Sparks From the Rock Pile: 2005
FROM THE CHAIR
As I sit down to write, I can’t help but feel that a geological era is about to end. After thirty-six years at Cornell, Paul Garvin retires this May. To put this into some perspective, Paul began teaching at Cornell the year I was born. The number of students whose lives and careers he affected is tremendous, and I know from personal experience what a wonderful mentor and dear friend he is. But never fear – Paul will maintain a presence in Norton Geology. As always, he is actively engaged in research and will be moving upstairs to the top floor (perhaps to be nearer to the mineral collection?). Invitations to his retirement dinner this May should have already arrived and we’d love to have you come. The first event in Paul’s retirement celebration is our hosting of the Iowa Academy of Science meeting here at Cornell in late April. One of the symposia is titled Geologic Contributions to Archaeological Method and Theory and is a tribute to Paul and one of his diverse scientific interests.
Paul certainly can’t be replaced, but he will be succeeded. Emily Walsh will become Cornell’s new hard-rock geologist beginning next fall. Emily attended Middlebury College and did her Ph.D. at the University of California at Santa Cruz where she studied rocks from Norway that have been buried to tremendous depths (100 km!) and then rapidly exhumed. Emily is currently a visiting professor at Union College in Schnechtady, New York, and we are excited that she agreed to join our department.
From where I sit, it is clear that our program is as strong as ever. Geology maintains a central and active role in the Environmental Studies curriculum, and we have a good bunch of geology majors (and an unusually high number of minors), most of whom have become engaged in some demanding and interesting independent research projects. We’ve also changed the requirements for the major, and now require that students conduct at least one block’s worth of independent research. And Norton is getting some long-needed upgrades to our two most-used classrooms.
As always, we would love to hear from you (or better yet see you), so drop us a line anytime.
If you would like to recieve information from the Cornell College Geology Department or you simply want the department to have your information on record simply click on the link, print the form, fill it out and send it to the address on the bottom.
Hello Geology Alumni,
My family and I are still recovering from the culture shock we have experienced returning to Iowa after living in Perth, Western Australia for most of last year. During 2003-04, I had a full-year sabbatical (my first after 13 years of teaching) supported by two grants from the Petroleum Research Fund. I initiated a research project that compares modern coral reefs off the west coast of Australia to fossil coral reefs exposed along the coast. The fossil reefs are the same age as those I (and some of you) have worked on in the Caribbean and tropical western Atlantic regions. While on leave I was appointed a Visiting Research Fellow at the University of Western Australia in the School of Earth and Geographical Sciences. The project involves fieldwork in some very remote places between Cape Range (NW Australian coast) and Perth (SW Australian coast). Basically I worked at the university and took three separate trips to work in places along the coast. Cornell College geology students Meredith Clayton (’05) and Dustin Waite (’06) joined me for the month of March to work in the vicinity of Red Bluff. Abstracts of their research projects are included in this issue of Sparks. On our way to Red Bluff, we stopped at Hamelin Pool in Shark Bay to pay homage to the world famous stromatolites that live there. I return to Western Australia this summer with Jessica Harms (’06) and Megan Andresen (’06) to continue work on the project. This time we will spend most of our time in the Houtman-Abrolhos Islands. The islands are famous because they expose spectacular fossil coral reefs (this interests a few people) and they are the location of the first discovery and landfall in Australia by Western Europeans (this interests many more people).
My family lived with me in Perth, with the boys attending Perth Modern School – the oldest public school in Western Australia. Neither boy was particularly happy to leave their school at the end of the year, and certainly none of us were ready to leave Perth – a fantastically cosmopolitan city of 1.5 million people on the Indian Ocean. We also managed quite a lot of traveling while in Oz: we spent a month traveling to Perth after landing in Sydney, and my family visited some of my field areas. We also took a trip to Uluru, Darwin and Kakadu National Park during the April school holiday.
There are big changes in store for the Geology Department, as we welcome Emily Walsh to succeed Paul Garvin beginning next fall. I hope many of you are able to attend Paul’s retirement bash in May.
