Inland Sections Research Articles

Late Barremian–Aptian paleoenvironmental variations and OAE1a environmental effect in the eastern Crimea

The early Aptian Oceanic Anoxic Event 1a (OAE1a, or Selli Event) is widely known from many oceanic and inland sections as an interval of enhanced accumulation of sediments rich in total organic carbon (TOC), associated with the turnover in the global carbon budget and dramatic biotic variations. Our multidisciplinary study of the upper Barremian to lower upper Aptian deposits from the eastern part of Crimean Peninsula allowed us to confirm the presence of a layer that correlates to OAE1a and revealed significant reorganization in the planktonic and benthic foraminifera, nannofossils, ostracod and terrestrial plant communities at this level. The low-calcareous OAE1a deposits from the eastern Crimea lack in TOC that is not typical sedimentological response to this critical event. The OAE1a onset was associated with a nannoconid crisis, occurrence of low-abundance Hedbergella planktonic foraminifera, increased abundance of benthic foraminifera and ostracods and the bloom of Classopolis on the adjacent land. The calcareous microplankton biota was highly oppressed during OAE1a up to total elimination in the core of the event. Benthic assemblages indicate the occurrence of dysoxic conditions at the sea-floor. The absence of organic matter in the deposits of the OAE1a interval points to the low basinal biotic productivity and low input of terrestrial organic matter. We suggest that oligotrophication of the basin was related to the transgressive pulse, which led to small-scale landward moving of the coastal line barriered by coastal highland. The hot arid climatic conditions indicated by terrestrial plants, prevented the supply of nutrients and terrestrial organic matter into the basin that caused low algal and bacterial productivity and prevented accumulation of TOC-rich sediments. The termination of OAE1a coincides with the occurrence of warm humid climate and erosion of ephemeral coastal highland, more likely, built up by soft clayey sediments. The transit restoration of the normal marine biota in the early late Aptian was interrupted in the middle late Aptian by new long-lived regression led to enhanced terrestrial runoff and, possibly, fresh water input killed marine biota and caused the accumulation of low-calcareous clay.

Lost in the wind: An integrated approach for the recognition of mixed clastic–carbonate continental aeolianites

AbstractAeolianites with a mixed clastic and carbonate detrital mineralogy are typical deposits of tropical coastal desert environments. These deposits are genetically related to transgressive–regressive cycles, with the shallow‐marine carbonate detrital component being deflated from the exposed seafloor during episodes of glacial sea‐level lowstands, transported and later accumulated onto more continental areas. A detailed investigation of the granulometric and petrographic properties of the Late Pleistocene to Holocene Ghayathi Formation in the United Arab Emirates provides a comprehensive numerical dataset that reveals the complex spatio‐temporal depositional and diagenetic evolution of a mixed siliciclastic–carbonate continental aeolianite. Fifty‐one thin sections and forty‐four rock samples of three sedimentary units (Madinat‐Zayed, Ghayathi and Fuwayrit formations) from the United Arab Emirates were analyzed for their grain‐size distribution, mineralogy and the bulk stable‐carbon and oxygen isotopic composition. Sorting, skewness and kurtosis of the grain‐size distributions provide evidence for a divergent aerodynamic behaviour between the carbonate and siliciclastic particles. The different grain‐size distributions between the inland and coastal sections of the Ghayathi Formation indicate that continental mixed clastic−carbonate aeolianites are affected by density‐driven selective transport and consequent traction sorting due to the nature of carbonate detritus. The transport decoupling of the different detrital components resulted in a ‘continental sorting’ effect, with the inland sections yielding layers characterized by a better sorted detritus than the coastal areas. All detritus originally composed of aragonite has been removed by dissolution during early meteoric diagenesis, with its shapes frequently preserved by micritic envelopes. The bulk stable‐isotope composition of the carbonate fraction reflects a decreasing degree of meteoric cementation from coastal to inland areas. The high complexity of the lateral and vertical distribution of the sedimentary, diagenetic and isotopic properties of continental mixed aeolianites, such as the Ghayathi Formation, highlights the problem of recognizing such deposits in the pre‐Quaternary sedimentary record.

