Formation mechanisms of paleokarst and karst collapse columns of the Middle Cambrian-Lower Ordovician carbonates in Huainan coalfield, Northern China

2021 ◽  
pp. 126634
Author(s):  
Haitao Zhang ◽  
Guangquan Xu ◽  
Hongbin Zhan ◽  
Jianbin Zheng ◽  
Minhua Wang ◽  
...  
Keyword(s):  
Northern China ◽  
Formation Mechanisms ◽  
Karst Collapse ◽  
Middle Cambrian ◽  
Huainan Coalfield ◽  
Lower Ordovician

scholarly journals Characteristics of Horizontal Precipitation in Semi-Humid Forestland in Northern China

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 975
Author(s):  
Jianbo Jia ◽  
Wende Yan ◽  
Xiaoyong Chen ◽  
Wenna Liu
Keyword(s):  
Growing Season ◽  
Northern China ◽  
Formation Mechanisms ◽  
Ecological Significance ◽  
Forest Land ◽  
Mountainous Areas ◽  
Humid Climate ◽  
Climate Region ◽  
Typical Day ◽  
The One

Little information is available on horizontal precipitation in forest land in semi-humid climate regions. In this study, the quantity and duration of horizontal precipitation were investigated using the high precision weighing lysimeter system in the mountainous areas of northern China during the experiment year 2011 and 2012. The purpose of this study was to better understand the formation mechanisms of horizontal precipitation in the semi-humid climate region. The results showed that hourly values of horizontal precipitation distributed between 0 and 0.1 mm, and that the one-night values distributed between 0.2 and 0.4 mm. The number of days with horizontal precipitation accounted for about 45% of the whole year. The average monthly amount of horizontal precipitation was 4.5 mm in the non-growing season, while it was a mere 1.6 mm in the growing season. The total amount of horizontal precipitation in the year was about 33 mm. Horizontal precipitation represented about 4.61% and 4.23% of the annual precipitation in 2011 and 2012. During the non-growing season, water vapor absorbed by the soil was greater than canopy and soil condensation, not only in terms of frequency, but also in the cumulated quantity. On a typical day, the canopy and soil condensation was 0.07 mm, accounting for 31.81% of total quantity of horizontal precipitation (0.22 mm). Air temperature, soil temperature and wind speed were negatively correlated with the quantity and duration of horizontal precipitation. This research could provide information for a better understanding of the ecological significance of horizontal precipitation in the semi-humid climate region in northern China.

scholarly journals Lithostratigraphic and allostratigraphic framework of the Cambrian–Ordovician Potsdam Group and correlations across Early Paleozoic southern Laurentia

2017 ◽  
Vol 54 (5) ◽  
pp. 550-585 ◽  
Author(s):  
David G. Lowe ◽  
R.W.C. Arnott ◽  
Godfrey S. Nowlan ◽  
A.D. McCracken
Keyword(s):  
Climate Change ◽  
Early Paleozoic ◽  
Middle Cambrian ◽  
Shallow Marine ◽  
Upper Cambrian ◽  
Subaerial Exposure ◽  
Marine Sedimentation ◽  
Lower Ordovician ◽  
Fluvial Sedimentation ◽  
Mixed Carbonate

The Potsdam Group is a Cambrian to Lower Ordovician siliciclastic unit that crops out along the southeastern margins of the Ottawa graben. From its base upward, the Potsdam consists of the Ausable, Hannawa Falls, and Keeseville formations. In addition, the Potsdam is subdivided into three allounits: allounit 1 comprises the Ausable and Hannawa Falls, and allounits 2 and 3, respectively, the lower and upper parts of the Keeseville. Allounit 1 records Early to Middle Cambrian syn-rift arkosic fluvial sedimentation (Ausable Formation) with interfingering mudstone, arkose, and dolostone of the marine Altona Member recording transgression of the easternmost part of the Ottawa graben. Rift sedimentation was followed by a Middle Cambrian climate change resulting in local quartzose aeolian sedimentation (Hannawa Falls Formation). Allounit 1 sedimentation termination coincided with latest(?) Middle Cambrian tectonic reactivation of parts of the Ottawa graben. Allounit 2 (lower Keeseville) records mainly Upper Cambrian quartzose fluvial sedimentation, with transgression of the northern Ottawa graben resulting in deposition of mixed carbonate–siliciclastic strata of the marine Rivière Aux Outardes Member. Sedimentation was then terminated by an earliest Ordovician regression and unconformity development. Allounit 3 (upper Keeseville) records diachronous transgression across the Ottawa graben that by the Arenigian culminated in mixed carbonate–siliciclastic, shallow marine sedimentation (Theresa Formation). The contact separating the Potsdam Group and Theresa Formation is conformable, except locally in parts of the northern Ottawa graben where the presence of localized islands and (or) coastal salients resulted in subaerial exposure and erosion of the uppermost Potsdam strata, and accordingly unconformity development.

scholarly journals Stratigraphy and geochemical composition of the Cambrian Alum Shale Formation in the Porsgrunn core, Skien–Langesund district, southern Norway.