I’m about to finish my fifth year here at Cornell and only recently have I begun to feel settled. What an amazingly busy (and enjoyable) time it has been! My research program in paleoclimatology continues although I’ve expanded my geographic horizons. For part of last summer, a student, Alyssa Borowske, and I explored caves in Portugal with an American archeologist and a Portuguese geologist. We returned with several stalagmites and the preliminary results are quite promising. Then, for most of July and August, I worked in the radiogenic isotope lab at the University of New Mexico with two different students, Brian Hoye and Peter Cole. Brian was using uranium-thorium methods to date a stalagmite from an Arkansas cave, and Peter was trying (successfully, it seems) to date a fossil coral with uranium-lead techniques. The coral research is funded by a $35,000 grant from the Petroleum Research Fund, and the results we’ve obtained may lead to additional grant monies from some of my collaborators. Alexa Clements did some more high-resolution sampling of New Zealand flowstone last summer (funded by a $17,000 grant from the Center for Global and Regional Environmental Research), as well, although we just received the results a few weeks ago and thus we haven’t had a chance to analyze the data in detail.
I continue to develop new courses, and while this is a bit of a burden, the rewards are sometimes extraordinary. For example, I have changed the location of our field mapping course, Geology of a Region, from west Texas to New Zealand. Last February, I took eleven students (and one alum) to the northern tip of the South Island for three weeks. The rocks there are terrific for mapping and you couldn’t ask for more beautiful countryside. New Zealand is wonderfully diverse geologically, and we walked on an ophiolite, tectonic plate boundaries, a glacier, and part of Gondwanaland (if you’d like to see pictures from the trip, please check out my course homepage at http://www.cornellcollege.edu/geology/rdenniston/classes.shtml). For the next trip I’m expanding our field areas to include an extinct volcano and the very top of the Southern Alps. The mines of Moria will come later…
I hope you are well, and would love to hear your news.
Spring is slowly coming to Iowa and the Hilltop. Crocuses are in bloom and daffodils and tulips are well out of the ground. It is hard to believe that within a few weeks it will be time to “plant the seeds and fight the weeds”.
This year has been an unusually busy one for me. The Iowa Academy of Science is holding its Annual Meeting at Cornell this year (our first hosting since 1979). I am the local events coordinator, and I am finding that there is a fair amount to do. I am excited about having the meeting here. All of the events (general lectures, symposia, section papers, committee meetings, etc.) will be held in the Commons and in the Armstrong/Kimmel complex. All of the classrooms in Armstrong are new and each has a computer and an LCD projector. Cornell students will serve as room monitors for the papers and symposia (in return for which they get free passes to all events). Several Cornell students (including at least four from Geology) will be giving papers at the meeting. I will be participating in a symposium on geoarchaeology and writing a chapter for a field trip guidebook that will be used on a Geological Society of Iowa field trip, held in conjunction with the IAS meeting.
Our Geology students are actively involved in independent research. Ben’s coral reef research and Rhawn’s paleoclimate research are attracting good students. Eight of our students will be making oral presentations at the upcoming Cornell Student Symposium. We have our own session! In addition, one of our students is presenting a poster. We have two students doing honors theses this year. Several will present papers at North Central GSA. You will learn more about their accomplishments elsewhere in this newsletter. I am impressed by the quality of our students and their eagerness to engage in undergraduate research. We are very fortunate to be able to provide them with summer research support. Through external grants, the Cornell Faculty Development Fund, the Hendriks Student Research Fund (HSRF) and the Cedar Valley Rock and Mineral Society Fund, we were able to fund seven students last summer. HSRF continues to grow and we are close to being able to fund three student projects per year (with a student stipend of $3,000 and a few hundred dollars for associated research expenses). We are most grateful to you for your monetary and other support for this fund and for other contributions to the Department. I think I can safely say that the Department is stronger and more research-active now than at any previous time in my 36 years at the College.
