GEOLOGICAL SITES IN SIERRA ESPUÑA-MULA DEPRESSION AREA (MURCIA PROVINCE, SE SPAIN)
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43
Revista de la Sociedad Geológica de España 34 (1)
ISSN (versión impresa): 0214-2708
ISSN (Internet): 2255-1379
GEOLOGICAL SITES IN SIERRA ESPUÑA-MULA
DEPRESSION AREA (MURCIA PROVINCE, SE SPAIN)
Sitos geológicos en el área de Sierra Espuña-Depresión de Mula (provincia de Murcia, SE España)
Santiago Moliner-Aznar1, Manuel Martín-Martín1, Tomás Rodríguez-Estrella2, Gregorio Romero-Sánchez3 and Andrés
García-Lara4
1
Department of Earth and Environmental Sciences, University of Alicante, 03080 Alicante, Spain. samoaz01@gmail.
com, manuel.martin.m3@gmail.com
2
Departamento de Ingeniería Minera, Geológica y Cartográfica, Universidad Politécnica de Cartagena, 30202
Murcia, Spain. tomasrestrella@hotmail.com
3
Servicio de Patrimonio Histórico, Consejería de Educación y Cultura de la Región de Murcia, 30005 Murcia, Spain.
gromero@um.es
4
Hospedería Bajoelcejo, 30848 Murcia, Spain. info@bajoelcejo.com
Abstract: 55 geological sites have been selected in Sierra Espuña-Mula Depression area
(Murcia province, SE Spain). These sites have been grouped into 8 geotrails of which 5 in
Sierra Espuña and 3 in the Mula Depression. The selected sites display a great variety of
relevant geological features regarding diverse geoscience disciplines, such as structural
geology, stratigraphy, sedimentology, paleontology, petrology, mineralogy, geomorphology
and hydrogeology. The sites and geotrails have been evaluated and ranked with a numerical
methodology based on recent pertinent literature that tends to decrease the subjectivity
related with any assessment process. The assessment includes Scientific Value (SV),
Potential Educational Use (PEU), Potential Touristic Use (PTU) and Degradation Risk
(DR), which have been quantified by using several criteria. This allows visitors to select the
most suitable route according to their goals. The publication of these geological sites and
geotrails could be used for scientific and educational purposes (within the Earth Sciences),
and also to promote nature tourism. This could increase economic activity and sustainable
development in the area by attracting more visitors to the region.
Keywords: Murcia geological heritage, geological sites, geotrails, assessment criteria.
Resumen: Se han seleccionado 55 sitos geológicos en la zona de Sierra Espuña-Depresión
de Mula (provincia de Murcia, SE España). Estos sitos han sido agrupados en 8 geo-rutas: 5
en la Sierra Espuña y 3 en la Depresión de Mula. Los sitos seleccionados presentan una gran
variedad de rasgos geológicos relevantes para diversas disciplinas de las geosciencias como
geología estructural, estratigrafía, sedimentología, paleontología, petrología, mineralogía,
geomorfología e hidrogeología. Los sitos y geo-rutas han sido evaluados y clasificados
con una metodología numérica basada en la literatura reciente que tiende a disminuir la
subjetividad relacionada con cualquier proceso de valorización. La valorización incluye el
Valor Científico (SV), el Uso Educativo Potencial (PEU), el Uso Turístico Potencial (PTU) y
el Riesgo de Degradación (DR), los cuales han sido cuantificados mediante varios criterios.
Esto permitirá a los visitantes seleccionar la ruta más adecuada según sus objetivos. La
publicación de estos sitos y geo-rutas podría utilizarse con fines científicos y educativos
(dentro de las Ciencias de la Tierra), y también promover el turismo de la naturaleza en
favor de la actividad económica y el desarrollo sostenible en el área al atraer más visitantes
a la región.
Revista de la Sociedad Geológica de España, 34 (1), 2021
44 GEOLOGICAL SITES IN SIERRA ESPUÑA-MULA DEPRESSION AREA
Palabras clave: Patrimonio geológico de Murcia, sitos geológicos, geo-rutas, criterios de
valorización.
Moliner-Aznar, F., Martín-Martín, M., Rodríguez-Estrella, T., Romero-Sánchez, G., García-
Lara, A., 2021. Geological sites in Sierra Espuña-Mula Depression area (Murcia province,
SE Spain). Revista de la Sociedad Geológica de España, 34 (1): 43-56.
Introduction pe (Brilha, 2016; Aoulad-Sidi-Mend et al., 2019). In recent
years the geoheritage is reaching more interest, but politi-
The heritage of a region is made of several elements of cians and managers of the local and regional administrations
which the most commons are the cultural and natural featu- are not interested in its promotion. The geological heritage
res. The geological heritage although being a part of natural can be an economical input in a region due to the visits of
heritage is much less known than flora, fauna and landsca- tourist, student and scientific researchers loving the geology.
Fig. 1.- Geological map of the Sierra Espuña-Mula area (modified from Martín-Martín et al., 2006a): A) geographical sketch of the
Murcia province with the location of the study area; B) geological map with location of geotrails and sites (numbers inside the circles
refer to places detailed in Table 2); C) geological cross section located in Fig. 2B (doted blue line).
