Boletín Geológico y Minero

First tracks of giant land turtles from the Iberian Lower Cretaceous (Soria, Spain): Testudopodus iberiae, new ichnogenus new ichnospecies

Sat, 30 Mar 2024 00:00:00 +0100

This paper analyzes the footprints of the “Valdelalosa III” site, belonging to the eastern sub-basin of the Cameros Basin (Iberian Mountains), Huérteles Formation, dated to the middle-upper Berriasian (basal Cretaceous) and located in the Valles de Valdelalosa, in the San Pedro Manrique municipality (Soria, Spain). The footprint impressions are circular or oval in shape and occasionally impress three-four short, rounded nails. There are 106 footprints at the site, of which 76 are isolated tracks, 11 make up a track, 15 are sub-tracks and 4 are partial tracks. The trakway is made up of parallel footprints that maintain a constant distance from each other, a diagnostic characteristic of turtle trackways. The footprints have been compared morphologically and morphometrically with other fossil turtle footprints, with current turtle footprints, and with the pes and manus of various current specimens of giant terrestrial turtles. The results obtained from the analysis of the footprints of the “Valdelalosa III” site allow us to attribute them to the passage of
large terrestial turtles, and due to their features the new ichnotaxon Testudopodus iberiae new ichnogen. new ichnosp. is proposed.

Statistical Evaluation of the classification-milling loop of the carbon in pulp plant of Antapite of the Company Sierra Sun Group (Peru) using regression analysis and ANOVA

Sat, 30 Mar 2024 00:00:00 +0100

This manuscript involved a statistical evaluation of the milling-classification loop of the Antapite gold plant in Perú. The current metallurgical process is based on the carbon in pulp, which treats a head gold grade ore of 29.5 g/t. Nowadays, the milling loop uses a ball mill, whose discharged ore feeds a conventional Krebs hydrocyclone. Under current operating conditions, 71.30% of the gold concentrate is <74 μm (of 10 inches). Nevertheless, the objective was to increase at least 5 points in percentage the gold content in the concentrate to optimize the gold recovery in the cycyanidation-adsorption loop. This objective was solved by means of a multivariate statistics regression model to study the dependency of the variables in three different scenarios, eliminating
the non-significative statistical variables. The first scenario included the dependence of the cut size, d50C, with respect to the pressure and the feeding flow to the hydrocyclone. The second scenario involved the analysis of the dependence of the gold concentrate <74 μm with respect to the feeding flow, pressure, d50 and d50C. Finally, the third scenario included the evaluation of the gold concentrate <74 μm and d50C. Later, and once defined the parameter that would have influenced the variable of the gold concentrate <74 μm with the studied variables, it was possible to find the value of d50 correlated with the flow and working pressure to obtain the objective cut size of 77.39% of gold concentrate with < 74 μm.

Evidences for a Rotational Variscan Deformation from Distorted Brachiopods (Meseta, Morocco)

Kawtar Nassri, Abdessamad El Adraoui — Sat, 30 Mar 2024 00:00:00 +0100

In 2021-2022, the construction work of the coastal road R322, connecting the Kasbah of Oudayas (Rabat) with the seaside resort of Bouznika, has made it possible to observe schists with brachiopods (Spirifer sp.) of the Upper Visean in the Val d’Or beach, 12 km at the SW of Rabat. The structural analysis of the collected samples shows deformed fossils on the XY plane of the slaty cleavage (S1), affected by D2 recumbent, west-vergent folds and an associated N-S trending crenulation cleavage (S2). The fossils of Spirifer sp. are triangular in shape, recalling a butterfly. The fossils show a bilateral symmetry in their undeformed state, with two perpendicular directions forming a T (sinus or symmetrical line and hinge). After deformation, these lines intersect with an acute/obtuse angle indicating the distortion of fossils. Measurements of the shear angles lead us to reconstruct the Mohr circle referred to strained conditions and obtain the shape and orientation of the finite deformation ellipse. This method makes it possible to find the axial ratio of the finite strain ellipse from Mohr circles. Our results are compared with those obtained by Wellman’s method and Breddin abacus. A structural model is proposed to explain the studied ductile deformation, which we suggest it is related to dextral, N-S trending shear zones.

Increase in the geotechnical heritage of rock cut-tomb builders between the Old and Middle Kingdom (Qubbet el-Hawa Necropolis, Aswan)

Juan Antonio Martínez Hermoso, Israel García Mellado, Mario Sánchez Gómez — Sat, 30 Mar 2024 00:00:00 +0100

The hill of Qubbet el-Hawa was the site chosen for the cemetery of the high officials of the southernmost province of Ancient Egypt, from the end of the Old Kingdom to the end of the Middle Kingdom. To date, around a hundred tombs excavated in the rock have been discovered in the middle of the hillside, distributed throughout several superimposed terraces. From the geological/geotechnical study it was the best possible location, in a section where sandstone predominates, delimited by two especially resistant strata that serve as the floor and roof of the hypogea, which in principle guaranteed their stability. In this article we analyze two representative tombs from the two most important periods of the cemetery: QH34h (Sixth Dynasty) and QH33 (Twelfth Dynasty), built with a time difference of about 400 years. From the fracturing study and the analysis of the geological stability in these tombs, we verified that the most modern (QH33), compared to the oldest (QH34h), presents construction and design innovations that solved the stability problems
that some of the oldest tombs presented. the oldest graves. This study shows that, firstly, the choice of the location of the tombs was made based on the resistant nature of the strata, secondly, that the construction methods used by the ancient Egyptians were conditioned by the geology of the hill and, thirdly that, as a result of the experience acquired over the years, the design of the tombs evolved to solve the stability problems of the rock mass.