Speaking of 36 years, this will be my last. I have decided to retire. I do so with a mix of emotions. I will not miss: faculty meetings, grading exams, reading poorly written papers and cleaning my office. I will miss: wonderful associations with Cornell students and with faculty colleagues, especially with Ben and Rhawn. I have learned that collegiality is not a common virtue in academic departments nationwide, and even at Cornell. But it is, and has been, during all of my time here. I will miss that a lot.
My replacement is Emily Walsh, with whom you will become well acquainted in the years ahead. Emily was our first choice and she is a dandy. She is a very capable teacher and researcher and a warm, personable young woman. I have no doubt that she will move hard-rock geology at Cornell ahead with great energy and enthusiasm. We need a strong presence here to counter the followers of Gene Hinman and his “sexy sediments” vs. “ugly igneous”!
For the next year or so (during which time Ellen will work to her retirement) I will continue and try to finish up some research on Linwood barites and on Shoshonean pottery. I also will do some long-anticipated historical biographical research and writing, and some archival work with photographic prints and slides that my father generated over many years as an amateur photographer. I also plan to continue to play bongo drums with Cornell’s steel drum band. After Ellen’s retirement, we plan to serve a one- or two-year mission for our church (Mormon). I am hopeful that we will be sent somewhere in Latin America. After that, more reading, research, writing and archiving, and enjoying my wife, two children and nine grandchildren.
We plan to be in Mount Vernon for the next year or so. As always, our home is open and we would love to see you if/when you are out this way.
With warm regards,
Geology Majors & Minors 2004-2005
2005 Majors: Alexa Clements, Peter Cole, Adam Majeski, Rory Martin, Steph Penn
2005 Minors: Patrick Farrell
2006 Majors: Jessica Harms, Brian Hoye, Lara Moellers, Dustin Waite
2006 Minors: Megan Andresen, Amelinda Webb
2007 Majors: Jill Hopper, Frank Najera, Charles Trodick, Joseph Valenta
2007 Minors: Alyssa Borowske, Diana Krogmeier
Student Awards and Honors
Herbert Hendriks Award (to the top senior geology major)
2004. Andrew Sorensen
2005. Alexa Clements
William H. Norton Geology Prize (to the top junior geology major)
2004. Alexa Clements
2005. Brian Hoye
Gene Hinman Geology Prize (for excellence in field research)
2004. Martin Krulatz
2005. Rory Martin
Hendriks Student Research Fund
2004. Dustin Waite, Amelinda Webb
2005. Megan Andresen, Charles Trodick
Geology Department Honors
2005. Adam Majeski
Merry Clayton ‘05
Response Of Pleistocene Epibiont Communities To Terrigenous Sedimentation On The Western Australian Coast 1,2,4,6
Peter Cole ’05
Uranium-Lead Dating of a Coral from the Neogene Gurabo Formation, Dominican Republic 1,2,4
Adam Majeski ’05
Silicification of Corals, Stromatoporids and Brachiopods at the Weathered Surface Within the Devonian-Age Little Cedar Formation (Solon & Rapid Members) of Eastern Iowa 1,4,5
Rory Martin ‘05
Marine Influence on the Pennsylvanian Caseyville Formation of Muscatine County Iowa 1
Brian Hoye ’06
Stable Isotopic Trends In 23,000-16,000 Year Old Arkansas Stalagmite 1,2,4
Dustin Waite ’06
Carbonate Sediments Of Western Australia: An Introductory Investigation 1,2,4
Amelinda Webb ’06
Interpretation of a Devonian Encrusted Brachiopod Assemblage: Solon Member, Cedar Valley Formation, Iowa 1,2,3,4
Alyssa Borowske ’07
A Stable Isotopic Analysis Of An End Pleistocene-Age Stalagmite From Almonda Cave, West-Central Portugal 1,2,4
1 Presented at Cornell College Student Symposium
2 Presented at North Central Geological Society of America Meeting
3 Presented at Geological Society of American Annual Meeting
4 Presented at Iowa Academy of Science Annual Meeting
5 Geological Honors Thesis
6 Environmental Studies Honors Thesis
A Stable Isotopic Analysis Of An End Pleistocene-Age Stalagmite From Almonda Cave, West-Central Portugal
Little is known about the climate and vegetation of western Iberia during the last deglaciation. However, cores of marine sediments taken off the coast of southwestern Portugal suggest that southward shifts in the North Atlantic polar front caused two major sea surface cooling events between 17,000 and 9,000 cal- 14C yr BP. During these cool periods, steppe taxa expanded and trees receded, likely because of increased aridity.
