Chunk Formation Research Articles

A new inclination shallowing correction of the Mauch Chunk Formation of Pennsylvania, based on high-field AIR results: Implications for the Carboniferous North American APW path and Pangea reconstructions

A new magnetic anisotropy study was performed on samples of the Lower Carboniferous Mauch Chunk Formation of Pennsylvania. These red beds had been sampled for an inclination shallowing study by Tan and Kodama (2002), however, application of a high-field anisotropy of isothermal remanence magnetization (hf-AIR) technique specifically designed to measure the anisotropy of hematite provides considerably different results from those previously reported. The newly measured fabric has smaller anisotropy (~ 9–17% as opposed to ~ 25–40%) and shows a pronounced ENE–WSW magnetic lineation that is sub-parallel to the trend of the Appalachians and interpretable as a hematite intersection lineation that occurred during local NNW-directed shortening. The measured magnetic fabric yields a new inclination correction with a corrected paleopole that is in better agreement with recently corrected Carboniferous paleopoles than the previously corrected Mauch Chunk paleopole, defining a more consistent APW path. The corrected paleopoles allow calculation of new mean Early (~ 325 Ma) and Late (~ 312 Ma) Carboniferous inclination-corrected paleopoles for North America, which can be compared to coeval, but uncorrected, paleopoles from Gondwana. Results suggest a Pangea B assemblage unless inclination shallowing is considered for Gondwana. Estimating an inclination correction for Gondwana sedimentary rock-derived paleopoles permits a Pangea A-type assemblage at higher southern latitudes than previous reconstructions, which we term Pangea A3.

Amphibian Body Impressions from the Mississippian of Pennsylvania, USA

Temnocorpichnus isaacleai is a new ichnogenus and ichnospecies of temnospondyl amphibian body impression from the Mississippian (Visean) Mauch Chunk Formation of eastern Pennsylvania, United States. The shovel-shaped head, robust limbs, relatively short trunk and smooth integument diagnose the ichnotaxon and readily distinguish it from Hermundurichnus and Sauropleura, the only other named body impressions of Paleozoic tetrapods. Temnocorpichnus is a compound ichnogenus in which the footprint ichnogenus Batrachichnus is a behaviorally distinct component. The temnospondyl identity of Temnocorpichnus adds to the sparse and earliest records of temnspondyls, which are of Visean age. The smooth integument of the ichnogenus does not support the presence of ventral scales or armor in the earliest temnospondyls, but body proportions of the Mauch Chunk body impressions indicate a relatively terrestrial temnospondyl not matched by any taxon now known from bones. Three closely associated impressions of Temnocorpichnus on a single bedding plane suggest some sort of gregarious behavior in Mississippian temnospondyls and may support speculation that internal fertilization and associated courtship behavior evolved independently in one group of amphibians more than 300 million years ago.

The Mississippian Tetrapod Footprint Ichnogenus Palaeosauropus: Extramorphological Variation and Ichnotaxonomy

Palaeosauropus primaevus is a tetrapod footprint ichnotaxon first described from the Upper Mississippian (Visean) Mauch Chunk Formation near Pottsville, Pennsylvania, United States. Our relocation of the type locality and stratigraphic horizon of P. primaevus, a long-available but unstudied collection of tetrapod footprints from these strata, and our new collections allow a much fuller characterization of this ichnotaxon and the range of extramorphological variation encompassed by it. P. primaevus is characterized as the footprints of a quadruped with a pentadactyl pes and a tetradactyl manus, in which the pes frequently oversteps the manus and with which tail drags are common. In the manus, all digits are relatively broad and have rounded tips, digit III is longest, and digit IV is more widely separated from digit III than the other digits are from each other. The pes has five digits that are also wide and blunt-tipped, digit IV is longest, and digit V projects nearly laterally. P. primaevus is the track of a relatively large temnospondyl (∼400 mm gleno-acetabular length) and documents the Mississippian presence of such large amphibians long before their body fossil record. Palaeosauropus also occurs in Mississippian strata in Indiana and is distinguished from the geologically younger but similar temnospondyl footprint ichnogenus Limnopus by its relatively narrower manus and pes that lack broad and rounded sole impressions.