Tephrochronological constraints on the timing and nature of sea-level change prior to and during glacial termination V

Glacial-interglacial variations in ice volume and sea level are essential components of the Pleistocene global climate evolution. Deciphering the timing of change of these key climate parameters with respect to the insolation forcing is central to understanding the processes controlling glacial terminations. Here we exploit the sensitivity of the Paleo Tiber River (central Italy) to sea-level forced changes in the base level and the frequent occurrence of datable tephra layers in its sedimentary successions to reconstruct the timing of the relative sea-level (RSL) change between 450 and 403 ka, i.e., across the glacial termination (T-V) that marks the transition between Marine Isotope Stage (MIS) 12 and MIS 11. The analysis hinges on new stratigraphic data, tephra geochemical fingerprinting, and 40Ar/39Ar dating from a fluvial section that represents the inland counterpart of the near mouth, coastal aggradational successions of the San Paolo Formation (SPF). Tephra correlation indicates that the morpho-stratigraphic record of the inland section is as sensitive to the sea-level change as its coastal counterparts, which makes it ideal to complement previous RSL reconstructions from the Tiber River catchment basin, thereby providing a more detailed picture of the sea-level history across T-V. Combined sedimentological and morphological proxies of the composed inland-coastal SPF record document the occurrence of two phases of relatively rapid sea-level rise, here interpreted as meltwater pulse (MWP) events. The earlier MWP occurred between ∼450 and ∼445 ka and matches a relatively minor episode of the sea-level rise documented in an existing RSL record, while the younger MWP at ∼430 ka corresponds to the high amplitude sea-level rise that marks T-V. We find that both MWPs coincide with episodes of ice-rafted debris deposition in the North Atlantic (Heinrich-like events) and with attendant Southern Hemisphere warming, plausibly associated with the bipolar seesaw.

Volcanic constraints on the unzipping of Africa from South America: Insights from new geochronological controls along the Angola margin

The breakup of Africa from South America is associated with the emplacement of the Paraná-Etendeka flood basalt province from around 134 Ma and the Tristan da Cunha plume. Yet many additional volcanic events occur that are younger than the main pulse of the Paraná-Etendeka and straddle the rift to drift phases of the main breakup. This contribution reports on new geochronological constraints from the Angolan part of the African Margin. Three coastal and one inland section have been sampled stretching across some 400 Km, with 39Ar/40Ar, U-Pb and Palaeontology used to provide age constraints. Ages from the new data range from ~100 to 81 Ma, with three main events (cr. 100, 91 and 82–81 Ma). Volcanic events are occurring within the Early to Late Cretaceous, along this part of the margin with a general younging towards Namibia. With the constraints of additional age information both onshore and offshore Angola, a clear younging trend at the early stages of rift to drift is recorded in the volcanic events that unzip from North to South. Similar age volcanic events are reported from the Brazilian side of the conjugate margin, and highlight the need to fully incorporate these relatively low volume volcanic pulses into the plate tectonic breakup models of the South Atlantic Margin.

The impacts of “urban-induced heavy rains” on the distribution of deposition fluxes of inorganic acidic substances in the Tokyo metropolitan area in summer

