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Title:Ultrahigh-resolution paragenesis of the Cambrian-age Mt. Simon Sandstone at a burial depth of 1.8-2.1 km, Illinois basin, USA
Author(s):Miller, Philip A.
Advisor(s):Fouke, Bruce W.
Department / Program:Geology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Illinois Basin
Mt. Simon Sandstone
Ultrahigh-resolution microscopy
Abstract:A multidisciplinary study utilizing new ultrahigh-resolution microscopy techniques has been undertaken to reconstruct the paragenesis of Cambrian-age Mt. Simon Sandstone quartz arenites buried at 1.8-2.1 km within the Illinois Basin. Results have yielded valuable new insight into the evolution of this important subsurface reservoir and provided the depositional and diagenetic history required to enhance carbon capture and storage (CCS) strategies within early Paleozoic strata of the Illinois Basin. Petrographic analyses of the host quartz arenite Mt. Simon Sandstone lithologies, coupled with wireline log data and formation on Sr-isotope water geochemistry, have permitted the construction and interpretation of a complex sequence of paragenetic events. Core samples were collected from the Illinois Basin-Decatur Project CCS injection well. The 1.8-2.1 km interval of the well was sampled using a Schlumberger mechanical sidewall coring tool, a Modular Formation Dynamics Tester (MDT) and openhole wireline tools. Sidewall cores were extracted from seven stratigraphic horizons (1783 m [5851 ft], 1785 m [5856 ft], 1829 m [6000 ft], 2061 m [6763 ft], 2085 m [6841 ft], 2147 m [7045 ft] and 2148 m [7048 ft]), which have been grouped into lower (2148 - 2061m [7048 - 6763 ft]) and upper (1829 - 1783 m [6000 ft - 5851 ft]) stratigraphic intervals. Polished thin sections were analyzed under plane-light (PL), polarized-light using a Zeiss Axiovert 200M Inverted Fluorescence Microscope (optical resolution of 250 nm), in coordination with analyses on a stand-alone cathodoluminescence-light (CL) stage. The combination of core sample microscopy and wireline log data indicate the lower sampling interval (2.0 - 2.1 km) is a clean quartz arenite with high porosity and permeability. Conversely, the upper sampling interval (1.8 - 1.9 km) exhibit significantly greater clay content and the formation of quartz cement overgrowths that have served to reduce primary porosity and permeability. This represents an up-section depositional shift from distal to more proximal positions within deltaic alluvial fans in arid high-relief terrestrial depositional environments during the Cambrian. Furthermore, the microscopy has been used to document a multistage paragenetic sequence of grain contact suturing during an early compaction event, followed by iron oxide (hematite and goethite) and clay cement precipitation. These were followed by two events of syntaxial, euhedral quartz cement overgrowths and a final ensuing event of iron oxide cements on the quartz cement overgrowths. Comparison of this paragenetic sequence with results from previous studies of the Mt. Simon Sandstone and other early Paleozoic strata in the Midwest, suggest that the quartz overgrowth cements were formed at a maximum burial depth of no more than 2.4 km and maximum burial temperatures greater than 100°C during the late-Paleozoic to early-Mesozoic (Fishman 1997). The modern formation waters have 87Sr/86Sr analyses that more radiogenic than younger Paleozoic strata within the Illinois Basin, and reconstructed values for Cambrian seawater (Stueber et al. 1987; Veizer et al. 1999), suggesting potential sources of radiogenic Sr from internal Mt. Simon Sandstone sands and shales or the Precambrian basement. These results indicate that, due to multiple events of heterogeneous subsurface fluid flow and associated diagenesis, the Mt. Simon Sandstone experienced low to moderate porosity and permeability occlusion during its burial and uplift history within the Illinois Basin.
Issue Date:2011-05-25
Rights Information:Copyright 2011 Philip A. Miller
Date Available in IDEALS:2011-05-25
Date Deposited:2011-05

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