PALEOKARST IN THE LOWER ORDOVICIAN BEEKMANTOWN GROUP, OTTAWA EMBAYMENT - STRUCTURAL CONTROL INBOARD OF THE APPALACHIAN OROGEN

Citation
Gr. Dix et al., PALEOKARST IN THE LOWER ORDOVICIAN BEEKMANTOWN GROUP, OTTAWA EMBAYMENT - STRUCTURAL CONTROL INBOARD OF THE APPALACHIAN OROGEN, Geological Society of America bulletin, 110(8), 1998, pp. 1046-1059
Citations number
73
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geosciences, Interdisciplinary
ISSN journal
0016-7606
Volume
110
Issue
8
Year of publication
1998
Pages
1046 - 1059
Database
ISI
SICI code
0016-7606(1998)110:8<1046:PITLOB>2.0.ZU;2-4
Abstract
Two paleokarsts, different in age, character, and origin, occur in dol ostones of the Lower Ordovician Beekmantown Group of eastern Ontario, well within the interior of the Laurentian paleoplatform, Surficial to shallow subsurface (<2 m) epikarst formed during the latter stage Gat e Arenig to Llanvirn) of Sauk platform development in this region, res ulting from local change to base level and patterns of meteoric circul ation Likely initiated by reactivation of shallowly buried Precambrian structures along a cratonic fault system, now defined by the Ottawa-B onnechere Graben, Faulting was contemporaneous,vith initiation of the crustal forebulge within the distal, developing Taconic orogen. Minera lized, intrastratal, vuggy to local cavernous porosity composes a prom inent second, more regional paleokarst, Dissolution followed burial ch emical compaction, but predated a history of further burial and tecton ism defined by stages of geopetal cavity-fill sedimentation, cavity-fi ll mineralization, calcite veining, and renewed stylolitization. Regio nal paleokarst is interpreted to have arisen from changes in pCO(2) an d H2S concentrations arising from mixing of continentally derived pore waters with brines derived from dissolution of Beekmantown evaporites . Compared to the region's geologic history, a pre-late Paleozoic age for formation of the regional paleokarst and mineralization is likely. The two platform-interior paleokarsts demonstrate unexpected links be tween tectonism, changes in paleohydrological patterns, and porosity d evelopment well inboard of the Appalachian orogen.