Revista de la Sociedad Geológica de España, 34 (1), 2021
S. Moliner-Aznar, M. Martín-Martín, T. Rodríguez-Estrella, G. Romero-Sánchez and A. García-Lara 45
Nevertheless, for the moment, there is much more interest Geological framework
in vacation or cultural tourism than in geoheritage. In order
to enhance the geological heritage of a region the first step The Sierra Espuña-Mula Depression area is in the Mur-
should concern an inventory of geological sites. The second cia province in SE Spain (Fig. 1A). The following main
step should be the assessment in order to know what could towns can be found in this area: Alhama de Murcia, Bullas,
be interesting for the people, and mainly to know the conser- Librilla, Mula and Pliego (Fig 1B). The outcrops of this
vation measures that should be introduced. The aim of every area are of high quality and with a quite continuous sedi-
study in geological heritage is the conservation and manage- mentary record from the Mesozoic-Cenozoic succession so
ment of the sites of geological interest and then to announce that many papers have been published in the last three de-
and publicize them to the public. The conservation of the cades (Moliner-Aznar et al., 2021, and references therein).
geological heritage of a region implies the introduction of The area for which a promotion of the cultural asset is
protection measures, which require a previous and accurate suggested belongs to the Malaguide Complex (the upper
geological study of the region focused in geoheritage. and mainly not affected by metamorphism) from the Inter-
In Spain the development of characterizing the geolo- nal Betic Zone (Martín-Martín et al., 2001, 2006a, b; Perri
gical heritage took place over the XX century. From 70`s et al., 2017; Jabaloy-Sánchez et al., 2019; Martín-Martín
on, a national inventory of geological sites has been perfor- and Robles-Marín, 2020). The Betic Cordillera belongs to
med and enriched over the years by the Instituto Geológico the western Mediterranean Alpine belts (Martín-Martín et
y Minero de España (IGME) (Díaz-Martínez et al., 2014). al., 2001; Martín-Martín et al., 2020a, b; Guerrera et al.,
Furthermore, there is a national legislation in charge of pro- 2021). In this area, there is a Mesozoic-Cenozoic cover
tecting the geological heritage enacted in 2007. The study of over a few meters thick Paleozoic succession. The struc-
Carcavilla et al. (2007) can be proposed as a good synthesis ture of this area (Martín-Martín and Martín-Algarra, 2002;
of the situation of the Spanish geological heritage. Martín-Martín et al., 1997a, 2006a; Martín-Rojas et al.,
With this perspective, the goal of this work is to show the 2007) consist of an antiformal stack in the Sierra Espuña
geology of the Sierra Espuña-Mula Depression (Murcia pro- (Fig. 1B, C). This structure is followed northward by a sy-
vince, SE Spain) as a key area of conservation due to its geo- nclinorium in the Mula Depression, with minor structural
logical heritage. To achieve this goal, 55 sites of geological highs related to fold-thrust (Fig. 1B, C).
interest organized into 8 geotrails have been selected. These The stratigraphic succession (Fig. 2), from bottom to
have been characterized and evaluated in order to establish the top, consists of Paleozoic slates and greywackes, Triassic
bases for protection measures, but also for scientific research, continental red beds (conglomerates, sandstones, clays
education, and geotourism in a sustainable framework. and gypsums) and shallow marine dolostones and limes-
Fig. 2.- Stratigraphic columns of the Mesozoic-Cenozoic succession of the Sierra Espuña-Mula Depression area (modified from
Martín-Martín et al., 2006a).
Revista de la Sociedad Geológica de España, 34 (1), 2021
46 GEOLOGICAL SITES IN SIERRA ESPUÑA-MULA DEPRESSION AREA
tones (Martín-Martín et al., 2006a). Parts Criteria score Weighting (%)
This is followed by Jurassic dolos- Representativeness (R) 30
tones and several types of marine Key locality (Kl) 20
limestones (Martín-Martín et al., Scientific value
Scientific knowledge (Sn) 5
2006b) and the Cretaceous massi- Integrity (I) 15
(SV)
ve marine limestones and phospha- Geological diversity (Gd) 5
Rarity (R) 15
te-glauconitic sandstones (Perri et
Use limitations (Ul) 10
al., 2017). The Cenozoic succes- Vulnerability (V) 10
sion (Perri et al., 2017) consists of Accessibility (A) 10
three cycles: preorogenic (Paleoce- Use limitations (Ul) 5
ne-Lowermost Oligocene), syno- Safety (S) 10
rogenic (Lower Oligocene-middle Potential
Logistics (L) 5
Burdigalian), postorogenic (upper Density of population (Dp) 5
Educational Use
Burdigalian-Messinian). The preo- Associations with other values (Av) 5
(PEU)
Scenery (Sc) 5
rogenic is made of several shallow
Uniqueness (U) 5
marine (beach conglomerates and Observation conditions (Oc) 10
limestones) or transitional (marshy Didactic potential (Dp) 20
marls) stratigraphic formations rich Geological diversity (Gd) 10
in larger foraminifera (Martín-Mar- Vulnerability (V) 10
tín et al., 1997b; Martín-Martín Accessibility (A) 10
et al., 1998; Martín-Martín et al., Use limitations (Ul) 5
2020c; Martín et al., 2021). The sy- Safety (S) 10
Logistics (L) 5
norogenic cycle is made up of three
Potential Density of population (Dp) 5
stratigraphic formations consisting Touristic Use Associations with other values (Av) 5
in a transgressive succession from (PTU) Scenery (Sc) 15
shallow marine (deltaic conglome- Uniqueness (U) 10
rates and limestone platform) to Observation conditions (Oc) 5
deep turbiditic (sandstones, conglo- Interpretative potential (Ip) 10
merates and silexites) deposits. The Economic level (El) 5
postorogenic cycle is made of seve- Proximity recreational areas (Pr) 5
Deterioration geological elements (Dg) 35
ral shallow marine (deltaic conglo-
Degradation Proximity activities cause of degradation (Pa) 20
merates, platform limestones and Risk Legal protection (Lp) 20
marls with gypsums) to continental (DR) Accessibility (Ac) 15
(lacustrine limestones and redbeds) Density of population (Dpp) 10
stratigraphic formations.
