Volume 12, Number 1 March, 1993
I am pleased and honored to be serving as the chair of the Structural Geology and Tectonics Division this year. Rick Groshong is the first vice-chair, Ed Beutner is the newly elected second vice-chair, and Don Secor continues as the Division secretary and treasurer.
The 1992 Annual GSA meeting was held in Cincinnati and was very successful; there were a total of 15 structure and tectonics sessions. The number of tectonics abstracts was down significantly from the previous year in San Diego (139 as compared to 292) although the number of structural geology abstracts was about the same (107 as compared to 129). Many thanks to Jim Evans, Ben van der Pluijm, Bob Miller, Jim Hibbard, Rich Groshong and Darrel Cowan for serving as reviewers for the abstracts, and to Darrel Cowan and Mark Cloos for their help in Boulder in August in arranging all the Division sessions. Win Means ran the Division's two day pre-meeting short course entitled "How to do anything with Mohr Circles (except fry an egg)". The course was well-organized and informative and the workbook he prepared is very user-friendly. The Division's Symposium on "The role of fluids in deformation" was organized by Terry Engelder and myself. Theme Sessions with a strong interest for SG&T Division members included the following: "Tectonic settings and paleoenvironments of the Paleo-Pacific margin - Antarctic and related Gondwana Sequences"; "Intraplate neotectonics"; "Thrust fault sesquicentennial"; "Time and place of compressional events in the Appalachian orogen"; "Formation of fault systems"; and "Late Proterozoic rifting of the North American craton".
The annual business meeting of the Division at Cincinnati was well attended (no conflicts with scheduled sessions this time!). Citationist Art Sylvester presented the 1992 Career Contribution Award to John Crowell (both the citation and John's response will soon be published in the Bulletin.) The Best Paper Award was presented to Paul Hoffman for his paper on "The United Plates of America". Sam Bowring's citation and Hoffman's acceptance comments are printed in this Newsletter. The Division's Student Research Award was presented to Ramon Arrowsmith of Stanford for his study "The temporal and spatial development of deformation and degradation within a restraining bend along the San Andreas Fault, central California'. Also at the business meeting Mark Cloos lead a discussion of possible new funding initiatives to support research in structural geology and tectonics. One possible new source of funds is the recently signed National Mapping Act, if funding is approved this year. Tom Wright and Carol Simpson affirmed that there is a need for Division members to speak up and supply them with 'ammunition'. Mark Cloos (who serves on the NAS-NRC Board of Earth Sciences and Resources) plans to organize a follow-up workshop at the Cordilleran Section meeting this spring.
Plans for the 1993 Annual Meeting in Boston are already underway. The Symposium will be on the subject of "Inferring paleoearthquakes from fault-rock fabrics: experimental and field evidence"; it will be convened by Fred Chester and Ron Bruhn. A two-day, pre-meeting Short Course on "Fracture mechanics of rock" will be presented by Terry Engelder with assistance from Mike Gross and Mark Fischer. The Board has decided to appoint a four-member 'Short Course and Symposium Committee', whose duty it will be to come up with a list of short course and symposium topics (and possible conveners) of interest to Division members. The names of these committee members will be published in the next newsletter, but meanwhile feel free to send suggestions to Ed, Rick, or myself.
At our meeting in Cincinnati I asked whether others might be interested in a workshop on "Teaching structural Ggeology". My idea was threefold: first, to try to obtain some (outside) expertise on modern ideas as to different modes of learning; second, for participants to share experiences of different teaching methods, classroom demonstrations, lab exercises, writing assignments, etc., which we have found to be successful; and third, for participants to bring a set of 35 mm slides (with accompanying notes) illustrating some 'case study'. For example, I could provide good illustrations of deformation microstructures in experimentally deformed quartzo-feldspathic rocks (as a function of increasing strain, and of increasing temperature) - and I would like to acquire sets of slides of outcrop or regional scale structures. (Win Means started this idea by making available, at cost, sets of slides from his in situ analog deformation experiments.) At present I am thinking of organizing a workshop on teaching structural geology for the Seattle meeting. I would be very glad to hear of your interest and/or suggestions!
Along similar lines of improving the annual meetings, I would like to stress the usefulness of the Theme Session concept, as a way for an individual to identify a timely topic and solicit volunteered abstracts addressing that topic, often from diverse perspectives. This is an excellent way to get the stimulation of interdisciplinary communication. There are obvious links between structural geology and metamorphic petrology, for example, or between tectonics and geophysics, but there is no way for the program committees of the various divisions to construct cross-disciplinary sessions. Thus it is up to individuals to take the initiative to suggest Themes.
The shifting world situation and US economy have affected not only our basic research funding, but also the size and make-up of college and university geology departments as well as the employment picture for structural geologists (see "Have You Heard ... ?" column); many of these changes do not seem good. Many structural geologists are out of work due to layoffs in the petroleum industry, and there are very few academic openings. Clearly we need to be thinking about what it is we are training graduate students for, and what our role is in undergraduate education, both for geology majors and general education students. I am interested in your thoughts as to how we, as a Division, can help all of us maintain enthusiasm, intellectual vigor, and productivity in these changing times. For example, should we be more active in interdisciplinary areas, such as hydrology, environmental geology, geophysics, and natural hazards, perhaps by joint sponsorship of symposia or short courses? Should we attempt to educate experimentalists and theoretical modelers about the importance of field work by inviting some of them to participate in symposia and theme sessions at GSA, and by submitting problem-oriented abstracts on field studies to AGU meetings? Would new sorts of formats or sessions at the national (and sectional) meetings be helpful?
Finally, let me reiterate what Darrel stressed last year: effective
service by the officers of this Division depends on member input
and communication. Please take the initiative to suggest Symposium
and Short Course topics you would like to see offered; get together
with a colleague and suggest a Theme Session for the next annual
meeting; send in nominations for the Career Contribution and Best
Paper awards; write letters or articles for the Newsletter;
and let us know what new functions you think the Division could
serve. In the interest of ready access, here are the fax numbers
and E-mail addresses for the chairs this year:
Jan Tullis fax 401-863-2058 E-mail: email@example.com
Rich Groshong fax 205-348-9268 E-mail: (not used)
Ed Beutner fax 717-291-4186 E-mail: firstname.lastname@example.org
Jan Tullis, Department of Geological Sciences, Brown
University, Providence, R. I., 02912
To add to Jan's comments above, we are continuing to try to improve our efforts to provide you with a fun, yet informative Newsletter , and we wish to thank those of you who have sent in materials for publication. We particularly wish to thank Tom Wright for his continued efforts in writing the "NSF NEWS" column. Your personal views on scientific or professional matters of interest to the membership will be welcomed. In addition, please send us your letters, comments, or information for our various columns (e.g., "Have You Heard... ?", "The Resource Bin", "Read a Great Book Lately?", "Symposia/Theme Session Summaries" [sorry, but none this issue because our requests for such summaries went unanswered]). We will also welcome suggestions for other types of material that you would find useful in future Newsletters. Call us, write us, send us E-mail or fax messages, but please don't be shy in helping us out! The deadline for inclusion of materials in the next issue is July 1, 1992. Please send lengthly items on a Mac floppy if possible. Greg Davis: Phone, (213) 740-6726, fax: (213) 740-8801; Scott Paterson: Phone, (213) 740-6103, E-mail - Scott@coda.USC.EDU.
Citation by Samuel A. Bowring
The Structural Geology and Tectonics Division has chosen the 1988 paper by Paul Hoffman entitled "United Plates of America, the birth of a craton: early Proterozoic assembly and growth of Laurentia" (Ann. Rev. Earth Planet. Sci., v. 16, p. 543-603), for its 1992 Best Paper Award. There is no question that it is one of the most influential contributions to the study of the continents in the last decade. A simple measure of the impact that this paper has had and continues to have is the frequency of appearance of its geologic map of North America or derivatives of it at every GSA and AGU meeting as well as in a large number of papers and books.
This paper was the culmination of more than six years of compilation of the Precambrian history of North America that began when Paul published his first edition of the North American map in the first DNAG publication in 1982. This was in the last years of Paul's field work in the Wopmay orogen and he sought to put the geology of the northwest Canadian shield in a more global context. Paul was a pioneer in proposing and testing plate-tectonic models for the Precambrian of the northwest shield and he felt hat many of the lessons learned in Wopmay could be applied to other similar-aged orogenic belts of Laurentia. This paper represents a small plateau in Paul's evolving view of Laurentia because he has continually accomodated and integrated new data into his model.
Why is a paper on the Precambrian evolution of Laurentia so important?
