Manodisciplines Applied to Understand the Complexity of Mudstones and its Links with the Instability of Slopes: Interrelationships between Endogenous and Exogenous Contributing Factors, Weathering Agents & Dynamics, Next to other Environmental Considerations

The Kip have a sedimentary origin, with a strong siliciclastic contribution (represented by quartz, muscovite and clays), deposited in marine environments of the warm Lower Cretaceous (from shallow basins in the Sea of Tethys, which connected large oceans from E to W), with their particular organic components and non-crystalline phases, which were later lithified. Its micro biolytic contents are high (discrete organic carbon, dispersed and in organo-mineralogical aggregates), millimeter fragments of Phaeophyta abound, occasionally Girogonites of charophytes, and small ammonia associated with a possible ‘bloom’, together with sulfides (framboidal pyrite is abundant, which defines euxinic conditions), made concordant with the views [6] and papers of Dr. Silva. Sulphates and some inorganic phosphates, carbonates being scarce (dolomite/ankerite, calcite minor). Several oxidesoxyhydroxides and sodalite, crystoballite; other phyllosilicates, nacrite and pyrophyllite (up to 21%); dickite, illite, gibbsite, halloysite, kaolinite, phlogopite, vermiculite and zeolite as products of weathering [3,7]. Thus, total crystalline phase around 55-69%, while the high biogenic signature is up to TOC>5, sulfur (4.8%) and they are considered non-calcareous rocks (Ca <4.3%).

To obtain all this detailed characterization were used petrography, physicochemical tests (of waters, soils and rocks), added techniques combined to nano disciplines: RXD, RXF, SEM, FTIR+RAMAN Spect., TOC-TS. It is important to contrast the images captured with reflected and incident light microscopy (where the internal details of the allochemicals of brown algae are evident), with the distribution, mixture and composition obtained by SEM, for comprehensive, real and very detailed interpretations.

Other precise data, contents and results of these very finesized and overconsolidated terrestrial materials are summarized in Ríos et al. [7], which is also about the discovery of cubic habit Na A Zeolites within this lithobiounit, of samples collected by the present author.

Such solid substances (rocks) of the central-northern part of the Eastern Cordillera of Colombia were folded, lifted, shortened and exhumed, which originate broad outcropping patterns, subject to processes of hydric or fluvial erosion, with hazardous mass movements and torrential events. Then covered by scant soils and abundant colluvial deposits; in addition to seismotectonic, petrological and geomorphological aspects, they seasonally facilitate MM in the typologies of translational landslides, debris flows and soil creep, with some rocks falls and subsidence, due to climatic, hydrological, biological and anthropic conditions.

That is why they matter the endogenous (emphasizing the apparently monotonous geofeatures of texture, structure and composition, with the relationships of these «intrinsic properties», like structural geology, tectonics, hydrogeology, slope, etc.) and exogenous factors (vg land use, vegetation cover, climate, identified and zoned).

De visu they tend to be massive – and it is convenient to call them mudstones – but at the level of millimeters to microns their primary structures stand out: incipient lamination, wavy and nonparallel lenticular, locally flat-parallel, all discontinuous. Primary intragranular, intergranular, intercrystalline porosity was identified, low compared with secondary porosity, associated with structural discontinuities. The thick layers dip smoothly and favorably, but these areas with fracturing systems and joints (irregular and inclined, in several families) create important channels for fluids. All this increases microporosity, caused by oxidation/dissolution, and permeability (storage capacity and flow, respectively): the mobilization of fluids is facilitated (acids, with salts, ions, etc.), becoming aureoles of weakness and more prone to the attack of the rocky massif.

Hydroclasticism (physical weathering) is due to volumetric changes, on a milli and micron scale, in the face of alternating cycles of humidity and drying, according to climatic conditions, climatic variability, biotic activity, affected by altitude and latitude, and micro-scale granulometric heterogeneity, in addition to packing of phyllosilicates and organic matter. This “orchestra of degradation” makes the rock massif friable: it reduces the volume of the faces closest to the surface and increases its reactive area, being a geochemically very efficient phenomenon (it creates more and more specific micro-surfaces). Compared with fresh bedrock, ferric oxides increase due to weathering up to more than 11%. In turn, its uninterrupted degradation is evidenced, quantifiable by nanosciences: progressively generated mold porosities can be measured (from BSE+BSED images) and opening of the lamina sets with MO (that are ‘washed’,). Similarly, thanks to field inspections, sampling, petrographic analyzes and the use of SEM (microanalysis report, based on EDS and multi-elemental mapping), only in this way could a microlaminated gypsum facies be determined, which produces a significant subsidence to the south of the urban area of Vélez (Santander). Specific, larger and more reactive micro-surfaces are created hydrobiogeochemically.