We report preliminary results from analysis of a Portuguese stalagmite that has been dated by two U/Th alpha spectrometry techniques to ~12,000 – 10,000 yr BP (note that the chronology is should not be considered robust as it is based only on two alpha spectrometry dates from a low U sample). This stalagmite, identified as ALM-04-01, is 21 cm long and is composed of clear, coarsely crystalline calcite. ALM-04-04, was collected from Almonda Cave, which is part of an expansive karst system formed in Mesozoic dolomites and limestones in west-central Portugal.
ALM-04-01 was sampled for stable isotopic analysis at 5 mm intervals. Oxygen isotopic values average –3.2 per mil PDB, but vary by ~1 per mil during two discrete intervals. The d 18 O values of speleothems are determined by the d 18 O of the infiltrating water (meteoric precipitation) and the temperature of the cave, but may be modified by a variety of variables including kinetic effects. It remains unclear at this point whether the observed oxygen isotopic fluctuations represent rapid and large-scale changes in climate, possibly linked to those observed in marine cores.
The carbon isotopic composition of the bedrock hosting the cave averages–2 per mil, and because stalagmite d 13 C values reflect C from both bedrock and soil, the -9 per mil stalagmite carbon isotopic value likely corresponds to C3 vegetation over the cave.
Response Of Pleistocene Epibiont Communities To Terrigenous Sedimentation On The Western Australian Coast
Fossil reefs from the Last Interglacial (Marine Isotope Stage 5e) are exposed at Red Bluff, Western Australia. Acroporid corals with plate-form colonies dominate the reef framework that is exposed along a marine terrace approximately 5 m thick. Coral plates were systematically removed from the outcrop along a vertical transect, and the epibiont communities preserved on them were examined. Community growth sequences found on these plates were strikingly different from the complex patterns established in the
Caribbean and South America, as nearly all plates sustained epibiont growth only to very early stages of succession. Both coarse and fine sediments were plainly observed in association with the coral plates. Epibiont growth persisted during deposition of fine sediment, but ceased after the appearance of the coarser sediment. Petrographic analysis revealed that the sediments are similar in basic composition, but a distinct boundary is present between a coarse-grained packstone and a finer-grained, carbonate mud-rich, wackestone. These differing clasts suggest deposition during respectively high and low energy regimes. Thus, terrigenous sedimentation appears to be an important control on epibiont community structure.
Uranium-Lead Dating of a Coral from the Neogene Gurabo Formation, Dominican Republic
Closure of the Central American Gateway at approximately 4 million years ago is believed to have changed the temperature and salinity of Caribbean surface waters, resulting in extinctions of several marine taxa including some corals. Extinction rates for this period rely on age models for sedimentary sequences, many of which are generated using biostratigraphy. Differences in these models have resulted in a range in rates of faunal turnover. Here we present the results of our attempt to constrain the age of one of these sedimentary units, the Neogene Gurabo Formation, northern Dominican Republic, using U-Pb dating methods on an extremely well-preserved coral.
U-Pb dating of corals is rarely attempted because their highly porous and aragonitic skeleton is highly susceptible to diagenetic alteration. Coral samples were intially screened using petrographic microscopy, X-ray diffraction, and stable isotope analysis. Using these tests, a sample of Goniopora hilli was determined to be largely free of diagenetic alteration. 238U/ 234U and 234U/ 230Th ratios were measured using TIMS in eight chips from this sample and three contained secular equilibrium values for both isotopic ratios. Subsamples from these three chips were dated using 206Pb/ 204Pb vs 238U/ 204Pb methods to an age of 7.0 MA +/- 0.66 Mya.