2018 ◽  
Vol 66 ◽  
pp. 1-20
Author(s):  
Niels Hemmingsen Schovsbo ◽  
Arne Thorshøj Nielsen ◽  
Andreas Olaus Harstad ◽  
David L. Bruton
Keyword(s):  
Gamma Ray ◽  
Geochemical Composition ◽  
Middle Cambrian ◽  
Alum Shale ◽  
Carbon Isotope Excursion ◽  
Lower Ordovician ◽  
Shale Formation ◽  
Sedimentary Succession ◽  
Southern Norway ◽  
Spice Event

The fully cored BHD-03-99 borehole (hereafter referred to as the Porsgrunn borehole and core) penetrated Ordovician and Cambrian strata in the Skien–Langesund district, southern part of the Oslo region in Norway. Hand-held X-ray fluorescence (HH-XRF) measurements combined with spectral gamma ray and density core scanning of the Middle Cambrian – Furongian Alum Shale Formation have been made and compared with similar measurements obtained on Alum Shale cores from Scania (southernmost Sweden) and Bornholm (Denmark). The Porsgrunn drill site is located in an area that was only mildly overprinted by Caledonian tectonics and represents one of the few sites in the Oslo area where a nearly untectonised sedimentary succession can be studied in terms of thickness and geochemistry. The Alum Shale Formation is 28.8 m thick in the Porsgrunn core, excluding the thickness of five 0.9–5.5 m thick dolerite sills of assumed Permian age. In the Alum Shale Formation the bulk densities are around 2.7 g/cm3 with a slightly decreasing trend up through the formation. The shale has total organic carbon (TOC) values up to 14 wt%, which is comparable to the TOC levels for the Alum Shale elsewhere in the Oslo area and for dry gas matured Alum Shale in Scania and Bornholm. The basal Furongian is characterised by a gamma ray low and an increase in Mo interpreted to reflect the Steptoean Positive Carbon Isotope Excursion (SPICE) event. The Porsgrunn core data suggest that the Mo concentration remained high also after the SPICE event. Characteristic, readily identified features in the gamma log motif are named the Andrarum gamma low (AGL), base Furongian gamma low (BFGL), Olenus triple gamma spike (OTGS) and the Peltura gamma spike (PGS). No Lower Ordovician Alum Shale is present. The 14.8 m thick Furongian part of the Alum Shale represents the Olenus, Parabolina, Leptoplastus, Protopeltura and Peltura trilobite superzones judging from log-stratigraphic correlations to Scania and Bornholm. The Middle Cambrian interval is 14.0 m thick and includes the Exsulans Limestone Bed and 1.4 m of quartz sandstone. A 0.3 m thick primary limestone bed may be an equivalent to the Andrarum Limestone Bed. The succession represents the Paradoxides paradoxissimus and P. forchhammeri superzones. The Alum Shale Formation rests atop the 13.0 m thick Lower Cambrian Stokkevannet sandstone (new informal name) that in turn directly overlies the basement. Overall, the stratigraphic development of the comparatively thin Alum Shale Formation resembles the condensed sequence seen on Bornholm.

scholarly journals Summary account of the Lower Ordovician (Arenig) graptolite biostratigraphy of the Cow Head Group, western Newfoundland

1987 ◽  
Vol 35 ◽  
pp. 259-270
Author(s):  
S. Henry Williams ◽  
Robert K. Stevens
Keyword(s):  
Continental Margin ◽  
North American ◽  
Repeated Exposure ◽  
Head Group ◽  
Middle Cambrian ◽  
Lower Ordovician ◽  
Evolutionary Step ◽  
American Standard ◽  
Lower Slope

