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- Geology (5)
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Articles 1 - 13 of 13
Full-Text Articles in Physical Sciences and Mathematics
Size-Frequency Distribution Of Orbitolina Texana Foraminifera, Jeremy Foote
Size-Frequency Distribution Of Orbitolina Texana Foraminifera, Jeremy Foote
Undergraduate Review
This study examined size-frequency distributions for an extinct Cretaceous-age benthic foraminifera called Orbitolina Texana in order to determine the health of this foram community during the time of accumulation. Forams were collected from limestone outcrops of the Glen Rose Formation in central Texas. Based on paleontological and sedimentological evidence, Orbitolina Texana are interpreted to be a shallow water (<10 m) benthic organism that was most abundant in back-reef environments. Sizefrequency distributions were generated from the diameters of 4,245 Orbitolina Texana fossils. The results indicate that the Orbitolina Texana population is characterized by a Gaussian (normal) size distribution. Size-frequency distributions of fossilized foraminifera in the stratigraphic record are controlled by two principle variables; environmental controls that affect the biology of the organisms (e.g., environmental stressors, like food availability and ambient conditions) and sedimentological controls that affect how the organisms are distributed (e.g., hydrodynamic parameters, like waves and currents). Based on a sedimentological characterization of the host limestone including lack of high-energy sedimentary structures, high mud content and back-reef position on the depositional profile, hydrodynamic parameters are interpreted to not have exerted a significant effect on the distribution of the forams preserved in the rock record. As such, the biological controls are interpreted to be the dominate control on the foram sizefrequency distribution. Therefore, the Gaussian (normal) size distribution suggests that the mortality rate is independent of size/age, which is classified as Type II survivorship. As this result is consistent with similar taxon, the results indicate that this Orbitolina Texana population was a healthy biologic community, despite the low biologic diversity observed in the Glen Rose Formation.
The Effect Of Hydrochloric Acid Strength On The Nanometer-Scale Dissolution Topography Of Calcite Crystal Surfaces, Jennifer Fruzzetti
The Effect Of Hydrochloric Acid Strength On The Nanometer-Scale Dissolution Topography Of Calcite Crystal Surfaces, Jennifer Fruzzetti
Undergraduate Review
The physico-chemical mechanisms by which rock-forming minerals dissolve in natural fluids are controlled by a number of environmental factors. In this study, we investigate dissolution mechanisms by observing how the nanometer-scale surface topography of calcite is affected by the acidity of etching solutions. Here we report atomic force microscope (AFM) observations of calcite crystal surfaces both before and after chemical etching for 10 seconds in 0.01%, 0.1%, and 1.0% HCl solutions. AFM observations show that unetched, freshly-cleaved calcite {10ī4} crystal surfaces are characterized by flat layers separated by steps oriented parallel to calcite cleavage planes. Calcite {10ī4} crystal surfaces etched …
Sedimentary Petrology And Provenance Of The Teddy Creek Group Sw Montana, Renee Holt
Sedimentary Petrology And Provenance Of The Teddy Creek Group Sw Montana, Renee Holt
Undergraduate Review
A previously undocumented sequence of sedimentary rocks has been identified within SW Montana and informally named the Teddy Creek Group (TCG). This project focuses on the field relations, mineral compositions, and textures of these rocks to determine their origin and relationship to the more regionally extensive Cenozoic Renova Formation.