Invertebrate trace fossils in semi-arid to arid braided-ephemeral-river deposits of the Mississippian middle member of the Mauch Chunk Formation, eastern Pennsylvania, USA

The rapid diversification of terrestrial ecosystems was initiated in the Silurian and subsequently continued through the Mississippian. Detailed collecting of the middle member of the Mississippian Mauch Chunk Formation in eastern Pennsylvania has yielded a number of important vertebrate and invertebrate trace fossils, indicating the presence of a significant terrestrial biotic diversity during the Early Carboniferous. This report illustrates the diverse invertebrate trace fossil assemblage associated with the ephemeral-river systems of the Mauch Chunk. The Mauch Chunk invertebrate ichnoassemblage consists of backfilled burrows of deposit feeders, both meniscate ( Taenidium) and non-meniscate ( Planolites) that typically cross-cut bedding; arthropod trackways ( Diplichnites, Diplopodichnus, Stiaria, Kouphichnium and Stialla); striated trails ( Cruziana) and resting traces ( Rusophycus); and surface or shallow subsurface grazing trails or burrows ( Gordia). Tetrapod footprints, mostly made by temnospondyl amphibians, are also part of this ichnoassemblage. The Mauch Chunk invertebrate ichnoassemblage corresponds well to the Scoyenia ichnofacies in consisting of simple burrows, trackways, striate and bilobate trails and pits and simple meniscate burrows. Typically, trace fossils of the Scoyenia ichnofacies indicate opportunistic behaviors in subaerial environments that are temporarily or periodically inundated. Indeed, the palaeoenvironmental setting of these traces is a semi-arid to possibly arid, braided-ephemeral-river system with extensive overbank deposits. The invertebrate traces were developed both as infaunal burrows in the tops and within channel sandstones and as surface and grazing traces on in-channel mudstone-draped bedforms and in proximal overbank deposits. The in-channel mudstone-draped bedforms display both vertebrate and invertebrate trace fossils. The Mauch Chunk invertebrate ichnofossil assemblage resembles other Devonian through Triassic ichnoassemblages from ephemeral fluvial red beds, confirming that the terrestrial invertebrate fauna had already fully colonized fluvial environments by Mississippian time. Furthermore, the development of the Scoyenia ichnoguild in the Mauch Chunk Formation, in the form of abundant traces of deposit feeders of a shallow to intermediate depth infauna (esp. Taenidium), is unusually early, when compared to the previously known Palaeozoic record.

Isaac Lea's Palaeosauropus (= “Sauropus”) primaevus: A Review of His Discovery

In 1849, Isaac Lea named Sauropus primaevus for footprints from Mount Carbon, Pennsylvania, USA, then the oldest fossil vertebrate footprints reported. In 1902, O. P. Hay constructed a new ichnogenus Palaeosauropus for this ichnospecies. Palaeosauropus has been one of the most frequently reported Mississippian footprint ichnogenera in North America and remains a valid ichnotaxon. The holotype of Palaeosauropus (= “Sauropus”) primaevus (referred to as P. primaevus), consisting of a single manus/pes pair, is described and illustrated in Lea (1853) and is housed at the Academy of Natural Sciences in Philadelphia, Pennsylvania (ANS9752). Lea's large specimen of P. primaevus (approximately 86 cm by 53 cm), that included a trackway of six manus/pes pairs, described and illustrated in 1853 and 1855, was a combination of ANS9752 and a second specimen represented by a plaster cast housed at the National Museum of Natural History (USNM487148). Historical documents and examination of the Mauch Chunk Formation at Mount Carbon, Pennsylvania, enabled the identification of Lea's tracksite, originally reported to be a few hundred feet (about 75 m) from the former Mount Carbon Hotel. Our forensic evidence indicates the type locality for P. primaevus is approximately 90 m south from the southwest corner of Centre and Main Streets in Mount Carbon, Pennsylvania, with geographical coordinates of N 40° 40' 25.7”, W 76° 11' 14.9”. The type locality is within the middle member of the Mauch Chunk Formation, a fluvial sequence of late Mississippian (Visean) Age.