We analyzed the trends in rainfall amounts and the number of heavy rain events with hourly rainfall amounts over 30mm at the inland section of the 23-ward Tokyo metropolitan area (nine wards and ten sites) in the warm season (July to September) from 1978 to 2008. Heavy rain events in the Nerima Ward occurred nine times during decade I (1978–1987; 0.90times/yr), 13 times during decade II (1988–1997; 1.3times/yr), and 23 times during decade III (1998–2008; 2.1times/yr). The annual average number of heavy rain events was 1.43times/yr in Nerima from 1978 to 2008, while it was 0.98times/yr on average at nine locations excluding Nerima. The frequency of extremely strong heavy rain events with hourly rainfall amounts greater than 50mm during decade III was the highest in Nerima (six times) among ten sites. These data suggest that the frequency of heavy rain events has increased at Nerima during the past 30years. Bulk precipitation data were collected biweekly by filtration-type collectors at 14 sites around Nerima from 2008 to 2010 to determine the impacts of urban-induced heavy rains (hereafter UHR), defined as a heavy rain event other than typhoons and frontal heavy rains, on the distribution of deposition fluxes of inorganic acidic substances. The NO3− and nss-SO42− concentrations in bulk precipitation were higher during the periods including UHR than those not including UHR. The deposition fluxes of NO3− and SO42− showed clear differences at the center of UHR (NO3−: 231μeq/m2/d, SO42−: 234μeq/m2/d) and its surrounding area (NO3−: 76.4μeq/m2/d, SO42−: 86.1μeq/m2/d). Our results suggest that large amounts of inorganic acidic substances are deposited locally by UHR in urban areas in summer.

Palaeoclimate characteristics in interior Siberia of MIS 6–2: first insights from the Batagay permafrost mega-thaw slump in the Yana Highlands

Abstract. Syngenetic permafrost deposits formed extensively on and around the arising Beringian subcontinent during the Late Pleistocene sea level lowstands. Syngenetic deposition implies that all material, both mineral and organic, freezes parallel to sedimentation and remains frozen until degradation of the permafrost. Permafrost is therefore a unique archive of Late Pleistocene palaeoclimate. Most studied permafrost outcrops are situated in the coastal lowlands of northeastern Siberia; inland sections are, however, scarcely available. Here, we describe the stratigraphical, cryolithological, and geochronological characteristics of a permafrost sequence near Batagay in the Siberian Yana Highlands, the interior of the Sakha Republic (Yakutia), Russia, with focus on the Late Pleistocene Yedoma ice complex (YIC). The recently formed Batagay mega-thaw slump exposes permafrost deposits to a depth of up to 80 m and gives insight into a climate record close to Verkhoyansk, which has the most severe continental climate in the Northern Hemisphere. Geochronological dating (optically stimulated luminescence, OSL, and 14C ages) and stratigraphic implications delivered a temporal frame from the Middle Pleistocene to the Holocene for our sedimentological interpretations and also revealed interruptions in the deposition. The sequence of lithological units indicates a succession of several distinct climate phases: a Middle Pleistocene ice complex indicates cold stage climate. Then, ice wedge growth stopped due to highly increased sedimentation rates and eventually a rise in temperature. Full interglacial climate conditions existed during accumulation of an organic-rich layer – plant macrofossils reflected open forest vegetation existing under dry conditions during Marine Isotope Stage (MIS) 5e. The Late Pleistocene YIC (MIS 4–MIS 2) suggests severe cold-stage climate conditions. No alas deposits, potentially indicating thermokarst processes, were detected at the site. A detailed comparison of the permafrost deposits exposed in the Batagay thaw slump with well-studied permafrost sequences, both coastal and inland, is made to highlight common features and differences in their formation processes and palaeoclimatic histories. Fluvial and lacustrine influence is temporarily common in the majority of permafrost exposures, but has to be excluded for the Batagay sequence. We interpret the characteristics of permafrost deposits at this location as a result of various climatically induced processes that are partly seasonally controlled. Nival deposition might have been dominant during winter time, whereas proluvial and aeolian deposition could have prevailed during the snowmelt period and the dry summer season.

