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Copyright of Spanish Journal of Palaeontology is the property of Socieadad Espanola de Paleontologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the northeastern zone of the department of Boyacá, in the locality of Socha, areas with a high fossiliferous potential of microvertebrates and vertebrates, as fish, crocodiles and, particularly, turtles, of middle and upper Paleocene age of the Arcillolitas de Socha Formation have been identified. Along this sector, detailed stratigraphic sections and geological profiles were elaborated, which together with lithostratigraphic and biostratigraphic techniques, allowed us to differentiate the formation into three members and to identify the prospecting areas of two fossiliferous levels of interest, as well as a group of key sandstones located in the intermediate levels. The paleoenvironments identified for the formation indicate a lagoonal, marshy, paludal, and deltaic sedimentation for the sandstones, generally sedimented in a continental depositional environment. All the information obtained could be applied for the eventual location of fossils in prospecting and exploration in subsequent research, as well as highlighting the imperative need to strengthen local laws in favor of the protection and preservation of these paleontological deposits in the region. [ABSTRACT FROM AUTHOR]

San Cayetano Formation, of Lower Jurassic?- Upper Jurassic (Oxfordian) age, constitutes the oldest and most extensive stratigraphic unit in the Guaniguanico Mountain Range (western Cuba) and is part of: Alturas de Pizarra del Sur (APS) and Sierra del Rosario/Alturas de Pizarra del Norte/Esperanza (SR/APN/E), separated by carbonate sequences. Lithologically, it is composed by shale, siltstone and sandstone, in apparently monotonous and somewhat metamorphosed sections; towards the upper part limestone and conglomerate interbedding is reported. Information on mineralogical composition and sediments source area for sandstones has been limited. A review and reinterpretation of these rocks is carried out, with special attention to the petrographic characterization of quartz, lithoclasts, feldspars and zircon grains (with age reports from the Paleoproterozoic to early Devonian). As a result, it is found that the source area for these rocks classifies as from: internal craton and recycled orogens. Based on these results, and the report of a granitic intrusive recorded at site M0077A with an age of 326 ± 5 Ma (25 km from the Yucatan coastline), it is possible to specify some parts of the Maya block as the source area (northern part, currently under the Chicxulub impact structure and its coverage). It is also shown that the APS sequences resemble flood and shoreline sediments (predominance of pelites) while those of SR/APN/E are more varied: fan, slope and foot-slope sediments (sandstones predominate). [ABSTRACT FROM AUTHOR]

The geomechanical strength of rock masses plays a key role in the planning and design of civil and mining construction projects. The uniaxial compressive strength (UCS) of rocks is a crucial property that is widely used in geotechnical engineering to understand the strength and deformability of rock masses. Determination of geomechanical properties both in the field and in the laboratory is time consuming, tedious, and expensive. However, ultrasonic techniques, such as P-wave propagation velocity (VP) measurement, are a simple, cost-effective, and non-destructive method for evaluating the UCS of rocks. In this study, a review of the state of knowledge of the type of empirical correlations that exist for sandstones to predict the value of UCS from VP is developed. The main objective developed is a meta-study on the relationship between UCS and VP. For this, UCS and VP data for sandstonetype sedimentary rock are compiled from various sources. With the results obtained, empirical formulas are proposed that correlate UCS and VP, which can be used as a geotechnical engineering tool to predict the value of UCS from VP in sandstones. [ABSTRACT FROM AUTHOR]

Copyright of Complutum is the property of Universidad Complutense de Madrid and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Expulsar II archaeological site is located in the Angical village, a rural area in the municipality of Quiterianópolis, State of Ceará, Brazil. It consists of a small sandstone shelter, where a raised rock platform and a niche stand out, in which the only panel of rock paintings currently still visible is observed. The figures are miniaturized, and have been identified as anthropomorphs, zoomorphs (among which jaguar, cervids, birds and rheas), and abstract motifs, in addition to some ink stains without a defined outline. The paintings were done in different shades of red. Delicate and graceful, the figures are typical of the Nordeste Tradition, most of them showing movement, which gives them dynamism. Two major scenes stand out: the hunting of a jaguar and the cornering of cervids and a rhea. No less important is the recurrence of pairs or trios of anthropomorphs, whose body shape and size are variable. A diagnosis of the main conservation problems completes this survey. [ABSTRACT FROM AUTHOR]