The Cow Head Group is an allochthonous sequence of Middle Cambrian to late Arenig sedimentary brec­cias, limestones and shales deposited in a deep lower slope environment close to a continental margin. Im­bricate thrusting has resulted in repeated exposure of laterally equivalent "proximal" to "distal" facies which may be correlated using graptolitic control in the interbeds. "Proximal" sections are characterised by massive, coarse breccias with interbedded limestones and green/dark grey shales. More distal ex­posures have fewer and thinner breccias and limestones, while the green/grey shales are replaced pro­gressively by red, non-graptolitic ones. Although the succession is by no mean unbroken or complete, it furnishes one of the best and most con­tinuously graptolitic sections through the Arenig. A new zonal scheme is erected for the Cow Head Group, which could prove suitable as a new North American standard. Furthermore, several limestones and siliceous shales have yielded exquisitely preserved isolated material, permitting integration of fine growth detail with complete flattened specimens. With the exception of the uppermost Arenig U. austrodentatus Zone, Arenig graptoloids possess a pro­sicular origin for thl1• The earliest graptoloids with a metasicular origin for the first theca appear in this zone, including Undulograptus, Cryptograptus and Paraglossograptus. This interval, equivalent to Dai of the Australasian scheme, therefore represents a hitherto unrecorded major evolutionary step in graptolite evolution.

scholarly journals Multiphase MCM–CAPRAM modeling of the formation and processing of secondary aerosol constituents observed during the Mt. Tai summer campaign in 2014

2020 ◽  
Vol 20 (11) ◽  
pp. 6725-6747 ◽  
Author(s):  
Yanhong Zhu ◽  
Andreas Tilgner ◽  
Erik Hans Hoffmann ◽  
Hartmut Herrmann ◽  
Kimitaka Kawamura ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Aqueous Phase ◽  
Glyoxylic Acid ◽  
Northern China ◽  
Chemical Mechanism ◽  
Radical Mechanism ◽  
Formation Mechanisms ◽  
Major Pathway ◽  
Voc Emissions ◽  
Secondary Aerosol

Abstract. Despite the high abundance of secondary aerosols in the atmosphere, their formation mechanisms remain poorly understood. In this study, the Master Chemical Mechanism (MCM) and the Chemical Aqueous-Phase Radical Mechanism (CAPRAM) are used to investigate the multiphase formation and processing of secondary aerosol constituents during the advection of air masses towards the measurement site of Mt. Tai in northern China. Trajectories with and without chemical–cloud interaction are modeled. Modeled radical and non-radical concentrations demonstrate that the summit of Mt. Tai, with an altitude of ∼1.5 km a.m.s.l., is characterized by a suburban oxidants budget. The modeled maximum gas-phase concentrations of the OH radical are 3.2×106 and 3.5×106 molec. cm−3 in simulations with and without cloud passages in the air parcel, respectively. In contrast with previous studies at Mt. Tai, this study has modeled chemical formation processes of secondary aerosol constituents under day vs. night and cloud vs. non-cloud cases along the trajectories towards Mt. Tai in detail. The model studies show that sulfate is mainly produced in simulations where the air parcel is influenced by cloud chemistry. Under the simulated conditions, the aqueous reaction of HSO3- with H2O2 is the major contributor to sulfate formation, contributing 67 % and 60 % in the simulations with cloud and non-cloud passages, respectively. The modeled nitrate formation is higher at nighttime than during daytime. The major pathway is aqueous-phase N2O5 hydrolysis, with a contribution of 72 % when cloud passages are considered and 70 % when they are not. Secondary organic aerosol (SOA) compounds, e.g., glyoxylic, oxalic, pyruvic and malonic acid, are found to be mostly produced from the aqueous oxidations of hydrated glyoxal, hydrated glyoxylic acid, nitro-2-oxopropanoate and hydrated 3-oxopropanoic acid, respectively. Sensitivity studies reveal that gaseous volatile organic compound (VOC) emissions have a huge impact on the concentrations of modeled secondary aerosol compounds. Increasing the VOC emissions by a factor of 2 leads to linearly increased concentrations of the corresponding SOA compounds. Studies using the relative incremental reactivity (RIR) method have identified isoprene, 1,3-butadiene and toluene as the key precursors for glyoxylic and oxalic acid, but only isoprene is found to be a key precursor for pyruvic acid. Additionally, the model investigations demonstrate that an increased aerosol partitioning of glyoxal can play an important role in the aqueous-phase formation of glyoxylic and oxalic acid. Overall, the present study is the first that provides more detailed insights in the formation pathways of secondary aerosol constituents at Mt. Tai and clearly emphasizes the importance of aqueous-phase chemical processes on the production of multifunctional carboxylic acids.