Consideration on Accepting Aspect of 'Daemyeong Iltongji' of 'Cheoncha Daegwan' - Focused on Inland Section of Shandong -

Consideration on Accepting Aspect of 'Daemyeong Iltongji' of 'Cheoncha Daegwan' - Focused on Inland Section of Shandong -

U-Pb geochronology of the Santa Cruz Formation (early Miocene) at the Río Bote and Río Santa Cruz (southernmost Patagonia, Argentina): Implications for the correlation of fossil vertebrate localities

The early Miocene Santa Cruz Formation (SCF) in southern Patagonia hosts the Santacrucian South American Land Mammal Age (SALMA), whose age is known mainly from exposures along the Atlantic coast. Zircon U-Pb ages were obtained from intercalated tuffs from four inland sections of the SCF: 17.36 ± 0.63 Ma for the westernmost Río Bote locality, and 17.04 ± 0.55 Ma–16.32 ± 0.62 Ma for central Río Santa Cruz localities. All ages agree with the bounding age of underlying marine units and with equivalent strata in coastal exposures. New ages and available sedimentation rates imply time spans for each section of ∼18.2 to 17.36 Ma for Río Bote and 17.45–15.63 Ma for central Río Santa Cruz (Burdigalian). These estimates support the view that deposition of the SCF began at western localities ∼1 Ma earlier than at eastern localities, and that the central Río Santa Cruz localities expose the youngest SCF in southern Santa Cruz Province. Associated vertebrate faunas are consistent with our geochronologic synthesis, showing older (Notohippidian) taxa in western localities and younger (Santacrucian) taxa in central localities. The Notohippidian fauna (19.0–18.0 Ma) of the western localities is synchronous with Pinturan faunas (19.0–18.0 Ma), but older than Santacrucian faunas of the Río Santa Cruz (17.2–15.6 Ma) and coastal localities (18.0–16.2 Ma). The Santacrucian faunas of the central Río Santa Cruz localities temporally overlap Colloncuran (15.7 Ma), Friasian (16.5 Ma), and eastern Santacrucian faunas.

Potential genesis and implications of calcium nitrate in Antarctic snow

Abstract. Among the large variety of particulates in the atmosphere, calcic mineral dust particles have highly reactive surfaces that undergo heterogeneous reactions with atmospheric acids contiguously. The association between nssCa2+, an important proxy indicator of mineral dust, and NO3−, a dominant anion in the Antarctic snowpack, was analysed. A total of 41 snow cores ( ∼ 1 m each) that represent snow deposited during 2008–2009 were studied along coastal–inland transects from two different regions in East Antarctica – the Princess Elizabeth Land (PEL) and central Dronning Maud Land (cDML). Correlation statistics showed a strong association (at 99 % significance level) between NO3− and nssCa2+ at the near-coastal sections of both PEL (r = 0.74) and cDML (r = 0.82) transects. Similarly, a strong association between these ions was also observed in snow deposits at the inland sections of PEL (r = 0.73) and cDML (r = 0.84). Such systematic associations between nssCa2+ and NO3− are attributed to the interaction between calcic mineral dust and nitric acid in the atmosphere, leading to the formation of calcium nitrate (Ca(NO3)2) aerosol. Principal component analysis revealed common transport and depositional processes for nssCa2+ and NO3− both in PEL and cDML. Forward- and back-trajectory analyses using HYSPLIT model v. 4 revealed that southern South America (SSA) was an important dust-emitting source to the study region, aided by the westerlies. Particle size distribution showed that over 90 % of the dust was in the range < 4 µm, indicating that these dust particles reached the Antarctic region via long-range transport from the SSA region. We propose that the association between nssCa2+ and NO3− occurs during the long-range transport due to the formation of Ca(NO3)2 rather than to local neutralisation processes. However, the influence of local dust sources from the nunataks in cDML and the contribution of high sea salt in coastal PEL evidently mask such association in the mountainous and coastal regions respectively. Ionic balance calculations showed that 70–75 % of NO3− in the coastal sections was associated with nssCa2+ (to form Ca(NO3)2). However, in the inland sections, 50–55 % of NO3− was present as HNO3. The study indicates that the input of dust-bound NO3− contributes a significant fraction of the total NO3− deposited in coastal Antarctic snow.

