Evolution of the Bükk Mountains (NE Hungary) during the Middle–Late Triassic asymmetric rifting of the Vardar-Meliata branch of the Neotethys Ocean

Based on sedimentological and biostratigraphic investigations of the Middle–Late Triassic successions of the Bükk Mountains, the evolution of an upper plate margin of a rifting area was reconstructed. The Middle Anisian shallow water carbonates are succeeded by terrestrial sediments. Simultaneously with the uplift, volcanic activity starts, indicating the beginning of the rifting. The emersion was followed by rapid subsidence in the Late Anisian–Early Ladinian which corresponds to the synrift stage. Based on facies distribution of Ladinian–Carnian sediments, the half-graben structure of the basement can be outlined. Coeval existence of platforms and basins is characteristic of this period. From the end of the Fassanian, the subsidence slows down: postrift stage. At this time the thermal cooling controls the subsidence of the area. During the Late Triassic, the edges of the platforms were gradually drowned and basins conquered bigger and bigger areas. Sediments deposited on the southern shelf of the opening Vardar-Meliata branch of the Neotethys Ocean show features characteristic to the upper plate part of a rifting area, whereas sediments of the northern shelf show features characteristic to the lower plate. The opening of the Vardar-Meliata branch of the Neotethys Ocean follows the asymmetric rifting model of Wernicke (Can J Earth Sci 22:108–125, 1985) and Dixon et al. (Tectonics 8(6):1193–1216, 1989).     

The effects of differential subsidence and coastal topography on high-order transgressive-regressive cycles: Pliocene nearshore deposits of the Val d'Orcia Basin, Northern Apennines, Italy

This study focuses on the lowstand and early transgressive systems tracts of a basin-fill sequence of lower Pliocene nearshore deposits in the Val d'Orcia Basin of the Northern Apennines, Italy. The basin at that time was a semi-enclosed marine embayment, and, in the study area, its margin was subject to highly variable subsidence along the depositional strike, attributed to a decrease in tectonic displacement. The nearshore succession in the more rapidly-subsiding segment of the basin is around 20 m thick, comprising three storeys of laterally-stacked Gilbert-type delta lobes overlain by a shoal-water delta, whereas the nearshore succession in the adjacent, more slowly-subsiding segment, is up to 9 m thick. This succession is characterised by alternation of shoreface and offshore deposits, moderately wave-worked and covered by shoal-water deltaic facies.These coeval nearshore successions consist of several transgressive-regressive cyclothems. The development and lateral variation of the cyclothems was controlled by the local subsidence rate and coastal topographic gradient. Some of the cyclothems are considered to be higher-order sequences and others to be parasequences, with the former passing laterally into the latter in the area where the sea-level fall was countered by fast local subsidence. Some of the bounding surfaces are of limited lateral extent, with two parasequences passing laterally into a single one.Coastal topography controlled particularly the thickness of transgressive deposits. In the low-gradient setting of a delta plain, the relative sea-level rises caused major landward shifts of the shoreline and reduced fluvial sediment supply, with the formation of a transgressive lag in sediment-starved conditions. In the high-gradient coastal setting of the non-deltaic zone, the shoreline shift was minimal and had relatively little impact on local sediment supply, which promoted an accretionary transgression.At the end of the lowstand stage, the rate of sediment accumulation in the non-deltaic nearshore zone was lower, allowing the onset of subsequent transgression to be recorded considerably earlier than in the deltaic nearshore zone. This diachroneity suggests that facies criteria alone may not necessarily be a reliable basis for the recognition of systems tract boundaries.     

Rocky relationships: the petroglyphs of the Murujuga (Burrup Peninsula and Dampier Archipelago) in Western Australia

