Terrestrial Clastic Sediments Research Articles

Resource utilization of stone waste and loess to prepare grouting materials

Loess, a terrestrial clastic sediment, is formed essentially by the accumulation of wind-blown dust, while stone waste (SW) is an industrial waste produced during stone machining. Utilising loess and SW to prepare environmentally-friendly supplementary cementitious materials can not only address environmental issues caused by solid waste landfills but also meet the demand of reinforcement of coal-seam floor aquifer for grouting materials. In this paper, the effects of the loess/SW mass ratio and calcination temperature on the transformation of calcined products are investigated and their pozzolanic activities are evaluated. The workability, environmental impact and cost of grouting materials based on cement and calcined products are also assessed. Experimental results reveal that higher temperatures favour the formation of free lime and periclase, which tend to be involved in solid-state reactions. Higher temperature and loess/SW mass ratio strengthens the diffraction peaks of dodecalcium hepta-aluminate (C12A7), dicalcium ferrite (C2F) and dicalcium silicate (C2S). The clay minerals in loess become completely dehydroxylated before 825 °C, generating amorphous SiO2 and Al2O3. Covalent Si–O bonds are interrupted and that disordered silicate networks are generated in the calcined products, which is confirmed by the increased strength of the Si29 resonance region at −60 ppm to −80 ppm. Although co-calcined loess and SW contain the most four-fold aluminium at 950 °C, recrystallisation depresses the pozzolanic activity. Hence, the loess/SW sample designated LS2-825 exhibits the better hydration activity. Additionally, grouting materials composed of cement and LS2-825 exhibit good setting times, fluidity, strength and a low carbon footprint in practical engineering applications, and they also provide the additional benefit of being cost effective.

Decoding the signals of sediment weathering: Toward a quantitative approach

In order to better interpret the signals of weathering intensity recorded in terrigenous sediment archives, it is essential to appropriately assess the effects of hydrodynamic sorting and sedimentary recycling. To achieve this, we utilized a compiled dataset of major element geochemistry of river sediments from East Asia to develop a quantitative index for evaluating the extent of quartz enrichment related to hydrodynamic sorting and sedimentary recycling. By leveraging the trend of present-cycle weathering products in the CIA-WIP diagram, we proposed the chemical index of quartz-enrichmen (CIQ), which can assess the hydrodynamic sorting and sedimentary recycling effects on the present-cycle weathering products. The CIQ vs. CIA/WIP diagram clearly discriminates the influences of weathering intensity, hydrodynamic sorting and sedimentary recycling on bulk sediment chemistry. In this diagram, representative sediments for the present-cycle weathering product typically cluster around CIQ = 0, and the CIA/WIP (or CIA) of which reflect the recorded weathering intensity. The application of our method to depth profiles from the world's largest rivers provides evidence supporting the utilization of sedimentary records to reconstruct paleo-weathering intensity. This study provides a practical and efficient approach to assess whether or to what extent siliciclastic sediments can accurately depict the present-cycle weathering products. This sheds new light on the quantitative deciphering of weathering intensity signals in terrestrial clastic sediments.

Source of selenium in Handan geochemical anomaly belt: Evidences from petrology and geochemistry of Upper Paleozoic in western Handan, China