This paper presents a brief review of the archaeological research carried out at the Pedra do Atlas site, a sandstone shelter located in the rural area of the municipality of Piripiri, State of Piauí, Brazil. The rock walls contain 423 rock paintings in various colors and some engravings. Several ceramic fragments and vestiges of red and yellow mineral pigments were found in the sediments, as well as some lithics. During the last thirteen years, eleven expeditions have been conducted to the site and the vestiges of ancient human activities have been investigated 'in situ' and in the laboratory. Archaeometry has been applied in most of the work performed, and an experimental strategy with different analytical techniques has made it possible to obtain consistent results. [ABSTRACT FROM AUTHOR]

A methodology based on digital rock physics is proposed for a group of tomographic images taken from a core of sandstone extracted from an oil well, considering an anisotropic model of the material during the segmentation process. The rock sample, provided by the Colombian Petroleum Institute, is composed mainly of minerals such as quartz and calcite. First, a three-dimensional model is generated from the tomographic images. Then, a finite element mesh is created considering a material model that relates density and elastic modulus with the Hounsfield scale. Finally, a parametric study of the numerical model is performed and the results are compared with the reference values. Three different tests are proposed for the evaluation of elastic properties, where the minerals are studied individually (quartz and calcite) and as a composite (sandstone). The results of these tests are compared with reference values, showing difference percentages between 3 - 10% for the elastic modulus and between 0.7 - 2.1% for the Poisson's ratio. [ABSTRACT FROM AUTHOR]

Copyright of Boletin de Geologia is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Intersecciones en Antropología is the property of Universidad Nacional del Centro de la Provincia de Buenos Aires, Facultad de Ciencias Sociales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Instituto Superior de Correlacion Geologica, Serie Correlacion Geologica is the property of Instituto Superior de Correlacion Geologica (INSUGEO-CONICET) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Mundo de Antes is the property of Revista Mundo de Antes and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work aims to be a contribution to the study of «sacred stones» or «stones sanctuaries». The objective is to present an unprecedented case in the province of Guadalajara. It is a rocky support of sandstone, of natural formation, which has small notches that give access to an upper part decorated with cups, buckets and channels. This striking sanctuary shows a cruciform engraved to the right of the notch line, which implies a continuity of use until medieval times and it allows us to associate it with a set of cave hermitages that are a few meters away. [ABSTRACT FROM AUTHOR]

Copyright of Boletin de Geologia is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista del Museo de Antropología is the property of Museo de Antropologia - IDACOR and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista del Museo de Antropología is the property of Museo de Antropologia - IDACOR and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista del Museo de Antropología is the property of Museo de Antropologia - IDACOR and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

During the Late Jurassic to Early Cretaceous, two large sedimentary basins in northeastern Mexico, the Sabinas basin and the Monterrey through, accumulated thick clastic sequences. Two examples of these clastic sequences are the Patula Arkose (Early Cretaceous) and La Casita Formation (Late Jurassic - Early Cretaceous), which were petrographically and statistically analyzed in this study. The Patula Arkose, a feldsphatic arenite (Q54F38L8,-with a confidence level of the 99 %), was deposited into continental blocks with trends to continental transition (Qm54F41L5, 99 % of the confidence level).The petrographic characteristics and the mineralogical relationships suggest that the source rocks of the Patula Arkose were mainly low-grade metamorphic rocks (pelitic or psammitic schists), granite or granodiorite, limestone and sandstone. La Casita Fomation is composed of lithic arenite and feldesphatic arenite (Q52F27L21, with a confidence level of the 99 %) deposited in a dissected arc or a continental transition area (Qm52F64L14, with a confidence level of the 99 %). The sandstone petrography of La Casita Formation in the Monterrey trough shows a very complex provenance that implicates medium to high grade metamorphic rocks, andesite, rhyolite, limestone, sandstone, and shale sources. A multivariate statistical analysis of the main components, and the application of binary diagrams of petrographic index with additive and centered logratio transformation (alr and clr) confirmed the source rocks composition, suggesting that: i) the Patula Arkose is richer in low-grade metamorphic fragments, which are probably related with the Ouachita Mountains with 99 % of confidence level, and with granitic or granodioritic rocks of Permian-Triassic age; ii) La Casita Formation has affinity with the Paleozoic Las Delicias volcanic arc, Permian-Triassic and Early Jurassic arcs, and with medium to high grade metamorphic rocks that were possibly part of the Novillo Complex. [ABSTRACT FROM AUTHOR]