Simplification of the anisotropy-based inclination correction technique for magnetite- and haematite-bearing rocks: a case study for the Carboniferous Glenshaw and Mauch Chunk Formations, North America

SUMMARY An anisotropy-based inclination correction was applied to the Carboniferous Glenshaw Formation from southwestern Pennsylvania. A combination of low-temperature thermal demagnetization followed by alternating field demagnetization isolated a palaeomagnetic remanence direction similar to that previously reported for these rocks. The inclination correction was conducted by fitting the samples’ anisotropy of anhysteretic remanence (AAR) to the theoretical correction curves for a magnetite remanence that yielded a remanence individual magnetic particle anisotropy, the aγ factor, equal to 1.86. Direct measurement of individual particle anisotropy in magnetic grain extracts, yielded an aγ value of 2 in good agreement with the curve fitting technique. The inclination-corrected formation mean directions for these two a factors were statistically indistinguishable. This result shows that curve fitting is an easier, but accurate, method of applying an anisotropy-based inclination correction than direct measurement of the individual grain anisotropy in magnetic grain extracts. The corrected Glendale Formation magnetite-based palaeopole is very similar to haematite-based palaeopoles from the Carboniferous Canadian Maritimes. A new technique is described that extracts the detrital haematite grains from red sedimentary rocks. The measured haematite aγ factors from the Carboniferous Mauch Chunk and Cretaceous Kapusaliang Formations yield values consistent with susceptibility individual particle anisotropies, aχ , determined previously by curve fitting techniques, extending the use of curve fitting for individual particle anisotropy determination to haematite-bearing rocks. However, the corrected Mauch Chunk Formation palaeopole is significantly different from the corrected Glendale Formation palaeopole, calling the accuracy of the Mauch Chunk palaeopole into question. Tectonic strain during folding may have added to the compaction strain in the rocks, leading to an overcorrection of the inclination. A new, inclination-corrected palaeopole for the North American Carboniferous is reported for the Glenshaw Formation at 28.6uN, 119.9uE.

Biostratigraphy of crinoids from the Wymps Gap member of the Greenbrier Formation (Mississippian, Chesterian) in northern West Virginia

Crowns of four crinoid species, Talarocrinus planus Weller, 1920, Phacelocrinus longidactylus (McChesney, 1860), Ampelocrinus mundus? Kirk, 1942, and Phanocrinus maniformis (Yandell and Shumard, 1847) are reported from the limestones of the Wymps Gap Member of the Greenbrier Formation in northern West Virginia. Collectively these species indicate an early Chesterian age for the Wymps Gap Member, with the occurrence of T. planus indicating correlation with the Ridenhower (Paint Creek) Formation of the Illinois Basin. A review of the 17 species currently placed in Talarocrinus suggests that the Talarocrinus zone ranges no higher than the Ridenhower Formation in the Upper Gnathodus bilineatus conodont zone of the late Visean. The new occurrence of A. mundus extends its range upwards from the Genevievian substage of the Chesterian.Previous studies have used sequence stratigraphy to correlate the Wymps Gap Member with the lower part of the Union Limestone Formation of the Greenbrier Group in southern West Virginia, which in turn has been correlated with the Ridenhower Formation. The occurrence of T. planus in the Wymps Gap Member provides independent confirmation of the correlations based on sequence stratigraphy between the Appalachian and Illinois basins. Correlation of the overlying Reynolds Member of the Mauch Chunk Formation with the Glen Dean Formation of the Illinois Basin suggests a significant unconformity between the Greenbrier Formation and Mauch Chunk Formation in northern West Virginia.