Handan lies in a geochemical anomaly belt characterized by enrichment of selenium (Se) in rock, soil, and water, contrasted with deficiency of Se in the North China Plain. In this study, 27 environmental soil samples and 96 rock samples in the Upper Paleozoic were analyzed by inductively coupled plasma optical emission spectrometer (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) for major and trace element concentrations to determine the source of Se in the environment.Se concentrations in soil vary from 0.054 μg/g to 2.869 μg/g, with an average of 0.598 μg/g. Ignoring the anthropogenic contamination, Se concentrations in soils elevate with the decrease of distance from outcrops in Mountain Zishan (Mt. Zishan). There is a strong positive correlation between Se and Al2O3 (r = 0.679, P < 0.01, n = 27), and between Se and TiO2 (r = 0.638, P < 0.05, n = 27). Furthermore, Se is significantly negatively correlated with MgO, Na2O, K2O, and Sr (r = −0.674, −0.755, −0.716, −0.739, respectively, P < 0.01 for all, n = 27). It indicates that Se in the soil is derived from weathering products.Se is the most highly enriched trace element within Upper Paleozoic, which is composed of Benxi Formation (BX Fm.), Taiyuan Formation (TY Fm.), Shanxi Formation (SX Fm.), and Shihezi Formation (SHZ Fm.), in outcrops in Mt. Zishan area, western Handan. Se concentrations of rock samples vary from 0.021 μg/g to 4.971 μg/g, with an average of 0.401 μg/g. The maximum of Se concentration is 99.41 times higher than the Upper Continental Crust (UCC). The order of the rest trace elements enrichment degrees is S > Pb > As > Ga > Li > Bi > Th > Sc > In > U > Cd > Y > Rb > Ba > Cr > V > Be > Cs > Ni > Zn > Tl > Sr > Co > Mo > Cu. Se enrichment appears in two types of rocks, which are gray clay rocks and black mudstones and shales (including coal and gangue). Stratigraphically, Se is more highly enriched in TY Fm. and SX Fm., with average enrichment factor (EF) values of 14.64 and 5.59, respectively.Chemical index of alteration (CIA) and several environmentally sensitive elements, such as Th, U, Sr, Ba, V, Cr, and Ce, were employed for sedimentary environment analysis. The results revealed that Se-enriched rocks were deposited mainly in a weak, reducing freshwater environment, and their sediments were subject to an intermediate chemical weathering process. The discrimination diagrams of SiO2-TiO2, F1-F2, ∑REE-La/Yb, and La/Sc-Co/Th indicate that the terrestrial clastic sediments were dominated by multiple types of original rocks. Se-laden clastic materials derived from mafic and ultramafic rocks in Yinshan ancient land provided main source of Se in Upper Paleozoic in western Handan, and adsorption of clayey and organic materials and biological accumulation induced Se enrichment ultimately.

Detrital apatite fission track constraints on Cenozoic tectonic evolution of the northeastern Qinghai-Tibet Plateau, China: Evidence from Cenozoic strata in Lulehe section, Northern Qaidam Basin

The Northern Qaidam Basin is located at the northeastern part of the Qinghai-Tibetan Plateau. It contains very thick Cenozoic terrestrial clastic sediments, which records the formation of the northern Qaidam Basin due to compressional deformation during the Indo-Asian collision. In this paper, we used detrital apatite fission-track thermochronology, including 4 sandstones and 2 conglomerates samples from the Lulehe section, to reveal the Cenozoic evolution of the northern Qaidam Basin. Fission-track dating indicated the source region of the Lulehe section has experienced important cooling and uplifting in the Late Cretaceous (at ~85.1 Ma and ~65 Ma) and the Eocene (~52 Ma), respectively. The AFT age distribution on the section suggested that the provenance of Lulehe section sediments were mainly derived from the south Qilian Shan (Qilian Mountains) and Altun Shan (Altun Mountains), and two significantly provenance changes may occur at 43.4-46.1 Ma and ~37.8 Ma, respectively. The results may have strong constrains on the Cenozoic deformation and tectonic evolution of the northern Qaidam Basin and Qinghai-Tibet Plateau.

Sedimentary microfacies and organic geochemical characterization of mudstones in the Keluke Formation in northeastern Qaidam, China

During the Early Carboniferous, the northeastern Qaidam Basin probably formed in an active continental margin setting. Due to marine regression after the late Early Carboniferous, the marginal shelf began to receive more terrestrial clastic sediments, and alternating occurrence of carbonates and siliciclastics characterized this region. Consequently, shales or mudstones with considerable thickness were deposited in the Upper Carboniferous, especially in the Keluke Formation. In order to illuminate a more accurate sedimentary environment of shales and further evaluate the shale gas potential, multidisciplinary traditional methods were conducted including rock core examinations and laboratory analysis. Results reveal that the sedimentary microfacies of shales in the Keluke Formation can be divided into the upper shoreface, the lower shoreface, and the upper to transition offshore. These microfacies developed on a homoclinal carbonate ramp with a gentle slope. The thickest succession of mudstone develops in the lower shoreface, which is a counterpart with the lagoonal setting of a stationary hydraulic system. The quartz content of shale samples ranges from 30% to 66% and clay minerals from 24% to 43% by bulk compositional analysis, which indicates the content of brittle minerals and shales fissility to some extent. The total organic carbon content ranges from 0.5% to 7.6% by weight, with an average value of 2.69% in ZK1‐1 and 1.11% in ZK3‐2, indicating abundant organic matter richness. The kerogen is mainly of type II, which indicates that source for the organic matter is a mixture of higher terrestrial plants and acquatic organisms. The vitrinite reflectance ranges from 1.22% to 1.55%, indicating a moderate to high thermal maturity. Three types of pores are recognized in the shales, including organic pores, intrapartical pores, and interparticle pores. The significance of this work emphasizes two aspects. First, it gives a more detailed classification of sedimentary environment of the mudstone succession; second, it acquires the preliminary subsurface data regarding to the shale gas potential evaluation.

