Preliminary organic petrography of Palaeozoic rocks from the Grand Banks,Newfoundland     

F. Goodarzi  L.R. Snowdon  P.R. Gunther  W.A.M. Jenkins 《Marine and Petroleum Geology》1985,2(3):254-259

Samples of lower Palaeozoic bedrock from the Grand Banks of Newfoundland were examined using reflected light microscopy and Rock-Eval pyrolysis. These samples contained organic material which included bitumen (structureless organic material), acritarchs, chitinozoa, scolecodonts and graptolites. The reflectance of the organic material increased from acritarchs towards graptolites with bitumen showing a wide range of reflectance. Multiple phases of oil migration through one sample were inferred by examination of the bitumens: the lowest reflecting being more recent than the highest reflecting bitumen. Combined reflectance and Rock-Eval analysis indicate that these samples are mature to overmature. The two oldest samples (Arenig-Llanvirn, Ordovician) are assessed as mature and as having potential for generation of liquid hydrocarbons, but must be considered as mainly gas prone.  相似文献   

Organic petrography of graptolite fragments from Turkey     

Fariborz Goodarzi 《Marine and Petroleum Geology》1984,1(3):202-210

The reflectance and bireflectance of graptolite fragments (Silurian-Ordovician) from southeast Turkey were examined and the morphology was described using reflected light microscopy. The dispersion of maximum and minimum reflectance of graptolites sectioned parallel and perpendicular to the bedding was also determined. The graptolites were anisotropic and the anisotropy was stronger for sections perpendicular to the bedding. The graptolite fragments show two types of surface morphology: granular and non-granular. The granular type had a rough surface and granular anisotropy, the non-granular fragments showed a smooth surface and basic anisotropy. The fine internal structure of graptolite was evident under crossed-polars. The reflectance of graptolite increased with depth and was higher than other organic material, e.g. bitumen, found in the same sediment. The present study indicates that the reflectance of graptolite in sediment can be used to determine the maturity of the dediment.  相似文献   

Factors affecting spatial and temporal variability in material exchange between the Southern Everglades wetlands and Florida Bay (USA)     

Martha A. Sutula  Brian C. Perez  Enrique Reyes  Daniel L. Childers  Steve Davis  John W. Day  Jr.  David Rudnick  Fred Sklar 《Estuarine, Coastal and Shelf Science》2003,57(5-6):757-781

Physical and biological processes controlling spatial and temporal variations in material concentration and exchange between the Southern Everglades wetlands and Florida Bay were studied for 2.5 years in three of the five major creek systems draining the watershed. Daily total nitrogen (TN), and total phosphorus (TP) fluxes were measured for 2 years in Taylor River, and ten 10-day intensive studies were conducted in this creek to estimate the seasonal flux of dissolved inorganic nitrogen (N), phosphorus (P), total organic carbon (TOC), and suspended matter. Four 10-day studies were conducted simultaneously in Taylor, McCormick, and Trout Creeks to study the spatial variation in concentration and flux. The annual fluxes of TOC, TN, and TP from the Southern Everglades were estimated from regression equations. The Southern Everglades watershed, a 460-km² area that includes Taylor Slough and the area south of the C-111 canal, exported 7.1 g C m⁻², 0.46 g N m⁻², and 0.007 g P m⁻², annually. Everglades P flux is three to four orders of magnitude lower than published flux estimates from wetlands influenced by terrigenous sedimentary inputs. These low P flux values reflect both the inherently low P content of Everglades surface water and the efficiency of Everglades carbonate sediments and biota in conserving and recycling this limiting nutrient. The seasonal variation of freshwater input to the watershed was responsible for major temporal variations in N, P, and C export to Florida Bay; approximately 99% of the export occurred during the rainy season. Wind-driven forcing was most important during the later stages of the dry season when low freshwater head coincided with southerly winds, resulting in a net import of water and materials into the wetlands. We also observed an east to west decrease in TN:TP ratio from 212:1 to 127:1. Major spatial gradients in N:P ratios and nutrient concentration and flux among the creek were consistent with the westward decrease in surface water runoff from the P-limited Everglades and increased advection of relatively P-rich Gulf of Mexico (GOM) waters into Florida Bay. Comparison of measured nutrient flux from Everglades surface water inputs from this study with published estimates of other sources of nutrients to Florida Bay (i.e. atmospheric deposition, anthropogenic inputs from the Florida Keys, advection from the GOM) show that Everglades runoff represents only 2% of N inputs and 0.5% of P input to Florida Bay.  相似文献   