The field of structure and tectonics is in large part concerned with the record of plate motions recorded within orogenic belts. For most of Earth history we have no direct record of plate tectonics, only what we can glean from the record preserved in Precambrian orogens. Questions concerned with the long term consequences of a planet dominated by plate tectonics and the possibility of secular change in the style of plate interactions, crust-mantle relationships, and the thermal history of the continents and ocean basin can only be tested using the Precambrian rock record. In addition, there is a growing realization that much of the style of Phanerozoic orogenic belts and the chemical and isotopic signature of magmatic rocks in these belts is directly related to lithosopheric-scale structures developed in the Precambrian. Clearly, understanding the development of continental lithosphere is an extremely important and ambitious task. In this paper, Paul has shown in detail how the 15 major early Proterozoic orogens of Laurentia can be explained as the assembly of diverse tectonic elements involving consumption of oceanic lithosphere, an assembly he compares with that of Eurasia in the Phanerozoic.
This is a landmark paper for several reasons. I do not think it is an exaggeration to say that this paper has forever changed the study of Precambrian cratons and their orogenic belts. It has stimulated many to test and refine tectonic models, and it has played a major role in eliminating the notion that somehow things were different in the Precambrian. Many of us have forgotten the resistance to interpreting complex Precambrian orogenic belts in terms of plate tectonic models that were rampant in the 70's and early 80's. This paper builds on the pioneering papers published in 1973 by Kevin Burke and John Dewey who speculated on the Precambrian plate-tectonic hisory of the Canadian shield. Today, it is common to seen in papers concerned with the evolution of Earth the statement that plate tectonics can be proven back to 1.0 Ga with a reference to "Hoffman (1988)". His paper represents much more than a compilation of the geologic history of North America. It integrates the latest developments in geologic mapping, geochronology, isotope geochemistry, and geophysics, and is full of new, original, and oftentimes speculative interpretations. The figures in this paper are worth many, many ages of text and often contain new interpretations that are not aways obvious to the casual reader until one studies Paul's map of their field area with a handlens.
The other reason that this is truly a landmark paper is that it has played a very important role in how we view Laurentia and its relationship to other cratons. Paul's speculations about Laurentia's position in a Precambrian supercontinent and the idea that we should look for rifted portions in other cratons has rekindled intense interest in inter-cratonic correlations as well as in understanding the growth and dispersal of supercontinents prior to Gondwana. Much of the current discussions of the late Proterozoic supercontinent and relationships between Gondwana and Laurentia are an outgrowth of this paper. Many have and will take issue with some of the details of interpretations put forth in this paper, but there is no question that it has stimulated a tremendous amount of new and focused research. In fact, research on Precambrian orogenic belts has expanded with such vigor in the last five years, and much of what Paul said in this paper so fully integrated into our thinking, that it is easy to lose sight of the role that this paper has played.
Paul has brought, in the words of our president, "that vision
thing" to the study of Laurentia and its role in earth history.
Acceptance by Paul F. Hoffman (School of Earth and Ocean
Sciences, Univ. of Victoria)
I am thrilled to share the honors at this meeting with three old friends named John. From John Crowell I learned that sedimentologists ignore structure at their peril. From John Dewey I learned that parochialism is the bane of tectonics. From John Grotzinger I learned how little of what I had seen in the field I understood.
The "United Plates of America" is a synthesis based on generations of field work. It is an honor to be shared by many. Its recognition by the Structural Geology and Tectonics Division indicates a growing awareness of the significance of Precambrian studies. The origin of continental crust, given its mean age of almost two billion years, is largely a Precambrian problem. However, the realization that lithospheric recycling has been going on continuously since the beginning of the Archean means that the problem must not be set apart from Phanerozoic continental accretion. Archean granite-greenstone belts, for example, bear comparison with regions of Phanerozoic accretion like the Canadian Cordillera. However, the continental lithosphere is rheologically heterogeneous and the distinctive rigidity of cratons older than about 2 Ga has influenced regional patterns of lithospheric deformation right up to the present day. We need to better understand the nature and origin of the refractory mantle roots beneath the ancient cratons, including their time of formation and influence on sublithospheric mantle flow. Composite continents like North America reflect many episodes of tectonic aggregation and fragmentation. Its Paleozoic land trade with Africa, Baltica, and South America, and its subsequent acquisitive foray into the Pacific are only the latest moves in four billion years of corporate manoeuvering on a sphere. The implications of our shared ancestry with other continents are far from being fully appreciated.
Until recently, the bugaboo for Precambrian studies was the lack of precise age control. That has now changed, thanks chiefly to Tom Krogh of the Royal Ontario Musueum. The importance of precise and reliable U-Pb ages cannot be exaggerated. In the bad old days, tectonic models were difficult to test. If they were attractively presented, they were accepted and enshrined in textbooks. As most tectonic models make specific predictions about age relations, they can be decisively falsified geochronologically. Nowadays, tectonic interpretations evolve rapidly, where formerly they stagnated. The current fluidity of ideas is a sign of a healthy science. Moreover, the quantification of geological processes demands constraints on rates -- no dates, no rates! Of course, producing precise ages is demaning -- intellectually, financially, and physically -- as is the geological field work required to ensure their proper interpretation. My citationist is one of the new breed of geoscientists who does both. Sam and I have had much fun turning our interpretations of Wopmay orogen inside out -- more than once.
"The United Plates of America" has been a very exciting
project -- a chance to extend my experience on the ground in Wopmay
orogen to the scale of a continent. It is now time for me to
move on to another field area (the Namibian Kaoko belt), another
continent (Gondwanaland) and another time interval (the Neoproterozoic).
Thank you for supporting my conviction that the Precambrian is
neither alien nor intractable, and that we shoud not be satisfied
to investigate only the later part of Earth's history.
As this Newsletter article is written, Washington, D.C. is gearing up for the change in administrations. The town is abuzz with words like protocol, policies, initiatives, priorities, studies, regulations, and directives. Meanwhile the rest of the country goes about the task of trying to get something done. This difference is not new; cynics claim that the interstate highway that rings Washington divide things into "inside the beltway," which has to do with government and its shenanigans, and "outside the beltway," which are the activities of everybody else. Occupants on each side of the beltway claim that they, in fact, are in the real world and those on the other side are living in dreamland. This applies to NSF (inside) and researchers (outside), and also to the Tectonics program and you, the people who actually study structural and tectonics problems. This different perspective generally causes harmless consequences and even provides the source of "can you believe this?" - type jokes. (For example: "What has NSF done with the one-page proposal cover sheet to help reduce paperwork and shorten proposals? Answer - made it a 2-page form!). However, the basic misunderstandings between "inside" and "outside" can lead to more substantive problems.
I think science in general and our field specifically have more to offer than our society is presently inclined to support. Increased investment of public funds in basic research, in my opinion, would be an excellent investment of tax dollars. In order to accomplish this goal, however, the value of the ideas practicing scientists want to pursue (the "outside" view) must be converted, packaged and promoted to appeal to the managers of the public's purse-strings (the beltway bunch). For an excellent article on this subject, see "Science-Government interaction" by Kenneth B. Taylor in the January, 1993, issue of GSA Today or a number of other recent articles on this theme. Most structure and tectonics researchers get a bad case of MEGO (my eyes glaze over) when things like public policy, science priorities, initiatives and long-range planning come up -- everyone would much rather be in the field or lab actually doing the research. But we are improving, as witnessed by the discussion session held after the Structural Geology and Tectonics Division meeting in Cincinnati that resulted in the approval of a Structural Geology and Tectonic Division Committee to look into some of these issues. These are encouraging developments. Lets keep up the momentum; give Mark Cloos and the committee your ideas and support.
The overall quality of proposals submitted to the Tectonics program is important from several perspectives. The proposer wants their proposal to be seen as high quality so it might be able to compete successfully for funding. The program appreciates receiving strong, well-written proposals because that gives us ammunition when the subject of budget allocations comes up and becomes clear, interesting proposals are a lot more fun to deal with an opaque and deadly dull ones.
Talking about clear, well written and exciting proposals is much easier than writing one. As the competition becomes more challenging, more effort is being expended to write stronger proposals, and we are more frequently asked, "O.K., what do you see in my proposal that is a problem?". Your Newsletter editors thought that a general discussion of the question "What are the 5 biggest problems with unfunded proposals?" would be useful, so here goes. The first three, in order, are significance, significance and significance. Really. By far the biggest deficiency is failing to communicate why this project is so important to do -- right now. Of course, there are all sorts of legitimate reasons why a specific project is important to do (working out deformation history of a classic area, resolving conflicting, multiple hypotheses or an unresolved issue, developing new tools or new understanding of mechanisms, etc.), but it is a mistake to leave this important point to your reviewers to sort out by themselves. If you do, it is the equivalent of saying "I know why this is so important, but I'm not going to tell you!" - not a particularly useful sales tactic. No one deliberately does this, but simply because you are so close to your subject it is really easy to let this critical step pass by without the attention it deserves. To help counteract this, try to ask yourself a few questions designed to see the proposal through the eyes of others. First, ask yourself how many people would likely care if you did the work proposed and published the results?" Or another one might be: "If I didn't do this and publish it, who or what would suffer as a result?" If you are applying relatively standard techniques to study a particular place (mapping, dating, PTt and isotopic analysis of the so-and-so area), try changing the place name and see what difference that would make. You get the idea -- if you have trouble answering this type of question the reviewers probably will also.