Stable isotope data from loess malacofauna: Evidence for climate changes in the Pannonian Basin during the Late Pleistocene

Loess is terrestrial clastic sediment, composed dominantly of silt-sized particles formed by the accumulation of wind-blown dust. It is usually inter-bedded with palaeosol horizons forming loess-palaeosol successions (LPS). Due to its characteristics loess represents a high quality record of climate changes in the Late Pleistocene. The thickest and best-studied loess sections in the Republic of Croatia are located in the eastern Croatian province of Baranja, near the Danube River. This area is a southern part of the Pannonian Basin. Zmajevas LPS was selected in this study. Grain-size distribution indicates that the loess from Zmajevac LPS in Baranja is typical loess, comparable with other loess profiles in the Pannonian Basin.The faunal assemblages in the loess samples prove the dominance of transitional palaeoecological assemblage types, whereas uniformly defined types are rare. Helicopsis striata assemblage is dominant, while Columella columella and Chondrula tridens assemblages are present in smaller proportion. For additional information about palaeoclimate and palaeoecology in Pannonian Basin, stable oxygen and carbon isotope ratios were measured in mollusc shells. Stable oxygen values range from −5.76‰ to −2.45‰. Stable carbon isotope values range from −8.83‰ to −6.84‰. Stable oxygen values show significant palaeotemperature changes during the Late Pleistocene, with the average growing season (AGS) temperature range of 13.24 °C or 9.457 °C, depending on which formula is applied. The overall climate was much cooler then present. Stable carbon isotope values point to dominance of C3 vegetation type during the Late Pleistocene in southern part of the Pannonian Basin.

Detrital apatite fission track evidence for provenance change in the Subei Basin and implications for the tectonic uplift of the Danghe Nan Shan (NW China) since the mid-Miocene

The Subei Basin is located at the intersection of the northeastern end of the Altyn Tagh Fault (ATF) and the western end of the Danghe Nan Shan in the northeastern Tibetan Plateau. The Basin contains (up to) 4000m-thick Cenozoic terrestrial clastic sediments, which contain information on the uplift of the Danghe Nan Shan. In order to estimate the detrital apatite thermochronology with fission track dating, we collected eight sandstone samples from the Tiejianggou section of the Subei Basin, which has an established depositional age range from 22.8 to 9Ma. We found that a distinct change in slope of the peak age and lag time of the detrital apatite fission track occurred at ∼14Ma, which we interpret as a provenance change caused by the uplift of the western end of the Danghe Nan Shan. Combined with previous studies in adjacent areas, this work implies that the initiation of successive episodes of surface uplift in the northeastern margin of the Tibetan Plateau took place in the mid-Miocene.

OSL and 14C chronologies of a Holocene sedimentary record (Garding‐2 core) from the German North Sea coast

The history of sea‐level change and sediment accumulation since the last deglaciation along the German North Sea coast is still controversial because of a limitation in the quantity and quality of chronological data. In the current study, the chronology of a 16‐ka coastal sedimentary record from the Garding‐2 core, retrieved from the Eiderstedt Peninsula in Schleswig‐Holstein, northern Germany, was established using OSL and AMS 14C dating techniques. The robust chronology using 14 radiocarbon and 25 OSL dates from the Garding‐2 core is the first long‐term record that covers the Holocene as well as the last deglaciation period in one succession in the German North Sea area. It provides a new insight into understanding the Holocene transgression and coastal accumulation histories. The combined evidence from the sedimentology and chronology investigations indicates that an estuarine environment dominated in Eiderstedt Peninsula from 16 to 13 ka, followed by a depositional hiatus between 13 and 8.3 ka, attributed to erosion caused by the Holocene transgression; the onset of the Holocene transgression at the core site occurred at around 8.3 ka. The sea level continued to rise with a decelerated rate until around 3 ka. Since 3 ka, the shoreline has begun to prograde. Foreshore (tidal flat) sediments have been deposited at the drilling site with a very high sedimentation rate of about 10 m ka−1. At around 2 ka, a sandy beach deposit accumulated in the sedimentary succession, indicating that the coastline shifted landward, which may represent a small‐scale transgression in the late Holocene. At around 1.5 ka, terrestrial clastic sediment started to accumulate, indicating a retreat of the relative sea level in this area, which may be related to local diking activities undertaken since the 11th century.

