Pedro A. Ruiz-Ortiz

Lower Aptian carbon isotope stratigraphy from a distal carbonate shelf setting: the Cau section, Prebetic zone, SE Spain

A N 13 C curve is reported for the latest Barremian to Early Aptian at a section located in the Prebetic zone (Cau section, SE Spain). The studied section records a hemipelagic succession of dark shales, deposited on a distal carbonate ramp with a high subsidence rate, adjacent to shallow carbonate environments. The integrated biostratigraphy of the section is based on ammonites, planktonic foraminifera and calcareous nannofossils, and it has allowed an accurate dating of the succession. The N 13 C curve presented shows a distinctive evolution, leading to the recognition of three major excursions, as well as a subdivision into eight segments, which represents an improvement of the current biostratigraphic resolution. The correlation, both isotopic and biostratigraphical, with other well resolved sections is very accurate even at the higher resolution attained. Correlation with sections with lowresolution biostratigraphic characterisation from shallow platform limestones also gives good results, which supports the effectiveness of carbon isotope stratigraphy as a correlation tool.

Calcareous tempestites in pelagic facies (Jurassic, Betic Cordilleras, Southern Spain)

Calcareous tempestite levels interbedded with Ammonitico Rosso and other related pelagic facies have been recognized. The previously described examples of calcareous tempestites in pelagic facies are scarce. The studied outcrops are Middle and Late Jurassic in age and correspond to ancient sediments in the Southern Iberian Continental Paleomargin. These outcrops are now included in a notably deformed geological unit (External Subbetic) in the External Zones of the Betic Cordillera. The calcareous tempestites are calcarenite and calcisiltite beds, grainstone and packstone with peloids and bioclasts (mainly ‘filaments’ and Saccocoma), showing an internal structure with hummocky cross-stratification. The deposits are thought to be formed by tropical storms and hurricanes and their recurrence intervals have been estimated (200 ka in average). The presence of these calcareous tempestite levels and the symmetrical wave-ripples on the top of the beds are two important arguments in favour of a palaeobathymetric interpretation of related pelagic sediments in the sense that the deposition occurred below, but near to the storm wave base, and that calcareous tempestites are episodic resedimentation, mainly coincident with relative sea-level falls (lowstand phases), in which major storm waves affect the sea bottom.

A review of polyphase karstification in extensional tectonic regimes: Jurassic and Cretaceous examples, Betic Cordillera, southern Spain

Abstract Five karstification phases are recognized and analysed in the Mesozoic carbonate sequences of the External and Internal Subbetic (Betic Cordilleras, southern Spain). These phases are related to important stratigraphic discontinuities in the following ages: (1) Intra-Carixian, (2) Early–Middle Jurassic boundary, (3) late Bathonian–early Callovian, (4) Intra-Kimmeridgian, and (6) late Albian. The importance of each karstification phase is variable according to the region. Moreover, not all the karstic phases occur in every area, although in some places several phases may be superimposed, appearing as discrete palaeokarst features or overprinting earlier ones. In the case of polyphase karstification each successive karstic process modified earlier features and was also conditioned by them. This interdependence complicates any attempt to isolate the individual karst events. The interpretation of the genetic history of the palaeokarst as a whole, therefore, requires the integration of data from different outcrops, where they need to be particularly well exposed. This is the only way to arrive at an accurate hypothesis. The five described palaeokarst phases are closely related to the rifting evolution of the Southern Iberian palaeomargin. They coincide with episodes of sudden sea-level fall in the External and Internal Subbetic caused by local tectonic events, commonly involving block-tilting related to the movement of listric faults differing in magnitude in each palaeogeographic–palaeotectonic range, and eustatic sea-level changes.

Evolution of pelagic swells from hardground analysis (Bathonian–Oxfordian, Eastern External Subbetic, southern Spain)

The Middle Bathonian to Middle Oxfordian interval in the Eastern External Subbetic (Betic Cordillera, SE Spain) is characterized by Ammonitico Rosso facies including various stratigraphic breaks. Five hardground-bounded units are recognized in relation to hiatuses in the ammonite record at the following stratigraphic boundaries: Hg1 (Lower–Middle Bathonian), Hg2 (Middle–Upper Bathonian), Hg3 (Lower–Middle Callovian), Hg4 (Middle–Upper Callovian), and Hg5 (Callovian–Oxfordian). Interesting features of these hardgrounds include their microfacies, ferruginous crusts and macro-oncoids, taphonomy of macroinvertebrates, trace fossils, neptunian dykes, and the hiatuses associated with each of them. The main hardgrounds (Hg1, Hg2, and Hg5) contain trace fossils of the Cruziana and Trypanites ichnofacies as well as abundant fossil macroinvertebrates with taphonomic features evidencing corrasion, early diagenesis, and reworking, indicating substrate evolution from softground to hardground. Neptunian dykes affected the trace fossils and ammonoid moulds, and their walls and the hardground surfaces were colonized by ferruginous microbial crusts. These features are characteristic of the External Subbetic pelagic swells, where the absence of sedimentation, sediment bypassing and erosion, and early diagenesis during relative sea-level falls produced hardgrounds. The neptunian dykes are indicative of tectonic activity in the areas of pelagic swells. Ferruginous crusts and macro-oncoids developed only on hardground surfaces and neptunian dykes walls prior to deposition of condensed bioclastic beds, which are interpreted as the first deposits after hardground development and are related to the onset of transgression. The varying ranges of the gaps as well as lateral facies changes are related to different local paleobathymetry controlled by the activity of listric faults.

An integrated analysis (microfacies and ichnology) of a shallow carbonate-platform succession: upper Aptian, Lower Cretaceous, Betic Cordillera

Four lithofacies and 12 microfacies types recognized in an upper Aptian section in the Sierra de Bedmar-Jódar (Prebetic of Jaén) represent shallow lagoonal environments (marl and marly limestone) and sand bars that delimited the lagoon. The lagoonal facies reflect subtidal restricted water circulation with low energy. The sand bar facies (intertidal environment) have upper surfaces that show the effects of supratidal and subaerial conditions. The presence of early fractures in particular lithofacies shows the importance of local synsedimentary tectonics during sedimentation. Thalassinoides, ?Arenicolites, Diplocraterion, Circolites, Gastrochaenolites and Trypanites are recorded in different beds of this section, reflecting various states of substrate consistency, in the form of firmground, hardground, and rockground. Whereas firmground conditions were dominant in the lower part of the section, hardgrounds and rockgrounds are mainly present in the upper part of the section. Four types of shallowing-upward elementary sequence are recognized. All the sequences show at the base mudstone or wackestone microfacies representing a lagoonal environment, overlain by sand-bar grain-pack-stone facies corresponding to a bar bounding the lagoon. The factors that controlled their development were carbonate production and tectonic movements.