Due to the high quality in out- Table 1.- Criteria scores (from 1 to 4, except for SV where score 3 is not used) and weight-
crops and the complete sedimen- ing (%) for the SV, PEU, PTU and DR assessment.
tary succession, some works have
also been published highlighting the geological heritage to 4 (in the case of SV score 3 is not used). These scores
of the area (Martín-Martín et al., 2006c, 2010; Mancheño were also weighted according to a percentage (Table 1).
et al., 2010; Moliner-Aznar et al., 2021; and references For example, the first criterion from the SV is the Repre-
therein). sentativeness (R) with a weight of 30 (Table 1). So, if
this criterion is scored 4 (score 3 is not used in SV) the
Methods weighted value will be 30; if it is scored 1, the weighted
value will be 7.5; and if it is scored 2, the weighted value
The methodology follows a classical procedure based will be 15. For more details, see Brilha (2016).
on the study of previous literature, fieldworks and cabinet In Table 1 there is a summary of the criteria considered
works. In a first phase, the sites mentioned in the geolo- for each one of the assessment cases. Thus SV is based on
gical heritage literature of the area were visited together seven criteria, PEU on twelve, PTU on thirteen (coinciding
with a field survey of the entire area, which allows the in part with the criteria used for PEU but with three new
selection of 55 geological sites. This selection was not specific criteria) and DR on five criteria. Four thresholds
based in any value of assessment but in shocking geolo- were used for the final values of each group of criteria (SV,
gical features from diverse geoscience disciplines. In a PEU, PTU and DR): 0-25 low, 26-50 moderate, 51-75 high,
second phase, an assessment of these sites was performed 76-100 very high. The mentioned sites were grouped into
following the procedures of Brilha (2016), Aoulad-Si- 8 geotrails (5 in Sierra Espuña and 3 in the Mula Depres-
di-Mend et al. (2019) and Moliner-Aznar et al. (2021). sion) taking into account the access and proximity (Fig.
Scientific Value (SV), Potential Educational Use (PEU), 1B). These geotrails have also been quantified by a mean
Potential Touristic Use (PTU) and Degradation Risk value of the different group of criteria (SV, PEU, PTU and
(DR) were evaluated (Brilha, 2016) and scored from 1 DR) according to Bollati et al. (2017).
Revista de la Sociedad Geológica de España, 34 (1), 2021
S. Moliner-Aznar, M. Martín-Martín, T. Rodríguez-Estrella, G. Romero-Sánchez and A. García-Lara 47
N° Name (coordinates of the central point) F SV PEU PTU DR
Geotrail 1. El Berro
Barranco de las Brujas High High High Low
1.1 G
(632812/4192837) (55) (63.75) (58.75) (25)
Leyva Walls High High High Low
1.2 G
(625110/4193948) (75) (66.25) (56.25) (25)
Collado Blanco High High High Low
1.3 S
(626575/4194125) (68.75) (68.75) (56.25) (25)
Neptunian Dykes del Bco. de la Hoz High High High Low
1.4 SD
(628336/4196389) (70) (60) (56.25) (25)
As Mines Moderate High High Moderate
1.5 P
(627433/4196580) (40) (52.50) (51.25) (33.75)
Barranco de la Hoz High High High Low
1.6 S
(628966/4197168) (55) (68.75) (58.75) (25)
Prado Chico Spring High High High Low
1.7 H
(629610/4197086) (70) (56.25) (56.25) (25)
Valdelaparra thrust High High High Low
1.8 S
(630267/4196889) (57.50) (63.75) (56.25) (25)
Geotrail 2. Las Alquerías
Paleozoic from Campix High High High Low
2.1 P
(629140/4188775) (75) (61.25) (57.50) (25)
Lower Triassic Serie High High High Low
2.2 E
(630596/4188763) (75) (68.75) (60) (25)
Ricardo Codorníu Center Very high Very high Very high High
2.3 N
(630925/4191003) (76.25) (90) (76.25) (51.25)
Hilo Srping Moderate Very high Very high High
2.4 H
(630189/4191207) (41.25) (78.75) (77.50) (51.25)
Morrón de Alhama structure Very high High High Low
2.5 S
(629296/4191906) (77.50) (66.25) (60) (25)
Upper Triassic Serie High High High Low
2.6 E
(627184/4191793) (67.50) (66.25) (60) (25)
El Purgatorio gupsum quarries High High High Low
2.7 G/M
(624655/4198826) (62.50) (58.75) (60) (25)
Geotrail 3. Espuña Peaks
Morra De las Moscas Lapiaz High High High Low
3.1 G/E
(626635/4192788) (75) (61.25) (57.50) (25)
Tres Carrascas Sinkhole High High High Low
3.2 G
(627903/4192979) (75) (68.75) (60) (25)
Fuenteblanca Very high Very high Very high High
3.3 H
(626408/4194335) (76.25) (90) (76.25) (51.25)
Prado Mayor Fossils High Very high Very high High
3.4 PA
(626070/4194616) (70) (78.75) (77.50) (51.25)
