Tectonic evolution Southern Oklahoma Aulacogen

an illustration of formation history of southern oklahoma aulacogen. in a, volcanoes form along continental plate boundary. b shows triple junction s basic appearance following formation. c shows 1 of 3 arms has not split while other 2 do, continuing d, in iapetus ocean forms.

the southern oklahoma aulacogen formed sometime in late proterozoic eon, between 525 , 550 million years ago, during rifting of laurentia supercontinent or north american craton, geological core of north america. formation , bimodal igneous activity occurred simultaneously, 2 definite episodes of magma activity, mafic , felsic, former of being chiefly composed of gabbro-heavy magma , latter phase being composed of rhyolitic magma. hypothesized between mafic , felsic stages of magmatic activity substantial uplift occurred, correlates lack of coarse-grained massif anorthosites presented previously. remaining 2 arms of original triple-junction became spreading zones nascent iapetus ocean. aulacogen penetrated craton, causing normal faults form in became anadarko basin.

the aulacogen underwent crustal shortening , inversion sometime in mississippian period permian period, 330–280 million years ago. coincides closing of iapetus spreading zones , overthrusting of ouachita uplift on anadarko basin, forming wichita mountains. resulted in reactivation of cambrian rift faults, becoming reverse or listric thrust faults. anticlines formed in sedimentary rock layers of basin, contributing formation of deep hydrocarbon reservoir of anadarko basin. formation of these listric faults , anticlines indicates crustal shortening significant, 10–15 km or more.

the igneous rocks found in aulacogen uplifted during ouachita uplift , subsequently reburied both local , transported sediments. there no major deformation of midsection of north america during mesozoic , cenozoic eras, aulacogen s structure , rift assembly preserved. erosion in recent eras has eroded sediments overlying section of plutonic , volcanic rocks once formed bedrock of aulacogen, , result aulacogen 1 of best preserved , best exposed selections of igneous results of ancient rift activity. consequently, southern oklahoma aulacogen designated type in united states.