In the vicinity of the city of Guanajuato, a marine volcanosedimentary sequence crops out hosting two volcanogenic massive sulfide (VMS) occurrences: Los Mexicanos with Fe-Cu-Zn, and Guapillos with Fe-Cu-Pb-Zn±Au-Ag. This sequence, from base to top, consists of: (a) submarine vitreous tuffs with clasts of andesitic composition, (b) interbedded andesitic lavas, laminar limestones, conglomeratic sandstones with andesite clasts and black shales, (c) lava flows of andesitic, dacitic and rhyolitic composition, and (d) black shales with interbedded rhyolitic pyroclastic deposits. This sequence is intruded by subvolcanic bodies of granitic composition. The submarine volcanic rocks are calc-alkaline, while the trace element signature (including REE) of andesites, suggests that these rocks formed in a back-arc basin associated to an oceanic island arc. This setting favoured the development of submarine volcanism. Moreover, the development of submarine hydrothermal systems was triggered by felsic volcanism of explosive and submarine nature, probably associated to submarine calderas. The processes of formation of VMS deposits in the sequence in the Sierra de Guanajuato are associated to dacitic-riolitic volcanism. [ABSTRACT FROM AUTHOR]

A stratigraphical analysis performed at the Arroyo San Dionisio provided data on the evolution of the western margin of the San Jose del Cabo basin in Baja California, which evolution started in the late Miocene and is part of the Extensional Province of the Gulf of California. The half graben basin is bounded in its western margin by the listric fault of San José del Cabo. The marginal fault and three stratigraphic formations at the Arroyo San Dionisio are exposed perpendicularly to the basin margin, and were informally grouped into two sequences (lower and upper) separated by an angular unconformity. The lower sequence consists of the Trinidad and Los Barriles formations, while the upper sequence is constituted by the El Chorro Formation. In the western part of the arroyo, next to the San José del Cabo fault and due to the rotation along it, only the El Chorro Formation is exposed. This formation is composed of conglomerate and conglomeratic sandstone deposited in an alluvial fan environment. In outcrops farther to the east, conglomeratic sandstone and conglomerate of the Los Barriles Formation, which reflect an alluvial fan depositional environment as well, underlie the El Chorro Formation. The sediments of both formations are derived from the basement exposed in the sierra La Victoria. The Los Barriles and Trinidad Formations interfinger approximately 7 km east to the marginal fault. The Trinidad Formation is composed of coarse sandstone, muddy sandstone, and mudstone of a shallow marine environment. The interfingering evidences the contemporaneity of both formations, probably in the Pliocene, and reveals the existence of a coastal area with a delta fan during deposition of the sediments. No clinoforms were developed in this delta fan deposits, probably due to the lack of space in an area far from the marginal fault. The angular unconformity between the lower and upper sequences probably reflects a basin reorganization resulting in the partial erosion of the lower sequence in the Pliocene or early Pleistocene. Subsequently, the rotation along the fault confined the alluvial deposits of the El Chorro Formation to the western part of the basin. The youngest deposits of the El Chorro Formation cover the San José del Cabo fault and also show their original sedimentary disposition, suggesting little or no activity along the fault since the late Pleistocene. [ABSTRACT FROM AUTHOR]