The petroglyphs of the Murujuga (Burrup Peninsula and Dampier Archipelago) in Western Australia are of exceptional cultural value for the nation. It is Australia’s largest and most significant collection of aboriginal rock art essentially as petroglyphs, with the number estimated at more than one million engravings. The Murujuga is a textbook example of ancient and modern times colliding as it also hosts potentially polluting, major industrial complexes such as iron ore and salt ports; liquefied natural gas, liquid ammonia and ammonium nitrate plants; railway lines, pipelines and rock quarries. The work presented in this paper is underpinned by an annual monitoring study of 10 selected sites including two control sites located on Dolphin and Gidley islands and eight test sites located closer to the industrial areas. The main rock types of the Murujuga, gabbro and granophyre, have been affected by weathering consisting of a cm-thick leached zone capped by a skin of orange and red iron and manganese oxides. The petroglyphs were engraved by removing the few top millimetres of the iron oxide-rich layer and the contrast with the paler leached zone clearly showing the carved motifs. Phosphorus is abnormally enriched in the leached zone and the surface coating, with manganese exclusively on the surface coating, demonstrating the impact of bird droppings and ‘desert varnish’ on the rocks. The colour difference and the hematite–goethite ratio, measured with a field portable reflectance spectrometer, between the background and engraving provides a tool to estimate the relative age of the petroglyphs and the selection of the backgrounds. As the fine-grained granophyres were preferentially chosen from the coarser-grained gabbros to host the petroglyphs, the goethitic (or yellower) backgrounds were prepared as canvas before being engraved. Many petroglyphs register the food items of the area, which changed as the last ice age ended and sea levels rose. We hypothesise that based on their locations and colour difference the constraint for the oldest age of the petroglyphs exceeds 17 000?years BP.     

Stratigraphy of the Upper Permian Kennedy Group of the onshore Carnarvon Basin (Merlinleigh Sub‐basin), Western Australia

Upper Permian strata contain many examples of cyclic deposition, despite the prevailing view that greenhouse conditions existed at the time. The shallow marine Upper Permian Kennedy Group, onshore Carnarvon Basin, has been studied in detail in the Kennedy Range 150 km east of the town of Carnarvon, Western Australia. The Kennedy Group exhibits cyclicity on a scale of 3–10 m, and also some larger scale changes in sedimentation. In this study, the Kennedy Group is divided into twelve informal units, designated with letters from A to L. The small‐scale cyclicity consists of stacked regressive cycles that comprise only thin highstand systems tracts and regressive systems tracts. Transgressive systems tracts are only sometimes represented by highly bioturbated green sandstone layers at cycle boundaries. Cycle tops are planar and often have extensive vertical trace fossil development down from them, as well as surface traces on them. The twelve informal units can be interpreted as being caused by changes in relative sea‐level.     

Genesis of the channel iron deposits (CID) of the Pilbara region,Western Australia

Miocene fluvial goethite/hematite channel iron deposits (CID) are part of the Cenozoic Detritals 2 (CzD2), of the Western Australian Pilbara region. They range from gravelly mudstones through granular rocks to intraformational pebble, cobble and rare boulder conglomerates, as infill in numerous meandering palaeochannels in a mature surface that includes Precambrian granitoids, volcanics, metasediments, BIF and ferruginous Palaeogene valley fill. In the Hamersley Province of the Pilbara, the consolidated fine gravels and subordinate interbedded conglomerates, with their leached equivalents, are a major source of export iron ore. This granular ore typically comprises pedogenically derived pelletoids comprising hematite nuclei and goethite cortices (ooids and lesser pisoids), with abundant coarser goethitised wood/charcoal fragments and goethitic peloids, minor clay, and generally minimal porous goethitic matrix, with late-stage episodic solution and partial infill by secondary goethite, silica and siderite (now oxidised) in places. Clay horizons and non-ore polymictic basal and marginal conglomerates are also present. The accretionary pedogenic pelletoids were mostly derived from stripping of a mature ferruginous but apparently well-vegetated surface, developed in the Early to Middle Miocene on a wide variety of susceptible rock types including BIF, basic intrusives and sediments. This deep ferruginisation effectively destroyed most remnants of the original rock textures producing a unique surface, very different to those that produced the underlying CzD1 (Palaeogene) and the overlying CzD3 (Pliocene – Quaternary). The peloids were derived both intraformationally from fragmentation and reworking of desiccated goethite-rich muds, and from the regolith. Tiny wood/charcoal fragments replaced in soil by goethite, and dehydrated to hematite, formed nuclei for many pelletoids. Additionally, abundant small (≤10 mm) fragments of wood/charcoal, now goethite, were probably replaced in situ within the consolidating CID. This profusion of fossil wood, both as pelletoid nuclei and as discrete fragments, suggests major episodic wild fires in heavily vegetated catchments, a point supported by the abundance of kenomagnetite – maghemite developed from goethite in the pelletoids, but less commonly in the peloids. The matrix to the heterogeneous colluvial and intraformational components is essentially goethite, primarily derived from modified chemically precipitated iron hydroxyoxides, resulting from leaching of iron-rich soils in an organic environment, together with goethitic soil-derived alluvial material. Major variations in the granular ore CID after deposition have resulted from intermittent groundwater flow in the channels causing dissolution and reprecipitation of goethite and silica, particularly in the basal CID zones, with surface weathering of eroded exposures playing a role in masking some of these effects. However, significant variations in rock types in both the general CID and the granular ore CID have also resulted from the effects of varied provenance.     

