Geomorphological map of the Montelago area

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Geomorphological map of the Montelago area (North
Marche Apennines, central Italy): constrains for two
relict lakes
a
a
a
b
Daniele Savelli , Olivia Nesci , Francesco Troiani , Andrea Dignani & Sauro Teodori
a
a
Department of Earth, Life and Environmental Sciences, University of Urbino ‘Carlo Bo’,
Urbino, PU, Italy
b
External collaborator of the University of Urbino ‘Carlo Bo’, Sunesis Ambiente, Jesi,
AN, Italy
Available online: 26 Mar 2012
To cite this article: Daniele Savelli, Olivia Nesci, Francesco Troiani, Andrea Dignani & Sauro Teodori (2012):
Geomorphological map of the Montelago area (North Marche Apennines, central Italy): constrains for two relict lakes,
Journal of Maps, 8:1, 113-119
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Journal of Maps
Vol. 8, No. 1, March 2012, 113–119
SCIENCE
Geomorphological map of the Montelago area (North Marche Apennines, central
Italy): constrains for two relict lakes
Daniele Savellia, Olivia Nescia, Francesco Troiania∗ , Andrea Dignanib and Sauro Teodoria
a
b
Department of Earth, Life and Environmental Sciences, University of Urbino ‘Carlo Bo’, Urbino, PU, Italy;
External collaborator of the University of Urbino ‘Carlo Bo’, Sunesis Ambiente, Jesi, AN, Italy
Downloaded by [Biblioteca Universitaria] at 03:01 08 June 2012
(Received 20 April 2011; Resubmitted 9 December 2011; Accepted 22 December 2011)
The hamlet of Montelago (‘Mountain of the Lake’) lies within the northern Marche Apennines close to the
watershed of Fosso del Lago (‘Stream of the Lake’): both Italian toponyms clearly suggest the presence of a
paleolake. Official geological maps reported lacustrine sediments within the upper basin of the Fosso del Lago
stream, where outcrops of lacustrine sediments have also been noted for about five decades. The nineteenthcentury Gregorian cadastral map also reports water ponds roughly in the area where lacustrine sediments were
found: nonetheless, their position is clearly shifted upstream with respect to the reported lacustrine sediments.
In this context, we have recently performed a targeted geomorphological survey addressed at unravelling such
apparent discrepancy. Our study confirms the occurrence of lacustrine sediments spanning from Atlantic up to
Sub-Boreal exactly in the place reported by previous geological works. The detailed geomorphological map
created for the area allowed us to adequately locate previously published subsurface prospecting both
highlighting landslide damming as the process responsible for lake formation and providing information for an
adequate morphoevolutive reconstruction of the area. Geomorphological mapping also resolved the problem of
the different position of the ponds mapped by the Gregorian Cadastre, stating that these had no direct
relationships with the former lake but rather consisted of a small man-made reservoir directly connected by
broad channels to springs which are currently dried-out.
Keywords: landslide-dam; lacustrine sediments; holocene; geomorphology; Montelago; Italy; GregorianCadastre; Apennines
1.
Introduction
The upstream sector of the Fosso del Lago (‘Stream of the Lake’), which is a minor left tributary of the Sentino
River (Esino River basin), close to the village of Montelago (‘Mountain of the Lake’) consists of a broad valley
floor relatively flattened by alluvial and talus slope deposits, in sharp contrast with the downstream sectors that, in
turn, are deeply entrenched in bedrock. The study site is located at the height of 600– 800 metres a.s.l. in the inland
sector of the Marche territory (Figure 1) and is encircled by mountains slightly exceeding 1100– 1200 m a.s.l. The
present day rainfall regime in the area is of equinoctial type with an autumnal maximum in November, while the
driest month is July. The medium annual rainfall is about 1800 mm. The coldest month is January (medium temperature of about 38C), whereas the warmest month is July (medium temperature of about 218C).