Assuming that you have successfully captured the reviewer's interest, the rest of the proposal is usually more straightforward, but there are still several ways to snatch defeat from the hands of victory. One way is to set up a great problem, but then fail to show how the methods and data you want to employ or gather will lead to a solution or help discriminate between competing hypotheses, etc. Reviewers could conclude that your project's goals are wonderful but they can not see how your shopping list of techniques or their expected precision will do the job. Here again, putting yourself mentally on the reviewer's side might help.
Our choice for the last of the "5 biggest problems" as seen by the program is in somehow allowing reviewers to be able to question whether the project, as proposed, could be reasonably seen through to publication and delivered at a competitive cost/value ratio. There are a number of ways to cause this, including unrealistic and over-ambitious plans, huge and undefended/unjustified salary or other costs, or by building a reputation for not publishing results of your research. Here too, it seems to us that these could be avoided or mitigated by using a bit of common sense.
Over the last few years the Tectonics program has received more and more proposals that in aggregate request steadily increasing amounts while our budget has either remained flat or increased at a small rate. One of the consequences has been a relative rise in the number of resubmitted proposals; currently 37% of Tectonics proposals are resubmissions. It is not uncommon for a proposal to be turned down, re-written incorporating the suggestions or reviewers, resubmitted, favorably reviewed and funded. This has been an important way for researchers to help each other design strong, well thought-out projects, but it comes at considerable cost in re-writing time and in reviewing time. Another thing that is happening is that the average review scores and the degree of support expressed in reviewer comments are increasing for this group of proposals. Some previously declined proposals are significantly improved by the process of re-writing, only to face a tougher competition the next time through and still not receive funding. The improvement in proposal quality gets offset by the increased competition, so the proposal winds up in just about the same priority slot where it started. From a proposer's point of view this is extremely trying. (I have conversations in which I hear something like "The first proposal received pretty good reviews and you indicated it wasn't far from the funding line. So, I took the reviewer's points and my own rethinking and I know I resubmitted a much better proposal -- the reviews are better, yet it still isn't funded. What's going on?").
This general subject has been discussed within the Earth Sciences Division, with the review panel, and with other advisory groups. It is mostly agreed that more principal investigator, NSF, and reviewer time and effort is being expended on resubmitted proposals than might be necessary or desirable, but no alternative to the present system seems any better. Suggestions include specifying a minimum amount of change in resubmitted proposals, a limitation on the number of times a project can be resubmitted, a minimum review score (or program priority assignment) before a proposal could be resubmitted, reviewing resubmittals differently from new proposals, and setting aside a specific amount of money for a separate resubmittal category of proposals. What do you think? Please send us your views on how to handle this situation and suggest what, if anything, we should do differently.
Peer review is the most important factor in determining the fate of a particular proposal. We are sometimes asked "What makes a perfect review?" or "What kinds of things do you really want to find in a review?" or "How am I doing in my reviews? Are they useful to you?". Reviewing a proposal takes time and thought, so it is worth ensuring that the product -- the review itself -- efficiently and effectively transmits your input. In the review, you are addressing the program and the proposer, and it helps to keep the needs of both in mind.
From the program's view, what we need is an assessment of the overall significance - is this of crucial importance or is it an inconsequential geopuzzle-type project? Flat statements without elaboration leave room for misunderstanding and questions about your reasons. Next, we need some indication about how likely the research will be "do-able". How does it fit in with prior and present work on this subject? Is it new and useful, is it premature for some reason, or is it just a reiteration of something already studied? Are the methods carefully assessed and chosen or are they an undigested shopping list for the old "try everything and see what happens" approach? Try and avoid personal attacks. Don't write "so and so wouldn't know a trilobite if he saw one crawling across the floor, when you meant "so and so didn't document that he knows the trilobite taxonomy needed to do this part of the work".
From the proposer's point of view, your comments, especially critical ones, should be as clear as possible with explanations. Don't beat around the bush. A lengthy recounting of what the proposal is about is a lot less useful to the proposer than what's wrong or right with it. For the proposers benefit (funded or not) your review should constructively point out weaknesses and where possible, indicate ways these weaknesses could be overcome. If after reading your reviews, the proposer says to himself "Why, this is really good! I haven't really thought of these points as clearly as I should have", then you have done a better service than if he says "Gee, I don't think this person even bothered to read my proposal".
Congratulations to the following people who received a Tectonics
grant during the last six months.
Tom Wright, Tectonics Program, National Science Foundation,
1800 G Street, N. W., Washington, D. C. 20550
P.I. NAMEINSTITUTIONTITLEAve Lallemant, HansWilliam Marsh Rice Univ. Tectonic Evolution of the Chortis Block: Implications for Caribbean TectonicsBartley, JohnUniversity of UtahCOLLABORATIVE RESEARCH: Mechanics of Footwall Uplift During Detachment FaultingBeck, MyrlWestern Washington Univ. Paleomagnetic Investigation of the Atacama Fault, ChileByrne, TimothyUniv. of ConnecticutCOLLABORATIVE RESEARCH: Kinematic History of Hinterland in an Arc-Continent Collision, TaiwanCowan, DarrelUniv. of WashingtonKinematic Analysis of Brittle Fault Zones Using Landslide Deposits as AnalogsDeMets, DennisUniv. of Wisconsin MadisonPost-3.0 No Variations in East Pacific Plate Velocities and Implications for Studies of Plate KinematicsDilek, YildirimVassar CollegeRUI: Structure and Tectonics of an Inner-Tauride Ohiolite and Associated Shear Zone in Southern TurkeyDunne, GeorgeCal State Univ. NorthridgeCOLLABORATIVE RESEARCH: RUI: Deformational and Magmatic History, Eastern Sierran Arc, East-Central CaliforniaEllis, MichaelMemphis State UniversityChapman Conference on Tectonics and TopographyGardner, ThomasPA St. U University ParkTectonic Escape of the Panama Microplate? Kinematics Along the Western Boundary, Costa RicaGirty, GarySan Diego State Univ. Fdn.
RUI: COLLABORATIVE RESEARCH: Pluton Emplacement
in Relation to Jurassic Volcanic Arc Evolution and Orogenesis
in the Northern Sierra Terrane, California
Texas Christian Univ.
COLLABORATIVE RESEARCH: Pluton Emplacement in Relation
to Jurassic Volcanic Arc Evolution and Orogenesis in the Northern
Sierra Terrane, California
Univ. of Pittsburgh
Tectonics and Paleomagnetism of the Kamenskoye-Penzhinskaya
Guba Regions, Koryak Superterrane, Northeastern Russia
Louisiana St. Baton Rouge
Mesozoic-Cenozoic Tectonic Evolution of the Mojave
North Carolina State Univ.
