Facies development of a Late Ordovician mixed carbonate-siliciclastic ramp proximal to the developing Taconic orogen: Lourdes Formation, Newfoundland, Canada

The Upper Ordovician (late Whiterockian to Mohawkian) Lourdes Formation represents a narrow (tens of kilometers), short-lived [∼5–7 million years (my)], open-ocean (high-energy) mixed siliciclastic-carbonate ramp that onlapped allochthonous strata along the orogen side of the local Taconic foreland basin. Platform development followed a 6–8 my hiatus during which weathering had concentrated chemically mature siliciclastics that were admixed with initial carbonate sediments. A cross-platform facies gradient contains paleokarst and peritidal carbonates and sandstones, shallow-ramp carbonate bioherms and skeletal shoals, and deeper ramp calcareous shales. Transgressive systems tracts are marked by ramp-wide sheets and shoals of skeletal grainstone and low accumulation rates, and highstand systems tracts are marked by significant admixture and interbedding of siliciclastics with cross-ramp carbonate facies. Platform demise coincides with increased siliciclastic input, which is likely tectonically influenced. The Lourdes platform is equivalent to epicontinental foreland ramps along eastern Laurentia, but its narrower width precluded formation of oceanographically restricted platform-interior facies.     

Mesozoic tectono-sedimentary evolution of Rocca Busambra in western Sicily

The Rocca Busambra ridge in western Sicily is a shallow to pelagic Meso-Cenozoic carbonate structural unit of the Sicilian Chain with a variety of tectono-sedimentary features. Palaeofaults, unconformities (buttress unconformity, onlap, downlap), a network of neptunian dykes with several infilling generations, several large hiatuses, different facies and lateral facies changes, and erosional submarine and subaerial surfaces are observed. Detailed fieldwork and structural analyses have indicated the occurrence of fault planes with different orientations. These data, combined with facies studies and physical-stratigraphy analyses, allow for the distinction of different depositional regions. A lateral change from an open-marine carbonate platform with a stepped fault margin (located in the westernmost sector) to a deeper basinal depositional setting in the east, in the context of an upper slope scalloped margin and base-of-slope systems with talus breccias, is envisaged here. Extensional to transtensional tectonic pulses punctuated the sedimentary evolution during Early Toarcian, Late Jurassic, Early Cretaceous, Late Cretaceous, and Early Miocene times. The collected data show that most fault planes have preserved their original orientations throughout the reactivation processes. The reconstructed Meso-Cenozoic tectono-sedimentary evolution is closely related to the late syn-rift and post-rift tectonic evolution of the Tethyan continental margin.     

Carbonate facies evolution from the late albian to Middle Cenomanian in Southern Istria (Croatia): influence of synsedimentary tectonics and extensive organic carbonate production

Summary During the Late Albian, Early and Middle Cenomanian in the NW part of the Adriatic Carbonate Platform (presentday Istria) specific depositional systems characterised by frequent lateral and vertical facies variations were established within a formerly homogeneous area, ranging from peritidal and barrier bars to the offshore-transition zone. In southern Istria this period is represented by the following succession: thin-bedded peritidal peloidal and stromatolitic limestones (Upper Albian); well-bedded foreshore to shoreface packstones/grainstones with synsedimentary dliding and slumping (Vraconian-lowermost Cenomanian); shoreface to off-shore storm-generated limestones (Lower Cenomanian); massive off-shore to shoreface carbonate sand bodies (Lower Cenomanian); prograding rudist bioclastic subaqueous dunes (Lower to Middle Cenomanian); rudist biostromes (Lower to Middle Cenomanian), and high-energy rudist and ostreid coquina beds within skeletal wackestones/packstones (Middle Cenomanian). Rapid changes of depositional systems near the Albian/Cenomanian transition in Istria are mainly the result of synsedimentary tectonics and the establishment of extensive rudist colonies producing enormous quantities of bioclastic material rather than the influence of eustatic changes. Tectonism is evidenced by the occurrence of sliding scars, slumps, small-scale synsedimentary faults and conspicuous bathymetric changes in formerly corresponding environments. Consequently, during the Early Cenomanian in the region of southern Istria, a deepening of the sedimentary environments occurred towards the SE, resulting in the establishment of a carbonate ramp system. Deeper parts of the ramp were below fair-weather wave base (FWWB), while the shallower parts were characterised by high-energy environments with extensive rudist colonies, and high organic production leading to the progradation of bioclastic subaqueous dunes. This resulted in numerous shallowing- and coarsening-upwards clinostratified sequences completely infilling formerly deeper environments, and the final re-establishment of the shallow-water environments over the entire area during the Middle Cenomanian.     