Several toponyms in this area suggest the occurrence of a former lake for which, at present, scant explicit geomorphological evidence is preserved, even though small ponds were already reported in the maps of the Gregorian
Cadastre in use in the nineteenth century. In this work a detailed geomorphological map, which encompasses an
area of about 7 km2 within the upstream sector of the Fosso del Lago basin, is presented. The map is aimed at
identifying and describing landforms and Quaternary deposits effective for providing information about the
origin and extinction of the paleolake. The map is also aimed at unravelling the difference between the position
of lacustrine sediments reported in the official geological maps and the location of the ponds already mapped in
the Gregorian cadastral map of the nineteenth century.
∗
Corresponding author. Email: [email protected]
ISSN 1744-5647 online
# 2012 Daniele Savelli, Olivia Nesci, Francesco Troiani, Andrea Dignani and Sauro Teodori
http://dx.doi.org/10.1080/17445647.2012.668771
http://www.tandfonline.com
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D. Savelli et al.
Figure 1.
2.
Geological sketch of the north Marche Apennines and location of the study area.
Geological and geomorphological setting
The Montelago area is located in the Umbria-Marche Apennines, a northeast verging fold-and-thrust belt (Calamita
& Deiana, 1987). Thrust-faults affected a Meso-Cenozoic mainly carbonate and marly-carbonate multilayer and
propagated upward and north-eastward into the overlying Mio-Plio-Pleistocene hemipelagic, turbiditic and evaporitic units (Mazzoli, Deiana, Galdenzi, & Cello, 2002) (Figure 1). Strike-slip faults, ranging from north-south
(oblique) to east-west (transversal), dissect the overall northwest-southeast-oriented fold-and-thrust structural
pattern (Di Bucci et al., 2003).
From the geomorphological standpoint, the study area sits on the Adriatic side of the central Apennines, a midlatitude extra-glacial territory characterized by relief largely matching uplifting tectonic structures. The northern
Marche territory consists of an inland hilly mountain area merging towards the north-east into a hilly coastal
zone. The first pertains to the Meso-Cenozoic authocton multilayer, while the latter zone is shaped in Noegene
formations (Figure 1). The relief of the study area is largely constrained by both lithology and geological structures,
even if deep-seated gravitational slope-deformations (sensu Dramis & Sorriso-Valvo, 1994) and landslides play a
crucial role on hillslope morphology (Aringoli, Gentili, Materazzi, & Pambianchi, 2010; Guzzetti, Cardinali, &
Reichenbach, 1996).
In this frame, the Montelago area is placed near the Tyrrhenian-Adriatic divide of the Apennines and sets within
the Umbria-Marche calcareous ridge, which is the most inland structure of this sector of the chain. This latter structure is a complex anticlinorium, which can be locally approximated by three major northwest-southeast striking
anticlines locally displaced by oblique strike-slip faults. The three anticlines culminate (from west towards east)
in the peaks Cucco (1566 m a.s.l.), Catria (1,701 m a.s.l.), and Strega (1276 m a.s.l.) and are separated by
narrow thrusted synclines. The bedrock of the Montelago area consists of cherty-limestones, marly-limestones
and marls of the Maiolica formation (upper Tithonian –lower Aptian), Marne a Fucoidi formation (lower
Aptian – lower Cenomanian), and Scaglia Group (middle Cenomanian – Priobanian), which are part of the
Umbria-Marche stratigraphic succession (Cresta, Monechi, & Parisi, 1989 and references therein).