Effects of alongshore morphology on groundwater flow and solute transport in a nearshore aquifer

AbstractVariations of beach morphology in both the cross‐shore and alongshore directions, associated with tidal creeks, are common at natural coasts, as observed at a field site on the east coast of Rarotonga, Cook Islands. Field investigations and three‐dimensional (3‐D) numerical simulations were conducted to study the nearshore groundwater flow and solute transport in such a system. The results show that the beach morphology, combined with tides, induced a significant alongshore flow and modified local pore water circulation and salt transport in the intertidal zone substantially. The bathymetry and hydraulic head of the creek enabled further and more rapid landward intrusion of seawater along the creek than in the aquifer, which created alongshore hydraulic gradient and solute concentration gradient to drive pore water flow and salt transport in the alongshore direction within the aquifer. The effects of the creek led to the formation of a saltwater plume in groundwater at an intermediate depth between fresher water zones on a cross‐shore transect. The 3‐D pore water flow in the nearshore zone was also complicated by the landward hydraulic head condition, resulting in freshwater drainage across the inland section of the creek while seawater infiltrating the seaward section. These results provided new insights into the complexity, intensity, and time scales of mixing among fresh groundwater, recirculating seawater and creek water in three dimensions. The 3‐D characteristics of nearshore pore water flow and solute transport have important implications for studies of submarine groundwater discharge and associated chemical input to the coastal sea, and for evaluation of the beach habitat conditions.

Forest clearance and agricultural expansion on Rapa, Austral Archipelago, French Polynesia

Palynological records from Holocene wetland deposits in East Polynesia have demonstrated widespread ecological changes following Polynesian arrival after c. ad 1200, but linking inferences of human activities to archaeological records has been limited by equivocal fossil proxies and a lack of chronological controls. To address these limitations, multiple sedimentary profiles were examined from a coastal marsh on the remote East Polynesian island of Rapa. These profiles span 8000 years of ecological change and record mid-Holocene sea-level highstand conditions which receded to modern levels by ad 500. Depositional models were constructed for each profile using Bayesian inferences to characterise the spatial and temporal changes in fossil proxy representation. Just prior to human arrival there are high pollen concentrations of Pandanus and the presence of an extinct palm, both indicative of an extensive lowland swamp forest that developed after ad 500. Indicators of Polynesian arrival and agricultural expansion include unprecedented amounts of charcoal particles and pollen from the introduced cultigen, Colocasia esculenta (taro). The swamp forest was progressively cleared, beginning in the most inland section at ad 1110–1230. The Colocasia-based agricultural system reached its greatest extent from ad 1590 to 1740. The last appearance of the extinct palm was recorded at ad 1520–1660 and the entire area was cleared of indigenous trees soon after European colonisation at ad 1830–1880. By modelling the chronologies of individual fossil proxies across each profile, we have developed a framework for defining the processes behind vegetation change and for matching palynological-based inferences of human activity with archaeological records.

Identifying fluvio–lacustrine intervals in thick playa-lake successions: An integrated sedimentology and ichnology of arenaceous members in the mid–late Triassic Mercia Mudstone Group of south-west England, UK

