EAST TENNESSEE GEOLOGICAL SOCIETY
May 2009 Meeting
Monday, May
11, 2009
6:00 - 7:30 pm
Pellissippi
State Technical Community College
10915 Hardin
Valley Road, Knoxville
J.L. Goins Administration Building, Cafeteria Annex
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Pizza and
soft drinks will be provided. Be on time; don't miss out! |
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MAY
PRESENTATIONS
A
Series of Three Short Presentations
by
Award-Winning Student Presenters
University of Tennessee, Department of Earth and Planetary Sciences
Knoxville, Tennessee
This month&rsquos ETGS meeting will follow a slightly different format than is usual. Instead of having one speaker give a 50-minute-long presentation, we will be featuring three &ldquomini&rdquo presentations (each approximately 15 minutes long) by students from the Department of Earth and Planetary Sciences (EPS) at the University of Tennessee - Knoxville. Each year EPS offers a course on &ldquoProfessional Presentations&rdquo (Geology 596) to provide a formal opportunity for students to develop their oral communication skills. This one-credit course involves writing an abstract, and preparing, practicing, and delivering a professional presentation on any geological topic of interest.
The students present
their talks at a departmental seminar, and they are ranked by the seminar
attendees and a five-person committee consisting faculty and students. This year
ETGS has partnered with EPS to further broaden this valuable experience by
offering awards to the top three student presenters and hosting them at our May
meeting where they will give their talks to a professional audience. We hope you
can join us to support this new generation of geologists and see their
award-winning presentations. Abstracts of their presentations are provided
below.
From Left to Right
ETGS Award Recipients: Christina Viviano, Steven Jarret, and
Brittany Davis
ETGS Past and Current Presidents: Ed Perfect and Jim Morgan
 |
Using THEMIS to Extend the by |
The Mars Express
OMEGA and Mars Reconnaissance Orbiter CRISM experiments have discovered and
mapped mineralogically diverse phyllosilicate deposits on Mars. These
instruments operate in the visible and near-infrared wavelength portion of the
spectrum, and are sensitive to interlayer water and cation-hydroxyl bonds within
the phyllosilicate structure. Unlike OMEGA and CRISM, the Mars Odyssey THEMIS
experiment has acquired images with nearly global coverage. THEMIS is a
multispectral imager that operates in the thermal infrared portion of the
spectrum, sensitive to Si-O bonds and cation-hydroxyl bonds in the
phyllosilicate structure. It would be advantageous to use THEMIS (due to its
superior coverage) to extend mapping of phyllosilicate-rich regions into areas
where CRISM and OMEGA have not yet covered. With this as our impetus, we have
empirically derived a THEMIS Phyllosilicate Index (TPI) that is sensitive to the
phyllosilicate-rich regions that CRISM and OMEGA have mapped. The TPI has been
used in Terra Sirenum, revealing new outcrops of potential phyllosilicate-bearing
material. In this region, the phyllosilicates are found to commonly occur in
crater floors, suggesting these local lows act as areas for phyllosilicate
accumulation. TPI-detected deposits appearing to emanate from Terra Fossae may
imply hydrothermal alteration and fluid flow along this fracture. The TPI
identification of new phyllosilicate deposits demonstrates the potential for a
THEMIS-based global TPI map, which would help to further constrain the
environments and processes of phyllosilicate formation on Mars.
 Mr. Jaret was unable to attend our May meeting to give his presentation. |
The Tenoumer Impact Crater: by and |
The identification and study of small simple meteorite impact craters (<2km) is often problematic because these structures lack the macroscopic, distinctive features associated with impact craters. Studying simple craters, however, plays an important role in our understanding of the cratering process, particularly low shock deformation.
This mineralogic and petrographic study combines two principles of cratering modeling and experimentation: 1) During impact cratering, the deformation pressure decreases with depth from the point of compression and 2) Material from greatest pre-impact depth gets deposited closest to the crater rim after excavation. Thus, material located closest to the crater rim would have experiences lower deformation pressure than material found farther away (which was at a lower pre-impact depth). The goal of this study is to use shock features to trace this pressure gradient from the crater rim outward away from the crater.
This study
highlights one of the continual struggles in understanding the impact crater
process. I was unable to trace the pressure gradient. Experimental and
theoretical impact barometry calculations are based on deformation in quartz (&ldquoPlanar
Deformation Features&rdquo or &ldquoPDF&rsquos&rdquo) above 12 GPa. Many samples
did not show any PDF&rsquos. However, textures and microraman spectral data of
feldspars suggest these rocks were affected by the impact, and as predicted the
samples from furthest away showed the most deformation. In order to fully
understand impact cratering at all levels, experimental and theoretical work
needs to be done on additional minerals other than quartz. Such work would allow
us to apply impact cratering to environments which either lack quartz or
experiences lower shock pressures than required to deform quartz.
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A Fault and Curved Anomalies Identified from
Aeromagnetic Data by |
Detailed geologic mapping is being conducted in the Mansfield and Farrar 7.5-minute quadrangles in the central Georgia Inner Piedmont (IP) to trace the possible extension of the Brindle Creek fault (BCf) and Cat Square terrane (CSt). A large fault has been identified in aeromagnetic data as a prominent lineament that truncates a suite of curved magnetic anomalies. This fault may be the suture between the western IP Tugaloo terrane (Tt) from the CSt and is interpreted as a large-scale SW-directed type-F thrust sheet. The Tt in North Carolina and northeast Georgia consists of the Neoproterozoic to early Paleozoic(?) Tallulah Falls Fm. and the Mid-Ordovician Poor Mountain Fm., both intruded by Ordovician-Silurian granitoids. CSt rocks in North Caroliona consist of Silurian-Devonian sillimanite-schist, metagraywacke, and Devonian-Mississippian anatectic granitoids. Peri-Gondwanan (500-600 Ma), Laurentian (1500-1000 Ma), and 430 Ma zircons have been identified in the CSt in North Carolina and South Carolina. One detrital zircon sample from the study area contains Laurentian and peri-Gondwanan (630 Ma) zircons. In central Georgia the BCf (?) exhibits a dextral shear sense, much like that of the BCf located in North Carolina and South Carolina. The dip of the BCf transitions from a shallowly dipping fault in North Carolina and South Carolina to a steeply dipping fault in the central Georgia IP. This transition could be attributed to the fault proximity to the Central Piedmont suture, which is the bounding fault to the east of the IP. The curved anomalies truncated against the fault may track the trends of dominant S2 foliation and L2 mineral stretching lineation and possibly correlate with crustal scale transport in the IP.
Page updated May 26, 2018 |