3. Previous studies on the Montelago paleolake
The first geological evidence for the presence of a paleolake close to the Montelago village came to light through
the work of Massoli-Novelli (1960): in fact, he noticed blackish, thinly stratified organic-rich clays exposed in a
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small outcrop along the present channel, thus supporting the possible existence of a relict lake previously testified
only by local toponyms and historical maps. This author also indicated, in an article featured in a local magazine
(Massoli-Novelli, 2008), landslide damming as the genetic cause for the ancient lake. Later on, the sheet ‘Pergola’
of the Geological Map of Italy at the scale 1:50,000 (Centamore et al., 1975a) mapped lacustrine deposits inside the
valley. In this regard, the illustrative notes of the map (Centamore et al., 1975b) only reported that ‘near Montelago
lacustrine clayey deposits crop out in a small depression’, stating that they are not correlated to other lacustrine
sediments, which in nearby areas are strictly associated with Quaternary terraced fluvial deposits. The lacustrine
deposits previously mapped by Centamore et al. (1975a) have also been represented with about the same surface
extension and boundaries in the more recent geological and geomorphological maps of the Marche Region at the
scale of 1:50,000 (Sarti, 2003; VV.AA., 2000). Such recent maps also reported landslide deposits on both valley
sides and at the downvalley end of the described lacustrine deposits. Nonetheless, after the first report by MassoliNovelli (1960), except for cartographic acknowledgement of lacustrine deposits and landslides, no specific investigation has been carried out in order to better constrain the chronology, extension and genesis of the ancient lake.
Further, if the relatively recent geologic and geomorphologic maps are compared with those belonging to the nineteenth-century Gregorian Cadastre, a major question arises about the exact positioning of the lake, which in the
older cadastral map is shifted several tens of metres upstream of the reported lacustrine deposits. Based on such
considerations, detailed analyses consisting of geomorphological field and remote sensing mapping, geophysical
prospecting and sediment-coring, started in 2008. This study was aimed at reconstructing the geomorphological
evolution of the territory of Montelago mainly focusing on the former lake. Dignani (2009) have preliminary synthesized in a technical report the main results of such analyses, providing data to constrain the paleolake formation
and extinction. In this regard, this work aims at presenting the detailed geomorphological map produced as a result
of these studies.
4.
Methodology
The geomorphological survey was performed primarily, also based on previous maps, in order to choose the best
sites for prospecting and drilling the lacustrine sediments and finally, with the aim of both obtaining a suitable
interpretation of the data achieved and producing a well-constrained evolution model. An assessment of local geological features has been primarily done on the basis of the aforementioned official maps, accurately checking
boundaries and overall structural arrangement and coming to some minor adjustments. Ex-novo geomorphological
mapping including continental Quaternary deposits has thus been carried out. The sheet 291140 ‘Montelago’ of the
Digital Topographic Map in vector format edited by the Cartographic Office of the Marche Region at the scale of
1:10,000 has been used as the base map for field work. Further, where the density of landforms and deposits and/or
their dimensions required more detail mapping, the topographic map was enlarged to 1:5000.
The field survey was supported by analysis of aerial photographs taken in 1984 at the scale of about 1:33,000.
Ortho-photos (year of collection: 1988; ground resolution: 5 m) have also been used to improve the accuracy of the
survey. A handheld GPS, with accuracy of 2 m, has been used to position some critical points, as springs and features related to ancient water-pounds. The legend was arranged following the guidelines for the production of the
Geomorphologic Map of Italy (VV.AA., 1994) suitably adapted to the purpose of this work and in relation to the
variety of landforms in the area.
5.
Results and discussion
In the Montelago area a landslide damming the valley floor produced a topographic depression that for several
millennia hosted a small lake, which at present is extinct (Dignani, 2009) (Figure 2). The lacustrine depression
sits between the foothills of mount Strega (1276 m a.s.l., northeast), mount Foria (1115 m a.s.l., southwest),
and Poggio Prato Tondo (1017 m a.s.l., northwest). The valley trough where the paleolake was contained is
almost completely bounded by concave hillslopes where either upper Pleistocene stratified talus deposits or
Holocene slope-waste deposits can be found.
The Fosso del Lago stream originates from the junction of two ephemeral streams at the uppermost margin of
the topographic depression where the paleolake was placed; from here the main stream flows towards the southeast
gouging out the axis of a narrow syncline included in the broader anticlinorial structure of the Umbria-Marche
Ridge (Figure 1). A relatively narrow and elongated, topographically constrained, alluvial fan radiates downslope
from the point where the north-eastern stream joins the up-lake area. On the opposite side, a small alluvial fan is
found associated with talus-slope deposits. Landforms related to both gravitational and running water processes
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D. Savelli et al.