Origin and evolution of an Upper Jurassic complex of carbonate buildups from Zegarowe Rocks (Kraków–Wieluń Upland, Poland)

The Upper Jurassic complex of Zegarowe Rocks is situated on the Kraków–Wieluń Upland in southern Poland. The complex is dominated by massive limestones representing carbonate buildups. The successive stages of carbonate buildup development include: colonisation, aggradational growth and progradation phases. In the colonisation phase, on top of loose peloidal-ooid sands micritic peloidal thrombolites developed. Peloidal and agglutinated thrombolites and stromatolites proliferated during the aggradational growth phase, whereas the progradation phase was characterised by shallowing and related development of agglutinated stromatolites with coprolites. The latter were the effect of periodical stabilisation of detrital sediments by microbial mats. The Zegarowe Rocks complex developed upon an elevation of the Late Jurassic stable northern shelf of the Tethys. This elevation was formed due to local decrease in subsidence rate, induced by the presence of a Palaeozoic granitoid intrusion in the shelf substratum. The carbonate buildups of the Zegarowe Rocks complex, initially developing as sediment-starved mounds upon fault-controlled intraplatform highs under strongly restricted background sedimentation rate, were replaced by agglutinated microbial reefs.     

Facies patterns of a tectonically-controlled Upper Triassic platform-slope carbonate depositional system (Carnian Prealps, Northeastern Italy)

Summary Upper Triassic (Middle-Upper Norian) shallow-water carbonates of the Dolomia Principale and its deep-water counterparts (Forni Dolomite) have been studied in the Carnian Prealps (northeastern Italy). The Dolomia Principale was a storm-dominated carbonate platform; in the Mt. Pramaggiore area, along a well-preserved 3.5 km-long platform-to-basin transition, the inner platform facies of the Dolomia Principale, characterized by m-scale shallowing upward cycles, give way seaward to open marine storm-dominated shallow subtidal lagoon deposits with frequent hardgrounds and evidence of microbial stabilization of the bottom sediment. The margin of the Dolomia Principale platform was colonized by meter-scale stromatolites and serpulid-microbial mounds that thrived due to the local highly stressed environment, characterized by drastic salinity fluctuations and turbid waters, that excluded the Upper Triassic coral-sponge communities. The Forni Dolomite slope-basin complex was characterized by an upper slope facies with debris flows, megabreccias, turbidites and serpulid-microbial mounds. The lower slope and basinal facies show thinning and fining trends. After restoring the original geometry of the slope, the depositional angles of the clinoforms range between 11 and 36 degrees, reflecting closely the coarse-grained character of the Forni Dolomite slope complex, which can be interpreted as a slope apron that, as a model, can be extended to steeply inclined carbonate slopes. The onset of synsedimentary extensional tectonics at the Middle-Late Norian boundary affected the platform-slope depositional system via: 1) localized inner platform collapses and the formation of an intraplatform anoxic depression at Mt. Valmenone, 2) a switch from platform lateral progradation during the Middle Norian to vertical aggradation in the Late Norian, reflected in an increase in platform relief, steeper foreslope angles and coarser-grained slope facies, and 3) controlling the spatial orientation of the margin of the Dolomia Principale.     

Anisian (middle triassic) buildups of the Northern Dolomites (Italy): The recovery of reef communities after the permian/triassic crisis

