ALBERT

Description: The Santa Lucía Formation represents the major phase in Devonian reef development of the Cantabrian Zone (Cantabrian Mountains, northwest Spain). In the present study the transition from the carbonate platform deposits of the Santa Lucía Formation to the overlying euxinic basinal deposits of the Huergas Formation is described. These transitional strata are connected to the Basal Choteč Event and represent a condensed sedimentation of micritic dark-grey and black limestones with an upward increase of dark shale intercalations with iron mineralisation surfaces and storm-induced brachiopod coquinas. The transitional beds are grouped into a new unit, the Cabornera Bed, which consists of limestone, limestone-shale and shale facies associations, representing a sediment-starved euxinic offshore area just below the storm wave base. Four stages in reef decline can be recognised: a reef stage, an oxygen-depleted, nutrient-rich stage, a siliciclastic-influx stage and a pelagic-siliciclastic stage. Additional geochemical and geophysical investigations are needed to verify the results presented herein.

Description: Relative sea level fluctuations during the Frasnian generated two shallow-marine, mixed siliciclastic-carbonate successions in the Devonian Asturo-Leonese Basin. Each system represents a third-order sequence-stratigraphical unit deposited in the same basin during comparable extreme greenhouse conditions without nearby fluvial entry points. Depositional control on the siliciclastic and carbonate distribution was driven by relative sea level fluctuations, basin geometry, availability of sand and the way sediment was distributed by shelf currents. Early Variscan flexural bending of the continental crust changed the basin shape from a shelf with a gradual profile and low dip (early Frasnian) towards a shelf with a steep depositional dip (late Frasnian). Shelf distribution changed from along-shelf transport (early Frasnian) towards offshore-directed gravity flows (late Frasnian). As a consequence, siliciclastic-carbonate distribution changed from a predominance of skeletal carbonate in the proximal shoreface – foreshore area and siliciclastic predominance distally (early Frasnian), to a distribution pattern with proximal shoreface skeletal carbonates, offshore muddy carbonates and a siliciclastic zone in between where gravity flows distributed the siliciclastic sediment down dip (late Frasnian).

Description: During the Late Devonian, deposition in the Cantabrian Mountains was largely controlled by movements along faults. By way of intermitting subsidence of the area south of the Sabero-Gordón line and the connected progradation of the coast during the Frasnian and early Famennian, three regressive sequences were deposited. On account of these sequences the Nocedo Formation is divided into three units. Before the late Famennian transgression, after which the upper part of the Ermita Formation was deposited, the area was peneplained. Six facies maps show the changes in palaeogeography during the Late Devonian.

