{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/20273"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/20273","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Origin and stratigraphic significance of limestone discontinuity surfaces, Ordovician (Whiterockian) of Nevada","abstract":"Results indicate that discontinuity surfaces enhance correlations between sections only after a well-established biostratigraphic zonation is in place. Chronostratigraphically significant discontinuities parallel biozone boundaries or occur in roughly equivalent abundances within zones. Diachronous surfaces may demonstrably converge into single discontinuity surfaces in other sections. Diachronous surfaces appear, in part, to be a function of topographic irregularities within the depositional system.","abstract_html":"Results indicate that discontinuity surfaces enhance correlations between sections only after a well-established biostratigraphic zonation is in place. Chronostratigraphically significant discontinuities parallel biozone boundaries or occur in roughly equivalent abundances within zones. Diachronous surfaces may demonstrably converge into single discontinuity surfaces in other sections. Diachronous surfaces appear, in part, to be a function of topographic irregularities within the depositional system.","abstract_has_math":false,"creators":["Siewers, Fredrick Deschweinitz"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Geology","degree_department":null,"school":null,"contributors":["Sandberg, Philip A."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T12:34:28Z","date_published":"2011-05-07T12:34:28Z","updated_at":"2026-07-22T22:25:15Z","subjects":["Geology"],"languages":["eng"],"rights":["Copyright 1995 Siewers, Fredrick Deschweinitz"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9522175","(UMI)AAI9522175"],"render_values":[{"text":"AAI9522175","href":null,"code":true},{"text":"(UMI)AAI9522175","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/20273","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Sandberg, Philip A."]},{"key":"dc:creator","label":"Author","values":["Siewers, Fredrick Deschweinitz"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T12:34:28Z","10000-01-01","1995"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Geology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Geology"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1995 Siewers, Fredrick Deschweinitz"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9522175","(UMI)AAI9522175","http://hdl.handle.net/2142/20273"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Results indicate that discontinuity surfaces enhance correlations between sections only after a well-established biostratigraphic zonation is in place. Chronostratigraphically significant discontinuities parallel biozone boundaries or occur in roughly equivalent abundances within zones. Diachronous surfaces may demonstrably converge into single discontinuity surfaces in other sections. Diachronous surfaces appear, in part, to be a function of topographic irregularities within the depositional system.","Discontinuity surfaces in Ordovician (Whiterockian) limestones of central and southern Nevada have been studied to: (1) establish new, general criteria for their recognition in Lower Paleozoic limestones; (2) constrain factors influencing their development in various depositional settings; (3) evaluate their use in stratigraphic correlations; and (4) examine their chronostratigraphic and sequence stratigraphic significance. The discontinuities studied include coastal paleokarst surfaces, submarine hardgrounds, and submarine omission surfaces, differentiated by their surface features, facies associations, and, in some examples, geochemical relationships. Coastal paleokarst surfaces in Lower Paleozoic limestones are distinguishable from submarine hardgrounds by slight depletions ($\\le1\\perthous$) in $\\delta\\sp{18}$O content of grain and cement components below surfaces relative to $\\delta\\sp{18}$O content of similar components in overlying lithologies.","In the Ordovician limestones examined, discontinuity surfaces formed whenever synsedimentary lithification and erosion were essentially in equilibrium. With the exception of omission surfaces, discontinuity lithification occurred by early marine cementation, driven either by wave and tidal pumping or by oceanic current pumping. Locally, lithification was controlled by the degree of substrate stability, mineralogical composition of the grain components, and the depositional porosity-permeability of the sediments. Regionally, discontinuity surface formation was governed by relative sea level fluctuations which regulated the absolute space available for sediment accumulation (accommodation space). Variations in accommodation space, in turn, controlled processes of near-surface porewater circulation and lithification, influenced the degree of synsedimentary sea floor erosion, and regulated cyclic phosphogenesis in some deep-water settings.","\"Spatially widespread facies successions bounded by closely-spaced discontinuity surfaces define an \"\"accommodation minimum zone\"\" which is interpreted as the stratigraphic expression, in the study area, of the Sauk-Tippecanoe unconformity. Contrary to some proposed interpretations of Ordovician sea level history, closely spaced discontinuity surfaces suggest a relative sea level lowstand during the latest Ibexian-earliest Whiterockian prior to an Early Whiterockian relative sea level rise.