Phosfate Mines Very high High High Low
3.5 P
(625921/4194008) (77.5) (66.25) (60) (25)
Revista de la Sociedad Geológica de España, 34 (1), 2021
48 GEOLOGICAL SITES IN SIERRA ESPUÑA-MULA DEPRESSION AREA
Los Carrascales Jurassic High High High Low
3.6 E
(626722/4193322) (67.50) (66.25) (60) (25)
Pozos de Murcia High High High Low
3.7 P
(626477/4192989) (62.50) (58.75) (60) (25)
Geotrail 4. Malvariche Valley
Pinnacle of Morrón de Totana High High High Low
4.1 S/G
(624770/4191620) (75) (61.25) (62.50) (25)
Cuevas de La Plata High High High Low
4.2 G
(622665/4190886) (66.25) (58.75) (55) (33.75)
Malvariche Valley Jurassic High High High Low
4.3 E
(623198/4192995) (53.75) (67.5) (58.75) (25)
Malvariche Valley K-T High High High Low
4.4 E
(623188/4193205) (67.5) (70) (63.75) (25)
Lower Eocene Fossils Malvariche High High High Low
4.5 PA
(623048/4193625) (75) (70) (62.5) (25)
Middle Eocene Fossils Malvariche High High High Low
4.6 PA
(623075/4194580) (75) (70) (62.5) (25)
Conglomerates with pebbles of quartzites High High High Low
4.7 E
(621507/4193486) (76.25) (63.75) (57.5) (25)
La Rotura Fold High High High Low
4.8 S
(620826/4192476) (77.5) (70) (62.5) (25)
Middle Eocene Fossils Loma de Cánovas High High High Low
4.9 PA
(623125/4192877) (73.75) (70) (62.5) (25)
Geotrail 5. Aledo-La Santa
El Ángel panoramic view High Very high Very high High
5.1 E/G
(626305/4185005) (58.75) (77.50) (76.25) (58.75)
Vía Crucis panoramic view High High High High
5.2 G
(627220/4184775) (56.25) (70) (68.75) (58.75)
Corazón de Jesús panoramic view High High High High
5.3 E
(627195/4184696) (56.25) (68.75) (66.25) (58.75)
Virgen Blanca panoramic view High High High High
5.4 E
(627189/4185280) (56.25) (71.25) (68.75) (58.75)
Virgen Blanca landslide Very high High High Very high
5.5 G
(626905/4185545) (77.5) (63.75) (62.50) (76.25)
Geotrail 6. Pliego-Casas Nuevas depression
Pliego Mesa High Very high High Moderate
6.1 E/G
(631945/4206118) (63.75) (77.50) (73.75) (47.50)
Cejo de Las Palomas Anticline High High High Moderate
6.2 S
(625606/4198317) (75) (67.5) (65) (32.50)
La Sabina Syncline High High High Moderate
6.3 S
(626383/4198087) (73.75) (72.50) (67.50) (32.50)
Loma de Miñano Fossils Very high High High Moderate
6.4 PA
(622388/4197463) (78.75) (68.75) (67.50) (47.50)
Palomeque Sheets Very high High High Moderate
6.5 S
(618918/4196228) (82.50) (60) (60) (47.50)
Revista de la Sociedad Geológica de España, 34 (1), 2021
S. Moliner-Aznar, M. Martín-Martín, T. Rodríguez-Estrella, G. Romero-Sánchez and A. García-Lara 49
La Almoloya Butte and Glacis High High High Moderate
6.6 G
(617704/4192988) (66.25) (63.75) (60) (47.50)
Geotrail 7. Gebas Place
Sierra de la Muela travertines Moderate High High Very high
7.1 G
(641606/4194103) (47.5) (63.25) (58.75) (76.25)
Rambla de Algeciras High High Very high Moderate
7.2 H
(641108/4194229) (73.75) (73.75) (76.25) (43.75)
Sierra de la Muela Panoramic View High Very high High High
7.3 G
(636773/4193468) (63.75) (80) (73.75) (58.75)
Badlands from Gebas Very high High High High
7.4 G
(637102/4195916) (77.50) (72.50) (71.25) (58.75)
Barqueros Vulcanites Very high High High High
7.5 P
(643978/4204392) (87.50) (67.50) (71.25) (67.50)
Barqueros Diatomites Moderate High High High
7.6 P
(643029/4200789) (50) (65) (60) (72.50)
Barranco del Infierno Gypsums High High High Low
7.7 P
(642917/44200103) (55) (68.75) (63.75) (55)
Geotrail 8. Mula
Mula Baths High High High Very high
8.1 H
(638305/4211422) (56.25) (63.75) (65) (85)
Castillo de Puebla de Mula Hill Very high Very high Very high Very high
8.2 G
(637436/4210423) (78.75) (77.50) (80) (76.25)
Río Pliego Turbidites High High High Very high
8.3 SD
(635138/4210715) (73.75) (63.75) (62.50) (76.25)
Castillo de Mula High Serie and Fossils Very high Very high High High
8.4 E/PA
(632967/4212165) (82.5) (76.25) (75) (58.75)
Castillo de Mula High Structures Very high High High High
8.5 S
(632345/4212223) (82.50) (75) (72.50) (58.75)
Lomo del Herrero Quarries High High High Very high
8.6 P
(627988/4214036) (55) (62.50) (58.75) (85)
Table 2.- Table with the Scientific Value (SV), Potential Educational Use (PEU), Potential Touristic Use (PTU) and
Degradation Risk (DR) values for the 55 geological sites grouped in the respective geotrails. Features (F) evaluated:
H: Hydrogeology; G: Geomorfology S: Structural geology; E: Stratigraphy; P: Petrography; SD: Sedimentology; M:
Mineralogy; A: Didactic Calssroom; PA: Paleontolology.