Figure 2. The upstream sector of the Fosso del Lago, where a landslide (L) dammed the stream forming a small lake (a) drilled
in 2008 (1). After the lake extinction a small reservoir (b) was dug. The simplified lithostratigraphy of the sediment core from
the paleolake site has been reported (2) (modified after Dignani (2009)).
characterize the hillsides enclosing the paleolake depression. Landslide-related landforms, such as scarps, trenches,
and counter-slopes are widespread in the area and can be found in correspondence with large landslide bodies,
manly rock- and block-slides, and subordinate shallow landslides, which characterize the two sides of the
Fosso del Lago valley. Further, rills and gullies cut into the hillsides, mainly where these latter consist of debris
slopes. At heights exceeding approximately 1000 m a.s.l., nivation landforms can be detected. In this respect, it
is worth mentioning the occurrence, on the south-western flank of mount Strega, an active avalanche channel
forming a small avalanche cone at its downslope end.
The hillslopes of the two sides of the Fosso del Lago valley are quite different from each other, also developing
a asymmetrical stream network. Several small hillslope hollows (sensu Crozier, 2006), containing ephemeral
streams, converge into the depression on the right valley-side. Conversely, the left valley-side hosts the large landslide responsible for the lake formation, which prevents any significant development of a stream network. This
valley-side culminates in the sharp rocky crest separating mount Strega peak from mount La Penna. The hillside
is characterized by an upslope quite rectilinear and steep profile that sharply joins, at the footslope, the wide
terrace-like bench on which Montelago village stands. The bench lies between 720 and 820 m a.s.l., and is
separated from the present stream by a steep toe-slope scarp from 20 up to 120 m in height. The streamdamming landslide overran just the up-valley sector of this bench.
Large landslides affect both sides of the Fosso del Lago valley and, at the toe, reach the valley floor. The slope
failures from the left valley-side, which are generally inactive rockslides, markedly deflected the stream course -as
clearly manifest eastward of Montelago village- damming the stream and thus creating the conditions for the development of a small lacustrine basin (Figure 2). The damming landslide is a partial reactivation of a larger ‘first time
landslide’ (sensu Borgatti et al., 2005) post-dating the upper Pleistocene coldest stages, the present day remnant of
which is a wide landslide body perched high on the left-valley hillside, close to the Le Fonti locality. The downslope-dip of the bedrock strata favoured the failure of both the bedrock and the overlaying thick, partially cemented, talus: as a result, large amounts of calcareous breccia boulders were incorporated into the landslide runout. The
landslide invaded the former valley-trough partially filled-up by more than 15 metres of detrital/fluvial deposits
(Figure 2) as demonstrated by subsurface data (Dignani, 2009). Above such detrital deposits about 11 metres of
lacustrine sediments – mainly gyttja, silty-gyttja and decomposed peat – were deposited. The radiocarbon ages
of the lacustrine sequence range from 7735 + 50 yr BP up to 2850 + 40 yr BP, thence from Atlantic up to
sub-Boreal times (Dignani, 2009). Above the lacustrine sediments a thin colluvial veneer was deposited (Figure
2). The flattened valley-floor immediately upstream of the landslide is what remains of the former lake: slopewaste and alluvial fan deposits on both upstream and right valley-sides suggest a progressive detrital/alluvial occupation of the hollow with the consequent contraction of the pond. The topmost lacustrine sediments and the
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overlying alluvium have been slightly terraced: as a result, a 2 – 3 m-wide plain developed fairly entrenched in
former deposits. Few tens of metres upstream of the paleolake site, the plain is flatter and wide with respect to
the downstream sector. The gradient of the plain diminishes and the bounding scarps, although locally remoulded,
hinting at earlier rectilinear plan forms. It is just such a landform assemblage that forms key evidence for the ponds
reported by the maps of the Gregorian Cadastre (Figure 3). These ponds were clearly shaped by man in order to
create a small reservoir, probably taking advantage of previous small wet areas which – once the former lake
became extinct – survived or reformed in a more upstream position. Significantly, several extinct seepage
zones and springs have been detected in the area up to several metres in height above the present valley floor,
likely hinting at past higher levels of the water table fit for forming and maintaining water ponds and/or wet
zones. In this respect, two channels join the sides of the old reservoir connecting it to several important springs
presently dried-out. Another channel connects the upstream end of the reservoir to the downstream one,
perhaps with the function of preventing excessive sediment supply to the reservoir during flood stages.