Biostratigraphy of crinoids from the Wymps Gap member of the Greenbrier Formation (Mississippian, Chesterian) in northern West Virginia

Crowns of four crinoid species, Talarocrinus planus Weller, 1920, Phacelocrinus longidactylus (McChesney, 1860), Ampelocrinus mundus? Kirk, 1942, and Phanocrinus maniformis (Yandell and Shumard, 1847) are reported from the limestones of the Wymps Gap Member of the Greenbrier Formation in northern West Virginia. Collectively these species indicate an early Chesterian age for the Wymps Gap Member, with the occurrence of T. planus indicating correlation with the Ridenhower (Paint Creek) Formation of the Illinois Basin. A review of the 17 species currently placed in Talarocrinus suggests that the Talarocrinus zone ranges no higher than the Ridenhower Formation in the Upper Gnathodus bilineatus conodont zone of the late Visean. The new occurrence of A. mundus extends its range upwards from the Genevievian substage of the Chesterian. Previous studies have used sequence stratigraphy to correlate the Wymps Gap Member with the lower part of the Union Limestone Formation of the Greenbrier Group in southern West Virginia, which in turn has been correlated with the Ridenhower Formation. The occurrence of T. planus in the Wymps Gap Member provides independent confirmation of the correlations based on sequence stratigraphy between the Appalachian and Illinois basins. Correlation of the overlying Reynolds Member of the Mauch Chunk Formation with the Glen Dean Formation of the Illinois Basin suggests a significant unconformity between the Greenbrier Formation and Mauch Chunk Formation in northern West Virginia.

Earliest Report Of the Genus Phyricodothyris George (Brachiopoda: Reticularioidea) In North America

Described from the Wymps Gap Member of the Mauch Chunk Formation of southwestern Pennsylvania and adjacent Maryland is a new species, Phyricodothyris lauriegrahamae, of the Upper Mississippian reticulariod brachiopod Phyricodothyris George, 1932. The Wymps Gap Limestone from which the type material was collected is middle Chesterian (late Viséan) in age. This is the first report of this genus from confirmed Mississippian rocks in North America.

Tetrapod tracks from the Mauch Chunk Formation (middle to upper Mississippian) of Pennsylvania, U.S.A

ABSTRACT Evidence of tetrapods is scarce in the early Mississippian. Following Romer's Gap, a time of some 15 million years at the beginning of the Mississippian when remains of tetrapods and other continental organisms are rare, only sporadic skeletal and footprint fossils are found. We report here on new specimens of the tetrapod ichnogenera Hylopus and Palaeosauropus from the middle of the Mauch Chunk Formation (middle to upper Mississippian) of Eastern Pennsylvania. These document walking and swimming behaviors by at least two basal tetrapod taxa, perhaps an anthracosaur and a temnospondyl, and show evidence for the beginning of the second period of tetrapod diversification.

Taking patterns for chunks: is there any evidence of chunk learning in continuous serial reaction-time tasks?

When exposed to a regular sequence, people learn to exploit its predictable structure. There have been two major ways of thinking about learning under these conditions: either as the acquisition of general statistical information about the transition probabilities displayed by the sequence or as a process of memorizing and using separate chunks that can later become progressively composed with extended practice. Even though chunk learning has been adopted by some theories of skill acquisition as their main building block, the evidence for chunk formation is scarce in some areas, and is especially so in the continuous serial reaction-time (SRT) task, which has become a major research tool in the study of implicit learning. This article presents a reappraisal, replication and extension of an experiment that stands so far as one of the few alleged demonstrations of chunk learning in the SRT task (Koch and Hoffmann, Psychological Res., 63:22-35, 2000). It shows that the effects which were taken as evidence for chunk learning can indeed be obtained before any systematic training and thus surely reflect a preexistent tendency rather than a learned outcome. Further analyses of the effects after extended practice confirm that this tendency remains essentially unchanged over continuous training unlike what could be expected from a chunk-based account of sequence learning.