Rheological controls on extensional styles and the structural evolution of the Northern Carnarvon Basin,North West Shelf,Australia

The extensional architecture of the Northern Carnarvon Basin can be explained in terms of changes in lithospheric rheology during multiphase extension and lower crustal flow. Low‐angle detachments, while playing a minor role, are not considered to have been the primary mechanism for extension as suggested in previous models. Early extension (Cambrian‐Ordovician) in the Northern Carnarvon Basin is characterised by low‐angle detachment structures of limited regional extent. These structures have a spatial association with a Proterozoic mobile belt on the margin of the Pilbara Craton. Thermo‐mechanical conditions in the mobile belt may have predisposed the highly deformed crust to thin‐skinned extension and detachment development. Permo‐Carboniferous extension generated an extensive wide rift basin, suggesting ductile rheologies associated with intermediate lithospheric temperatures and crustal thickness. Thick Upper Permian to Upper Triassic post‐rift sequences and marked thinning of the lower crust occurred in association with only a small amount of extension in the upper crust. This observation can be reconciled by considering outward lower crustal flow, from beneath the basin towards the basin margin, following extension. Strong mid‐crustal reflectors, which occur over large areas of the Northern Carnarvon Basin, probably represent a boundary between flow and non‐flow regimes rather than detachment fault surfaces as in previous models. Crustal thinning and thermal decay following Permo‐Carboniferous extension contributed to the increased strength and brittle behaviour of the lithosphere. Consequently, Late Triassic to Early Cretaceous extension resulted in the development of far more localised narrow rift systems on the margins of the preceding wide rift basin. Diapiric intrusions are associated with the narrow rift basin development, resulting from either remobilisation of ductile lower crustal rock or the initial formation of sea‐floor spreading centres.     

西太平洋暖池扩张对华北平原气候变化的影响——华北平原4万年以来升温事件的新证据

河北省黄骅市关家堡孔（ＨＧ１）,孔深４１．３ｍ,地层连续、化石丰富、分辨率高,其所含微体化石,清楚地揭示了华北平原４万年以来两次大的突发性升温事件,据研究这两次升温事件在时序上与全球性的升温事件是同步的：第一次由冷变暖起始于４００００ａＢ．Ｐ．（沧州海进期）;第二次为１００００ａＢ．Ｐ．（天津海进期）。第一次升温事件（沧州海进期）华北平原的年平均温度比今高７℃左右;比其以前的降温事件期（沧州海进与白洋淀海进之间的海退期）至少高１３℃,如此大幅度的升温事件可能是受西太平洋赤道暖池扩张影响的结果。第一次升温事件期间存在着一个短暂的变冷事件。第二次升温事件期（天津海进期）,其年平均温度比今高２～３℃。     

Discussion of ‘Oceanographic and eustatic control of carbonate platform evolution and sequence stratigraphy on the Cretaceous (Valanginian–Campanian) passive margin,northern Gulf of Mexico’ by Phelps et al. (2014), Sedimentology, 61, 461–496

Errors in Phelps et al. ( 2014 ) arise from: (i) inclusion of the East Texas Basin and basin‐flank formations in a regional stratigraphic transect purported to represent the San Marcos Arch (axis of the Comanche Platform, central and south Texas); and (ii) revision of Edwards Group strata (Person Formation) that ignores well‐documented studies in the subsurface and adjacent outcrops in the Balcones fault zone and Edwards Plateau. Consequently, the Upper Albian Composite Sequence 104–101 of Phelps et al. ( 2014 ) should be revised from one cycle to three and the upper boundary of the Albian Supersequence should be elevated to 99·6 Ma.