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- Kalefa, Mohamed, 1971-
(författare)
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Diagenesis and Sequence Stratigraphy : Predictive Models for Reservoir Quality Evolution of Fluvial and Glaciogenic and Non-glaciogenic, Paralic Deposits
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Development of a predictive model for the distribution of diagenetic alterations and related evolution of reservoir quality of sandstones was achieved by integrating the knowledge of diagenesis to sequence stratigraphy. This approach allows a better elucidation of the distribution of eogenetic alterations within sequence stratigraphy, because changes in the relative sea level induce changes to: (i) pore water chemistry, (ii) residence time of sediments under certain near-surface geochemical conditions, (iii) variations in the detrital composition, and (iv) amounts and type of organic matter.This thesis revealed that eogenetic alterations, which are linked to sequence stratigraphy and have an impact on reservoir quality evolution, include formation of: (i) pseudomatrix and mechanically infiltrated clays in fluvial sandstones of the lowstand and highstand systems tracts (LST and HST, respectively), (ii) kaolinite in tide-dominated deltaic and foreshore-shoreface sandstones of HST, Gilbert-type deltaic sandstones of LST and fluvial deltaic sandstones of LST, (iii) kaolinite and mechanically infiltrated clays in sandstones lying below sequence boundary, (iv) K-feldspar overgrowths in fluvial deltaic LST, (v) glaucony towards the top of fluvial deltaic LST immediately below and at transgressive surface (TS) and in foreshore and shoreface transgressive systems tracts (TST) below parasequence boundaries (PB) and maximum flooding surface (MFS), (vi) framboidal pyrite and extensive cementation by calcite and dolomite in foreshore and shoreface and tide-dominated deltaic TST, and shoreface and tidal flat HST bioclastic-rich arenites particularly in the vicinity of PB, TS and MFS, (vii) pervasive cementation by iron oxide in shoreface-offshore and shoreface sandstones of TST immediately below the MFS, (viii) zeolites and palygroskite in shoreface sandstones of TST and HST, particularly above PB, and (ix) cementation by siderite in Gilbert-type deltaic sandstones of LST, tide-dominated deltaic and foreshore-shoreface sandstones of HST and in tide-dominated deltaic sandstones of TST, particularly at MFS. Moreover, this thesis revealed that the distribution of eogenetic alterations strongly control, and thus provide information for constraining the distribution patterns of mesogenetic alterations, such as illitization of mechanically infiltrated clays and dickitization of kaolinite, and hence of related reservoir quality evolution of sandstones during progressive burial.
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| 2. |
- Shahabi-Ghahfarokhi, Sina
(författare)
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Baltic Sea sediments : Source and sink for metal contamination
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Baltic Sea sediments record spatial and temporal information about metalsand metalloids (hereafter referred to as metals), which could help to understandthe past and present contamination sinks in different basins. In addition, giventhe expanding anoxic zones in the Baltic Sea, the response of metals to artificialreoxygenation is poorly understood. This thesis calculated background valuesfor As, Cd, Co, Cu, Pb, U, and Zn and measured their concentration in sedimentsfrom pre-industrial to recent times. Metal concentration peaks during the1970—1980s and clearly decline till present-day, possibly owing to effectivepollution control measures. Furthermore, anoxic Baltic Proper sedimentssubjected to reoxygenation experiments showed that As, Ba, Co, K, Mn, Rb, U,Sr, and Mo are released to bottom waters, suggesting possible aggravation ofmetal pollution if such mitigation option is applied.During previous coastline transgression (5000 years before CE), rich sulfidicsediments (known as potential acid sulfate soils) were deposited and laterexposed to air by natural processes and/or by artificial drainage systems ofcoastal areas of the present-day Baltic Sea. Oxidation of sulfidic phases resultedin the formation of acid sulfate soils, which are a potential source of metalcontamination to drainage areas. This thesis investigated an area in Kristianstad,southern Sweden, in which metal contamination is sourced from acid sulfatesoils. From the acid sulfate soil site, the dispersion showed enrichment of Fe inthe adjacent wetland in the form of akaganeite/schwertmannite, identified usingX-ray absorption spectroscopy. Furthermore, Be, U, rare-earth elements, and Alwere enriched in the drain sediments. Simultaneously, metals such as Mn, Co,Ni, Zn, and Cd were not or only marginally enriched in the drain sediment. Aremediation experiment to remove metals from the drainage water using spentcoffee-grounds and dissolved humic acid was performed. The spent coffeegroundsefficiently removed Al, Ca, Co, Fe, Mn, Ni, and Zn via adsorption, butfail to remove S from the acid sulfate soil drainage. However, the dissolvedhumic acid removed up to 25% of the S from the drainage.
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