Summary After the end-Permian crisis and a global ‘reef gap’ in the early Triassic, reefs appeared again during the early Middle Triassic. Records of Anisian reefs are rare in the Tethys as well as in non-Tethyan regions. Most Anisian reefs are known from the western part of the Tethys but there are only very few studies focused on biota, facies types and the paleogeographical situation of these reefs. From the eastern part of the Tethys, Anisian reefs, reefal buildups or potential reef-building organisms have been reported from different regions of southern China. Most of the Anisian reefs known from western and central Europe as well as from southern China seem to be of middle and late Pelsonian age. The study area is situated in the northern Dolomites (South Tyrol, Italy) southeast of Bruneck (Brunico). It comprises the area between Olang (Valdaora) and Prags (Braies). The study is based on detailed investigations of the regional geology, stratigraphy and lithofacies (R. Zühlke, T. Bechst?dt) as well as on a comprehensive inventory of Anisian reef organisms (B. Senowbari-Daryan, E. Flügel). These data are used in the discussion of the controls on the recovery of reefs during the early Middle Triassic. Most late Anisian reef carbonates studied are represented by allochthonous talus reef blocks of cubicmeter size. Small biostromal autochthonous mounds are extremely rare (Piz da Peres). The reef mounds as well as most of the reef blocks occur within the middle to late Pelsonian Recoaro Formation. They were formed on the middle reaches of carbonate ramps in subtidal depths, slightly above the storm wave base with only moderate water energy. Most lithotypes observed in the reef blocks correspond to sponge and/or algal bafflestones. Low-growing sessile organisms (Olangocoelia (sponge, alga?), sphinctozoan sponges, bryozoans, soleno-poracean algae, corals) and encrusting epibionts (sponges, porostromate algae, cyanophycean crusts, foraminifera, worms, microproblematica) created low cm-sized biogenic structures (bioconstructions) which baffled and bound sediment. Organic framework was only of minor importance; it is restricted to theOlangocoelia lithotype. Framework porosity was small in these reef mounds. Submarine carbonate cements, therefore, are only of minor importance s compared with Permian or Ladinian reefs. The relatively high number of lithotypes encountered in the reef blocks indicates a high biofacies diversity. Regarding the relative frequency, the diverse biota consist in descending order ofOlangocoelia, sponges (sphinctozoans, inozoans, siliceous sponges), bryozoans, porostromate algae and worm tubes. The sphinctozoans are characterized by small, mostly incrusting forms. The numerical diversity (species richness) is low compared with late Permian or Ladinian and late Triassic sphinctozoan faunas occurring within reefs. Following the sponges, monospecific bryozoans (Reptonoditrypa cautica Sch?fer & Fois) are the most common organisms in the reef limestones. Porostromate algae were restricted to areas within the bioconstructions not inhabited by sponges. The low-diverse corals had no importance in the construction of an organic framework. Surprisingly, microbial crusts are rare or even lacking in the investigated Anisian bioconstructions. This is in contrast to late Permian and Ladinian as well as Carnian reefs which are characterized by the abundance of specific organic crusts. The same comes true for‘Tubiphytes’ which is a common constituent in Permian, Ladinian and Carnian reef carbonates but is very rare in the Anisian of the Olang Dolomites. Instead of‘Tubiphytes’ different kinds of worm tubes (spirorbid tubes, Mg-calcitic tubes and agglutinated tubes) were of importance as epifaunal elements. Macrobial encrustations consisting of characteristic successions of sponges, bryozoans, algae, worm tubes and microproblematica seem to be of greater quantitative importance than in Ladinian reefs. Destruction of organic skeletons (predominantly of bryozoans) by macroborers (cirripedia?) is a common feature. The Anisian reef organisms are distinctly different from late Permian and from most Ladinian reef-builders. No Permian Lazarus taxa have been found. New taxa: Sphinctozoan sponges—Celyphia? minima n.sp.,Thaumastocoelia dolomitica n. sp.,Deningeria tenuireticulata n. sp.,Deningeria crassireticulata n. sp.,Anisothalamia minima n.g. n.sp., Inozoan sponges-Meandrostia triassica n.sp. Microproblematica-Anisocellula fecunda n.g. n.sp., Porostromate alga-Brandneria dolomitica n.g. n.sp. Most of our data are in agreement with the model described byFois & Gaetani (1984) for the recovery of reef-building communities during the Ansian but the biotic diversity seems to be considerably higher than previously assumed. Anisian deposition and the formation of the reef mounds within the Pelsonian Recoaro Formation of the Dolomites were controlled by the combined effects of synsedimentary tectonics and eustatic changes in sea-level. During several time intervals, especially the early Anisian (northern and western Dolomites: tectonic uplift), the early Pelsonian (eastern Dolomites: drowning) and the late Illyrian (wide parts of the Dolomites: uplift and drowning), the sedimentation was predominantly controlled by regionally different tectonic subsidence rates. The amount of terrigenous clastic input associated with synsedimentary tectonics (tectonic uplift of hinterlands) had a major influence on carbonate deposition and reef development. The re-appearance of reef environments in the Olang Dolomites was controlled by a combination of regional and global factors (paleogeographic situation: development of carbonate ramps; decreasing subsidence of horst blocks; reduced terrigenous input; moderate rise in sea-level).     

