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41286-B8
Strain Variations and Structural Geology of the Presidential Range, New Hampshire
This past academic year I was able to recommence the PRF funded research on strain variations and structural geology in the Presidential Range, after a year off from the work while I was on sabbatical doing another research project in New Zealand. In March 2007 I organized a theme session at the Northeast section meeting of the Geological Society of America titled “Strain partitioning and rheological variations”. I gave two papers there, both co-authored with student researchers, on the two main topics of the funded research; Late Acadian fold shortening and Early Acadian quantification of a mineral lineation.
I recruited two Bates Geology majors to participate in the PRF research. Caitlin Tamposi (Bates class of 2008) and Stephanie Higgins (Bates class of 2008) worked for the months of July and August collecting data on the fold shortening and lineation projects respectively. The work was above located treeline in the alpine zone of the Mt Jefferson region in the Presidential Range of New Hampshire. The students stayed in tents for the first few weeks then in a cabin, both at circa 4,200 feet elevation. Each day they hiked about 5 to 7 miles in and out of their field area collecting data and sampling rocks. I worked with them off and on throughout the field season for a total of about two weeks. The first week was spent training them in the field techniques and then later I simply met them on the mountain and we spent the time collecting data together.
We had a fantastic field season and the students collected a tremendous amount of data. A total of 52 localities across the Mt Jefferson cone yielded excellent fold shortening and lineation data. For the fold shortening project, at each locality in the exposed fold train the following features were measured: strike and dip of all fold limbs, strike and dip of fold axial planes, trend and plunge of fold hinge lines, schist/quartzite ratios, wavelength of all folds, and double amplitude of all folds. For the lineation project, 50 pseudoandalusite lineations were measured as well as the planar fabric that the lineations lie within (e.g. bedding and/or foliation).
Now the academic year has begun at Bates and the two students have started their two-semester senior honors theses in the Geology Department. Ms. Tamposi is studying the fold shortening and Ms. Higgins the lineation. To date each student has given two 30 minute PowerPoint presentations to our senior thesis seminar. The first was on the thesis topic and questions to be answered and the second presentation on methods. Later this semester each student will give a talk or two on preliminary results.
Ms. Tamposi has now plotted all of her fold train locations in Arc-GIS and is currently creating equal area projections of all the fold data. She has cut slabs from the rock samples collected in the field season so that they can be made into thin sections. She will study these in December using transmitted light microscopy to evaluate micro-scale shortening. Her macro-scale fold train shortening calculations will commence next month and she appears to be right on track to finish her data collection and analysis by early January.
Ms. Higgins has plotted all of her lineation data in Arc-GIS and is in the process of determining lineation intensity using multiple methods. She is using a standard running average rose plot of lineation trends to determine the longest petal and hence lineation intensity for each field station. She is also developing a new technique to plot spatially oriented, scaled, lineation development vectors on her base map. This technique promises to be quite useful in portraying the variable lineation intensity patterns across the study area. She plans on analyzing, in the same manner, the lineation data collected in two prior field seasons (2005 and 2004), to create a regional map of lineation development in Presidential Range.
Both students are doing very well on their thesis research in the early stages of this academic year and I predict that both will ultimately receive Honors for their efforts. In March they will each finish their respective thesis documents, present posters or talks at the Northeast section meeting of the Geological Society of America in Buffalo, NY and defend their theses in front of a panel consisting of three Bates faculty and one outside expert examiner form another university.
Abstracts (student co-authors in bold)
EUSDEN, J. Dykstra. Jr; KUGEL, Kelly; RODDA, Charles; 2007, LATE ACADIAN FOLD TRAIN SHORTENING AND STRAIN PARTITIONING: Geological Society of America Abstracts with Programs, Vol. 39, No. 1, p. 51
EUSDEN, J. Dykstra Jr; GUITERMAN, Christopher; PERRAULT, Lauren; RODDA, Charles; 2007, QUANTIFYING THE VARIABLE DEVELOPMENT OF AN EARLY ACADIAN L1 PSEUDOANDALUSITE MINERAL LINEATION: Geological Society of America Abstracts with Programs, Vol. 39, No. 1, p. 50