Latest Triassic climate humidification and kaolinite formation (Western Carpathians, Tatric Unit of the Tatra Mts)

The Tomanová Formation, of Rhaetian age, overlying the Norian Carpathian Keuper in the Tatra Mts. is built of cyclic parasequences of mudstones and sandstones. Quartz (15 to 70 wt.%), kaolinite (13 to 46 wt.%) and 2:1 Al dioctahedral phyllosilicates (dioct 2:1: muscovite, illite, illite/smectite: 5 to 39 wt.%) represent the major mineral phase. The kaolinite/dioct 2:1 ratio decreases upwards in the section (from 4.3 to 0.5) and signals variability in weathering/erosion intensity and changing water salinity. Major and trace elements (LILE, HSFS, REE) indicate a uniform source – felsic rocks located probably in the Vindelician Highlands. The sedimentation rate (83 mm/ky) was controlled by climate. Alternation of dry and humid periods is refered by sedimentary textures and by maturity of quartz (aeolian vs. fluvial grains), and organic matter content and composition (Corg and d13Corg). Authigenic siderite or bethierine documents wet and reduced conditions in the upper part of the Tomanová Formation. The sedimention rate of the marine Dudzinec Formation attained 25 mm/ka and the character of cycles preserved in the sequence is similar as that of the Tomanová Formation (fining upwards parasequences). However, the different clay mineralogy, the recycled character of the silicates, the different d13Corg and elevated imput of carbonate detritus with specific C and O isotopic patterns document a discontinuity in the section. The transgressive character of the Dudzinec Fm. was deduced from the stratigraphic distribution and environmental characteristics of the benthic foraminifera present. Involutinids and spirillinids dominate in the lower part, endothyrinids govern the middle part, and in the upper part nodosariids and Ammodiscus-type microfauna occur. These age-diagnostic microfossils indicate a late Rhaetian age. Sea level rise in the Tatric Zone triggered by thermal expansion of the Central Atlantic Rift was gradual, being affected by input of terrestrial clastic sediment both by freshwater and by wind. The Tatric Triassic sequence in the Western Carpathians helps understanding of the development of sedimentation, palaeoclimate (kaolinite weathering), and palaeogeography of the northernmost Tethyan Domain.

Sedimentary characteristics and source of loess in Baranja (Eastern Croatia)

Abstract Loess is a type of terrestrial clastic sediment formed by the accumulation of wind-blown dust, composed dominantly of silt-sized particles. It is usually inter-bedded with soil horizons forming loess–palaeosol successions (LPS). The thickest LPS in Croatia are found in Baranja, a region bounded by two large rivers, the Danube and the Drava. The results of grain-size and modal analysis provide information about source material and wind direction in different time periods during the Pleistocene. Grain-size distribution is in good accordance with other loess localities in the Pannonian Basin. Garnet, epidote and amphibole are the most abundant heavy minerals in samples of Danube river sediment. The comparison of heavy mineral assemblages (HMF) from LPS with that of the Danube river, shows that the main source area for loess in Baranja was in the Danube flood plain sediments. Main transport direction was from North or Northwest. Nevertheless the higher concentration of amphiboles in LPS (mean 26.3% in HMF) than in the Danube plain suggests an additional source area. Although the Western Carpathians with Neogene calc-alkaline volcanic rocks are the major source for amphiboles in the Pannonian Basin, those minerals may partly originated also from locally exposed volcanic and metamorphic rocks of the southward Slavonian Mountains. Mount Krndija and Mount Papuk, which of all Slavonian Mts. are closest to Baranja, consist indeed of amphibolites. In that case, a small amount of silt material for Baranja loess would be transported by WSW winds. Results obtained from sedimentological and SEM analyses show fairly good congruence with results from other LPS in the Pannonian Basin, with some differences in mineral composition which imply diversity and shifting of source area for Baranja loess during the Late Pleistocene.