The Removal of Dissolved Metals by Hydroxysulphate Precipitates during Oxidation and Neutralization of Acid Mine Waters, Iberian Pyrite Belt   总被引：4，自引：0，他引：4  

J. Sánchez España  E. López Pamo  E. Santofimia Pastor  J. Reyes Andrés  J. A. Martín Rubí 《Aquatic Geochemistry》2006,12(3):269-298

This study examines the removal of dissolved metals during the oxidation and neutralization of five acid mine drainage (AMD) waters from La Zarza, Lomero, Esperanza, Corta Atalaya and Poderosa mines (Iberian Pyrite Belt, Huelva, Spain). These waters were selected to cover the spectrum of pH (2.2–3.5) and chemical composition (e.g., 319–2,103 mg/L Fe; 2.85–33.3 g/L SO₄⁼) of the IPB mine waters. The experiments were conducted in the laboratory to simulate the geochemical evolution previously recognized in the field. This evolution includes two stages: (1) oxidation of dissolved Fe(II) followed by hydrolysis and precipitation of Fe(III), and (2) progressive pH increase during mixing with fresh waters. Fe(III) precipitates at pH < 3.5 (stages 1 and 2) in the form of schwertmannite, whereas Al precipitates during stage 2 at pH 5.0 in the form of several hydroxysulphates of variable composition (hydrobasaluminite, basaluminite, aluminite). During these stages, trace elements are totally or partially sorbed and/or coprecipitated at different rates depending basically on pH, as well as on the activity of the SO₄⁼ anion (which determines the speciation of metals). The general trend for the metals which are chiefly present as aqueous free cations (Pb²⁺, Zn²⁺, Cu²⁺, Cd²⁺, Mn²⁺, Co²⁺, Ni²⁺) is a progressive sorption at increasing pH. On the other hand, As and V (mainly present as anionic species) are completely scavenged during the oxidation stage at pH < 3.5. In waters with high activities (> 10⁻¹) of the SO ₄⁼ ion, some elements like Al, Zn, Cd, Pb and U can also form anionic bisulphate complexes and be significantly sorbed at pH < 5. The removal rates at pH 7.0 range from around 100% for As, V, Cu and U, and 60–80% for Pb, to less than 20% for Zn, Co, Ni and Mn. These processes of metal removal represent a significant mechanism of natural attenuation in the IPB.  相似文献   

Comparison of source rock geochemistry of selected rocks from the Schei Point group and Ringnes formation, Sverdrup basin, arctic Canada     