A complete Triassic succession is exposed in the cliffs of the Devon coast in south-west England, UK where it forms part of the Dorset & East Devon World Heritage Site. The upper part of the succession, the Middle to Late Triassic Mercia Mudstone Group, consists of c. 450 m of predominantly red mudstones and associated evaporites that were deposited in playa lakes in hot deserts. The Group has an extensive onshore and offshore outcrop and subcrop in the U.K. where it locally comprises over 3000 m of red beds with thick halites. The Devon coast section is the type for the Group and is the most complete exposure of the Keuper Marl facies in north-west Europe. In its middle part, the Dunscombe Mudstone Formation comprises a 25 to 40 m-thick laterally variable succession of green, purple and grey laminated mudstones with thin interbeds of calcareous siltstone/sandstone, and thicker beds of autobreccia related to gypsum/anhydrite and halite dissolution. It represents a fluvio–lacustrine and probably cooler climatic interval that is thought to have lasted, on the basis of palaeontological and magnetostratigraphic evidence, for most of the Carnian Stage (c. 12 Ma). Elsewhere in Europe the Carnian Stage is represented by fluvial deposits including the Esterienschichten and Schilfsandstein Formations in Germany. At the type section on the Devon coast the Dunscombe Mudstone includes a lenticular unit of bioturbated, predominantly fine-grained sandstone up to 4 m thick, the Lincombe Member, that has not been recorded in inland sections in the county. When traced northwards into Somerset, thin lenticular sandstones, the North Curry and Sutton Mallet Sandstone Members, are locally present at similar stratigraphical levels in the lower part of the Dunscombe Mudstone. A detailed analysis of the sedimentology of the three principal occurrences of these arenaceous units revealed 13 lithofacies and 6 ichnofabrics that suggest deposition in similar fluvio–lacustrine settings. Their palaeoenvironmental interpretation and correlation is more complex than previously thought. The Lincombe Member is interpreted as a geographically isolated sedimentary body that was deposited in a shallow, oxygenated freshwater lake. In Devon it passes upwards and laterally into lake-margin and lake delta-plain deposits. The North Curry Sandstone was deposited in a series of broad, shallow channels that crossed a low-relief topography. Laterally, along strike, the channel sands either pass into or terminate against more argillaceous lacustrine deposits. In contrast, the depositional environment of the Sutton Mallet Sandstone is interpreted as relatively small-scale channels with low flows and possible channel switching. Fluvio–lacustrine intervals are relatively common within playa-lake successions, but there are few published accounts of ancient examples that are sufficiently detailed to allow the complex interactions of these ephemeral shallow-water environments to be understood. The sedimentological and ichnological descriptions and analyses of the Triassic example presented here will be applicable to other fluvio–lacustrine sediments deposited in dryland environments.

Salt-marsh erosion associated with hurricane landfall in southern New England in the fifteenth and seventeenth centuries

Lithostratigraphic and radiocarbon data from the inland section of Pattagansett River Marsh, Connecticut, show that this sheltered part of the salt marsh underwent significant erosion twice during the past 600 yr, each time followed by rapid and complete infilling of the eroded space with tidal mud and low marsh and high marsh peat. We argue that the erosion cannot be attributed to increases in tidal prism or to lateral migration of tidal channels. The ±2σ age range (A.D. 1390–1470) for the first low marsh growth in the older regressive sequence agrees well with the age range (A.D. 1400–1440) for a hurricane deposit 60 km to the east. The younger regressive sequence is dated with the greatest probability to the period A.D. 1640–1670, i.e., shortly after the hurricanes of A.D. 1635 and 1638. Our conclusion that the most likely cause of the erosion was hurricane activity is relevant to paleostorm research and the study of marsh sensitivity to and recovery from storm erosion.

Downstream Migration of Juvenile European Sturgeon Acipenser sturio L. in the Gironde Estuary

The European sturgeon (Acipenser sturio) is an endangered diadromous fish species that spawns in the rivers in late spring and early summer. The juveniles spend their first years in the brackish waters (5‰ to 25‰) of the estuary zone before moving out to sea. This study describes the downstream migration pattern of juvenile sturgeon, belonging to the 1994 cohort, the only one born naturally in the Gironde basin, France since the end of the 1980s. During October 1994 to December 1996 the inland section of the Gironde estuary was sampled monthly by trawl (n=818 tows) and all European sturgeon caught (n=381) were marked and released. The first sturgeon of the 1994 cohort (TL=27 cm) were caught in early March 1995 in the zones furthest upstream. During their second fall of life, juveniles gradually acclimatized, and spread over a wide range of salinity conditions. A first incursion into marine water was also observed (at least for a few fish) by the end of the second winter. During this second period, sturgeon showed preference for two particular zones situated at 18 and 38 km, respectively, from the mouth of the estuary. These zones, belonging to two different salinity sectors of the estuary, did not appear to be any different to their neighbors with regards to depth and type of substrate. There were no significant size differences among estuarine zones. Seasonal movements of sturgeon seem to be motivated by a search for warmer temperatures. After a period of early acclimatization of 15 months, juvenile European sturgeon appear to be highly tolerant of salinity variations.