We propose formally the Chivillas Formation, as a key litostratigraphic unit to decrypt the sedimentary record of Cuicateca basin. Its type locality is along Barranca Las Salinas creek northeastern ward Tehuacán, Pue., where the rocks are virtually without deformation. Chivillas Formation consists of basaltic flows frequently with pillow structure and siliciclastic deposits of turbidite currents and debris flows, on a very thick volcanosedimentary succession cut by dikes of similar composition. Estimate a total thickness of more than 4,875 m. Chivillas Formation is assigned at Barremian based on the maximum age of detrital zircon within sandstones, this age is consistent with previously reported fossil content. We recognized 16 facies into five classes: conglomeratic, sandy, fine, calcareous and igneous, which are grouped as eight facies associations: A) Medium-grained turbidites, B) Coarse-grained turbidites, C) Fine-grained turbidites, D) Structureless sandstones; E) Debrites clast supported, F) Debrites matrix supported; G) Synsedimentary disharmonic folds and H) Lavas and pillow lavas. From the recognized facies associations, we interpreted an environment of submarine fan deposit. The volcanic rocks of Chivillas Formation are alkaline mafic to intermediate, geochemical affinity MORB or OIB, with common lead isotopic values similar to values of enriched mantle, the isotopic signature Pb/Pb of lavas suggests a source from lower crust. The sandstones studied are graywackes composed mainly of monocrystalline quartz, mylonitic polycrystalline quartz, mosaic polycrystalline quartz, perthitic microcline, and some plagioclase; very abundant siltstone and limestone lithics, and fewer volcanic and metamorphic lithics, similar to granite or granulite gneiss; the clasts are angular to subrounded. The clasts into conglomerates are of limestone, sandstone (cross-stratified) and gneiss. These lithologies are typical of the Sierra de Juárez mylonitic Complex and Oaxaca Complex, and its sedimentary cover. Only few volcanic lithic in sandstones and some levels with pyroclastic falls were observed. The sandstones have their source on continental blocks, specifically from inner craton or uplifted basement, so we can assume that came from Oaxaquia. The presence of Pan-African-Brazilian zircons indicates a source from Gondwana; probably, they were transported by complex river systems within an advanced step on the rifting process of Gulf of Mexico. [ABSTRACT FROM AUTHOR]

The El Chilar Complex, located in Queretaro State, is a strongly deformed sedimentary unit that forms a tectonic mélange. This complex contains autochthonous blocks of sandstone or sandstone interbedded with shale, as well as exotic blocks of radiolarian chert. It is pre-Jurassic in age, and contains sandstone or sandstone with interbedded shale autocthonous blocks as well as chert exotic blocks. The largest of the exotic blocks is 1.5 km. long, and crops out in the town of El Terrero. This chert block is intruded by microgabbro dikes, from which 13 samples were analyzed. Petrography, XRF, ICPMS, XRD and microprobe analyses were done in order to characterize the tectonic setting of the mafic rocks. Whole rock major and trace element analysis, including rare earth element analysis, allowed us to characterize two groups of samples. Group I comprises microgabbro with abundant clinopyroxene and albite and scarce mica. Clinopyroxene shows rims of amphibole, and albite is partially replaced by hyalophane. Group I is enriched in Ba (9000 ppm) which is concentrated in micas and hyalophane. Group II is formed by Na feldspar-rich microgabbro with few relicts of clinopyroxene. All samples show geochemical signatures of typical enriched mantle source (oceanic island basalts), similar to those reported from recent oceanic island basalts on the Pacific Ocean floor. Microgabbro dikes described in this paper have geochemical signatures similar to those of mafic rocks that form exotic blocks within an accretionary prism in northern Zacatecas State. This and other similarities suggest that both localities belong to the same accretionary prism of regional extent. Our results show that the exotic block of El Terrero contains dikes of geochemical affinity, We consider that shallow subduction fluids altered the microgabbro dikes during accretion, originating large ion lithophile elements enrichment (mainly Ba and K). [ABSTRACT FROM AUTHOR]