COLLABORATIVE RESEARCH: Structural Analysis, U-Pb
Geochronologic, and Nd Isotopic Characterization of the Carolina
Slate Belt and Milton Belt, Southern Appalachians
University of Maine
COLLABORATIVE RESEARCH: Crustal Profile of a Major
Transpressional Boundary: Tectonic Evolution of the Norumbega
Fault Zone, Maine
U of Minnesota-Twin Cities
Phyllosilicate Fabric in the Proterozoic Thompson
U of Minnesota-Twin Cities
Rheological Controls on Fold Shape and Strain Distribution
University of Arizona
Neogene Tectonic, Climatic and Depositional Evolution
of the Eastern Basin and Range: Seismic, Tectonic and Model Analyses
of the Great Salt Lake, UT
University of New Mexico
COLLABORATIVE RESEARCH: Evaluating Tectonic Boundaries:
Continuous Transect of a Proterozoic Orogen in the Grand Canyon
CUNY Queens College
COLLABORATIVE RESEARCH: Crustal Profile of a Major
Transpressional Boundary: Tectonic Evolution of the Norumbega
Fault Zone, Maine
Mann, W. Paul
Univ. of Texas Austin
Paired Zones of Divergence and Convergence in Orogenic
Belts: A Field Study in Western and Central Cuba
Formation of the Sole of the Oman Ophiolite
San Jose State University
RUI: COLLABORATIVE RESEARCH: Tectonic Setting and
Emplacement Models for Sheet-Lake Plutons, North Cascades Washington
Genesis and Tectonic Significance of the Extension-Related
Intrusive Complex of the Eldorado Mountains, Nevada
UNiv. of Calif., Davis
The Complejo Metamorfico of Chilenia: Implications
for the Paleozoic Tectonics of Western Argentina and Chile
Univ. of Texas Austin
Continued Investigation of the Formation and Evolution
of Grenville-age Crust in the Llano Uplift, Central Texas
Univ. of Florida
COLLABORATIVE RESEARCH: Early Archean Crustal Evolution
in the Northern Wyoming Province
Univ. of Southern California
COLLABORATIVE RESEARCH: Tectonic Setting and Emplacement
Models for Sheet-Like Plutons, North Cascades, Washington
COLLABORATIVE RESEARCH: Structural Analysis, U-Pb
Geochronologic, and Nd Isotopic Characterization of the Carolina
Slate Belt and Milton Belt, Southern Appalachians
Univ. of Nevada Reno
Nature of Paleozoic Crust of Western Nevada Deduced
From Paleozoic Island Arc Rocks: Implications for Tectonic Evolution
of Western Nevada
Univ. of Colorado Boulder
COLLABORATIVE RESEARCH: Mechanics of Footwall Uplift During Detachment Faulting: A Field Test of Kinematic and Dynamic ModelsSimpson, CarolJohns Hopkins UniversityMicrostructural Analysis of Steady and Non-Steady Flow in MylonitesSpear, FrankRensselaer Polytech InstThe Nature of the Basement-Cover Contact, Bronson Hill Anticlinorium, Western New HampshireStock, JoannCalifornia Inst of TechTectonics of the Early Gulf of California: Puertecitos Volcanic Province, NE Baja CaliforniaTwiss, RobertUniv. of Cal if., DavisInvestigation of the Kinematics of Block Rotations Through Patterns of Seismic P and T Axes and Fault Slickenline Using Micropolar TheoryWalker, J. DouglasUniv. of KS, Main CampusCOLLABORATIVE RESEARCH: Deformational and Magmatic History, Eastern Sierran Arc, East-Central CaliforniaWang, Chi-YuenUniv. of Calif., BerkeleyIntegrated Modeling of Mountain Building Processes in Fold-and-Thrust BeltsWilliams, MichaelUniv. of Mass., AmherstCOLLABORATIVE RESEARCH: Evaluating Tectonic Boundaries: Continuous Transect of a Proterozoic Orogen in the Grand CanyonWiltschko, DavidTexas A&M U Research FdnFluid Flow in a Deforming Thrust Terrane
Wright, JamesWilliam Marsh Rice UnivNature, Timing and Controls of Jurassic Orogenesis in the Western U.S.CordilleraYin, AnUniv. of Calif., Los AngelesHow and When Did Deformation Due to the India-Asia Collision Transmit to Northwestern Tibet and the Southern Tian Shan?Yonkee, W. A.Weber State Univ.RUI: Integrated Kinematic and Rheological Analysis of Thrust Sheet Emplacement, Willard Thrust System, Northern Utah
Dear Greg and Scott,
We recognize that your letter and reply (Newsletter , v. 11, no. 2, Sept. 1992) on "stretching lineations" were informal in nature. However, because the statements were published in a professional forum and we have disagreements with them, we feel compelled to comment. We assert that some of the material in the letter and reply reflect erroneous or antiquated points of view on basic principles of our subject, structural geology and tectonics.
Our comments address: (1) inaccurate or misleading references to well-established terms and concepts used to describe the kinematics of deformable bodies; (2) the use of terms and concepts independently invented by structural geologists who apparently were, or are, ignorant of this conceptual framework; and (3) the motivation for wishing to label something a "stretching lineation" in the first place.
(1) Paterson's statement that "all measurable strains are in fact finite strains, in contrast to infinitesimal strains, i.e., very small non measurable strains" is false and misleading. Strain is a second-order symmetric tensor quantity, specified by six numbers, its components. The components of the strain tensor are defined in terms of powers and products of the displacement gradients. In the treatment of strain, the terms "finite" and "infinitesimal" signal, respectively, the lack of any mathematical approximation, and the approximation of neglecting all but first-order terms in the displacement gradients. A structural geologist estimating the average infinitesimal shear strain for a fault by taking the ratio of the offset of a marker (say 50 cm) to the fault trace length (say 1.5 km) would be quite surprised to hear that this quantity is "non measurable." Equally surprised would be the rock mechanism using electrical strain gouges in laboratory or field settings, and the geophysicist using laser ranging instruments or global positioning system satellites along the San Andreas fault zone. In hundreds of applications on a daily basis, scientists and engineers are measuring strains that fall well within the range called infinitesimal. To speak of this physical quantity as "non measurable" is nonsense.
Paterson's remarks are correct in so far as they describe a displacement field between an arbitrary initial and arbitrary final state of a body. The deformation of the infinitesimal neighborhood of any particle can be decomposed into a translation, a rigid-body rotation, and a strain. However, he equates deformation with displacement field, which is not appropriate, nor is it appropriate to refer to the translation or rotation as components, since the term component is reserved for a specific technical use (as in components of a vector or tensor). Furthermore, "vortical component" is, for good reason, not a recognized synonym for rigid-body rotation, since the latter does not correspond to the integral of the vorticity. Also, the displacement field is not distinguished from displacement by characterizing the latter as "the amount of movement along a fault surface." Indeed, it is not the displacement, but the displacement discontinuity that characterizes a fault. Finally, the terms "total strain" and "incremental strain" are superfluous, and to use these terms to set up categories of "stretching lineation" is without merit.
Paterson argues, and we certainly agree, that "a clearly understood terminology is needed," but then he enunciates his own unique and revisionist definitions. What he fails to acknowledge is that a formal terminology is available for the description and analysis of the motion of particles in a deformable body, and has been available since the foundations of this subject were laid down by Augustine Louis Cauchy (1789-1857) and his colleagues over 150 years ago. How Paterson, or anyone else, might wish to revise the meaning of these terms is without significance, in the light of the long-established, rigorous, and complete mathematical definition of this subject.
(2) Structural geologists have long sought to imagine the processes responsible for the development of structures in a rock mass. For example, such structures would include the folds formed from initially planar beds of uniform thickness, or the cleavage and other elements of the internal fabric of the rock that are related to the folds. although the kinematics of a deformable body is available as a tool and a constraint on imagination, some structural geologists have created their own conceptual framework and terminology, and unfortunately may continue to do so. To the extent that these concepts and terms conflict with the established kinematics of deformable bodies, they lead to erroneous or meaningless results. To the extent that they agree with it, they are superfluous. Problematic terms and phases in Davis' letter include: "bulk flow direction," trend of bulk flow," "movement zones," "tectonic transport direction," and "movement direction". Paterson's phrase "direction of greatest movement in the regional displacement field," is another example.
The term "movement zone" strikes us as so nebulous that it deserves no further consideration, but we cannot refrain from asking if this is a fault zone, or possibly a shear zone? Or, as we might imagine, a region, of unspecified shape and volume, within which something is, or has been, moving in some manner?
The other terms in the above list suggest vectors. If what is being described by the "bulk flow direction" or "tectonic transport direction" is the rigid-body translation of a body, without rotation, then the velocity of the body at any instant, or the difference in its position at two times can be represented by single vectors. The corresponding velocity field or displacement field is homogeneous. On the other hand, the motion of particles in a deforming body can, at each instant, be described by the velocity vector field, and, if necessary, the velocity field can be described as a function of time. Similarly, a displacement field in a deforming body is the field of a vector that is the difference between the final and initial positions of a particle. What seems called for by terms such as "bulk flow direction" or "movement direction" is an operation acting on a heterogeneous field to produce a single vector. If this is the case, it would appear that the deformation has somehow been replaced by a translation of the body, and, in doing so, most of the interesting and measurable aspects of the kinematics have been lost. In this context it is worth recalling that homogeneous strain does not correspond to an homogeneous velocity or displacement field.
Paterson's "direction of greatest movement in the regional displacement field" seems to connote an averaging operation of some sort, or perhaps an operation of differentiation to find an extreme value. In this regard, consider a sheet of rock that has been shortened in a north-south direction and extended in an east-west direction in pure shear by as dense array of strike-slip faults. How might one determine the "direction of greatest movement?" We assert, without further comment on this example, that neither do we know how to do this, nor do we believe that it would be a useful endeavor.
(3) We find it puzzling that one would wish to denote any of the structures or fabric elements that are alluded to in the letter and reply as "stretching lineations" in the first place. Is it not more useful first to refer to any such feature with a simple descriptive phrase, or, if necessary, by a detailed and carefully-documented account of the field observations? And, second, is it not more constructive to make use of the assemblage of data for each such feature in a scheme of interpretation based explicitly on the fundamental concepts and existing language of kinematics?
