## 5 Discussion
Concerning the clay levels, there is a micritic and scarce cement (12-13% of carbonate) very sensitive to water, which favors its almost instantaneous dissolution, something that does not happen with the sparitic cement in the feldspathic arenites, which are less soluble, thus preventing their collapse. Some authors found similar behavior in saturated biocalcarenites [47], concluding that their strength was related to the origin of the type of bonding: when it is depositional and micrite, its bonding effect disappears when immersed in water, and so the sample collapses partially or completely. However, when bonding of diagenetic origin and the sparite nature of crystals overlap, the strength of the terrain increases and, in addition, the sample is less susceptible to collapse, at least in the short term. More research is required in the future regarding the role of carbonate in most of the COCs. Nevertheless, the fact that the carbonate reinforcement effect is higher for COCs than for MOCs can be highlighted. * Macrostructure  
The main macrostructural feature for COCs and MOCs is the existence of discontinuities. Sometimes they cause unexpected behaviours with fatal consequences [48; 49]. In addition, it can be stated that, when their presence is very intense, they cause materials with different geological histories to follow the same model of behavior [50]. In the more competent upper levels of the DC Formation, discontinuities are orientated according to the late-alpine orogenic processes [33; 34]; in the claye levels, they display a columnar disposition, which has been previously described as being related to graphic processes [41]. Moreover, no tectonic effect was observed. Although a more complex tectonic frame sometimes causes preferred orientations in the COC clays, as is the case, for example, in the Dagorda Clay (COC) [51; 52], the vertical pattern of the DC presents some differences among the MOCs and COCs, because, in the continental basins, the conditions for vertical fissures are imposed by the alternation of dry and wet periods. Due to its vertical disposition, they should be considered even more carefully, as this orientation reduces the strength of the clay to a minimum [50], and therefore becomes especially relevant for the COC mechanical behavior. * Microstructure  
On its clay levels, the DC displays a very dense and compact arrangement corresponding to a disperse and stacked structure on which no border-to-face contacts, typical in flocculation structures, were observed. This feature is different to the marine overconsolidated clays (MOCs), where flocculation structures can be seen in the London Clay [6], Oxford Clay [26], and Vallerica Clay [8], and in the Blue Clays of the Guadalquivir [3]. The precipitation of carbonate began after a non-deposition period, creating a coating at very early stages of their geological history, but not very intensely due to the low permeability associated with the fine grain size of the clay levels. At the same time, the absence of a sedimentation period favored the development of organic activity--manifested through bioturbations and s-matrix structures (Figure 4)--and bridges or joints between the clay particles that could be formed during their deposition time. Certain carbonate content is presented in most of the MOCs [8; 53], but formed in different moments of the geological history, because it precipitates as the sediments dewater during their burial or appear as occasional crystals [6], and within a different microstructure. A more opened microstructure may be expected for the DC due to the early cementation. However, its non-marine deposition environment prevented the sediment from being in a suspension of low electrolyte concentrations, which would cause the clay minerals to be negatively charged in both its surface and its edge. Such circumstances increase the diffuse double layer and therefore make the electric forces of repulsion predominant.