Extensional systems are characterized by multiphase reactivation of faults that are conducive to erosion, redistribution of sediments within the basin and affect the composition of the sandstones. The provenance analysis of these sedimentary sequences documents the stages of evolution of these systems, as well as the composition of the buried basement blocks. This paper is based on a rigorous petrographical analysis and point counting in 58 samples of sandstones from the Galeana sandstone member, Taraises Formation (Early Cretaceous). It documents the composition and location of source areas that led to the origin of the sandstones, and the petrotectonic evolution of the southern region of the Monterrey Trough during the Early Cretaceous. Petrographically, the Galeana sandstone member can be divided into three petrofacies and two provenance sequences that are closely related to the sedimentary environment in which they were deposited. Sedimentoclastic petrofacies A corresponds to tidal facies deposits and represents the erosion of preexisting rocks from the pre-Early Cretaceous, with a moderate influence of basement rocks of granitic and/or granodioritic and schistose composition. Sedimentary-plutonoclastic petrofacies B corresponds to a shift in lateral facies from petrofacies A (north-south). It shows a higher recycling index associated with the subaqueous dune sedimentary environment, changes in the source area composition, and internal recycling (intraformational or cannibalism). Petrofacies C marks the deposition of a second provenance sequence, represented by an east-west lateral change in petrofacies A and B. The sandstones represent the greatest exposure and erosion of deep basement rocks. The compositional differences between the lithic assemblages suggest that a sedimentary transport event occurred during the Early Cretaceous, from the Tamaulipas Arch and Terán Island in the east to the Monterrey Trough, favoring the erosion of the sedimentary cover, and to a minor degree plutonic, volcanic and low to medium-grade metamorphic rocks. Such erosion led to the deposition of the first provenance sequence (petrofacies A and B). On the other hand, the early Hauterivian represents a second provenance sequence (petrofacies C), and the major period of block exhumation. Therefore, this paper proposes that during the early Valanginian-middle Hauterivian, the Monterrey Trough was exposed to extensional processes related to strike-slip systems that produced the exhumation of basement rocks. [ABSTRACT FROM AUTHOR]

The paper presents the location of 10 translucent agate quarries discovered in the Catalanes Nacientes Arapey Archaeological Region (RACNA), which defines a procurement zone of agate in northern Uruguay. This raw material is the second-most used lithic resource in early stratigraphic contexts dated by 14C in northwestern Uruguay, following silicified sandstone. The frequency distribution of translucent agate is analyzed in two early residential hunter-gatherer sites, Pay Paso I (11,000 to 8,500 B.P.), and site K87 (10,420 B.P.), and at Catalan Seco 1 (CS-), which is a quarry-workshop site. A strong chronological basis is presented for the Pay Paso 1 site, which includes 32 radiocarbon dates that allow recognition of three early cultural components and a blade lithic technology for the initial occupation of the I site (10,930-10,880 B.P.). The paper discusses the main ways of distributing the translucent agate during the Pleistocene-Holocene transition, which are related to accessibility of the resource, lithic technology, territory, and mobility of early hunter-gatherers in the region. Movements were recorded between 140 and 170 km from residential sites to the procurement area of the agate. [ABSTRACT FROM AUTHOR]

We report the results of a magnetostratigraphic study of the San Marcos Formation in central Coahuila, at two localities along the San Marcos Fault. These localities are characterized by outcrops of a sequence of conglomerates, immature sandstone and red mudstone, cemented by hematite; the sequence was deposited in a continental environment, and has been assigned to the Early Cretaceous. All specimens, from a total of 35 paleomagnetic sites, were subjected to alternating field and thermal demagnetization, the latter being the most effective in isolating the (high temperature) characteristic magnetization. The characteristic component is unblocked between 625° and 660 °C. Both normal and reverse polarity magnetizations are represented, and the overall mean is of Dec = 352.7 °, Inc = 55.5 °, N = 3 localities (18 sites), k = 27.07, α95 = 6.8 °. This result suggests a small clockwise rotation with respect to the expected reference direction for the Cretaceous, estimated from the apparent polar wandering curve for cratonic North America. However, the data suggest that there was relative rotation between localities, and the observed rotations are more likely explained as local vertical-axis rotations. The magnetic polarity zonation in the San Marcos Formation suggests that this unit represents the Early Barremian through Early Aptian. The correlation to global magnetic polarity timescale suggests that this unit is correlative with Cupido Formation, and that the transgressive littoral facies of the Las Uvas Formation, as well as flooding of Coahuila paleo-island at Potrero Colorado, occurred in the Early Aptian. The best correlation with the global magnetic polarity time scale corresponds to the interval from M5n (normal) to M0r (inverse) approximately between 131-125 Ma. The sedimentation rate indicated by this correlation, assuming a constant rate, is relatively low (∼30-50 m/Ma) for an active tectonic environment and is more consistent with a region where accommodation is achieved by isostatic adjustment between crustal blocks (Coahuila Block and Sabinas Basin). [ABSTRACT FROM AUTHOR]