Stable Isotopic Constraints Of The Turpan Basin In Northwestern China, Allen J. Schaen
Stable Isotopic Constraints Of The Turpan Basin In Northwestern China, Allen J. Schaen
Undergraduate Review
Stable isotopic analysis of sedimentary rocks can be used to reconstruct past geologic changes in the elevation and climate of topographic features such as mountain ranges and plateaus. The Tibetan Plateau is an ideal field laboratory for conducting this type of study because of the Plateau’s extreme topographic relief and relatively recent geologic growth. Here we present oxygen and carbon isotope compositions from a suite of sedimentary rock samples taken from the western Turpan Basin in northwestern China. This area of the basin collects sediment from weathering and erosion of the Bogda Shan located to the north. The goal of …
Regional Vs. Local Impact Of Wind On Glaciers In The Andes Mountains, Derek Ferris
Regional Vs. Local Impact Of Wind On Glaciers In The Andes Mountains, Derek Ferris
Undergraduate Review
Northern Peru will face critical water resource issues in the near future as permanent ice in the Andes Mountains continues to rapidly melt. Ironically, the melt-water from these glaciers supports the culture of 100s of thousands of people living at lower elevations, particularly during the dry season, and predictions suggest some glaciers may be gone in less than 100 years. The impact of local warming of “U” shaped valleys running down the dryer western slope of the Andes range is largely disregarded in current climate model predictions because of the complexity of simulating the complex topography. Studies that compare the …
A Two-Dimensional, Linear–Elastic Model To Explain Radial Extensional Fractures, Pantheon Fossae, Caloris Basin, Mercury, Brianne Mcdonough
A Two-Dimensional, Linear–Elastic Model To Explain Radial Extensional Fractures, Pantheon Fossae, Caloris Basin, Mercury, Brianne Mcdonough
Undergraduate Review
In this study, two-dimensional linear elasticity theory is used to model the lithospheric stress field that produces radial extensional fractures observed at Pantheon Fossae in the Caloris Basin of Mercury. These fractures were imaged by the MESSENGER mission flyby of Mercury on January 14, 2008 and show radial fractures extending outward from a 40-kilometer impact crater named Apollodorus. Recent studies have proposed several different mechanisms to explain these fractures, including magmatic processes, central basin uplift, and stresses produced by the formation of the impact crater itself.
Effects Of Land Cover Variability On Evapotranspiration In The Llanganuco Valley, Aimee Higgins
Effects Of Land Cover Variability On Evapotranspiration In The Llanganuco Valley, Aimee Higgins
Undergraduate Review
A process-based understanding of the effect land cover has on evapotranspiration (ET) in alpine valleys is lacking. It is conventionally assumed that ET is a negligible part of the water cycle in the Peruvian Andes, a critical source of water for the local inhabitants, due to lack of precipitation during the 6-month dry season and high humidity during the 6-month wet season. However, recent research findings from an embedded sensor network indicate that ET is in fact an important part of the Andean water cycle in Peru. Water resources within Peru are affected by the glaciers within the Cordillera Blanca, …
Kinematic Analysis Of Mylonitic Rocks, Southern Ruby Mountains, Sw Montana: Evidence For Proterozoic Orogenic Crustal Thickening And Topographic Collapse, Jessica Sousa
Undergraduate Review
Mylonitic granitic rocks from a large shear zone within the southern Ruby Mountains in southwest Montana record evidence for a multiple tectonic movement history. The shear zone is 500 meters thick with ductile shear fabrics generally striking northeast and dipping to the northwest. Foliations in the adjacent country rocks are sub-parallel to the foliations within the mylonites suggesting shear zone development was contemporaneous with the regional deformation and metamorphism of the country rock. A well-developed mineral stretching lineation, defined by aligned sillimanite crystals, records predominantly dip-slip movement, but locally, oblique-slip is also preserved. Sheath-type folds developed in thin calc-silicate layers …
Unraveling The Geologic History Of The Avalon Terrane In Ma, Erin Nevens
Unraveling The Geologic History Of The Avalon Terrane In Ma, Erin Nevens
Undergraduate Review
No abstract provided.
Origin Of Gabbroic Xenoliths Within The Lone Mountain Dacite Intrusion, Big Sky, Montana: A Field And Petrographic Analysis, Emily Clement
Origin Of Gabbroic Xenoliths Within The Lone Mountain Dacite Intrusion, Big Sky, Montana: A Field And Petrographic Analysis, Emily Clement
Undergraduate Review
No abstract provided.
Microstructural Analysis Of The Rhode Island Formation, Narragansett Basin, Ma, Elizabeth Connell
Microstructural Analysis Of The Rhode Island Formation, Narragansett Basin, Ma, Elizabeth Connell
Undergraduate Review
No abstract provided.
Microstructural Analysis Of A Drill Core From The Rhode Island Formation: Upper 750 Feet, Ashlee Kirkwood
Microstructural Analysis Of A Drill Core From The Rhode Island Formation: Upper 750 Feet, Ashlee Kirkwood
Undergraduate Review
No abstract provided.
Field, Petrographic, And Geochemical Characteristics Of Price Creek, Russ Mccormack
Field, Petrographic, And Geochemical Characteristics Of Price Creek, Russ Mccormack
Undergraduate Review
No abstract provided.