Cambrian–Lower Ordovician of SW Quebec–NE New York

2021 ◽  
pp. 1-32
Author(s):  
Osman Salad Hersi ◽  
Ed Landing ◽  
David Franzi ◽  
James Hagadorn
Keyword(s):  
New York ◽  
Sediment Accumulation ◽  
Early Cambrian ◽  
Geological History ◽  
Middle Cambrian ◽  
Early Ordovician ◽  
Lower Ordovician ◽  
History Of ◽  
Rodinia Supercontinent ◽  
Stratigraphic Nomenclature

ABSTRACT The Ottawa aulacogen/graben on the NE US—Canadian (SW Quebec and eastern Ontario) border is a long ENE-trending structure formed with initial late Neo proterozoic rifting of the Rodinia supercontinent. This rifting formed the active spreading arms (New York Promontory and Quebec Reentrant) along the (presently) NE margin of the new Laurentia paleocontinent, with the Ottawa aulacogen commonly regarded as a failed arm of the rifting. However, no sediment accumulation in the aulacogen is recorded until the late early Cambrian subsidence of a SE- trending belt that includes the aulacogen and its extension, the Franklin Basin, in NW Vermont. Late early Cambrian marine onlap (Altona Formation) followed by more rapid late middle Cambrian subsidence and deposition of fluviatile arkoses (Covey Hill Formation of SW Quebec and Ausable Formation/Member of eastern New York) record rapid foundering of this “failed arm.” Subsequent deposition (latest middle Cambrian–Early Ordovician) in the Ottawa aulacogen produced a vertical succession of lithofacies that are fully comparable with those of the shelf of the New York Promontory. One of the greatest challenges in summarizing the geological history of the Ottawa aulacogen is the presence of a duplicate stratigraphic nomenclature with lithostratigraphic names changing as state and provincial borders are crossed.

3D geological models from combined interpretation of airborne-TEM and geological data- Two examples from Sweden

2020 ◽  
Author(s):  
Mehrdad Bastani ◽  
Lena Persson ◽  
Peter Dahlqvist ◽  
Eva Wendelin ◽  
Johan Daniels
Keyword(s):  
Groundwater Resources ◽  
Geophysical Data ◽  
Saline Groundwater ◽  
Middle Cambrian ◽  
3D Geological Modeling ◽  
Rock Types ◽  
Transient Electromagnetic ◽  
Lower Ordovician ◽  
Geological Models ◽  
Resistivity Image

<p><span><span>The geological survey of Sweden (SGU) has carried out several detailed airborne TEM (Transient Electromagnetic) surveys in recent years. The data collected in these surveys were inverted to provide models of the resistivity of the subsurface, down to a few hundred meters depth. </span></span><span>These resistivity models together with the data from existing boreholes and ground observations offer an excellent basis for further 3D geological modeling.  </span></p><p><span>The airborne TEM data presented in this study were collected between 2013 and 2016, covering large areas of the islands of Öland and Gotland, in Sweden. Both islands face problems with water supply due to limited groundwater resources. The aim of the surveys was to identify new groundwater resources, specify the depth to saline groundwater and to improve the understanding of the geology of the islands. On Öland, the Paleozoic sedimentary succession reaches thicknesses of approximately 250 m and is composed of Lower Cambrian sandstone, Middle Cambrian siltstone, and claystone followed by the Alum Shales of Upper Cambrian and Lower Ordovician age. Above this lies an up to 40 m thick Lower Ordovician limestone succession, which forms the bedrock at the surface across much of the island. The entire sedimentary sequence rests on Precambrian crystalline rocks. On the Island of Gotland, Silurian bedrock represents the upper part of a 250-800 m thick Paleozoic sequence overlying the crystalline basement. The Silurian bedrock is dominated by interbedded layers </span><span><span>of limestone and marlstone, where the interface between limestone and marlstone is often the primary hydraulic conductor.</span></span></p><p><span>After acquisition, these data were processed and inverted (1D inversions with lateral constraints), to provide a series of large airborne datasets, providing a resistivity image down to depths of about 250 m in some areas. The considerable resistivity contrast between lithologies, e.g. limestone and marlstone on Gotland, provided an excellent opportunity to resolve boundaries between the different rock types. Borehole information, geological maps, ground geophysical data and the inversion results were incorporated in a 3D geological modelling software. On comparison of the </span><span><span>airborne models, ground geophysical data and borehole information it was clear that the airborne resistivity models correlated well with the other available data. Hence, t</span>he resistivity models were used as the basis for constructing the 3D hydrogeological and geological models over significant parts of the islands. <span>In this study we present the 3D geological models over the islands of Öland and Gotland which were constructed from the integrated interpretation of all the available data. The models are composed of voxels, each representing a certain lithology classified using a statistical approach. The classification is based on the resistivity range, distance to the neighboring wells/boreholes and the geological observations at the surface. The 3D voxel models will be/have been utilized in hydrological modelling, societal planning, and groundwater management.</span></span></p>

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