Results features with relevance to diverse geoscience disciplines, such
as structural geology, stratigraphy, sedimentology, paleontolo-
The 55 selected sites are grouped into 8 geotrails (Table gy, geomorphology, hydrogeology, petrology and mineralogy.
2, Fig. 1B). In the Sierra Espuña area there are five of these We have selected in the following lines a few exam-
geotrails named geotrail 1 (El Berro) with 8 sites, geotrail 2 ples covering different geological key features to show the
(Las Alquerías) that shows 7 sites, geotrail 3 (Espuña Peaks) important variety of the geological heritage of the area.
with 7 sites, geotrail 4 (Malvariche Valley) including 9 sites, A good example of rock deformation can be seen at the
and geotrail 5 (Aledo-La Santa) located out of the protected site 1.6 (Barranco de la Hoz structures, Fig. 3) where the
area of the natural park Sierra Espuña with 5 sites. The other Morrón de Totana Unit is thrusted by the Perona Unit and
three geotrails are in the Mula Depression and are named geo- both are faulted (Martín-Martín et al., 2006a). In this site,
trail 6 (Pliego-Casas Nuevas depression) with 6 sites, geotrail the Morrón de Totana is made of Jurassic dolostones and
7 (Gebas Place) that shows 7 sites, and geotrail 8 (Mula) that white limestones and a thin Cenozoic succession of Eoce-
displays 6 sites. These sites show a great variety of geological ne-lower Oligocene in age (Valdelaparra and As fms, Fig.
Revista de la Sociedad Geológica de España, 34 (1), 2021
50 GEOLOGICAL SITES IN SIERRA ESPUÑA-MULA DEPRESSION AREA
1B, 2). This tectonic unit is thrusted by the Perona Unit. A
normal fault affects the tectonic superposition, and the en-
tire pile nappe is sealed by an upper Oligocene-Aquitanian
succession (El Bosque Fm, Fig. 1B, 2). Other sites with
significant structural geology features are: Collado Blan-
co (site 1.3), Valdelaparra Overthrust (site 1.8), Morrón
de Alhama structure (site 2.5), La Rotura fold (site 4.8),
Cejo de las Palomas anticline (site 6.2), La Sabina syncline
(site 6.3), Palomeque thrust sheets (site 6.5) and Castillo de
Mula structures (site 8.5).
To show places of important stratigraphic features the
site 4.3 (Malvariche Jurassic Succession, Fig. 4) has been
selected where a folded Jurassic succession crops out (Mar-
tín-Martín et al., 2006b). The site shows NE-SE minor folds
with a north dipping (sometimes reversal). In this section the
entire Jurassic succession (dolostones and massive limesto- Fig. 3.- Barranco de la Hoz structures (site 1.6). In the lower
nes from the Liassic, stratified limestones with chert ribbons part, the Morrón de Totana Unit comprising Liassic limestones
and nodules from the Dogger and brecciated and nodular and clays, and Eocene deposits of the Valdelaparra Fm. In the
limestones from the Malm) is visible even with fossiliferous upper part, the Perona Unit comprising Liassic dolostones and
levels such as Liassic lithiotis, crinoids, ammonites and be- limestones.
lemnites, and also Malm ammonites. Other sites with signi-
ficant stratigraphic features are the lower and upper Triassic
successions from the Morrón de Totana Tectonic Unit (sites
2.2 and 2.6), Jurassic succession from Los Carrascales (site
3.6), K/T contact from Malvariche (site 4.4) and Castillo de
Mula Cenozoic succession (site 8.4).
One of the most spectacular sedimentological features
can be observed in the site 8.3 (Río Pliego turbidites, Fig.
5) where an Upper Oligocene turbidite succession from
the Río Pliego Fm crops out (Martín-Rojas et al., 2007).