A revision of the biostratigraphy of the Late Namurian–Early Westphalian succession of Westward Ho!, North Devon

Newly discovered non-marine bivalve bands and other fossiliferous horizons, re-collection of some known horizons and re-examination of museum material from an inland section covered over for many years are utilized to correlate the succession at Westward Ho!. A non-marine bivalve band at Westward Ho! is correlated with one in the late Namurian of South Wales. The dated strata range from the late Namurian, very probably late R 1c in Cycle 3 of the Bideford Group, to the lower part of the Communis Chronozone in Cycle 9, which includes the Cornborough Sandstone and overlying ‘Culm Bed’. The adjacent Greencliff Beds, which have yielded a marine trace fossil, are briefly discussed and their structure is re-interpreted. They may possibly be of an earlier age than the Bideford Group. The Westward Ho! sequence, when compared with those of nearby Clovelly and Bude to the southwest, reveals stratigraphical gaps and lacks five black shale horizons with major goniatite bands. The possible significance of these differences in the Westward Ho! succession is briefly discussed.

The palaeomagnetism of the Tumblagooda Sandstone, Western Australia: Gondwana palaeozoic apparent polar wandering

Abstract A magnetic polarity reversal near the top of the Tumblagooda Sandstone, in the Carnarvon Basin, Western Australia, has been intensively investigated in five coastal sections and four inland sections, all located near the top of the formation. A further four inland sections towards the base of the formation were also sampled. Of the inland sections, all but two are suspected to have been largely remagnetized in similar fashion to Late Palaeozoic and Mesozoic sediments to the south. At the remaining seven sections a zone of normal magnetization overlies a zone of mixed (coexisting normal and reversed) magnetization, and the boundary between them coincides with a unique marker horizon of pebbly sandstone. The intimate relationship of the (virtual) reversal and the pebble marker horizon lends strong support to the suggestion that erosional stripping accompanied the formation of the pebble marker. The pebble marker is best interpreted as a lag deposit. The stratigraphic coincidence does not necessarily signify the concurrence of a reversal with the formation of the marker horizon, but rather that the relationship represents a variation on the unconformity test. The record of the actual geomagnetic reversal has been physically removed from most sections. These results show conclusively that the age of the magnetization of the Tumblagooda Sandstone is very close to the age of deposition, and can therefore provide an important pole for the definition of the Gondwana apparent polar wander path. However, the suggested Silurian age must be questioned on the basis of the palaeomagnetism which best accords with an Ordovician age. The lower parts of the sequence may be as old as the Cambrian. While the age of the palaeomagnetic pole from the Tumblagooda Sandstone is therefore not well constrained, its position is well defined and in combination with other Gondwana poles indicates a period of rapid polar motion during the Ordovician/Silurian. A collision with Laurasia at the end of the Silurian and beginning of the Devonian may explain the timing of the Caledonian/Acadian Orogenies.

Freeze-Thaw Days in the Northeastern United States

Abstract A freeze-thaw day is defined as a weather observation day with a maximum temperature of 0°C or above and a minimum temperature of −2.2°C or below recorded in an instrument shelter 1.5 m above the ground. The 30 winter during 1950–80 are examined at 228 stations in nine northeastern states. Average annual freeze-thaw days range from over 90 at high elevations in the north to less than 50 along the Long Island and New Jersey shores and in the Philadelphia area. Freeze-thaw days are most common during midwinter months in the south but peak in March across inland sections. Freeze-thaw days are most numerous with average monthly temperatures between −2°C and 0°C and approach zero at monthly temperatures below −13°C and above 11°C. The number of freeze-thaw days with less than 7.5 cm of snow cover is about 95% of the total number along the southern coasts and less than 50% of the total in northern snowy climates. The air at 15 cm height experiences 13% more freeze-thaw days than the air at 150 cm, due ...