Age-related differences in immediate serial recall: dissociating chunk formation and capacity.

We assessed the contribution of two hypothesized mechanisms to impaired memory performance of older adults in an immediate serial recall task: decreased temporary information storage in a capacity-limited mechanism, such as the focus of attention, and a deficit in binding together different components into cohesive chunks. Using a method in which paired associations between words were taught at varying levels to allow an identification of multiword chunks (Cowan, Chen, & Rouder, 2004), we found that older adults recalled considerably fewer chunks and, on average, smaller chunks than did young adults. Their performance was fairly well simulated by dividing attention in younger adults, unlike what has been found for long-term associative learning. Paired-associate knowledge may be used in an implicit manner in serial recall, given that younger adults under divided attention and older adults use it well despite the relatively small chunk capacities displayed by these groups.

The magnetic polarity stratigraphy of the Mauch Chunk Formation, Pennsylvania.

Three sections of Chesterian Mauch Chunk Formation in Pennsylvania have been studied paleomagnetically to determine a Late Mississippian magnetic polarity stratigraphy. The upper section at Lavelle includes a conglomerate with abundant red siltstone rip-up clasts that yielded a positive conglomerate test. All samples were subjected to progressive thermal demagnetization to temperatures as high as 700 degrees C. Two components of magnetization were isolated: a synfolding "B" component and the prefolding "C" component. The conglomerate test is positive, indicating that the C component was acquired very early in the history of the sediment. A coherent pattern of magnetic polarity reversals was identified. Five magnetozones were identified in the upper Lavelle section, which yields a pattern that is an excellent match with the pattern of reversals obtained from the upper Mauch Chunk at the original type section of the Mississippian/Pennsylvanian boundary at Pottsville, PA. The frequency of reversals in the upper Mississippian, as identified in the Mauch Chunk Formation, is approximately one to two per million years, which is an average for field reversal through time.

The cognitive architecture of complex movement

This article examines the cognitive architecture of complex movements, how it is organized over several levels and is built on specific building blocks. Basic Action Concepts (BACs) are identified as the major building blocks on the level of mental representations. These BACs are cognitive tools for mastering the functional demands of movement tasks. New experimental methods are introduced and applied in studies addressing the functional link between representation structures and human performance. Results from two different lines of research showed that not only is the structure formation of mental representations in long‐term memory built upon BACs, but so is chunk formation in working memory and systematically relates systematically to movement structures. Further lines of experimental research in various fields of sport showed that cognitive subsystems work together functionally with different levels of movement architecture in order to solve movement tasks. These results support the hypothesis that voluntary movements are planned, executed, and stored in memory directly through representations of their anticipated perceptual effects. Conclusions are drawn for new forms of mental training as well as new ways of carrying out technical preparation.

Evaluation of paleomagnetic and finite strain relationships due to the Alleghanian Orogeny in the Mississippian Mauch Chunk Formation, Pennsylvania

Three localities of the Mississippian Mauch Chunk Formation around the Pennsylvania Salient (Broad Top Synclinorium, Minersville Syncline, and a sublocality in the Minersville Syncline) were sampled for detailed paleomagnetic and strain analysis. Paleomagnetic analysis showed three magnetization components: an intermediate‐temperature B component (Tb < 650°C), a high‐temperature C component (Tb > 620°C), and an SW component, unblocked over a wide range of temperatures and observed only on the northern segment of the salient. Normalized Fry strain and Rf/ϕ strain were measured in three dimensions and correlated to the paleomagnetic results. At one site (JTSF locality), a clear correlation between the amount of strain (εs) and remanence direction indicates that axial planar cleavage formation has caused remanence rotation. The correlations at the Minersville Syncline and Broad Top Synclinorium are not definitive, but suggest that different mechanisms are operating. The observed heterogeneity in paleomagnetic response to strain indicates that the effects will be strongly dependent on the strain history at a particular site.

