Forward Modeling of High-Frequency, Glacio-Eustatic, Depositional Sequences: An Example from Middle Pennsylvanian Shelf Carbonates of the SW Paradox Basin, Honaker Trail, Utah: ABSTRACT

AAPG Bulletin ◽  
1990 ◽  
Vol 74 ◽  
Author(s):  
Robert K. Goldhammer, E. J. Oswald,
2002 ◽  
Vol 76 (3) ◽  
pp. 495-517 ◽  
Author(s):  
Scott M. Ritter ◽  
James E. Barrick ◽  
M. Randall Skinner

In cyclical Pennsylvanian strata, conodonts find their greatest stratigraphic utility as biotic signatures of physically defined stratigraphic entities (cycles, parasequences, high frequency sequences, etc.) rather then the primary means of stratigraphic subdivision (e.g., biostratigraphic interval zones). The practice of identifying depositional entities for purposes of regional correlation on the basis of their constituent conodont faunas is herein called conodont sequence biostratigraphy. In this paper, the concept is utilized to successfully correlate Pennsylvanian cycles of the Paradox basin with their Midcontinent counterparts.The Honaker Trail section is the most accessible and well-studied succession of carbonate shelf strata in the Paradox basin. Approximately 350 m of cyclically bedded limestone, sandstone, and shale comprising 53 fifth-order cycles are exposed along the cliffs of the deeply entrenched San Juan River. Maximum transgressive facies of 19 cycles yielded Idiognathodus-Neognathodus- and/or Streptognathodus-dominated conodont faunas. Those from the Chimney Rock, Gothic, LHT-5, UHT-3, UHT-5, UHT-8, unnamed limestone, and Shafer correspond to faunas from the Verdigris, Lower Fort Scott, Altamont (Lake Neosho), Lost Branch, Hertha (Mound City), Swope (Hushpuckney), Dennis (Stark), and South Bend cycles of the Midcontinent, respectively. By extrapolation, all minor cycles of the Marmaton, Pleasanton, and Bronson Groups (except for the Critzer) also appear to have counterparts at Honaker Trail.The position of the Desmoinesian–Missourian boundary in the Honaker Trail section can be approximated using conodonts in conjunction with fusulinids. The highest Desmoinesian conodont fauna, the Idiognathodus nodocarinatus fauna, occurs in cycle UHT-3 in the lower part of the Upper Honaker Trail sequence. The highest occurrence of Beedeina occurs in the same cycle. The lowest conodont fauna with the Missourian species I. eccentricus appears two cycles higher, in cycle UHT-5. Because in the Midcontinent region a small interval of strata separates the first appearance of I. eccentricus from the base of the Missourian, we place the base of the Missourian at the base of cycle UHT-4 (bed 105) at Honaker Trail. The appearance of Streptognathodus firmus and S. pawhuskaensis in the Shafer limestone indicates that the Missourian–Virgilian boundary lies slightly above or below this stratigraphic horizon.


1994 ◽  
Vol 37 (6) ◽  
Author(s):  
A. Mendez ◽  
F. Pacor

The Irpinia project, as carried out by ISMES under a commission from ENEL, had as objectives the developement of a general methodology to simulate broad-band seismic ground motion at near-source and regional distances, and the application of this methodology to the 1980 Irpinia earthquake. Within this general framework, one goal was the comparison of four previously published models for this earthquake in order to arrive at a plausible description of the source process. The comparative study was cast as an inverse problem: that of inferring the spatial extent and temporal behaviour of the rupture process, from geodetic measurements of surface deformation and near-source recordings of ground velocity. This study was complicated by the fact th the Irpinia earthquake was a complex event, involving at least three distinct rupture episodes in a time span of 40 s. However, this same complexity offers the opportunity of illustrating the use of inversion methodologies to 1) infer the spatial slip distribution on a multiple fault system; 2) address the problem of determining the accuracy of the inferred slip models, and 3) use information describing the static characteristics of an earthquakes as an aid in understanding the kinematics of the rupture. This last point is illustrated for the 40 s subevent through the results of a forward modeling study of high-frequency acceleration waveforms using a rupture model based on the inversion results.


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