Research Article| February 01, 1980 Update on feldspar and oxide thermometry in the Adirondack Mountains, New York STEVEN R. BOHLEN; STEVEN R. BOHLEN 1Department of Geology and Mineralogy, University of Michigan, Ann Arbor, Michigan 48109. Present address: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, California 90024 Search for other works by this author on: GSW Google Scholar ERIC J. ESSENE; ERIC J. ESSENE 1Department of Geology and Mineralogy, University of Michigan, Ann Arbor, Michigan 48109. Present address: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, California 90024 Search for other works by this author on: GSW Google Scholar KAREN S. HOFFMAN KAREN S. HOFFMAN 1Department of Geology and Mineralogy, University of Michigan, Ann Arbor, Michigan 48109. Present address: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, California 90024 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1980) 91 (2): 110–113. https://doi.org/10.1130/0016-7606(1980)91<110:UOFAOT>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation STEVEN R. BOHLEN, ERIC J. ESSENE, KAREN S. HOFFMAN; Update on feldspar and oxide thermometry in the Adirondack Mountains, New York. GSA Bulletin 1980;; 91 (2): 110–113. doi: https://doi.org/10.1130/0016-7606(1980)91<110:UOFAOT>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Recently obtained feldspar and oxide temperature data for orthogneiss and paragneiss in the Adirondack Mountains, New York, further constrain and generally support the regional thermometry previously established. Peak metamorphic temperatures were 700 to 750 °C throughout most of the Adirondack Highlands and 750 to 800 °C in the High Peaks region during the Granville metamorphic event. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
It is inherently difficult to visualize, map, model, and eventually analyze faulted prospects. Traditional two‐dimensional methods, whether applied by hand or computer, have severe limitations which too often result in the drilling of drained fault blocks, the relinquishing of prime prospects, or a missed opportunity to book additional reserves.
ABSTRACT The three-dimensional nature of salt bodies has historically been a problem in visualization and interpretation. Traditional approaches, based on two-dimensional grids, cannot handle the multi-valued surfaces of salt overhangs, lenses, or other features. Some three-dimensional modeling approaches allow multi-valued surfaces, but cannot combine the image of a salt body with surrounding structural layers. These limitations can be avoided by combining appropriate salt modeling techniques with a geospatial structural model. The geospatial modeling process treats faults and horizons as separate entities; this approach is ideally suited for modeling faulted structures. Horizons are truncated against fault surfaces (and/or other horizons), providing an internal consistency in the resulting structural model. Previously, the geospatial model required a three-dimensional object, such as a salt body, to be represented by a three-dimensional grid. This data structure, while useful, was too cumbersome to handle some of the fine detail of a salt body, and required a significant amount of data preparation. A new methodology of surface generation, which bypasses the gridding step, has been developed and incorporated into the geospatial modeling process. This new methodology allows more complicated shapes to be built and changed easily, while still providing all of the benefits of the structural model's fault block-oriented display. This approach has been used successfully to develop structural models for accurate and precise well planning, increasing the confidence in the interpretation and decreasing the uncertainty and risk often associated with drilling near salt.
ABSTRACT In the highly explored South Addition of the West Cameron Lease Area, Louisiana offshore, interpretation of a six-mile (10 km) seismic section across a single intraslope basin yielded 20 sediment packages. Several interpretive tools were necessary. Seismic stratigraphy indicated that the shallower zone was an outer shelf marked by 8 major sea level oscillations. In the portion between 1 and 3 seconds, seismic stratigraphy and paleontology led to the interpretation of depositional environments as upper slope, paleobathymetrically deeper with descent through the section. The intraslope basin, while small, may be viewed as a microcontinental margin. Each sea level oscillation cycle apparently made a distinct progradational unit, decipherable in the seismic data. Fourth order cycles have been provisionally interpreted throughout most of the entire 3.7 second section. Such precision is possible only in explored basins with excellent seismic data. The sequence thickness showed a seven-fold variability, from 0.08 to 0.58 seconds. The shallower section, deposited along an outer shelf, has an average individual sequence thickness of 0.13 seconds. Individual seismic sequences in the deeper section, interpreted to have been deposited on an upper slope, have average thicknesses of 0.25 seconds. The thinner sequences of the shallower section are compatible with the notion that the outer shelf was a bypass zone during a glacial epoch. The thicker sequences of the deeper section are the result of deposition onto an aggrading upper slope within an intraslope basin during a high stand.
Abstract Rigorous, internally consistent three-dimensional subsurface models are extremely useful in interpretation, mapping, well planning, and simulation pre-processing. The geospatial technique to create these models has been in use for several years, and complicated, highly faulted structures (including overthrusts and other multi-valued surfaces) have been modeled quite successfully. Often, however, the gridding process used to create the horizon surfaces required additional control points, and the shape of the overall structure was not necessarily continued from one fault block to another. A new algorithm has now been developed that uses a three-dimensional model of the faulting process itself to restore data to a pre-faulted condition. Displacement on a given fault surface can vary laterally as well as in depth, and faults which terminate within the model volume are of course accommodated. All horizons are used simultaneously in the process of creating the fault displacement model, which eliminates problems with sparse control or narrow fault blocks. The structural surfaces are then calculated in unfaulted space, and the faulting model is used to transform the resulting surfaces back to the proper structural position. Not only is this algorithm significantly faster, but it also mimics the post-depositional faulting process and produces a geologically consistent model. This consistency and integrity mean that greater confidence can be placed in the model, improving volume calculations and allowing placement of wells with greater precision. The reduced cycle time allows a greater range of scenarios to be modeled and evaluated, thus enabling better risk assessment in complexly faulted fields.