P. K. Mukhopadhyay  F. Goodarzi  M. A. Kruge  M. H. Alimi 《International Journal of Coal Geology》1997,34(3-4)

Organic-rich from the Schei Point group (middle to late Triassic in age) and the Ringnes formation (late Jurassic) from the Sverdrup basin of the Canadian arctic archipelago have been geochemically evaluated for source rock characterization. Most samples from the Schei Point group are organic-rich (> 2% TOC and are considered as immature to mature oil-prone source rocks [kerogen types I, I–II (IIA) and II (IIA)]. These kerogen types contain abundant AOM1, AOM2 and alginite (Tasmanales, Nostocopsis, Leiosphaeridia, acritarch and dinoflagellate) with variable amounts of vitrinite, inertinite and exinite. Samples from the Ringnes formation contain dominant vitrinite and inertinite with partially oxidized AOM2, alginite and exinite forming mostly immature to mature condensate- and gas-prone source rocks [kerogen type II–III (IIB), III and a few II (IIA)]. Schei Point samples contain higher bitumen extract, saturate hydrocarbons and saturate/ aromatic ratio than the Ringnes samples. Triterpane and sterane (dominant C₃₀) distribution patterns and stable carbon isotope of bitumen and kerogen suggest that the analyzed samples from the Schei Point group are at the onset of oil generation and contain a mixture of sapropelic (algal) and minor terrestrial humic organic matter. Sterane carbon number distributions in the Ringnes formation also suggest a mixed algal and terrestrial organic matter type. There are some variations in hopane carbon number distributions, but these are apparently a function of thermal maturity rather than significant genetic differences among samples. Pyrolysis-gas chromatography/mass spectrometry of the two samples with similar maturity shows that the Schei Point sample generates three times more pyrolyzate than the Ringnes sample. Both samples have a dominant aliphatic character, although the Ringnes sample contains phenol and an aromaticity that is higher than that of the Schei Point sample.  相似文献   

Assessing land use/cover changes: a nationwide multidate spatial database for Mexico     

Jean-Franois Mas  Alejandro Velzquez  Jos Reyes Díaz-Gallegos  Rafael Mayorga-Saucedo  Camilo Alcntara  Gerardo Bocco  Rutilio Castro  Tania Fernndez  Azucena Prez-Vega 《International Journal of Applied Earth Observation and Geoinformation》2004,5(4):249-261

A nationwide multidate GIS database was generated in order to carry out the quantification and spatial characterization of land use/cover changes (LUCC) in Mexico. Existing cartography on land use/cover at a 1:250,000 scale was revised to select compatible inputs regarding the scale, the classification scheme and the mapping method. Digital maps from three different dates (the late 1970s, 1993 and 2000) were revised, evaluated, corrected and integrated into a GIS database. In order to improve the reliability of the database, an attempt was made to assess the accuracy of the digitalisation procedure and to detect and correct unlikely changes due to thematic errors in the maps. Digital maps were overlaid in order to generate LUCC maps, transition matrices and to calculate rates of conversion. Based upon this database, rates of deforestation between 1976 and 2000 were evaluated as 0.25 and 0.76% per year for temperate and tropical forests, respectively.  相似文献   

The palaeoenvironmental and palaeohydrological evolution of Padul Peat Bog (Granada, Spain) over one million years, from elemental, isotopic and molecular organic geochemical proxies   总被引：1，自引：0，他引：1  

J.E. Ortiz  T. Torres  A. Delgado  R. Juli  M. Lucini  F.J. Llamas  E. Reyes  V. Soler  M. Valle 《Organic Geochemistry》2004,35(11-12):1243

The elemental (concentration of organic carbon, atomic H/C and C/N ratios), isotopic (δ¹³C values of organic matter) and molecular (predominant n-alkane chain length and carbon preference index (CPI)) organic components were measured for 600 samples taken from a 107-m long core from the Padul Basin (Andalusia, Spain). The record runs from the Lower Pleistocene (ca. 1 Ma B.P.) to the mid-Holocene (ca. 4.5 ka B.P.) with, in general, little diagenesis (removal of components). Two markedly different hydrogeological scenarios were interpreted: (1) From ca. 1 Ma to ca. 400 ka B.P. run-off recharge was significant and water depths were greater (lacustrine scenario). From ca. 400 to 4.5 ka B.P., the Padul Basin became a peat bog s.s. with the major water input coming from groundwater inflow. From ca. 400 to ca. 180 ka B.P. alternating episodes with either predominant grasses, trees or aquatic macrophytes which were linked to wet/dry phases, took place. An important deglaciation episode has been interpreted to occur between ca. 180 and 170 ka B.P. The global climatic changes occurring from ca. 170 to 25 ka B.P. were not recorded in the proxies, though they do show important variations linked to the Last Glacial Maximum and the beginning of the Holocene (ca. 25–10 ka B.P.): (2) Cold phases coexisting with dry periods produced the recession of forests and the development of grasses. After these periods, as both temperature and precipitation increased, forests expanded and the water level, linked to thaw, rose, especially at ca. 20 ka B.P. Few changes occurred during the Holocene, although there were short alternations between wet and dry episodes. Overall, the techniques applied proved to be excellent palaeoenvironmental proxies for studying the basin’s palaeoclimatological and palaeohydrological evolution.  相似文献   