It consists of reddish pelites interbedded with turbiditic
sandstone in a rhythmic succession. Other sites with rele-
vant sedimentological features are: Neptunian dykes (site
Fig. 4.- Malvariche Jurassic Succession showing the minor folds
1.4) and Sierra de la Mule travertines (site 7.1).
in the Dogger-Malm part (site 4.3).
Paleontological features can be observed at the site 3.4
(Prado Mayor Cenozoic fossils, Fig. 6). In this site the Espuña
and Valdelaparra fms are visible (Martín-Martín et al., 2020c;
2021). The first formation is characterized by alveoline-num-
mulite rich limestones (Fig. 6A) with occasional large fron-
descent and cephaloid corals (Fig. 6B); the second formation
is made of marshy marls and clays with gastropods (Fig. 6C)
from fresh-water limestones. Other sites with paleontological
features are: Eocene fossils from Malvariche Valley (sites 4.5,
4.6 and 4.9), Lomo del Herrero fossils (site 6.4) and Castillo de
Mula fossils (site 8.4).
In the case of geomorphological features, a good exam-
ple is the site 4.1 (Pinnacle of Morrón de Totana, Fig. 7) Fig. 5.- Turbidites of the Río Pliego Fm where the sandstone
turbidite levels stand out since they are less affected to erosion
formed as response to a jointing of the Jurassic succession.
(site 8.3).
The site consists of massive limestones from the Liassic
affected by a vertical jointing in which front slope a finger ma Sierra de la Muela relief (site 7.3), Badlands from Ge-
shape structure (pinnacle) is being separated by erosion bas (site 7.4) and Castillo de Puebla Mesa relief (site 8.2).
that may implies a future risk of detachment by overtur- A good example of hydrogeological features is the site
ning (Martín-Martín et al., 2010). Other sites with relevant 3.3 (Fuenteblanca spring, Fig. 8). In this site a water source
geomorphological features are: Barranco de las Brujas takes place tectonically controlled (Martín-Martín et al.,
(site 1.1), Leyva Walls (site 1.2), Morra de las Moscaz la- 2006c, 2010). The structure is a thrust fold (syncline). The
piaz (site 3.1), Tres Carrascas sinkhole (site 3.2), La Plata Upper Jurassic-Cenozoic succession of the Morrón de To-
caves (site 4.2), Montisol remnat surface (site 5.3), Virgen nana Tectonic Unit crops out and is thrusted by a sheet of
Blanca sliding (site 5.5), Muela de Pliego (Mesa) and La the same unit. In the footwall block clays and marls of the
Almoloya Butte (remnant relief) (sites 6.1 and 6.6), Alha- Valdelaparra Fm are the base impermeable level (Fig. 8A,
Revista de la Sociedad Geológica de España, 34 (1), 2021
S. Moliner-Aznar, M. Martín-Martín, T. Rodríguez-Estrella, G. Romero-Sánchez and A. García-Lara 51
Fig. 6.- Prado Mayor Cenozoic fossils (site 3.4): A) nummulite-rich limestones (Cuisian Espuña Fm), B) frondescent corals (Cuisian
Espuña Fm), C) limestones with fresh-water gastropods (lower Lutetian Valdelaparra Fm).
Quite interesting petrological features can be observed at
the site 2.1 (Paleozoic rocks from the Morrón de Totana Tecto-
nic Unit, Fig. 10). At the base of the geological unit of this site
a thin sheet of Paleozoic rocks (Martín-Martín et al., 2006a) are
visible in the geotrail 2 (Las Alquerías). These Carboniferous
rocks consist of greenish slates (Fig. 10A), greenish sandsto-
nes and micro-breccias (Fig. 10B) and golden greywackes (Fig.
10C). In the Betic Cordillera, Paleozoic rocks are only visible in
the Internal Zone but usually metamorphosed. Only the Mala-
guide Complex shows sedimentary or epimetamorphic Paleo-
zoic rocks. Moreover, this site is one of the few places where
Paleozoic rocks are visible within the eastern Betic Cordillera.
Other sites with significant petrological features are: conglome-
rates with quartzite pebbles (site 4.7) and Barqueros vulcanites
(site 7.5). On the other hand, other petrological features as the
Fig. 7.- Pinnacle of Morrón de Totana (site 4.1). The Liassic type of rocks can be observed at the site 8.6 (Lomo del Herrero
massive limestones are affected by a vertical jointing and a finger quarries, Fig. 11). In this site, in a fold (anticlinal)-thrust struc-
shape relief that formed due to erosion. ture the Eocene succession of the Espuña and Malvariche fms
crop outs (Martín-Martín et al., 2020c, 2021). The Eocene roc-
B). The hanging wall block is made of Jurassic limestones
and dolostones with reservoir properties. In the contact be- ks are much appreciated ornamental stones used for decorative
tween permeable and impermeable materials a small spring elements of buildings. Two quarries are in the eastern side of
takes place (Fig. 8C, D). It is not related to the important the anticline (Fig. 11A). These are open-cast mining (Fig. 11B)
aquifers that make up the Sierra Espuña Hydrogeological in which limestone or calcarenites with large foraminifera (visi-
Unit, which shows deeper piezometric levels (Rodríguez ble to naked eye) are exploited as ornamental stone (Fig. 11C).