Correlation of the Upper Cretaceous White Chalk (Turonian to Campanian) in the Anglo-Paris Basin

Using key lithological, biostratigraphic and geophysical borehole-log markers a correlation of the Upper Cretaceous Chalk stratigraphies across the whole Anglo-Paris Basin has been achieved. A common lithological marker bed stratigraphy applies and key fossil markers (inoceramids, Micraster and Echinocorys ) are consistently related to the same lithological markers throughout the basin. The major lithological changes consistently occur at the same levels but are not necessarily equally strongly developed. The magnificent dip section along the French Channel coast between the Somme and the Seine, and the inland sections at Precy-sur-Oise and Verlin (Loiret) illustrate the influence of long-lived tectonic lines on Chalk sedimentation history recognised by: (i) rapid thickness variations; (ii) channel flooring hardgrounds and associated anomalous bedding dips: (iii) stratigraphically anomalous infills of channels which may be metres to kilometres across; (iv) redeposited chalks containing abundant Bathichnus paramoudrae ; (v) tectonically induced slumps and slides with flint and chalk shatter beds (palaeoseismic horizons). These features are found along may axes including the Anticlinal du Bray at Precy and Dieppe, the Anticlinal de Margny-les-Compiegne at Nourard le-Franc and Le Treport (the Bresle Valley Axis) and the Fecamp and Verlin fault systems. The ‘events’ recognised along these axes link with similar events recognised in Sussex (e.g. Kingston Anticline), on Portsdown, at Culver Cliff, Isle of Wight (Sandown Pericline) and on the Weymouth Anticline (White Nothe). Such events are common in the high Turonian, low Coniacian, basal Santonian, and the low and mid Campanian. The recurrence of key marker beds dominated by a particular trace fossil association or sequence, Bathichnus-Thalassinoides suevicus-Zoophycos associated with major changes in lithology, micro and macro-fauna indicates more widespread ‘oceanographic’ cycles of transgression and regression related to Atlantic opening.

Crop water requirements for rainfed and irrigated rice (Paddy) in China

A parametric crop water use and yield model was used to calculate temporal and spatial water consumption for rice for the region of China and Korea. The objective was to investigate evapotranspiration (ET) demand and associated irrigation water application strategies for irrigated and rainfed crop production. A network of 241 stations provided the seasonal climatic input consisting of data averaged over approximately a 20 year period. Highest ET under full irrigation (first harvest) was observed in the northwestern, northcentral, and southwestern inland sections of China, whereas least ET occurred in son hcentral China. In order to achieve optimum crop yields, over 1000 mm of irrigation water was needed in the northwest and southwest, in contrast to about 500 mm in southcentral China. The number of required irrigations exceeded eight per growing season in the western and central interior, the edges of the Tibetan Plateau, and the south China littoral. A brief sensitivity analysis was conducted to determine the degree of error introduced by faulty or uncertain station input data.

Crop water requirements for rainfed and irrigated wheat in China and Korea

The parametric crop water use model (WATER) was applied for winter wheat to China and its environs in order to examine the evapotranspiration requirements under rainfed conditions and the associated irrigation water applications necessary for optimal production. A network of 241 stations provided climatic data averaged over a 20 year period. Highest ET under full irrigation (first growing season) was observed in the northwestern inland sections of China and the eastern portions of the Tibetan Plateau, while lowest ET occurred in the southeast; under rainfed conditions, these tendencies nearly reversed. About 400 mm of irrigation water was required in the northwest in order to achieve near-optimum yields in contrast with no such water requirements in the central east of China. A sensitivity analysis was conducted to determine the errors introduced by faulty, uncertain, or missing station data.