Weathering events recorded in uppermost Hauterivian–lower Barremian clay-dominated continental successions from the NW Iberian Range: climatic vs. tectonic controls

Abstract

The facies and clay mineral study of clay/marl-rich levels from the Torrelapaja Formation (latest Hauterivian–early Barremian, NW Iberian Range, NE Spain) allowed to establish the palaeoclimatic and palaeoenvironmental conditions under they were generated. The muddy levels and pisoids contained therein of two logs were sampled and studied by X-ray diffraction and optical and electron microscopy. A similar mineralogical upwards trend is recorded in both logs, with a decrease in calcite coupled with an increase in quartz and orthoclase content and constant proportions in goethite, hematite, diaspore, anatase, rutile, ilmenite, and clay mineral content. The lower muddy levels have higher kaolinite content than the upper levels, where illitic phases are the dominant clay minerals. Smectite and intergrowths of illitic phases and kaolinite are also detected upwards. The kaolinite and smectite textures indicate an authigenic origin, whereas the illitic phases are former phases acting as a substrate for kaolinite crystallization. Pisoids mineralogy and texture show an in-situ origin, but some are fractured, indicating reworking processes. The mineral association found in the muddy levels is characteristic of oxisols formed under warm and humid conditions. The upward decrease in kaolinite content is coeval with an increase in the illitic phases and quartz content, related to siliciclastic input, but is also coeval with the presence of authigenic smectite. This indicates a decrease in chemical weathering, not fully registered due to the siliciclastic contribution, which was possibly associated with a change to colder, drier conditions during the latest Hauterivian–early Barremian in the studied area.

Mineralogical and Sedimentological Characterization of the Clay-Rich Sediments from Ases Cave (Cova Dets Ases, Mallorca, Spain): Origin and Classification

“…This process has been described in other caves from Romania and Spain [11,20] where the authors described the in-situ transformation of the host rock into red clay-rich sediments formed by quartz, kaolinite, smectite, and montmorillonite (as well as iron oxides and hydroxides) by hydrolysis processes. In the sediments of the Ases Cave studied here, the presence of platy kaolinites with subhedral to euhedral morphologies (Figure 5) in the terrestrial and submerged sediments is not compatible with a detrital origin since the erosion and transport processes would have altered those morphologies [31,50,51]. An additional observation that supports this conclusion is the fact that the kaolinite crystals observed in the soil sample have anhedral morphologies (Figure 6f).…”

“…As mentioned above, the genesis of the illitic phases is typical of physical weathering environments [31,54], and therefore its origin is not related to the origin of kaolinite. However, the presence of kaolinite crystals over the illitic phases plates (see Figure 6a) may indicate that the illitic phases form earlier and that they act as substrates for kaolinite crystallization, as described in other weathering environments involving soil development [51,55]. Smectite crystals have also been found over these illitic phases plates, indicating their genesis from the illite degradation [56][57][58].…”

Evaluation of Ceramic Properties of Bauxitic Materials from SE of Iberian Range

“…In the northeastern part of the Iberian Plate, where the Iberian Range is situated, a seasonal subtropical climate prevailed during the Upper and Lower Cretaceous periods. These climatic conditions were conducive to the formation of clay deposits enriched with kaolinite and illite, as well as bauxites and lateritic clays [25][26][27]. More precisely, extensive bauxite reservoirs are predominantly distributed along the emerged areas of the region [28].…”

NanoSIMS as an analytical tool for measuring oxygen and hydrogen isotopes in clay minerals from palaeosols: Analytical procedure and preliminary results

“…Under warm and humid conditions (subtropical to tropical), very effective hydrolysis is produced by intense chemical weathering, giving rise to the formation of oxisols. In oxisols (commonly known as laterites), the main clay mineral is kaolinite, along with aluminium and iron oxides, oxyhydroxides and hydroxides (e.g., Mack et al, 1993;Do Campo et al, 2018;Laita et al, 2020;Laita et al, 2022). In contrast, under drier and colder conditions there is an absence of significant hydrolysis, enhancing the formation of smectite and illite (Dhillon and Dhillon, 1991;Do Campo et al, 2018;Laita et al, 2022).…”