Magnetic anisotropy and paleomagnetic inclination shallowing in red beds: Evidence from the Mississippian Mauch Chunk Formation, Pennsylvania

Red, hematite‐bearing sedimentary rocks are an important source of paleomagnetic data, particularly for continental apparent polar wander paths during the Paleozoic. This study presents magnetic anisotropy data from the Mississippian Mauch Chunk Formation of eastern Pennsylvania, indicating that these red beds have suffered from a significant amount of paleomagnetic inclination shallowing. Fourteen oriented block samples were collected from normal and reversed polarity strata identified in a previous study. Thermal demagnetization isolated the characteristic remanent magnetization at seven normal polarity horizons at unblocking temperatures greater than 670°C (mean direction, D = 354.0°, I = −18.4°, α95 = 10.2°). Anisotropy of remanence measurements (anisotropy of isothermal remanent magnetization and thermal remanent magnetization) indicate a bedding parallel, foliated magnetic fabric with foliations ranging from 1.1 to 1.35. Thermal demagnetization at 670°C of the isothermal remanent magnetization isolates the magnetic fabric of the characteristic remanence‐carrying grains and indicates stronger foliations (1.15–1.48). Anisotropy of magnetic susceptibility (AMS) also indicates bedding parallel magnetic foliations of 1.01–1.04, typical of red beds. Chemical leaching isolates the AMS of the characteristic remanence‐carrying grains to range from 1.02 to 1.07. This AMS fabric was used to correct the characteristic remanence inclination isolated by thermal demagnetization. The critical parameter needed for an accurate inclination correction, the individual particle anisotropy aχ, was determined from the correlation between the normalized principal axes of remanence and susceptibility anisotropy to be 1.06. The corrected Mauch Chunk direction, D = 354.5°, I = −56.4° results in a corrected Mauch Chunk Formation paleopole (12°N, 108°E) that is consistent with a European igneous paleopole.

Flexural flow folding and the paleomagnetic fold test: An example of strain reorientation of remanence in the Mauch Chunk Formation

The relationship between the remanent magnetization and the detailed strain geometry around a first‐order fold in the Appalachian Valley and Ridge Province was investigated to examine whether penetrative strains associated with folding can generate a apparent synfolding geometry from a prefolding magnetization. Paleomagnetic results from the Mississippian Mauch Chunk Formation on both limbs of the Frackville Anticline near Lavelle, Pennsylvania, yield two magnetic components, an intermediate unblocking temperature (300°C–600°C) Kiaman remagnetization and a two‐polarity high unblocking temperature (650°C–680°C) characteristic magnetization. When the magnetic directions are incrementally corrected for bedding tilt, the intermediate‐temperature component is most tightly clustered at 85% unfolding (D=176°, I=3°) and the high‐temperature component is most tightly clustered at 75% unfolding (D=184°, I=27°). Mesoscopic and microscopic structural fabric analyses suggest a strain history that includes a significant component of flexural slip/flow folding. In the coarser‐grained sandstone units, folding has largely been accommodated by slip on bedding, while in the finer‐grained beds, folding has been accommodated by grain‐scale deformation mechanisms such as pressure solution and low‐temperature plasticity. Finite strain measurements, determined from center‐to‐center distances between quartz grains, yield strain ellipsoids consistent with this folding model. Inclination of the characteristic component varies as a function of the magnitude of the finite strain. This variation suggests that the characteristic magnetization has been systematically reoriented with respect to bedding during folding. Remanence directions on the south dipping limb have been rotated to shallower inclinations, while those on the north dipping limb have been rotated to steeper directions causing the prefolding magnetization to appear synfolding. These rotations are in agreement with models of rigid particle rotation in deforming viscous media. Unlike the characteristic magnetization, the secondary component appears to be unaffected by the deformation, and its synfolding behavior is interpreted as the acquisition of a secondary magnetization during Alleghenian folding. These results show that it is important to consider penetrative strains when evaluating the significance of apparent synfolding magnetizations.