Burd Gol Granite Massif as a product of the Late Cambrian post-orogenic magmatism in the SE part of the Lake Zone, Gobi Altay, SW Mongolia

*Corresponding author Intrusion of the Cambrian Burd Gol Granite Massif into the Proterozoic metamorphic rocks of the Zamtyn Nuruu and molasse-like sediments of the Boomyn Khudag Fm. culminated the collisional events of the Caledonian evolution in the SE part of the Lake Zone, Gobi Altay, SW Mongolia. The monotonous leucogranites of the Burd Gol Massif have a high-K calc-alkaline, subaluminous to slightly peraluminous geochemical signature with an intermediate initial Sr ratio ( 87 Sr/ 86 Sr 510 = 0.7064) and rather unradiogenic Nd (e 5 Nd 10 = –1.5 and –0.2). The laser ablation ICP-MS U–Th–Pb radiometric dating of monazites and zircons from these rocks yields intrusive ages between 506.4 ± 5.4 and 513.4 ± 4.3 Ma (2σ). The final stage of magmatic activity is documented by the Ar–Ar dating of muscovite from a pegmatite dyke at 485.1 ± 3.2 Ma. The granites intruded and thermally influenced the terrestrial clastic sediments of the Boomyn Khudag Formation, whereby the thermal metamorphism of sediments was characterized by a muscovite growth. These new data argue against the previously assumed Permian age of the Burd Gol Massif and the Lower–Middle Devonian age of the Boomyn Khudag sedimentary formation and illustrates the terrestrial evolution in this part of the Lake Zone during the Cambrian.

Late Mesozoic basin and range tectonics and related magmatism in Southeast China

During the Late Mesozoic Middle Jurassic–Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic (Type I) and intra-continental extensional basins (Type II). Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tuffs and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous–Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geodynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc extensional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range tectonics between both shores of the Pacific, such as mantle plume formation, scales of extensional and igneous rock assemblages and the age of basin and range tectonics, were caused mainly by the Yellowstone mantle plume in the eastern shore of the Pacific.

The completeness of the continental fossil record and its impact on patterns of diversification

Did organisms diversify in different ways on land and in the marine realm over the Phanerozoic, or do the different diversification curves of continental and marine organisms reflect primarily methodological artifacts? To answer this question, a quantitative assessment of the completeness of the global continental fossil record is indispensable. We used comparisons between continental and marine fossil diversity and between past and present-day patterns of continental diversity to assess the absolute and relative completeness of the continental fossil record. Collector's curves of the number of described families over the past 200 years suggest that the global continental fossil record, and even that of European and North American tetrapods, is still highly incomplete. Nevertheless, relative proportions of major continental and marine taxa, patterns of tetrapod endemism, and familial durations suggest that the family-level continental fossil record is reasonably representative. We found that, although continental fossil richness is correlated with the amount of terrestrial clastic sediment available for sampling, the exponential diversification curve of continental metazoans is unlikely to be an artifact of this rock bias. Diversification of the continental fauna appears to have been essentially exponential since the Devonian, with little evidence of major extinction events.

Transtensional origin of the NE–SW Simitli basin along the Strouma (Strymon) Lineament, SW Bulgaria

Several depocentres have developed along the NNW–SSE-striking Strouma (Strymon) Lineament since the Miocene, forming the Strouma/Strymon graben system. Some of these basins, including the Dzherman and Simitli, strike at high angles to the lineament. The rhomboid-shaped Simitli basin is limited in the south by the NE–SW-striking, seismically active Kroupnik fault and contains terrestrial clastic sediments, which have been deposited since the Sarmatian. Its formation is attributed to ‘wrench-dominated transtension’ (D B event) which activated the basin's NE–SW-striking boundary faults as left-lateral strike-slip structures during the Early–Middle Miocene. This deformation was associated with NNE–SSW contraction and WNW–ESE extension and succeeded the NNE–SSW contraction caused by ‘pure shear-dominated transpression’ (D A event), which governed the region in Late Oligocene–Early Miocene times. During the Middle–Late Miocene, the D B event was followed by WNW–ESE ‘pure shear-dominated extension’ (D 1 event), which caused further widening of the basin. The transtensional origin of the Simitli basin is explained by lateral extrusion of the crustal mass squeezed between the Apulian–Adriatic microplate and the European foreland towards the North Aegean Sea. The subduction retreat of the Hellenic orogen possibly enhanced this lateral extrusion, and from the Late Miocene onwards the NE–SW-oriented back-arc extension balanced the continuing retreat.