A lineation may be found to represent, among other things: (i) the intersection between cleavage and bedding, (ii) a slickenline on a fault of given orientation and character, (iii) the long axis of non-equant grains seen in a joint surface; (iv) the long axis of grains in the plane of a cleavage, or (v) the long axis of pebbles in a deformed conglomerate. We would not want to replace any of these short descriptive phrases with a term such as "stretching lineation." One might wish to lump the information and its interpretation provided by one such feature with that from another, but only after an analysis demonstrated the appropriate kinematic or mechanical commonality.
In conclusion we admit not to understand, more than superficially, the physical and chemical processes involved in the development of the lineations mentioned in the previous paragraph. What we advocate is a methodology for unraveling at least the physical aspects of these complex processes: one that begins with careful field descriptions and is followed by analysis based on continuum mechanics. We assert that misuse of well-established concepts and terms from the kinematics of a deformable body and the free invention of new terms in this context is counterproductive. The free invention of terminology has proved useful in modern physics because, for example, the nature of the quark cannot be addressed with the mechanics of Newton and Dauchy. In contrast, we believe that the physical nature of the lineations mentioned above lies well within the framework established by these scientists and their colleagues.
Raymond C. Fletcher, Exxon Production Research Co., P. O. Box 2189, Houston, TX 77252-2189
David D. Pollard, Applied Earth Sciences, Dept., Stanford
University, Stanford, CA 94305-2225
Dear Ray and David,
Aw come on guys, lighten up! That having been said,
we do want to thank you for your reply to our last Newsletter's
informal letters on "stretching lineations". We appreciate
the fact that our friendly exhange of opinions prompted at least
two written replies (yours) from our 1300+ membership. Guess
we tried to beat a dead horse. Naturally we ( Davis and Paterson)
have different reactions to your rather negative response to both
our positions, but instead of responding ourselves we hope that
your letter generates responses from others in the Division.
Richard Lee Armstrong died, a victim of cancer, on August 9, 1991, at the pinnacle of his prolific and remarkable career as an earth scientist. He is survived by his mother, Bernice, children Becky, Karl, and Kathy, and their mother Julie.
Dick, as he was known to colleagues and friends, was born on August 4, 1937, in Seattle, Washington. During his illness, Dick remarked that his life was composed of three parts, each 18 years in duration. The first 18 years were spent in Seattle, where his aptitude for science was evident early on. The next 18 years were his Yale University days. He left home in 1955 to attend Yale, first as an undergraduate (B.S. 1959), then as a graduate student (Ph.D. 1964), and afterward until 1973 as assistant and associate professor in the geology department. During his time as a Yale professor, he spent two years away, first in 1963-1964 on a National Science Foundation Postdoctoral Fellowship at the University of Bern, and in 1968-1969 as a Morse and Guggenheim Fellow at the Australian National University and California Institute of Technology. At the beginning of the last 18 years, in 1973, Dick moved back to the west coast to the University of British Columbia in Vancouver, where he was associate and then full professor until his death. He became a Canadian citizen in 1979.
Dick's insight into an enormous variety of earth science problems is nothing short of remarkable. He was regarded as an expert in fields as diverse as isotope geochemistry and geochronology, geochemical evolution of the earth, geology of the entire North American Cordillera, and large-magnitude crustal extension. His passion, in the words of his former thesis supervisor Karl Turekian, "was to understand the earth." Dick pursued his goal throughout his career, and interwove these diverse fields into a research program that significantly affects our view of tectonic processes in the earth. His bibliography contains more than 170 published papers, and he strived to get nearly every isotopic study that he or his students produced into the professional literature. Dick's analytical work was not at the leading edge of high-tech and ultra precise measurement; he never strived for these goals. Instead, he applied methods that were reliable and suited the geological problems he wanted to solve. His work began with K-Ar methods, including neutron activation and isotope dilution methodologies, and then branched to include Rb-Sr, U-Pb and Nd-Sm. By maintaining an academic and laboratory environment with colleagues and students that was very productive, he produced a high volume of isotopic data that shed light on the chronology of magmatism, metamorphism, and tectonics over most regions of western North America. Several fundamental first-order syntheses of Mesozoic and Tertiary Magmatism in western North America were produced by Dick during the last 20 years of his career using this large data base.
Dick was a patient and caring teacher who always had time for those students who needed a bit of extra help. I recall him repeatedly editing my thesis manuscripts with numerous red pencil marks, and returning them to me usually within three days after he received them unannounced; his duty to students was not to delay or obstruct their progress. Dick was generous to a fault, particularly with students. His intellect and geological intuition moved at a pace that easily eclipsed his students, but I don't recall his revealing that he already knew the answer if it was a student project. He would gently nudge and direct, all the while letting his students discover for themselves and take pride in the accomplishment. This sense of generosity was also characteristic of his relationship to his family and friends outside of his professional life, though few of us saw that side of Dick because he was a very private person.
Dick was very active in the community of geoscientists in its broadest sense. In spite of his position in the forefront in several geoscience fields, Dick was not an "ivory tower" scientist. On the local scene, he was an active member of the Vancouver-Victoria geoscience community, which is dominated by mining exploration geologists. As part of his recreation, he attended local lectures and field trips whenever possible, the last being a field trip, one month before he was diagnosed as having cancer, in southern British Columbia organized for mining explorations.
He was an active member of the Geological Society of America and editorial boards for several journals, participated actively in the peer review process of the National Science Foundation and Canada's Natural Sciences and Engineering Research Council, and played an active role in Canada's Lithoprobe program. He did his duty in organizing meetings held locally, including the 1985 GSA Cordilleran Section and the 1987 IUGG meetings held in Vancouver. He was always available to act as a scientific sounding board and gave well-considered advice. His distinguished career was rewarded with election to the Royal Society of Canada in 1981, a Killam Prize at the University of British Columbia in 1986, and the Logan Medal of the Geological Association of Canada in 1990.
Richard Lee Armstrong's scientific contributions, which will be remembered decades from now, are numerous; perhaps surprisingly, three of these advances were conceived before 1970, during and within a few years after he received the Ph.D. degree. He published 43 papers prior to his 35th birthday, including most of the main conceptual breakthroughs of his career. The concepts advanced by Dick required both great intellect and intuition because at the time a convincing supportive data base did not exist; this put Dick squarely in the midst of professional controversy with well-established colleagues.
One of these breakthroughs evolved from his Ph.D. thesis work in the Sevier orogenic belt of Nevada-Utah. As part of this overall geological study, he examined existing maps of low-angle faults which mainly placed younger rocks on older ones, and he concluded that these were rotated Tertiary normal faults. His interest in Tertiary magmatism no doubt helped him focus on the involvement of these younger rocks in the faulting, and to conclude that many Great Basin low-angle faults were Tertiary extensional faults and not older thrust faults as was generally assumed. His 1972 paper on this subject was a watershed that spurred on a generation of scientists to fully describe and study the now famous metamorphic core complexes of the Great Basin of the Cordillera.
Second, Dick was interested in using isotopic methods to determine the chronology of magmatism, plutonism, and cooling of crystalline rocks, and thereby to understand crustal processes better. Through his Ph.D. work and the postdoctoral fellowship in Bern in 1963-1964, he recognized the effect of metamorphism and thermal disturbance on mineral isotopic ages, and interpreted dates in metamorphic areas as ages of cooling. His 1966 paper on the metamorphic veil remains a key seminal paper; subsequent research by many others involved quantifying the thermal retentivity of daughter isotopes into closure temperature theory.
The third main breakthrough was probably the most misunderstood and controversial of Dick's remarkable contributions; his formulation of a terrestrial geochemical model incorporating recycling of crustal materials, including sediments and continental crust, in a plate-tectonic context. This model was formulated at a time when most earth scientists did not even accept the main tenets of plate tectonics! It was a view 20 years ahead of its time. Using initially a very meager data base and arguments of continental freeboard, Dick explained the evolution of first Pb, then Sr, and finally Nd isotopes by a near-steady-state process of crustal recycling in a dynamic earth with near-constant volume of continental material from the early Archean.
His views were controversial, to say the least, and contested by many prominent isotope geochemists of the last 20 years. In his final paper on this subject, "The persistent myth of crustal growth," he was unrepentant and continued to argue that if all other planetary bodies in our solar system differentiated at their earliest stages, why then did Earth have to wait and have its own differentiation dragged out over billions of years?
A growing number of isotope geochemists are adopting Dick's view, after such a long period of gestation, and his 1968 proposal of crustal recycling has now clearly been proven with 10Be and other geochemical evidence. The evolution of this controversy is puzzing and ironic, but reminiscent of other brilliant scientists whose ideas had to wait decades for acceptance and vindication. Dick was very happy at the recognition he finally received for his model of crustal recycling at the 1990 ICOG meeting in Canberra. It is very fitting that the writing of his final paper on this subject and the vindication of his ideas occurred while he was still alive.