Using biostratigraphy, Saunders et al. (1986) and Vokes et al. (1989) assigned signficantly different ages to the Gurabo formation (5.1-4.2 Mya and 5.6-5.3 Mya, respectively). Our U-Pb date agrees with new paleomagnetic data which indicate that the Gurabo Formation represents a much longer time interval than previously thought. Thus the rates of faunal turnover during this interval must be recalculated.
Interpretation of a Devonian Encrusted Brachiopod Assemblage: Solon Member, Cedar Valley Formation, Iowa
Encrusting organisms offer a unique perspective in the fossil record because of the preservation of spatial and competitive relationships. Encrusters are preserved in life position, allowing interpretation of ecological interactions between encrusters and their hosts. However, techniques for sampling encrusted assemblages vary between fine, specific samples that are collected bed by bed, to coarse samples that can encompass an entire outcrop. Fine-scale sampling facilitates in-depth interpretation of ecological patterns. Encrusted brachiopods were collected from the Solon Member of the Cedar Valley Formation at Robins Quarry in Iowa. Four fine-scale samples were collected from single horizons within a 20 cm stratigraphic interval and a 10 square meter area. Several coarse samples were collected from the same area for comparison of general trends.
Both sampling techniques show the same general trend for encruster abundance and valve preference. However, the coarse samples do not show the average of the ecological patterns observed in the fine-scale samples and abundances of brachiopod taxa differ. Between the fine-scale samples, variations occur in the proportion of encrusted brachiopods and the amount of encrustation within each taxon. Encrustation gradually decreases through time, with the stratigraphically lowest sample having 38% of the brachiopods being encrusted, and the youngest sample showing 24% encrustation. The most common taxa of brachiopods were Independatrypa, Pseudatrypa, and Seratrypa. The most common encruster was Spirorbis (53-71% of the observed encrusters) followed by an encrusting bryozoan (14-23%) and Hederella (8-14%). Brachiopod diversity remains relatively stable through time; however the diversity of encrusters more than doubles from the lowest stratigraphic sample to the third sample. The fourth and youngest sample decreases to an average diversity. Competition among encrusters could account for the trends observed.
Carbonate Sediments Of Western Australia: An Introductory Investigation
Constituent particle analyses of carbonate sediments have been applied to many paleoenvironmental studies. However, such studies are lacking from Pleistocene coral reef facies exposed in coastal Western Australia. In this study, the results of sedimentologic analyses are reported. Samples of matrix enclosing fossil coral reefs distributed along a latitudinal gradient of approximately 12o were obtained from Cape Range, Red Bluff and Rottnest Island, Western Australia. Thin sections were analyzed for the relative abundance of carbonate and siliciclastic grains. Point counts revealed that coralline red algae dominate most of the sediment matrix surrounding the fossil coral reefs, with mollusks, coral fragments, and miscellaneous non-carbonate grains as the other major contributors. Foraminifera, Halimeda grains,
echinoderms, and sponges make up the remainder of the constituents. Red algae and foraminifera were the only constituents that can be directly correlated with specific localities along the WA coastline. Relatively weak correlations between latitude and the abundance of the main constituents (red algae, mollusks, corals, and non-carbonate grains) exist. The abundance of coral fragments is correlated positively with latitude, while mollusk fragment abundance shows a negative correlation with latitude. Multidimensional scaling illustrates that localities examined in Western Australia, modern fringing reef facies in Jamaica and ancient windward and leeward reef facies exposed in Curacao, Netherlands Antilles, are very dissimilar when the composition of the sediments enclosing them is compared. This pilot study of sediments off the western coast of Australia should provide the blueprints for further, more extensive sedimentological research in this remote area.