Summing up, two distinct small lakes existed in different times roughly in the same place within the upper
Figure 3. Morphoevolutive sketch of the lacustrine depression framing the small reservoir reported by the nineteenth-century
Gregorian Cadastre.
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D. Savelli et al.
sector of the Fosso del Lago stream (Figure 3): the oldest was a direct consequence of the landslide damming of the
Fosso del Lago stream, while the younger one was a small reservoir exploiting local springs.
4.
Conclusions
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The detailed geomorphological mapping of the headwater sector of Fosso del Lago watershed (northern Marche
Apennines, central Italy) allowed identification of former lakes. Based on landforms analysis, two distinct phases
of lake formation have been detected (Figure 3). The older and larger lake accounts for landslide damming of the
Fosso del Lago stream in Atlantic times. The sedimentary infilling of the lake produced a small plain enclosed by
an alluvial fan and slope-waste deposits. Headward erosion followed the damming of the stream forming a series of
stream-cut scarps on the outer margin of the landslide body and contributing to the extinction of the older lake. The
younger lake, which is the pond reported by the nineteenth-century Gregorian Cadastre, finally was formed: it was
actually a small reservoir partially dug by man taking advantage of a wet zone fed by springs. The recent
depression of the aquifer following both natural trends and water captation works, dried-out most of the springs
therefore producing the drying of the reservoir.
Software
The maps produced during both field surveys and aerial photo interpretation in paper format have been rasterized to
obtain TIFF images through a 600 dpi digital scanner, then inserted and georeferenced in the Terranovaw ShArch,
using the Gauss-Boaga coordinate system (Datum: Roma 1940). The final layout of the map was performed using
Corelw Draw.
Acknowledgements
The authors are very grateful to D. Castaldini and an anonymous reviewer for their helpful comments and suggestions that
enhanced the results reported in this manuscript and strongly improved both readability and contents of the map. The
authors are also grateful to Makram Murad-al-shaikh that contributed to enhancing both readability and design of the map.
References
Aringoli, D., Gentili, B., Materazzi, M., & Pambianchi, G. (2010). Deep-seated gravitational slope deformations in active
tectonics areas of the Umbria-Marche Apennine (Central Italy). Geografia Fisica e Dinamica Quaternaria, 33, 127– 140.
Borgatti, L., Corsini, A., Barbieri, M., Sartini, G., Truffelli, G., Caputo, G., et al. (2005). Large reactivated landslides in weak
rock masses: A case study from the Northern Apennines (Italy). Landslides, 3, 115–124.
Calamita, F., & Deiana, G. (1987). The arcuate shape of the Umbria-Marche-Sabina Apennines (central Italy). Tectonophysics,
146, 139 –147.
Centamore, E., Catenaccci, V., Chiocchini, M., Chiocchini, U., Jacobacci, A., & Martelli, G. (1975b). Note illustrative della
Carta Geologica d’Italia alla scala 1:50.000, F. 291-Pergola, Servizio Geologico d’Italia, Roma [Illustrative notes of the
Italian Geological Map at the scale 1:50.000, Sheet 291 ‘Pergola’, Italian Geological Survey, Rome], p. 40.