Magnetic polarity stratigraphy in the uppermost Mississippian Mauch Chunk Formation, Pottsville, Pennsylvania

Research Article| February 01, 1991 Magnetic polarity stratigraphy in the uppermost Mississippian Mauch Chunk Formation, Pottsville, Pennsylvania V. J. DiVenere; V. J. DiVenere 1Department of Geology, University of Florida, 1112 Turlington, Gainesville, Florida 32601 Search for other works by this author on: GSW Google Scholar N. D. Opdyke N. D. Opdyke 1Department of Geology, University of Florida, 1112 Turlington, Gainesville, Florida 32601 Search for other works by this author on: GSW Google Scholar Geology (1991) 19 (2): 127–130. https://doi.org/10.1130/0091-7613(1991)019<0127:MPSITU>2.3.CO;2 Article history first online: 02 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 V. J. DiVenere, N. D. Opdyke; Magnetic polarity stratigraphy in the uppermost Mississippian Mauch Chunk Formation, Pottsville, Pennsylvania. Geology 1991;; 19 (2): 127–130. doi: https://doi.org/10.1130/0091-7613(1991)019<0127:MPSITU>2.3.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 SocietyGeology Search Advanced Search Abstract We took 105 oriented cores from 340 m of the upper Mauch Chunk Formation at Pottsville, Pennsylvania, for a magnetostratigraphic study. The samples were subjected to progressive thermal demagnetization from 600 to 700 °C and analyzed by using principal-components analysis. A high-temperature component was isolated with a mean direction of declination = 351.7°, inclination = -28.4°, and α95 = 6.7°, and a corresponding paleopole at long 113.5°E, lat 33.7°N. Three normal and three reversed polarity magnetozones were defined, and it was found that the magnetic field was ∼59% normal and 41% reversed in the upper Chesterian. Herein we attempt to correlate the section to a previous study in New Brunswick on the basis of the paleolatitude (pole position) and the reversal pattern, and we postulate a correlation of the bottom part of the Maringouin section with the top off the Mauch Chunk. Such a correlation would place the Mississippian/Pennsylvanian boundary within the Maringouin Formation. Earth's magnetic field was of normal polarity at the time of the Mississippian/Pennsylvanian boundary. 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.

Outstanding student papers at the 1990 Spring Meeting

Three students received awards for outstanding presentations at this year's Spring Meeting. Several AGU sections award such certificates to recognize excellence in content and presentation, and to encourage student participation in AGU's national meetings.John Stamatakos was selected by the Geomagnetism and Paleomagnetism Section for his poster presentation, “Strained Remanence in the Mauch Chunk Formation.” Stamatakos received his B.A. from Franklin and Marshall College, Lancaster, Pennsylvania, (1981), and his M.S. (1988) and Ph.D. (September, 1990) from Lehigh University, Bethlehem, Pennsylvania. He currently has a 1‐year postdoctoral position at the Swiss Institute of Technology (ETH) in Zurich with William Lowrie and Ann Hirt.

Reduction of Cognitive Workload through Information Chunking

Two experiments were conducted to determine whether grouping of icons on complex graphic displays reduces information processing loads, as measured by the Subjective Workload Assessment Technique and errror rates. In Experiment 1, between 2 and 25 symbols were presented on a computer display. Participants were asked to chunk symbols under class labels and store these labels in short-term memory. Two different display formatting variables were tested: spatial proximity grouping of icons was manipulated across three levels, while temporal grouping was manipulated across two levels. Results suggest that display grouping helps operators organize, encode, and store information into task relevant chunks and, in turn, reduces subjective workload and error rates. Experiment 2 was similar to Experiment 1, except that participants were required to remember individual icon names (i.e., participants were asked to remember as many as 25 item names). Results suggest that for chunk formation, storage, and parsing tasks, display grouping may reduce subjective workload, but not error rates.