Silicification of Corals, Stromatoporids and Brachiopods at the Weathered Surface Within the Devonian-Age Little Cedar Formation (Solon & Rapid Members) of Eastern Iowa
Diagenesis of fossils in middle-Devonial limestone was studied at the Troy Mills and Robins quarries in Linn County, Iowa and at the Four County and Ernst quarries in Johnson County, Iowa. Fossils located at the weathered bedrock surfaces are preferentially silicified, and the silicification affects corals, stromatoporids and, to a limited extent, brachiopods, but not other fossils or the host rock. Furthermore, this siliceous horizon extends no more than 3 cm below the weathered surfaces, suggesting that it is an occurrence constrained by these surfaces. Silica for silicification could have come from a variety of sources, including sponge spicules or radiolarian tests, insoluble residues (fine-grained quartz and clay minerals) within the host rock, or from the weathering and alteration of clay minerals contained in Paleokarst-hosted Pennsylvanian fluviatile sediment. Once reaching the Devonian weathered surface, a change in pH or other chemical variable could have created an environment favorable to silica precipitation. As silica precipitated, it affected mostly the more porous corals, to a lesser extent the stromatoporids, and only a few of the low-porosity brachiopods. The matrix, and a few other fossil types are wholly unaffected, suggesting that their porosities were too low for quartz fill and/or replacement. The diagenetic sequence is: 1. Euhedral calcite void linings 2. Poikilotopic megaquartz 3. Length-slow filling and replacing chalcedony 4. Microquartz. 5. Blocky, anhedral calcite. Chert and dolomite are also present, but limited interaction with other mineral forms prevented paragenetic information from being determined.
Marine Influence on the Pennsylvanian Caseyville Formation of Muscatine County Iowa
Examination of eight IPSCO cores from Muscatine County Iowa has led to a new interpretation of the depositional environment of the Caseyville Formation. The Pennsylvanian sandstones and shales of the Caseyville Formation have long been thought to be channel filling deposits, however close examination of IPSCO core samples suggests that the Caseyville is more influenced by a marine environment than by a fluvial environment. The Caseyville would be better described as an estuarine fill of a river valley caused by multiple marine transgressions. Widely traceable coal seams, lingulid brachiopods, traces of tidal cyclicity, and limestone provide evidence of marine influence on deposition in the area.
Stable Isotopic Trends In 23,000-16,000-Year-Old Arkansas Stalagmite
We present stable isotopic data from a stalagmite from Cosmic Caverns, NW Arkansas, that has been dated by U/Th disequilibrium thermal ionization mass spectrometry (TIMS) to 22,800 - 15,700 year BP. Speleothems spanning this time interval are rare from the North American mid-continent, likely because cold and/or dry conditions minimized speleogenesis. The 22 cm-long cylindrical stalagmite (identified as CS-04-01) is composed of dense, optically-clear and finely-crystalline calcite, and exhibits stable isotopic variability that may reflect changing paleoclimatic conditions following the Last Glacial Maximum (LGM).
The chronology of CS-04-01 is derived from three TIMS dates (22,800 +/- 460, 21,050 +/- 280, and 16,250 +/- 400 yr BP). Carbon isotopic ratios in CS-04-01 average -9 per mil (PDB) between 22,800-21,600 years BP at which time they decrease sharply (over an estimated 300 years) to and remain at an average of -10.5 per mil. This decrease in carbon isotopic ratios could reflect a shift toward a denser forest covering over the cave, or it could also have been driven by a reduction in the contribution of bedrock carbon to the stalagmite.
Oxygen isotopic ratios decrease from approximately -4.3 to -5.3 per mil between 21,800 and 20,800 year BP, and then steadily rise to -3.8 per mil at 15,700 years BP. Neither the seasonality of precipitation nor the relationship between air temperature and the oxygen isotopic composition of precipitation is known for this region during the LGM. However, assuming that modern relationships apply, these elevated 18O/16O ratios could reflect significant (~4 degrees C) regional mean annual warming over this 5000-year interval.