The potential deformations of the ground (flows, of greater extension and very low kinematic rate) or rupture surfaces (landslides) are shallow. They occur under the vadose zones and facilitated by lithological contacts (stratigraphic discontinuities), before marked changes in the stress-deformation state, microporal hydrostatic over-pressure (recharge and discharge of infiltration waters). The MM are triggered by earthquakes of moderate to strong magnitude, drastic variations in hydroclimatic conditions (storms, intensity and persistence of rains, humidity vs increase in temperature due to high insolation), earth movements and anthropic excavations (urban planning, poorly confined landfills or not stabilized, road cuts, mining work, etc.).

The research is related to the meso-centi until micro-nano “Mudstone’s World”, generated in very high sulfide and ferruginous marine conditions, and the convenient applicability of instrumental analysis techniques combined with classical methods and geomatic tools, to truly know its complexity and interconnections (composition, structure and petrophysical properties come to play a determining role). Such highly dynamic interrelationships have environmental implications, such as increased weathering and susceptibility or propensity to MM, so extensive and reactive, in the mountain ranges that expose such Cretaceous rocks. Other considerations, for instance the use of geomatic tools and up scaling mapping, are not covered here.

They pose serious challenges for territorial planning, environmental management (for example, the preservation of hydrographic basins and restoration of degraded areas) for the sustainable development, stability and integrity of engineering works, causing serious effects on lives and properties, also compromising security, risk reduction, adaptation and resilience to the climate change, in both rural and urban areas of many severely impacted countries around the world, not just in Colombia.

Finally, they are misnamed ‘shales’, because in addition to their fine granulometry, not all of them are laminated and/or fissile, concept very much in agreement with other authors.

The author wishes to sincerely thank the personal contributions of teachers, researchers and various Colombian institutions. To the support of the personnel and availability of the laboratories at the UIS headquarters, in Bucaramanga and Piedecuesta, especially the PTG (the Guatiguará Technology Park).

No conflict of interest.

1. Fleming RW, Spencer GS, Banks D (1970) Empirical study of behavior of clay shale slopes. US Army Engineer Nuclear Cratering Group. 1: 1-103.
2. Reyes MGA (2013) Multi-temporal evaluation and landslide risk management: the case of the Las Ceibas river (Neiva - Colombia). Colombian Geotechnical Bulletin 'Disaster risk management due to mass movements', (17): 99-112.
3. Reyes-Mendoza GA (2018) Detailed evaluation and impact of weathered muddy rocks. The case of Vélez (Santander, Colombia). Poster & abstract, in Proceedings XIII Technical Week of Geology, Geological Engineering and Geosciences. Caldas University, Manizales, Colombia, pp. 3.
4. Reyes-Mendoza GA (2019) The Muddy Rocks of Vélez: from weathering to landslides. Oral presentation. Fest Station-Intelligent UIS. Seminar U18 Fest-Ideas to transform the World. Industrial University of Santander: Bucaramanga, Colombia.
5. Reyes-Mendoza GA (2021) Upscaling geoenvironmental analysis, thematic mapping and nanotechnological characterization combined in bituminous mudstone outcrops studies, Eastern Cordillera, Colombian Northern Andes: application in detailed zoning of susceptibility to mass movements of Vélez, Santander. Future Materials 2021 Conference, Nanotechnology. Proceedings (Peers Alley Media, in press), Paris.
6. Silva JC (2018) Sedimentological and geochemical expression of the anoxic oceanic events of the Cretaceous in Colombia, an unconventional vision. Oral presentation, in ‘Wednesday of Geology’, Auditorio Benjamín Alvarado, Servicio Geológico Colombiano. Bogotá, Colombia.
7. Ríos-Reyes CA, Reyes-Mendoza GA, Henao-Martínez JA, Williams C, Dyer A (2021) First Report on the Geologic Occurrence of Natural Na–A Zeolite and Associated Minerals in Cretaceous Mudstones of the Paja Formation of Vélez (Santander), Colombia. Crystals 11(2): 218.