Description: Within the Cantabrian zone during the Devonian and Early Carboniferous three large palaeogeographical units were of importance: the Asturian geanticline, the Palencian basin and the Asturo-Leonesian basin. These units have a different history of sedimentation, particularly the Palencian basin. Further, in the Asturo-Leonesian basin there were some important structural elements: the Intra-Asturo-Leonesian facies line, formed by an active, normal fault parallel to the border of the basin, and two structural highs: the Pardomino high and the Somiedo high which divided the basin into three pieces. The Asturo-Leonesian basin was a narrow, shallow continental shelf which in the south and west passed into the deeper part which extended over the West Asturian-Leonese zone. With help of biostratigraphic correlations of the Middle Devonian to Early Carboniferous deposits in the Cantabrian zone, based on conodonts, an overview is given of the depositional history of the entire area. Several times during the Givetian and Frasnian a biostromal platform developed in the Asturo-Leonesian basin with small bioherms of stromatoporoids and corals at the southern border along the facies line and in the east along the León line, with a lagoon behind. In the Palencian basin the sediment supply was always smaller. There, shales and nodular limestones with pelagic faunas (Gustalapiedra Formation) were deposited. Carbonate sedimentation started simultaneously with the formation of the first carbonate platform of the Portilla Formation in the Asturo-Leonesian basin. Repeatedly the Asturian geanticline was uplifted leading to tilting of the Asturo-Leonesian basin and to erosion of the uplifted parts. The siliciclastic erosion products were deposited in the subsided parts leading to progradation of the coast with the formation of coastal barriers notably along the facies line. As soon as the supply of siliciclastics decreased, a new carbonate platform could form. The last stromatoporoid-coral biostromes formed such a platform at the end of the Frasnian in the Esla area (Crémenes Limestone in the Nocedo Formation). At the same time, in the west of the Asturo-Leonesian basin fan-deltas formed along the facies line, with conglomerates which originated from erosion at the geanticline, which then apparently extended to the facies line. The Asturian geanticline had extended gradually during the Devonian and the differences between the basins had increased. Uplift of the geanticline resulted in the emergence of the entire Asturo-Leonesian basin during the early Famennian. Then, erosion products from the geanticline were also transported into the Palencian basin by turbidity currents (Murcia Formation) interrupting the sedimentation of nodular limestones which recovered later on (Vidrieros Formation). At the end of the Famennian, due to a transgression the sea spread rapidly over the truncated geanticline. South of the Intra-Asturo-Leonesian facies line initially turbiditic storm deposits (Fueyo Formation) formed while a thin layer of sands and crinoidal grainstones (Ermita Formation) was deposited on the geanticline and in the major part of the Asturo-Leonesian basin. The entire Cantabrian zone may have been emergent during the early Tournaisian and, together with deformations in the West Asturian-Leonese zone movements lead to an inversion of the relief in the Cantabrian zone with the formation of a number of small basins in the platform. When, during the late Tournaisian a transgression lead to the spread of cold, nutrient-rich water over the entire area, some of this water stagnated in the basins so that black shales, radiolarites and phosphatic nodules (Vegamián Formation) could be deposited at the same time as the carbonate sedimentation continued on other parts of the platform. The continuation of the transgression lead to the formation of nodular limestones (Alba Formation), first only on the shallow platforms but later also in the deeper parts because circulation in the basins improved. The Variscan orogenesis lead to deformations of which some are discussed in this paper. Lithological data indicate that the Esla nappe and the Valsurvio area were displaced towards the north and later the South Cantabrian block was shifted about 15 to 20 km towards the east along the Sabero-Gordón line. The different formations and smaller lithological units are described and an informal subdivision of the Portilla Formation is proposed. The conodont faunas which were found are described. A number of interesting or problematic species is treated more extensively. The conodont biozonation is discussed. For the early Carboniferous the regional zonation of Higgins (1974) is adapted: the Polygnathus fauna and Gnathodus pseudosemiglaber Zone are introduced. Rather extensively the palaeoecology of the conodonts will be discussed.