The Yegua Formation (Eocene) in the Burgos Basin is divided into three units. The lower Yegua is sandstone deposited in a near shore environment of a highstand systems tract (HST), whose top is truncated by a prominent unconformity and regional sequence boundary at around 39.5 Ma. The middle Yegua is a complex facies, which consists of basin-floor fan sandstones, channels, and unconformities corresponding to a lowstand systems tract and prograding wedge, but also includes a transgressive systems tract . The upper Yegua represents a HST, which underlies the maximum flood surface that constitutes the base of the Jackson Formation. The Yegua Formation possibly reflects the final sediment influx towards the ancestral Gulf of Mexico resulting from Laramide age uplift and orogenic deformation in Northeastern Mexico. [ABSTRACT FROM AUTHOR]

Copyright of Boletin de Geologia is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A succession of Middle Devonian sandstones and shales (Naranco Formation) occurs in the Bodón Nappe of the Cantabrian Zone. This succession extends along several tens of kilometres away and had previously been attributed to the Nocedo and/or Ermita formations of Upper Devonian age. The Naranco Formation in the western Bodón Nappe displays a wedge shape, as a result of its truncation by the Ermita angular unconformity. This geometry is correlatable with other tectonic units of the Cantabrian Zone, such as the Aramo and Corniero nappes and the Correcilla Thrust Sheet. [ABSTRACT FROM AUTHOR]

A subsurface geological modeling was carried out near the Soacha area. Based on both gravimetric and geoelectric measurements, the examination of surface geological data and the Terreros II well log, it is proposed that the basin deepens from southeast toward northwest, being the Guadalupe Group the bottom of the lithologic studied sequence. High resistivity values ranging from 300 to 380 ohm-m characterizes the Guadalupe Group, which is found at 60 m in the southeast and deepens to 240 m in the northwest of the area. Above this rock unit, following the same deeping tendence, should appear the Guaduas Formation (about 60 m thick), a thin belt of Tertiary sandstones (about 15 m thick) and non-diferentiated Tertiary-Quaternary unconsolidated sediments. Simple Bouguer Gravity anomaly map shows variations between -142 to -149 mgal, with a regional decreasing from SE to NW that coincides in amplitude and direction with previous values for this zone. The Residual Anomaly map (ranging from 12.4 to 15.5 mgals), that was used for modeling, shows a relative gravity minimum which matches the trend of deeping and position of the basin and it borders a strong gradient anomaly, suggesting the continuity of the Sucre Fault in the subsurface, with a N45°W direction. [ABSTRACT FROM AUTHOR]

The resistivity survey carried out at the upper valley of the Patía River, provided good information to define the sedimentary sequence of the area. A general sequence from top to base is described as follows: recent deposits with resistivity values between 20 and 400 Ohm-m, fine to medium grain, sandstones with resistivity values between 20 and 70 Ohm-m, fine grain sandstones and silstones with resistivity values between 8 and 20 Ohm-m, and clayli basement, with resistivity less than 20 Ohm-m. There are two kinds of aquifers; free, related to sands and gravels from alluvial fans and terraces (resistivity values between 70 and 400 Ohm-m and thickness between 25 and 75), semi-confined related to tertiary sandstones (resistivities values between 20 and 30 Ohm-m, thickness between 35 and 150 m). The water quality of the upper aquifers is good enough with small amounts of salt content. saline water is found at the lower aquifer. The resistivity method was useful to locate geological discontinuities; some of them found with surface expression associated with lineaments and faults. Some of these geological features have been mapped in previous geological works on the area. In general the interpretation based on the resistivity results shows a block tectonics environment affecting cretaceous and tertiary rocks and probably the quaternary deposit. [ABSTRACT FROM AUTHOR]

The spontaneous potentials, SP, has been observed in two different mediums. In one of them, soil is underlayed by clays and in the other by sandstones. In both cases, time dependency has been observed, and range of values has been established: 10 mv for clays and 0.6 mv for sadstones, if there exists lateral homogenity. Because the SP method is really fast and low cost, it provides a wide range of possibilities for doing research. [ABSTRACT FROM AUTHOR]