Salinisation des nappes côtières : cas de la nappe nord du Sahel de Sfax,Tunisie     

Rouaida Trabelsi  Moncef Zaïri  Habib Smida  Hamed Ben Dhia 《Comptes Rendus Geoscience》2005,337(5):515-524

The intensive agricultural and economic activities induce the increase of the risk of groundwater quality degradation through high groundwater pumping rates. The salinization and contamination are the main sources of this pollution, especially in coastal aquifers. The explanation of the origin of salinity for the shallow aquifer of Northern Sahel of Sfax was analysed by a chemical study of the groundwater main compounds. The partitioning of groundwaters into homogenous groups is undertaken by graphical techniques, including a Stiff pattern diagram, an expanded Durov diagram and several binary diagrams. The study indicates the presence of various salinization processes. In the recharge area, salinization is the result of dissolution/precipitation of the aquifer formation material (group I). The irrigation water return and the intensive pumping have been identified as major sources of salinization in the south by direct cation exchange and mixing reactions (groups II and III). The anomaly of high groundwater salinity observed near the Hazeg zone was explained by the presence of a seawater intrusion in this area. This hypothesis is related to the high chloride concentration, to the presence of inverse cation exchange reactions (group IV), and to the piezometric level inferior to sea level. To cite this article: R. Trabelsi et al., C. R. Geoscience 337 (2005).  相似文献   

Dynamics of the January 2013–June 2014 explosive-effusive episode in the eruption of Volcán de Colima,México: insights from seismic and video monitoring     

Vyacheslav M. Zobin  Raúl Arámbula  Mauricio Bretón  Gabriel Reyes  Imelda Plascencia  Carlos Navarro  Armando Téllez  Arnoldo Campos  Miguel González  Zoraida León  Alejandro Martínez  Carlos Ramírez 《Bulletin of Volcanology》2015,77(4):1-13

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Investigation of moment-rotation relation in different joint types and evaluation of their effects on segmental tunnel lining     

Abbas?Majdi  Hamed?Ajamzadeh  Siavash?NadimiEmail author 《Arabian Journal of Geosciences》2016,9(7):512

This paper presents the results of a numerical study that has been performed to investigate the different joint types that affect the moment-rotation relation and ultimate bending moment capacity of a joint. A 3D finite element method was adapted to establish elaborate numerical models of segments. To evaluate the possible differences in moment-rotation behavior between different joint types, 10 different joint types were simulated. Additionally, the effect of different joint types on behavior of a lining ring was investigated. The validity of the peridynamic simulation was tested by comparing results obtained in this paper against the results obtained in a study performed by Hordijk and Gijsbers. Observations of the results demonstrate that in a flat joint, the expanding of joint height increased the rotation stiffness of the joint in the linear branch, and accordingly, the ultimate bending moment of the joint increased. In the ring model, it was observed that the expanding of joint height led to the decreased of ring displacement and stress concentration in the joint. Whenever there were full surface contacts (contact two segment in total cross section) in the joints, the rotation stiffness of the joints in the linear branch became equal, and, as a result, the displacement in the ring model was the same in all joint types. In addition, it was observed that using a convex joint in the ring model increases the displacement of the ring. The ultimate bending moment of bolted joints was higher than that of joints without bolts, especially in the case of a negative moment.  相似文献