Centamore, E., Jacobacci, A., Malferrari, N., Martelli, G., & Valletta, M. (1975a). Carta Geologica d’Italia alla scala 1:50.000,
F. 291-Pergola, Servizio Geologico d’Italia, Stabilimento L. Salomone, Roma [Italian Geological Map at the scale 1:50.000,
Sheet 291 ‘Pergola’, Italian Geological Survey, Rome].
Cresta, S., Monechi, S., & Parisi, G. (1989). Mesozoic2Cenozoic stratigraphy in the Umbria2Marche area: Geological field
trips in the Umbria2Marche Apennines. Italy: Memorie Descrittive della Carta Geologica d’Italia, 39, 1–185.
Crozier, M.J. (2006). Hillslope hollow. In A.S. Goudie (Ed.), Encyclopedia of geomorphology (pp. 521–523). New York, NY:
Routledge.
Di Bucci, D., Mazzoli, S., Nesci, O., Savelli, D., Tramontana, M., De Donatis, M., et al. (2003). Active deformation in the
frontal part of the Northern Apennines: Insights from the lower Metauro River basin area (northern Marche, Italy) and
adjacent Adriatic off-shore. Journal of Geodynamics, 36, 213–238.
Dignani, A. (Ed.). (2009). Dal sistema aperto-integrato per il turismo sostenibile al «Parco Geomorfologico del Lago di
Montelago»: La valorizzazione di un’unità di paesaggio come supporto per l’economia locale [From the open-integrate
system for a suitable tourism to the ‘Geomorphological Park of Montelago’: The exploitation of a landscape unit to
support local development]. ANeA s.r.l. edition, Cerreto D’Esi (AN), p. 63.
Dramis, F., & Sorriso-Valvo, M. (1994). Deep seated slope deformations, related landslides and tectonics. Engineering Geology,
38, 231 –243.
Guzzetti, F., Cardinali, M., & Reichenbach, P. (1996). The influence of structural setting and lithology on landslide type and
pattern. Environmental and Engineering Geosciences, 2, 531–555.
Journal of Maps
119
Downloaded by [Biblioteca Universitaria] at 03:01 08 June 2012
Massoli-Novelli, R. (1960). Aspetti geologici ed idrogeologici del territorio tra Sassoferrato ed il Monte Strega [Geological and
hydrogeological outlines of the territory including Sassoferrato and Mount Strega]. Unpublished degree thesis, Department
of Earth Science, University of Rome ‘La Sapienza’.
Massoli-Novelli, R. (2008). Montelago: dov’è il lago?, Sassoferrato Mia, 2, 11–12.
Mazzoli, S., Deiana, G., Galdenzi, S., & Cello, G. (2002). Miocene fault-controlled sedimentation and thrust propagation in the
previously faulted external zones of the Umbria-Marche Apennines, Italy. EGU, Stephan Mueller Special Publication
Series, 1, 195 –209.
Sarti, M. (2003). Carta Geologica Regionale, Edizione CTR, Sezione 291140 Montelago, scala 1:10,000, Regione Marche,
[Regional Geological Map at the scale 1:10,000, Sheet 291140 ‘Montelago’, CTR edition]. Giunta Regionale, Servizio
Ambiente e Paesaggio [Environment and Landscape Office, Ancona, Italy].
VV.AA. (Gruppo Di Lavoro Per La Cartografia Geomorfologica [Working Group for the Geomorphological Mapping]). (1994).
Carta Geomorfologia d’Italia-1:50.000, Guida al rilevamento, APAT [Italian Geomorphological Map at the scale 1:50.000,
Guide for the field survey] (Italian Natural Environmental Agency), Servizio Geologico Nazionale [Italian Geological
Survey], Quaderni, serie III, 4, Istituto Poligrafico e Zecca dello Stato, Roma, p. 42.
VV.AA. (2000). Carta Geomorfologica Regionale, Sezione CTR 291140 Montelago, Scala 1:10,000, Regione Marche, Giunta
Regionale, Ufficio Cartografia e Informazioni Territoriali [Cartographic and Territorial Information Office, Ancona, Italy].