Are red wood ants (Formica rufa-group) tectonic indicators? A statistical approach

Recent research in seismically active areas indicated that the spatial distributions of geochemical soil gas anomalies and nests of red wood ants (RWA; Formica rufa-group) are strongly correlated. Here we applied a modified Hough Transform (mHT) and an Iterative Mode Detection (IMD) to RWA nest positions, which we mapped in two Southwest German study areas (Black Forest and Bodanrück), to test for statistical significance of correlation with tectonic features. RWA densities in the seismically active study areas reaching up to 1600 nests/100 ha are about 100× higher than overall values for Northern and Southern Germany. Since the shape of edges of the study area was found to strongly influence the selection of distribution patterns, all subsequent analyses were carried out for circular study areas. Results of the mHT applied on the RWA nests in both study areas clearly showed several modes which correspond to preferred directions. Centres of the modes further processed by IMD transferred into a GIS as RWA prototype lines showed very dominant directions of RWA nest distributions in right lateral strike-slip mode in WNW-ESE resp. NW-SE direction but also in extension direction caused by the recent main stress field in NW-SE resp. NNW-SSE direction. It could thus be clearly shown that the large scale spatial distribution of RWA nests directly reflects significant components of the present day stress field and its accompanying conjugated shear systems: Linear alignments of RWA nests indicate the course of active degassing faults zones and nest clusters indicate area-wide geochemical anomalies respectively crosscut zones of different fault systems. Furthermore, directions of re-activated shear systems, e.g. from Eocene-Oligocene but also from Late Jurassic that had been modified by overprinting due to changes of the main stress field could be identified. Therefore, RWA prototype lines complement and clarify the shear sense and the tectonic regime identified in previous tectonic studies. The high degree of statistical significance of these results will also allow a rating with former contrasting interpretations as to the drivers of RWA distributions.     

Uplift of the Ou Backbone Range in Northeast Japan at around 10 Ma and its implication for the tectonic evolution of the eastern margin of Asia

The Late Cenozoic uplift history of a sedimentary basin located in the axial part of the Ou Backbone Range, Northeast Japan, was studied using detailed mapping, fission-track dating and basin analysis. The subsidence analysis of the basin clarified the more complex stepwise uplift of the Ou Backbone Range. Three stages of uplift have been recognized and are interpreted to be the result of compressional stress, possibly accompanied by basin inversion. The three stages are identified as (1) a phase of surface uplift and regional unconformity (12-9 Ma), (2) a stage of differential uplift and compression (6.5-3 Ma) and (3) an intense compression stage (∼ 3 Ma). In the first stage, the eastern sector of the Backbone Range uplifted and a notable unconformity was formed at ∼ 10 Ma. The western sector remained submerged, suggesting that the eastern sector uplifted earlier than the western sector. Although the first uplift stage has been regarded as a tectonically quiet period in Northeast Japan, this tectonic event at ∼ 10 Ma is supposed to have a regional origin because coeval tectonic events took place across all Northeast Japan, as well as on the eastern margin of Asia. This study thus provides new insights into the Neogene tectonic evolution in the eastern margin of Asia.     

Tectonics, orbital forcing, global climate change, and human evolution in Africa: introduction to the African paleoclimate special volume

The late Cenozoic climate of Africa is a critical component for understanding human evolution. African climate is controlled by major tectonic changes, global climate transitions, and local variations in orbital forcing. We introduce the special African Paleoclimate Issue of the Journal of Human Evolution by providing a background for and synthesis of the latest work relating to the environmental context for human evolution. Records presented in this special issue suggest that the regional tectonics, appearance of C(4) plants in East Africa, and late Cenozoic global cooling combined to produce a long-term drying trend in East Africa. Of particular importance is the uplift associated with the East African Rift Valley formation, which altered wind flow patterns from a more zonal to more meridinal direction. Results in this volume suggest a marked difference in the climate history of southern and eastern Africa, though both are clearly influenced by the major global climate thresholds crossed in the last 3 million years. Papers in this volume present lake, speleothem, and marine paleoclimate records showing that the East African long-term drying trend is punctuated by episodes of short, alternating periods of extreme wetness and aridity. These periods of extreme climate variability are characterized by the precession-forced appearance and disappearance of large, deep lakes in the East African Rift Valley and paralleled by low and high wind-driven dust loads reaching the adjacent ocean basins. Dating of these records show that over the last 3 million years such periods only occur at the times of major global climatic transitions, such as the intensification of Northern Hemisphere Glaciation (2.7-2.5 Ma), intensification of the Walker Circulation (1.9-1.7 Ma), and the Mid-Pleistocene Revolution (1-0.7 Ma). Authors in this volume suggest this onset occurs as high latitude forcing in both Hemispheres compresses the Intertropical Convergence Zone so that East Africa becomes locally sensitive to precessional forcing, resulting in rapid shifts from wet to dry conditions. These periods of extreme climate variability may have provided a catalyst for evolutionary change and driven key speciation and dispersal events amongst mammals and hominins in Africa. In particular, hominin species seem to differentially originate and go extinct during periods of extreme climate variability. Results presented in this volume may represent the basis of a new theory of early human evolution in Africa.