Estrella, 1996). Other sites with hydrogeological features Other similar sites are: the As mines (site 1.5), El Purgatorio
are: Prado Chico spring (site 1.7), El Hilo Spring (site 2.4) gypsum mines (site 2.7), Murcia snow pits (site 3.7) and the
and Baños de Mula thermal waters with water temperatu- phosphate mines from Prado Mayor (site 3.5).
res of about 37 ºC and related to the Baños Fault (site 8.1). A good example to observe mineralogical features is the
An example of mixed geomorphological and hydro- site 7.7 (Barranco del Infierno gypsums, Fig. 12). It consists
geological features is also selected at the site 7.2 (Rambla of a continuous level of lower Messinian gypsums (Monte-
de Algeciras, Fig. 9). It consists of an area affected by de- nat and Serrano, 1997) (Fig. 12A). Gypsums usually are la-
sertification process where an ephemeral stream (Rambla minated and interstratified with marls (Fig. 12B) and display
de Algeciras) can be found. The river rides the impermea- a crystalline (Fig. 12C) or fibrous texture. Another site to
ble clayish late Miocene sediments (Montenat and Serra- observe interesting mineralogical features is the Barqueros
no, 1997). In this area, a gravity dam has been constructed diatomites (site 7.6) in the same geotrail.
using a narrow path of the Rambla de Algeciras in the Al-
hama Fm (calcarenites and conglomerates) near the locali- Discussion and conclusions
ty of Librilla (Fig. 1B). The dam uses the impermeable cla-
yish late Miocene deposits (Montenat and Serrano, 1997) The SV of the 55 sites is high or very high in almost
for the water reservoir and the emerged areas constitute all cases (Fig. 13). Only 3 sites show a SV below 50 but
a good example of badlands as geomorphological feature always above 25 (moderate). This indicates that the area
developed in the clayish rocks of the area. is very suitable for scientific research studies as already
Revista de la Sociedad Geológica de España, 34 (1), 2021
52 GEOLOGICAL SITES IN SIERRA ESPUÑA-MULA DEPRESSION AREA
mentioned because of the important
number of scientific papers (e.g.,
Brilha, 2016; Aoulad-Sidi-Mend
et al., 2019). Although some of the
sites proposed here were published
in the Sierra Espuña Guide (Mar-
tín-Martín et al., 2010), in the Spa-
nish inventory of geological sites
(IGME, 2021) only two sites from
these 55 are included: Barqueros
vulcanites (site 7.5) and Castillo de
Puebla Mesa relief (site 8.2). This
implies that much work is still pen-
ding in terms of geological heritage
in the area.
PEU and PTU reach high or very
high values in all the sites (Fig. 13).
In the case of PEU, this criterion even
reaches values above 75 (very high) in
several sites. In the case of PTU, even
a few of sites reach values above 75
(very high). The above mentioned as-
sessment values indicate that the pro-
posed sites are of interest for didacti-
cal (as part of educational activities of
schools and universities) and touristic
(attracting tourist interested in nature)
purposes (Brilha, 2016; Aoulad-Si-
di-Mend et al., 2019).
The DR values indicate mainly Fig. 8.- Fuenteblanca spring (site 3.3). A) Panoramic view of Prado Mayor, B) interpretative
low (or moderate in a few cases) risk structural section of the Prado Mayor area, C) Location of Fuenteblanca spring close to the
in the geotrails 1 to 4 (Sierra Espuña access track to Prado Mayor, D) detail of the trough for animals at Fuenteblanca spring.
area) (Fig. 13). In these geotrails only
a few sites reach the value of 50 (sites
2.3, 2.4, 3.3 and 3.4) while the other
sites have the value 25 (low risk). In
the case of the geotrail 5 (also Sierra
Espuña area) and 6 to 8 (Mula Depres-
sion) values of degradation risk are
higher with a moderate or high risk in
most of the cases, and very high in a
few of sites. Geotrail 5 shows values
in all the cases above 50 (high risk)
and site 5.5 above 75 (very high risk).
Geotrail 6 shows all the sites between
25 and 50 (moderate risk). Geotrails
7 and 8 show the sites mostly above
50 (high risk), a few cases above 75 Fig. 9.- Rambla de Algeciras Dam (site 7.2). The dam is constructed over calcarenite and con-
(very high risk) and a site below 50 glomerate levels (right side), while the reservoir (in the center) is over badlands clayish terrains.
(site 7.2) indicating moderate risk.
In our opinion, these differences between geotrails 1 to 4 In our opinion, geological sites should be known by local
and 5 to 8 are because the four first geotrails are located in and regional authorities and by nature park managers. La-
the nature park of Sierra Espuña area, which is a protected ter, when conservation and protection measures were taken
area and conservation measures are already implanted. Con- according to the obtained DR, the geological sites could be
versely, the Mula Depression and other parts of the Sierra promoted to be visited by people.
Espuña (as the area of geotrail 5) do not have any conserva- The evaluation performed for geotrails (Bollati et al.,
tion measures and their sites should be protected to prevent 2017; Aoulad-Sidi-Mend et al., 2019) as a whole (Fig. 14) is
their degradation risk. Although some sites show high DR also interesting for visitors to choose the most suitable route
we have decided to include them in the geotrails selection. according to their goals (scientific, educational or touristic).