The Chahe copper deposit—Its age and genesis

The Chahe copper deposit occurs in the Early Proterozoic metamorphic series in the area of Chahe and its chalcopyrite yielded a Pb−Pb isochron age of 951±36 Ma, providing evidence for copper mineralization at the early stage of the Jinning movement. The ore-forming material came from terrestrial clastic sediments and marine volcanic eruption and the ores were deposited in a relatively open beach environment. The Jinning movement led to folding and metamorphism of country strata, as well as to the rebomilization and transport of copper, resulting in ore deposition in structurally weak locations. This deposit is a volcano-sedimentary metamorphic deposit.

The nature, origin and accumulation of loess

Loess can be defined simply as a terrestrial clastic sediment, composed predominantly of silt-size particles, which is formed essentially by the accumulation of wind-blown dust. There are three fundamental requirements for its formation: (1) a sustained source of dust, (2) adequate wind energy to transport the dust, and (3) a suitable accumulation site. Most loess has been modified to some degree by local reworking, bioturbation and syn-depositional weathering, but a process of ‘loessification’ is not necessary for a dust deposit to qualify as loess. The terms ‘primary loess’ and ‘secondary loess’ have previously been used to described wind-deposited loess and redeposited loess, respectively, but it is more accurate to describe material reworked and redeposited by non-aeolian processes as ‘loess-derived colluvium’ or ‘loess-derived alluvium’. During the Quaternary, loess formed in three main situations: (1) mid-continental shield areas beyond the limits of ice sheets (periglacial loess), (2) on the margins of high mountain ranges (perimontane loess), and (3) on the semi-arid margins of some lowland deserts (peridesert loess). Peridesert loess is relatively poorly developed partly due to the limited efficiency of silt-generating mechanisms in low-land deserts compared with glaciation, but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition, particularly in areas which experience frequent climatic changes. The remarkably thick loess of China and Central Asia results from an unusual combination of conditions which has persisted for much of the last 2–3 million years, namely rapid uplift of the Tibetan Plateau and surrounding mountain ranges, high rates of sediment production and supply to adjacent basins, a strong northwesterly and westerly wind regime, and the existence of effective dust traps downwind of the source regions.

Paleodepositional setting of the Late Cretaceous Pautût Flora from West Greenland as determined by sedimentological and plant taphonomical data

Preservation of the Santonian/Campanian Pautût Flora in West Greenland is mainly the result of a high energy river system that flowed across a well vegetated delta plain to carry and deposit plant parts and terrestrial clastic sediments into a low energy marine setting. A diverse flora is represented mainly in three depositional settings: (1) a dominant angiosperm vegetation preserved with fern and a few conifer species is found within backswamp lakes possibly near rivers; (2) conifer organs and a sparse angiosperm leaf association occur in nearshore marine deltaic deposits dominated by fluvial sedimentation; and (3) a unique Pautût angiosperm vegetational assemblage with a few conifer and cycad species preserved in a brackish to fully marine bay setting. Fossil plant material preserved in the backswamp lakes and fluvial settings probably were deribed mostly from local sources indicating that angiosperms were able, to a degree, to invade into the backswamp Arctic habitats considered to have been dominated by conifers. However, these backswamp habitats probably were short-lived oxbow lakes with a successional angiosperm vegetation. Plant material in the fully marine setting is allochthonous, very diverse, and probably derived mostly from the upper delta palin. The observed differences within the fossil plant assemblages deposited in the marine setting, those containing mostly conifer parts occur in nearshore marine environments as compared to assemblages with mostly angiosperm leaves in more distal marine environments, are used to interpret sorting of different plant parts due to individual taphonomical characters. This means that the heavier conifer cones in the nearshore marine setting sank sooner than the lighter leaves, which were dispersed further out to sea. Strengthening the argument for sorting is that both types of plant parts had a final resting position due to subaqueous transport. The unique angiosperm leaf assemblage found in the fully marine setting is used to support the interpretation that the upper delta plain levees, or extrabasinal sites, were inhabited by a vegetational community distinct from that near the backswamp areas of the lower delta plain. There are a few angiosperm species in common between the distal and nearshore marine and the backswamp lake settings. These species are found througout the Pautût area and exemplify a riparian element which was more prone to enter a depositional regime. Nearshore habitats were inhabited by non-woody plants.