberian
Central System): Chronology and paleoenvironmental implications. Quaternaty Internatio-
nal, 470, 82-95.
* Carrasco et al., 2018: Near surface geophysical analysis of the Navamuño depression (Sierra
de Béjar, Iberian Central System): Geometry, sedimentary infill and genetic implications of
tectonic and glacial footprint. Geomorphology, 315,1-16.
*Carrasco et al., 2015: Caracterización de la geometría de la depresión de Navamuño (Siste-
ma Central Español) aplicando técnicas geofísicas. Geogaceta 57, 39-42
Geomorphological map and fracture network asso-
ciated with Navamuño depression
Location of the Navamuño Depression (ND) on the Iberian
Central System
A) Cuerpo de Hombre paleoglacier during the maximum ice extent and position of the available cosmogenic ages, arrows
showing the flow ice directions. B) Longitudinal profile across the Navamuño neighbouring Cuerpo de Hombre glaciated
valley (I-II, see Fig. A), showing the chronology and position of the different advance and recession phases from the
Cuerpo de Hombre paleoglacier. C) Former accumulation zone of Cuerpo de Hombre glacier. D) Panoramic view of
Cuerpo de Hombre valley showing basement scarp limiting sharply the glacier tongue extension in the Oldest Dryas.
The information obtained from geophysical, geological and geomorphological studies carried out in this research, enabled us to consider various
hypotheses as to the origin of this depression. According to these data, the Navamuño depression may be explained as the result of a transtensio-
nal process from the Puerto de Navamuño strike-slip fault during the reactivation of the Iberian Central System (Paleogene-Lower Miocene,
Alpine orogeny), and can be correlated with the pull-apart type basins described in these areas. The neotectonic activity of this fault and the
ice-dammed processes in these areas during the Last Glacial Cycle (MIS2) were the main causes of recent sedimentary infill in this depression.
The Cuerpo de Hombre paleoglacier had a marked influence on sedimentary evolution in the ND, as it was responsible for the shift from an exor-
heic hydrologic regime to a semi-endorheic regime with ponding. This process took place during the maximum glacial advance stage (25+1.3 ka
BP) and continued at least until silting-up occurred during the Holocene.
c o n c l u s i o n s
Sample CH-38
(22.61± 2.4 ka)
Multiple subsoil investigation procedures can provi-
de an integrated sedimentological, chronological
and environmental study of the Navamuño deposits.
The basin is filled with glaciolacustrine, glaciofluvial
and post-glacial deposits combining with local sha-
llow pond/peat bog sedimentation episodes.
The isopach map shows a de-
pocentre over 60 m deep in
the south and centre of the
basin with a longitudinal
NNE-SSW axis, parallel to the
fractures defining the wes-
tern edge of the basin. The
fracture families (PN and La
Jara faults) clear control the
ND basin at W and S borders.
The activity of these Cenozoic
fractures probably allow the
infill of the deepest (>35 m
depth) portion of this small
depression.
r e s u l t s
Three geolectrical layers have been detected in the ND, confirming and complemen-
ting previously obtained data. These layers are called G1, G2, and G3 from highest to
lowest. They can be grouped genetically into two sedimentary units: an ancient sedi-
mentary body (G3), of unkown age and type, beneath an Upper Pleistocene (G2) and
Holocene (G1) sedimentary infill.
The onlap contact shown in geolectrical layers G2 and G1 (ERT7), are indicators of
syntectonic sedimentation in ND. The same occurs with geolectrical layer G3 which is
limited by high dip faults (ETR2, ETR8). This rock threshold where the lateral moraine
of the Cuerpo de Hombre paleoglacies is found, corresponds to a raised block, and
would have acted as a limit to the path of the ice.
The main aquifer is found in
the first 35 m from the subsur-
face (G1 and G2).
In the deepest zone of the de-
pression differences in the re-
sistivity of unit G3 arise, asso-
ciated with a porous media.
Below 40 m depth water con-
tent diminishes and fall drama-
tically down to a depth of 80 m.
A) Laboratory AMS chronology and related sedimentation. B) Sedimentary
facies code. C) Texture. F) Alluvial facies association. H) DPSH. diagram
Magnetic Resonance Sounding inversion results.
A) Water content (%). B) Permeability (m/s)
ETR tomography (profiles 7 and 8) and geological interpretation including VES and MRS
The available radiocarbon dating provides an approxi-
mate age of 10 ka at depths of 5.65-5.70 m recording
the entire Holocene, while at 16 m depth a Late-gla-
cial age (≈16 ka) had been obtained. The bottom of
the glaciolacustrine deposits is located at ≈19 m
depth.
Glacial till (bottom of the glaciolacustrine sequence)
A B
Chronology, stratigraphy and geometry of an ice dammed paleolake depression in a complex tectonically context by using
direct and no-direct methods: A case-study of the Navamuño peatbog (Sierra de Béjar, Iberian Central System)
Valentí Turu [1]; Rosa M. Carrasco [2]; Javier Pedraza [3]; Alfonso Muñoz-Martin [4]; Xavier Ros [1]; Jesús Sánchez [2]; Blanca Ruiz-Zapata [5]; Antonio J. Olaiz [4]; Josep Soriano [6];
Albert Pélachs-Mañosa [6]; Elena Mur-Cacucho [6]; Anna Echeverria-Moreno [1]; Ramon Herrero-Simón [7]; David Dominguez-Villar [8]
[1] Marcel Chevalier Earth Science Foundation; [2] Dpt. of Geological and Mining Engineering, University of Castilla-La Mancha; [3] Dpt. of Geodynamic, Complutense University of Madrid; [4] Non Seismic Methods, REPSOL Explor.;
[5] Dpt. of Geology, University of Acalá; [6] Dpt. of Geography, Universitat Autònoma de Barcelona; [7] Dept. of Physocs and Nuclear Engineering, Polytechnic University of Catalonia