\"","Made available in DSpace on 2011-05-07T12:34:28Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9522175.pdf: 11856817 bytes, checksum: 39b38ad17fc045b3749b047037b60705 (MD5) Previous issue date: 1995","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:42:47Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:18:39-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"]},{"key":"dc:title","label":"Title","values":["Origin and stratigraphic significance of limestone discontinuity surfaces, Ordovician (Whiterockian) of Nevada"]}]}],"canonical_facts":{"dc:contributor":["Sandberg, Philip A."],"dc:creator":["Siewers, Fredrick Deschweinitz"],"dc:date":["2011-05-07T12:34:28Z","10000-01-01","1995"],"dc:description":["Results indicate that discontinuity surfaces enhance correlations between sections only after a well-established biostratigraphic zonation is in place. Chronostratigraphically significant discontinuities parallel biozone boundaries or occur in roughly equivalent abundances within zones. Diachronous surfaces may demonstrably converge into single discontinuity surfaces in other sections. Diachronous surfaces appear, in part, to be a function of topographic irregularities within the depositional system.","Discontinuity surfaces in Ordovician (Whiterockian) limestones of central and southern Nevada have been studied to: (1) establish new, general criteria for their recognition in Lower Paleozoic limestones; (2) constrain factors influencing their development in various depositional settings; (3) evaluate their use in stratigraphic correlations; and (4) examine their chronostratigraphic and sequence stratigraphic significance. The discontinuities studied include coastal paleokarst surfaces, submarine hardgrounds, and submarine omission surfaces, differentiated by their surface features, facies associations, and, in some examples, geochemical relationships. Coastal paleokarst surfaces in Lower Paleozoic limestones are distinguishable from submarine hardgrounds by slight depletions ($\\le1\\perthous$) in $\\delta\\sp{18}$O content of grain and cement components below surfaces relative to $\\delta\\sp{18}$O content of similar components in overlying lithologies.","In the Ordovician limestones examined, discontinuity surfaces formed whenever synsedimentary lithification and erosion were essentially in equilibrium. With the exception of omission surfaces, discontinuity lithification occurred by early marine cementation, driven either by wave and tidal pumping or by oceanic current pumping. Locally, lithification was controlled by the degree of substrate stability, mineralogical composition of the grain components, and the depositional porosity-permeability of the sediments. Regionally, discontinuity surface formation was governed by relative sea level fluctuations which regulated the absolute space available for sediment accumulation (accommodation space). Variations in accommodation space, in turn, controlled processes of near-surface porewater circulation and lithification, influenced the degree of synsedimentary sea floor erosion, and regulated cyclic phosphogenesis in some deep-water settings.","\"Spatially widespread facies successions bounded by closely-spaced discontinuity surfaces define an \"\"accommodation minimum zone\"\" which is interpreted as the stratigraphic expression, in the study area, of the Sauk-Tippecanoe unconformity. Contrary to some proposed interpretations of Ordovician sea level history, closely spaced discontinuity surfaces suggest a relative sea level lowstand during the latest Ibexian-earliest Whiterockian prior to an Early Whiterockian relative sea level rise.\"","Made available in DSpace on 2011-05-07T12:34:28Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9522175.pdf: 11856817 bytes, checksum: 39b38ad17fc045b3749b047037b60705 (MD5) Previous issue date: 1995","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:42:47Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:18:39-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"],"dc:identifier":["AAI9522175","(UMI)AAI9522175","http://hdl.handle.net/2142/20273"],"dc:language":["eng"],"dc:rights":["Copyright 1995 Siewers, Fredrick Deschweinitz"],"dc:subject":["Geology"],"dc:title":["Origin and stratigraphic significance of limestone discontinuity surfaces, Ordovician (Whiterockian) of Nevada"],"dc:type":["text"],"thesis:degree_discipline":["Geology"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:15Z"}