Finally, most of Dick's professional effort was spent not on
these lofty breakthroughs, but instead on the grueling effort
of systematicaly working with rock after rock, area after area,
student after student to build the enormous data base in the Cordillera.
A large number of geological colleagues are indebted to him for
his efforts, which have made their work more fruitful and interesting.
All those who knew Dick felt a great sense of loss at his premature
passing, and know that such talented, inspiring, and thoughtful
scientists as he touch our lives much too rarely. He was very
concerned that his work in radiogenic isotope geochemistry and
geochronology be carried on at the University of British Columbia
in a vigorous tradition, a hope that is shared by all of his students
and professional colleagues. An endowed scholarship in Dick's
name has been established at the Department of Earth Sciences,
University of British Columbia.
SELECTED BIBLIOGRAPHY OF R. L. ARMSTRONG
1966 K-ar dating of plutonic and volcanic rocks in orogenic belts: Age determination by potassium argon: Heidelberg, Springer-Verlag, p. 117-133.
____ K-Ar dating using neutron activation for Ar analysis; Granitic plutons of the eastern Great Basin, Nevada and Utah: Geochimica et Cosmochimica Acta, v. 30, p. 565-600.
____ (and Hansen, E. C.) Cordilleran infrastructure in the eastern Great Basin: American Journal of Science, v. 264, p. 112-127.
1967 The Sevier orogenic belt: Geological Society of America Bulletin, v. 78, p. 429-458.
1968 A model for Pb and Sr isotope evolution in a dynamic earth: Reviews of Geophysics, v. 6, p. 175-199.
____ Mantled gneiss domes in the Albion Range, southern Idaho: Geological Society of America Bulletin, v. 79, p. 1295-1314.
1969 (with Ekren, E. B., McKee, E. H., and Noble, D. C.) Space-time relations of Cenozoic silicic volcanism in the Great Basin of the western United States: American Journal of Science, v. 267, p. 478-490.
____ The control of sea level relative to the continents: Nature, v. 221, p. 1041-1043.
1970 Geochronology of Tertiary igneous rocks, eastern Basin and Range Province, western Utah, eastern Nevada, and vicinity, U.S.A.: Geochimica et Cosmochimica Acta, v. 34, p. 233-236.
1971 (and Cooper, J.) Lead isotopes in island arcs: Bulletin Volcanologique, v. 35, p. 27-63.
____ Glacial erosion as a cause of the variable isotopic composition of strontium in sea water: Nature, v. 230, p. 132-133.
____ Isotopic and chemical constraints on models of magma genesis in volcanic arcs: Earth and Planetary Science Letters, v. 13, p. 137-142.
1972 Low-angle faults, hinterland of the Sevier orogenic belt, eastern Nevada and western Utah: Geological Society of America Bulletin, v. 83, p. 1729-1754.
1973 (and Hein, S. M.) Computer simulation of Pb and Sr isotope evolution of the earth's crust and upper mantle: Geochimica et Cosmochinmica Acta, v. 37, p. 1-18.
1974 Magmatism, orogenic timing, and orogenic diachronism in the Cordillera from Mexico to Canada: Nature, v. 247, p. 348-351.
____ (and Dick, H. J. B.) A model for the development of thin overthrust sheets of crystalline rock: Geology, v. 2, p. 35-40.
1975 Precambrian (1500 m.y. old) rocks of central Idaho -- The Salmon River arch and its role in cordilleran sedimentation and tectonics: American Journal of Science, v. 275A, p. 437-467.
1977 (with Taubeneck, W. H., and Hales, P. O.) Rb-Sr and K-Ar geochronology of Mesozoic granitic rocks and their Sr isotopic composition, Oregon, Washington, and Idaho: Geological Society of America Bulletin, v. 88, p. 397-411.
1978 The pre-Cenozoic Phanerozoic time scale -- a computer file of critical dates and consequences of new and in-progress decay constant revision: American Association of Petroleum Geologists, Studies in Geology, no. 6, p. 73-91.
____ Cenozoic igneous history of the U.S. Cordillera from 41° to 49°N latitude; Geological Society of America Memoir 152, p. 265-282.
1981 Radiogenic isotopes; The case for crustal recycling on a near-steady-state no-continental-growth Earth: Royal Society of London Philosophical Transactions, v. 301, p. 443-472.
1982 Cordilleran metamorphic core complexes -- from Arizona to southern Canada: Annual Review of Earth and Planetary Sciences, v. 10, p. 129-154.
____ Late Triassic-Early Jurassic time-scale calibration in British Columbia, Canada in Odin, G. S. ed., Numerical dating in stratigraphy: Chichester, England, Wiley-Interscience, p. 509-513.
1988 Mesozoic and early Cenozoic magmatic evolution of the Canadian Cordillera, in Clark, S. P., Burchfiel, B. C., and Suppe, J., eds., Processes in continental lithospheric deformation: a symposium to honor John Rodgers: Geological Society of America Special Paper 218, p. 55-91.
1990 (and Parrish, R.) A geologic excursion across the Canadian Cordillera near 49°N (Highways 1 and 3 from Vancouver to southwestern Alberta and on to Calgary, Alberta): Geological Association of Canada Meeting, Vancouver, May, Field Trip Guidebook, 71 p.
____ (and Ward, P.) Evolving geographic patterns of Cenozoic magmatism in the North American Cordillera: The temporal and spatial association of magmatism and metamorphic core complexes: Journal of Geophysical Research, v. 96, p. 13,210-13,224.
1991 The persistent myth of crustal growth: Australian Journal
of Earth Sciences, v. 38, p. 613-630.
The "Resource Bin": a listing of non-commercial earth
science educational materials and services in the general areas
of structure and tectonics that are available for personal and/or
institutional use. Individuals with materials, e.g. software,
reading/reference lists, slide collections, etc., or services
that they are willing to share with others on an at-cost or non-profit
basis are encouraged to add to the "Bin" [contact Davis/Paterson,
Dept. of Geol. Sciences, Univ. So. California, Los Angeles, CA
90089-0740; phone (213) 740-6103 (SP) or 740-6726 (GD); fax (213)
740-8801; E-mail: Scott@coda.USC. EDU
Editors' note: Whoops, we goofed with respect to last issue's listing of the U.S.G.S. Earthquake Hazards Reduction Program Summaries of Technical Reports, Vol. XXXIII. The $5.00 price for the two-volume U.S.G.S. Open-File Report 92-0258 that we announced is incorrect (although it was the price quoted to us over the phone from Denver). The correct price for the paper copy of the 2 volume report is (gasp) $155.25! 25¢? But, if you want to go "fiche"ing, $7 is all you'll need. This grevious error on our part proves once again that old adage -- "If something seems to be too good to be true ... ", well, you know how it goes.
35-mm slide sets depicting geologic hazards throughout the world.
Another offering from the U.S. Government, but this time with
correct pricing. Did you know that the National Geophysical Data
Center offers 35 mm slide sets depicting geologic hazards throughout
the world? The 20-slide sets are in color and/or black and white
and come with written descriptions and documentation of locations,
dates, etc. Each set costs $30, except for an absolutely stunning
set of computer-generated slides of Earth showing full color shaded
relief, plus displays of plates and their relation to world seismicity
($45). Some of the 21 sets currently available include: the 1991
Mount Pinatubo eruptions; 1989 Loma Prieta earthquake damage (2
sets); 1988 Armenian and 1990 Northerrn Iran earthquakes; Hawaii
volcanism - impact on the environment; and, the 1980 eruption
of Mount Saint Helens. For descriptive material and ordering
information contact: National Geophysical Data Center, NOAA, E/GC1,
325 Broadway, Boulder, CO 80303; phone, (303) 497-6277; fax, (303)
497-6513; internet: email@example.com.
Macintosh Programs from Richard W. Allmendinger
I have put several of my Macintosh structural geology programs into our Internet anonymous FTP site here at Cornell. Downloading is free for non-commercial users. The programs, with the current version numbers, are:
ï Stereonet 4.5a (recent upgrade, lots of small improvements).
ï FaultKin 3.25a (formerly "Fault Kinematics").
ï Microstructure 2.5a (for iterative u-stage analysis of calcite, dolomite,
and quartz microstructures; includes Groshong strain gauge).
ï MacStress 1.05 (plots frictional-crystal plastic transition curves).
ï StrainSim 1.0 (simulates pure & simple shear deformation).
ï Fault-bend fold HyperCard "movie" (shows movement over a single
ï Duplex HyperCard "movie" (development of a two horse duplex).
ï Growth fault bend fold movie (development of Medwedeff style
ï HyperCard Bibliography stack with about 2000 references on structure,
western US and the Andes (can output formatted reference lists, etc. A poor man's EndNote customized for geology).