Revista de la Sociedad Geológica de España, 34 (1), 2021S. Moliner-Aznar, M. Martín-Martín, T. Rodríguez-Estrella, G. Romero-Sánchez and A. García-Lara 53
Fig. 10.- Paleozoic rocks (site 2.1): A) greenish slates, B) greenish sandstones and micro-breccias, C) golden micaceous greywackes.
Fig. 11.- Messinian gypsums of the Barranco del Infierno (site 7.7): A) general view of the gypsum level, B) detail of interstratified
gypsums, C) detail of the crystalline gypsums.
Fig. 12.- Lomo del Herrero quarries (site 8.6): A) orthophoto view of the Eastern side of the Lomo del Herrero with location of the two
quarries, B) detail of the quarry front of the easternmost quarry, C) detail of the exploited calcarenites.
Therefore, all the geotrails show mean values for SV, PEU very restrictive by limiting excessively the visits or even
and PTU between 50 and 75 indicating high interest for the forbidding the entrance in some areas of the park. In other
respective purposes. The highest SV mean value is obtained cases, the management of the parks is not very favorable
in the geotrail 6, followed by the geotrail 8. Conversely, the to introduce panels and signs announcing certain beauties,
lowest value for SV is found in geotrail 5, followed by the preferring to leave nature as it is and with the minimum of
geotrail 1. In the case of PEU, values are very similar in all human intervention. Popularization of the geological herita-
the cases. Only geotrail 1 is a little lower than the rest of geo- ge may contribute to improve the wealth of the region. The
trails. Lastly, for the PTU the highest mean value is obtained appropriate publishing, advertising and signaling of the sites
in the geotrail 8 followed by the geotrail 5, while the lowest and geotrails could increase the economic activity and a sus-
is found in the geotrail 1 followed by the geotrail 4. When tainable development in the area by attracting tourists, re-
the DR is considered, the highest mean value is obtained in searchers and students to the region (Carcavilla et al., 2007;
the geotrail 8 followed by the geotrails 5 and 7. By contrast, Díaz-Martínez et al., 2014; Brilha, 2016; Aoulad-Sidi-Mend
the lowest DR values are obtained in the geotrails 1 and 4, et al., 2019). It is true that the visit of many people could
followed by geotrails 2 and 3. also increase the DR of the sites or even produce additional
Our personal experience indicates that political autho- risks in a natural area. So the challenge is to find the equili-
rities and managers of nature parks usually underestimate brium between conservation and opening to the public. The
the geological heritage and are mostly interested in con- estimation of the values in the DR can give some light in
ventional tourism and other nature values as flora and fau- how conserve the sites. In the case of the low DR no ac-
na (Aoulad-Sidi-Mend et al., 2019). In the case of nature tions must be taken. When DR is moderate, it would require
parks (as the Sierra Espuña case), the management can be introducing regulatory measures in the sites, and when DR
Revista de la Sociedad Geológica de España, 34 (1), 202154 GEOLOGICAL SITES IN SIERRA ESPUÑA-MULA DEPRESSION AREA
Fig. 13.- Histograms with the Scientific Value (SV), Potential Educational Use (PEU), Potential Touristic Use (PTU) and Degradation
Risk (DR) values for the 55 sites grouped in the 8 geotrails (GT).
is high some protection and preserva-
tion measures should be taken. Luc-
kily, the DR very high is not applica-
ble in this area.
The sites, geotrails and the quan-
titative assessment presented in this
work can be a new steep for paying
tribute to the geological heritage of
a region of incomparable beauty and
geological diversity. This informa-
tion can be used by authorities and
managers in the case of considering
opening the region to new guests
interested in natural aspects as the
Fig. 14.- Histograms with the Scientific Value (SV), Potential Educational Use (PEU), Potential geological heritage of the Murcia
Touristic Use (PTU) and Degradation Risk (DR) mean values for the 8 geotrails (GT). region.
Revista de la Sociedad Geológica de España, 34 (1), 2021S. Moliner-Aznar, M. Martín-Martín, T. Rodríguez-Estrella, G. Romero-Sánchez and A. García-Lara 55
Acknowledgements and funding Martín-Martín, M., Robles-Marín, P., 2020. Alternative methods
for calculating compaction in sedimentary basins. Marine
The revision performed by Dr. Emilia Le Pera and and Petroleum Geology 113: 104132.
one anonymous reviewer is greatly acknowledged. This Martín-Martín, M., El Mamoune, B., Martín-Algarra, A., Martín-
Pérez, J.A., Serra-Kiel, J., 1997a. Timing of deformation in
research has been supported by the Research Project
the Malaguide of the Sierra Espuña (Southeastern Spain).
CGL2016-75679-P (Spanish Ministry of Education and Geodynamic evolution of the Internal Betic Zone. Geologie
Science) and by the Research Group VIGROB-053 (Uni- en Mijnbow, 75 (4): 309-316.
versity of Alicante). Martín-Martín, M., El Mamoune, B., Martín-Algarra, A., Serra-
Kiel, J., 1997b. La formation As, datée de l’Oligocène
Author contributions inferieur, est impliquée dans les charriages des unités
malaguides supérieures de la Sierra Espuña (Zones Internes
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Geosciences, 325: 861-868.
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