Description: Within the Cantabrian zone during the Devonian and Early Carboniferous three large palaeogeographical units were of importance: the Asturian geanticline, the Palencian basin and the Asturo-Leonesian basin. These units have a different history of sedimentation, particularly the Palencian basin. Further, in the Asturo-Leonesian basin there were some important structural elements: the Intra-Asturo-Leonesian facies line, formed by an active, normal fault parallel to the border of the basin, and two structural highs: the Pardomino high and the Somiedo high which divided the basin into three pieces. The Asturo-Leonesian basin was a narrow, shallow continental shelf which in the south and west passed into the deeper part which extended over the West Asturian-Leonese zone. With help of biostratigraphic correlations of the Middle Devonian to Early Carboniferous deposits in the Cantabrian zone, based on conodonts, an overview is given of the depositional history of the entire area.\nSeveral times during the Givetian and Frasnian a biostromal platform developed in the Asturo-Leonesian basin with small bioherms of stromatoporoids and corals at the southern border along the facies line and in the east along the Le\xc3\xb3n line, with a lagoon behind. In the Palencian basin the sediment supply was always smaller. There, shales and nodular limestones with pelagic faunas (Gustalapiedra Formation) were deposited. Carbonate sedimentation started simultaneously with the formation of the first carbonate platform of the Portilla Formation in the Asturo-Leonesian basin. Repeatedly the Asturian geanticline was uplifted leading to tilting of the Asturo-Leonesian basin and to erosion of the uplifted parts. The siliciclastic erosion products were deposited in the subsided parts leading to progradation of the coast with the formation of coastal barriers notably along the facies line. As soon as the supply of siliciclastics decreased, a new carbonate platform could form. The last stromatoporoid-coral biostromes formed such a platform at the end of the Frasnian in the Esla area (Cr\xc3\xa9menes Limestone in the Nocedo Formation). At the same time, in the west of the Asturo-Leonesian basin fan-deltas formed along the facies line, with conglomerates which originated from erosion at the geanticline, which then apparently extended to the facies line.\nThe Asturian geanticline had extended gradually during the Devonian and the differences between the basins had increased. Uplift of the geanticline resulted in the emergence of the entire Asturo-Leonesian basin during the early Famennian. Then, erosion products from the geanticline were also transported into the Palencian basin by turbidity currents (Murcia Formation) interrupting the sedimentation of nodular limestones which recovered later on (Vidrieros Formation). At the end of the Famennian, due to a transgression the sea spread rapidly over the truncated geanticline. South of the Intra-Asturo-Leonesian facies line initially turbiditic storm deposits (Fueyo Formation) formed while a thin layer of sands and crinoidal grainstones (Ermita Formation) was deposited on the geanticline and in the major part of the Asturo-Leonesian basin. The entire Cantabrian zone may have been emergent during the early Tournaisian and, together with deformations in the West Asturian-Leonese zone movements lead to an inversion of the relief in the Cantabrian zone with the formation of a number of small basins in the platform. When, during the late Tournaisian a transgression lead to the spread of cold, nutrient-rich water over the entire area, some of this water stagnated in the basins so that black shales, radiolarites and phosphatic nodules (Vegami\xc3\xa1n Formation) could be deposited at the same time as the carbonate sedimentation continued on other parts of the platform. The continuation of the transgression lead to the formation of nodular limestones (Alba Formation), first only on the shallow platforms but later also in the deeper parts because circulation in the basins improved.\nThe Variscan orogenesis lead to deformations of which some are discussed in this paper. Lithological data indicate that the Esla nappe and the Valsurvio area were displaced towards the north and later the South Cantabrian block was shifted about 15 to 20 km towards the east along the Sabero-Gord\xc3\xb3n line.\nThe different formations and smaller lithological units are described and an informal subdivision of the Portilla Formation is proposed. The conodont faunas which were found are described. A number of interesting or problematic species is treated more extensively. The conodont biozonation is discussed. For the early Carboniferous the regional zonation of Higgins (1974) is adapted: the Polygnathus fauna and Gnathodus pseudosemiglaber Zone are introduced. Rather extensively the palaeoecology of the conodonts will be discussed.

Description: In this paper the Miocene to recent melongenid species of northwest Borneo are discussed. The recent fauna is poor with three genera represented by one species each. In the Miocene three (possibly four) genera occur with eight (possibly nine) species of which three are described as new species: Melongena murifactor, uniquely characterized by the formation of a septum walling off the adapical sector of the aperture; Pugilina erecta, characterized (along with its close Miocene relative from Java, P. ickei) by a free-edged, erect inner lip; Volema goliath, large for the genus with later whorls progressively covering the upper row of spines of earlier whorls. The apertural septum of M. murifactor is unique within Gastropoda, whereas the erect inner lip of P. erecta and P. ickei is unique within Melongenidae. That these extralimital traits occur exclusively in the Miocene of southeast Asia is consistent with the hypothesis that adaptive innovations are most likely to arise in diverse, productive, shallow-water ecosystems.

Description: A review is given of the distribution of Chondrinidae species in the Cantabrian Mountains. Few species occur in that area, Chondrina kobeltoides being the only endemic. Chondrina kobelti and C. kobeltoides are discussed and their characters are compared in a table. The taxon cliendentata is considered to be a subspecies of C. kobeltoides and not of C. kobelti as which it was originally described.

Description: During the Late Devonian, deposition in the Cantabrian Mountains was largely controlled by movements along faults. By way of intermitting subsidence of the area south of the Sabero-Gord\xc3\xb3n line and the connected progradation of the coast during the Frasnian and early Famennian, three regressive sequences were deposited. On account of these sequences the Nocedo Formation is divided into three units. Before the late Famennian transgression, after which the upper part of the Ermita Formation was deposited, the area was peneplained.\nSix facies maps show the changes in palaeogeography during the Late Devonian.