Each one of these programs is in a Compact Pro self-extracting archive along with disk files of documentation (if it exists), converted to binhex format. To make them Mac-usable, one will have to de-binhex them using any of a number of public or shareware programs (i.e. Stuffit, Compact Pro, etc.). Then they just have to double click on the archive icon and select where to save the files on their disk. [The programs are still available via US mail for $5 per program & disk copy of the manual or $15 per program and paper copy of the users manual. Do nor send disks to me because it's a great way (for me) to get (your) computer viruses. I do not guarantee turn-around time on mail requests and encourage people to use the FTP site. They will always find the most recent versions there.].
The Internet address of our anonymous FTP site is: "silver.geo.cornell.edu". Once the user logs onto the server, they should look in the /pub/rwa_programs directory for the programs they want. I can also send this stuff directly to people via the Internet if they send me an e-mail message. Any system administrator should be able to help people getting any of these files and converting them to Mac format. At Cornell, our Macs are connected directly to our VAXES with MacTCP. Then with a couple of free programs, we have immediate access to Internet e-mail and FTP sites. Using "Eudora" a program written at U. Illinois my Mac checks my e-mail automatically at whatever time interval I set and presents it to me using Mac windows & menus, etc. Using the "Fetch" program written at Dartmouth, I can log onto any anonymous FTP site in the country and download (or upload) programs. Fetch performs the binhex conversion automatically. Many SG&T members may not be aware of how easy using the Internet now is. Perhaps the Newsletter should mention that these tools exist.
Have you heard that the number of newly filled academic positions in structure and tectonics may be as low as at any time since the late 1950's and early '60's? That's not an official pronouncement -- just a "seat-of-the-pants" guess -- but the number of recently filled faculty slots is dismally low. We've heard of only four appointments in the September to January time period. Last fall, Tim Kusky (Ph.D., Johns Hopkins) became Assistant Prof of structural geology and remote sensing at Boston University, Daniel Holm (Ph.D., Harvard) joined the faculty at Kent State University, and Jeff Connelly (Ph. D. Tennessee) was hired as Assistant Professor in Earth Sciences at the U. of Arkansas, Little Rock. Michael Wells , an NRC post-doc from the USGS (Menlo Park ) and a recent Ph.D. from Cornell, filled a structure/tectonics faculty vacancy at the University of Nevada, Las Vegas, in January; the UNLV search inspired more than 70 applications. Last October, Gary Axen (Harvard) joined CICESE (Centro de Investigación Científica y de Educación Superior de Ensenada -- it's a good thing this column has an unrestricted length!) in Ensenada, Baja California, Mexico as Investigador Titular; CICESE is a government research lab that accepts graduate students. Also in October, Al McGrew (Wyoming) began a two-year NSF Post-Doctoral fellowship at the Federal Institute of Technology (ETH) in Zürich, Switzerland, after having completed a two year stint as a visiting assistant prof at Earlham College (Richmond, Indiana). Karen Carter (Ph.D., Texas) has left a short-term teaching position at Baylor to take a post-doctoral appointment at the Los Alamos National Laboratory. Another Texas Ph.D.'er, Keith Klepeis, will begin an NSF post-doc this summer working in the wilds of northern British Columbia with Linc Hollister, Luisa Crawford, and Krishna Sinha. Recent Stanford Ph.D. Tom Parsons (geophysics) has just taken a post-doc appointment with the USGS in Menlo Park, where he'll join Jill McCarthy's research effort. Oh, by the way, the Department of Geology of the American University of Beirut has announced a faculty vacancy for a structural geologist (EOS, 1/5), but if you hold a U.S.passport please don't apply -- the State Department won't let you travel there for your interview. Oh, well, as W. C. Fields might have said under these circumstances, "I'd rather be in Philadelphia!" (with apologies to the University of Pennsylvania).
We hope you've heard that Division member Paul Hoffman (University of Victoria) received the 1992 Logan Medal of the Geological Association of Canada (see GEOLOG, v. 21, pt. 3, p. 23-24), and we apologize that we didn't announce the May award in last Fall's Newsletter. The medal is awarded "to an individual who has made outstanding contributions to geoscientific knowledge in Canada" (no argument there!; note: Sir William Edmond Logan was founding director  of the Geological Survey of Canada). Coming on top of Paul's recent election to membership in the National Academy of Sciences and his winning of our Division's Best Paper Award last Fall you might conclude that 1992 was a reasonably good year for him. Also elected to the Academy were George Thompson (Stanford), Tom Ahrens (Cal Tech), and Bill Dickinson (Arizona, ret.). Bill , who received GSA's 1991 Penrose Medal, will also receive the 1993 Special Teaching Award of the Pacific Section of the AAPG. Not a bad couple of years for him either!
More awards .... From The Main Thrust, the newsletter of GAC's Structural Geology and Tectonics Division comes word that Joseph White and Chris Mawer (both of the University of New Brunswick) have received the Division's '92 Best Paper Award for their paper "Deep-crustal deformation textures along megathrusts from Newfoundland and Ontario: implications for microstructural preservation, strain rates, and strength of the lithosphere" (CJES, 29, 328-337). Shoufa Lin, also of New Brunswick, won the Division's Best Thesis Award for his Ph.D. dissertation: "Stratigraphy and structural geology of the southeastern Cape Breton Highlands National Park and its implications for the tectonic evolution of Cape Breton Island, Nova Scotia." Way to go New Brunswick! Gordon Oakeshott, one of GSA's most senior fellows and a retired chief of the California Division of Mines, has just been named the 1993 recipient of AAPG's Public Service Award. His earthquake preparedness efforts in the 1950's and 1960's are credited by the AAPG as contributing to the relatively low loss of life and damage during California's three (3!) magnitude 7+ earthquakes in the last 3 years. Bob Dietz (Arizona State) is the recipient of the 1992 University of Illinois College of Liberal Arts and Sciences Alumni Achievement Award (an award he could have received more than 30 years ago with his seminal 1961 papers on sea-floor spreading and astroblemes). And finally in the award news, Donna Jurdy (Northwestern) has been awarded a NSF Faculty Award for Women for her research in tectonics.
People miscellany: George Viele took early retirement last August from the University of Missouri (Columbia), but finds himself no less busy in the office he still retains on campus. Ray "No-Stretching Lineation" Fletcher (see his letter to the editors elsewhere in the Newsletter ) has left Texas A&M to join Exxon Research. New executives of the the GAC's SG&T Division are Simon Hammer and Cees van Staal (Chair and Treasurer, respectively; both of GSC Ottawa), and Keith Benn (Secretary, Univ. of Ottawa). The new president of the Inter-Union Commission on the Lithosphere is Kevin Burke (U. of Houston). Question: what does an inter-union lithospheric commission monitor? Continental collision? Tom Nolan, director of the USGS from 1956 to 1965, passed away last August at the age of 91 -- leaving an impressive professional and scientific legacy that began with his Yale Ph.D. in 1924, and continued through publication of his last paper in 1989!
Structure and tectonics trivia: only 14% of the ballots mailed to Division members for the Fall '92 elections were returned to GSA. Although this is not in itself an impressive number, it is considerably better than the 0.003% oral and written response (5/1327) to your editors' opposing views on "stretching lineations" (at last count, responses favoring Paterson = 3; favoring Davis = 0; favoring neither of us = Pollard and Fletcher). Writing about polls introduces some interesting news from a recently released AAPG report on the "Status of North American Academic Geoscience Departments" by Barry J. Katz. 133 departments, about 50% of those queried, responded to questions about departmental demographics, curriculum, employment goals, etc. Some good news to balance our no-so-happy entry to this issue's column: 54% of the responding departments plan faculty additions and/or replacements in the next 3 years; only 12% predict a reduction in faculty (mostly through retirements). Among responding departments, inorganic geochemistry and sedimentology were most commonly listed as the strongest departmental programs, but "structural geology" and hydrology were the most commonly cited secondary department strengths. Not so good news: geoscience student enrollments appear to be declining at about 10% per year. The 133 departments have nearly 5000 (!) in-house M.S. and Ph.D. students, who far outnumber undergrads. Most graduating students are either taking environmental positions or continuing their education; only 13% of graduating students at any level enter the petroleum industry, and only 1/10 of those who do end up in industry research positions.
Have you heard that "Have you Heard ... ?" is just
another boring column? Want proof? The deepest borehole on the
planet is the Kola well on the Russian peninsula of the same name
with a depth of ca. 12,261 m; highly permeable, water-bearing
horizons were reportedly found at depths greater than 10 km; geothermal
gradients for different sections of the drilled crust range between
11 and 23 degrees C/km. Germany's active Hauptbohrung project
in the center of Europe is now at a depth of 6 km; fluid-filled
fractures were found below 3.4 km and at 4 km the temperature
of 118 degrees C was 1/3 higher than predicted (AAPG Explorer,
Jan., '93). The deepest hole in the ocean basins? As recently
reported in EOS (73, 537) it's DSDP/ODP 504B in
the eastern equatorial Pacific. With a just completed depth of
2 km, it is three times deeper than any previous hole in oceanic
basement and is the first oceanic borehole to intersect sheeted
dikes within the lower part of seismic Layer 2. Layer 3, hopefully
gabbro if ophiolitic crustal models are correct, is thought to
lie just below the 0.95 km-thick section of dikes. Random-oceanic-thought-of-this-issue
(that's a promise): what would we do without the ubiquitous spidery
white sea-floor crabs that always seem to provide scales for ocean
bottom photos? Think of all those crabs ....
Art Snoke (University of Wyoming) has and, with the arm-twisting
of the editors, tells us about it:
The Highlands Controversy, Constructing
Geological Knowledge through Fieldwork in Nineteenth-Century Britain.
By David R. Oldroyd. The University of Chicago Press, 1990,
478 p. [Cloth, ISBN: 0-226-62634-2, $65; Paper, ISBN: 0-226-62635-0,
$29.95]. University of Chicago Press, 5801 South Ellis Ave.,
This well-researched and well-illustrated volume analyzes the
history of nineteenth-century scientific research regarding the
complex structural evolution of the northwest Scottish Highlands.
A famous geologic controversy centered on the structural and
stratigraphic position of the metasedimentary Moines in regard
to a foreland sequence that includes Lewisian gneiss, "Torridonian"
sandstone, conglomerate, and shale, and Cambro-Ordovician sedimentary
rocks. The controversey lead to the discovery of the Moine thrust
zone and the first recognition of mylonite. It culminated with
the publication by the Geological Survey of Great Britain of probably
the finest nineteenth-century field structural study -- "The
Geological Structure of the North-west Highlands of Scotland"
(1907). The characters of this saga included Sir Roderick Murchison,
Sir Archibald Geikie, Charles Lapworth, Benjamin N. Peach, John
Horne, and many more. Oldroyd's account goes much beyond the
chronology of specific events, and looks carefully at the arguments,
personalities, rivalries, and geopolitics of the time -- all ingredients
of a delightful and fascinating scientific controversy. For anyone
interested in the history of geology, structural geology, field
geology, scientific debate, or just the evolution of an important
scientific discovery, this is a book that you should enjoy reading
[The editors will welcome your unsolicited reviews of other great books you'd like to share with members of the Division.]
Inferring Paleoearthquakes From Fault-Rock Fabrics: Experimental and Field Evidence
What type of structures are formed within crustal faults during
a single earthquake? When describing ancient deformation zones
we often speak of brittle and ductile behavior, or of cataclastic
and crystal plastic deformation mechanisms. We know that brittle
can not be equated with seismic. Processes such as fracture and
cataclasis can proceed at rates that are imperceptibly slow as
well as at rates approaching shear-wave velocity. Plastic mechanisms
often are interpreted to occur during stable aseismic creep.
Is this always the case? Does the preferred orientation of fabric
elements within deformation zones imply slow deformation? Does
a random fabric record paleoearthquakes? Are certain characteristics
of slickensides, veins, fracture networks, breccias and other
fault-rock structures diagnostic of slip rate? Are the different
deformation rates of fault zones undergoing seismic cycling recorded
in the rock record? These are the types of questions we hope
will be addressed this fall at the divisional symposium for the
Society's Annual Meeting in Boston, Massachusetts. We plan to
gather together a diverse group of researchers to summarize and
question what we know (and do not know) about the types of structures
formed in crystal deformation zones during slow aseismic creep,
fast but stable slip rates (e.g., slow earthquakes), and unstable
seismic slip. If you or someone you know has something to contribute
that is exciting, controversial, skeptical, perplexing or just
illustrates the complexity of mother nature, then contact one
of the congeners. In any case we hope you will attend the symposium
this fall and help us contemplate these and related topics.
Fred Chester, Saint Louis University, (314) 658-3124,
Ron Bruhn, University of Utah, (801) 581-6553, E-mail:
National Science Foundation, Earth Sciences June l; December 1, 1993
Petroleum Research Fund (PRF) October l; January 15, 1994
U.S.G.S. National Earthquake Hazard Reduction Program (NEHRP) Late April (tentative)
GSA Research Fund (student grants) February 15
Society of the Sigma Xi (student grants) February 1;
May 1; Nov. 1
[Notices of future events of interest to Division members are
welcomed by the editors]
April 1-3: Fractals in dynamic systems in geosciences
(international conference): Frankfurt, Germany [contact: J.
H. Kruhl, Geol.-Paleont. Institute, JW Goethe University, Senckenberganlage
32, D-6000 Frankfurt/Main, Germany; fax, 0049 68 7988383].
April 12-16: Mechanisms of deformation and failure in rocks
and ceramics (conference): San Francisco. See GSA Today,
May 10-13: Post-collisional tectonics and evolution of sedimentary basins between the Caucasus and the Zagros (international meeting): Erzurum, Turkey [contact: M
Salih Bayraktutan, Earthquake Research Center, Atatürk University,
25240 Erzurum, Turkey. Phone, 011 12808; fax, 011 17140].
May 17-19: GAC/MAC Annual Meeting: Edmonton, Canada.
Special sessions of particular interest: "Extensional tectonics
in the northern Cordillera", "Rock deformation: mechanisms
and models", "Devonian tectonics and related magmatism
in the Cordillera", and "Glacial deformation";
abstract deadline was in December. The GAC SG&T Division
will sponsor a short course "Microcomputer applications
in structural geology", to be taught by Henry Charlesworth
May 25-June 15: International basin tectonics and hydrocarbon
accumulation (conference): Nanjing, P. R. China. See GSA
Today, November, 1992.
June 27-30: 34th U. S. Symposium on rock mechanics: Madison,
Wisconsin. See GSA Today, November, 1992.
August: Intraplate volcanism: the Polynesian plume province
(international workshop): Tahiti, French Polynesia. See GSA
Today, November, 1992.
August 14-21: Belt Symposium III (field conference): Whitefish,
Montana. See GSA Today, November, 1992.
August 15-19: Carboniferous to Jurassic Pangea: a global
view of environments and resources: Calgary, Albta.
[contact: Benoit Beauchamp or Ashton Embry, GSC, 3303-33rd St.
NW, Calgary T2L 2A7; phone: (403) 292-7190; fax (403) 292- 4961].
Sept. 6-8: Structures and tectonics at different lithospheric
levels (international conference): Graz, Austria [contact:
Wolfgang Unzog, Dept. of Geology, University of Graz, Heinrichstrasse
26, A-8010 Graz, Austria; fax, 43 316 38 28 85]. See last Newsletter
Sept. 13-14: Thematic meeting on fractography (international conference): See GSA Today, November, 1992. or contact Dr. M.S. Ameen, P.O. Box 1468, Pimlico, London, SW1P 1AA. Fax 071 931 0354.
Sept. 21-23: Second international symposium on Andean geodynamics:
Oxford, England [contact: Pierre Soler, ISAG 93, ORSTROM, C.S.
de Géologie-Géophysique, 213 rue La Fayette, 75480
Paris CEDEX 10 FRANCE; fax 33 1 48 03 08 29]. Deadline for
all abstracts (in English only) will be April 1, 1993. See
last Newsletter for details. Registration fees: £50
or FF500 (students, £25 or FF250) until April l, 1993 (more
Sept. 25-Oct. 1: Ancient volcanism and modern analogues
(IAVCEI General Assembly meeting): Canberra, Australia [contact
IAVCEI ACTS, GPO Box 2200, Canberra ACT 2601, Australia' phone
61 6 2573299; fax 61 6 2573256].
Oct. 4-9: Basin inversion international conference: Oxford,
England. See GSA Today, November, 1992.
Nov. 5-21: International circum-Pacific and circum-Atlantic terrane conference: Guanajuato, Mexico. See GSA Today, November, 1992.
February: Deformation processes in the Earth's crust: from
microcracks to mountains belts (international conference
with field trips in the Lachlan Belt): Jindabyne, SE Australia
[sponsor: Specialist Group in Tectonics and Structural Geology
of the Geol. Society of Australia; contact: Mark Rattenbury,
Australian Geological Survey Organisation, P. O. Box 378, Canberra,
April 25-30: VII international syposium on the observation
of the continental crust through drilling: Santa Fe,
New Mexico [contact: Earl Hoskins, DOSECC, College of Geosciences
& Maritime Studies, Texas A&M, College Station, TX 77843-3148;
phone (409) 845-3651; fax (409) 845-0056]. Tentative themes
of special interest include "Active tectonic processes",
"Thermal regimes", and "Evolution of continental