GSW: 1996
MEETING MINUTES
Minutes of
the 1,272 nd meeting of the
Geological
Society of
Wednesday,
January 24, 1996
The 1,272nd
meeting that started at 8:08 p.m. was attended by 132 people.
Guests who
attended were
- Pedro Ugo
(
- Robert
Hatcher (
- Richard
Markey (
Announcements:
President
Helz announced the death of Art Baker at
the age of 98. Baker had been a member
for 74 years, served as secretary in 1928/29, Program Chairman in 1933,
Councilor in 1939 and President in 1953
Welcome to New Members:
Full members
- John
Farrell (Joint Oceanographic Institutions, Inc.)
- Paul
Tomascak (
Corresponding members
- Cynthia
Ocomb (
- Wynelle
Davis (
- Margie A.
Tripp (
Society Business
1. The President reminded members of the opportunities to help
judge in local school fairs. Any individuals interested should contact Jon
Jens.
2. Members were asked to provide their email addresses and indicate
whether they would prefer to receive program announcements by email or
not. At subsequent meetings the process will continue.
3. There is a concern that the IRS may interpret the fees of Corresponding Members as taxable income. The problem arises from the concern that it
may be interpreted that while the Corresponding
Members do not actively participate in the Society’s activities they benefit
from joining insurance and health programs at favorable rates. Options that may be considered to reduce this
vulnerability include elimination of the Corresponding Member Option or to
sever the arrangement with the insurance companies. Corresponding problems that arise are elimination
of the Society’s income (approximately one third of the Society’s income) from
Corresponding Memberships or reduction in health and/or insurance benefits for
some members. As a measure of participation
a show of hands indicate that 6 members in the attending audience took
advantage of the options.
4. The President expressed thanks to Craig Schiffries and Brooks Hanson, last year’s Program Committee, for the
excellent 1995-1996 program.
Presentations:
P.
Over the
past 18 months to two years the Geologic Division of the U.S. Geological Survey
has been buffeted by a number of significant changes. These include a threat of abolishment, major
reorganization of its management, major decreases in staff from a Reduction in
Force (RIF) and accelerated retirements, an emphasis on new priority program
areas and the transfer, to the Survey, of the functions and staff of the Bureau
of Mines.
The new
principal programmatic areas of the Geologic Division include Global Change
Research, Geologic Hazards, Energy Resources, Mineral Resources, Geologic
Framework and Marine and Coastal Geology.
Three main principles will govern choices for the Geologic Division of
the future. These are Scientific
Excellence, Formation of Partnerships and Proactive Management. While scientific excellence has always been a
primary factor, over emphasis on this criteria, in the past, has lead to a
narrowing of the Geologic Division’s constituency. In the future greater emphasis on
Partnerships and public service will lead to stronger internal collaboration as
a base for the establishment of more effective links to external user
communities such as the States, industry,
academia and the general public. Success
will depend on Proactive Management that will improve the efficiency of the
Agency, help empower its employees and lead to more useful and the highest
quality of products for the user community.
The
reorganization will lead to an emphasis on excellence in all areas of
responsibility, an agency that is more responsive to the public and will be
providing more relevant and timely data and reports. In addition, the priority setting of programmatic
directions will respect greater regional autonomy and better link the programs
to mission goals. In order to formulate
the Division’s Programs, Program Councils will coordinate the program priorities
and set policies for sharing responsibilities and maintaining high standards
through rigorous internal and external reviews.
Two
directions that will be emphasized are the study of surficial processes and
ecosystems. New understanding in these
areas will lead to improved strategies that will greatly improve the safety, health
and quality of life of our citizens and encourage the wise use of our natural
resources.
The Minerals
Information activities of the USGS that were transferred to the Bureau of Mines
in 1923 are now coming home. An
additional challenge will be to incorporate its functions and staff into the
operations of the GS. In addition to the
core functions, that include studies of the economic and natural factors that
affect the availability of mineral resources, there will be an emphasis on
improved management of the mining wastes and spoils that threaten the environment.
Questions were asked by John Farrell (Joint Oceanographic Institutions, Inc.), Greg Walsh (USGS), Cy Galvin and
Barbara Anne am Ende.
Holly Stein,
Holly Stein, the candidate, started the talk with a political
statement. The Re-Os program at the USGS which has been
very successful in developing new age dating techniques useful for rocks with
ages from the Archean to the Tertiary
has been terminated. This action has
been taken despite the following considerations:
- The
program was characterized by excellent science,
- Strong
partnerships with industry and other research groups resulted in considerable
financial assistance through external funding,
- The work
contributed to problems in a number of areas that included the study of
metamorphic rocks, granites, ore deposits, ocean sediments, volcanics and
meteorites, and
- Research
interests crossed the previous Office structures of the Survey.
Despite the mistaken action the Re-Os Group is now
being established as a Colorado State University-USGS partnership called the “Applied Isotope Research for Industry
and the Environment” (AIRIE) to promote the development and use of cutting-edge
scientific applications.
Holly Stein,
the scientist, then continued with the next portion of her presentation. Re-Os
dating of molybdenites may be applied to a wide range of geological
problems. Since molybdenite has a very
high Re/Os ratio with relatively abundant Re (.1 to 100,000 p.p.m.) and essentially
no common Os (less that 5 p.p.b.) it is ideally suited for dating
techniques. Technical developments have
reduced errors so that results on standard samples are now within plus or minus
0.13 % at the 95 % confidence limits.
The long half life of 187Re
(1.66 b.y) makes it suitable for dating rocks of a wide variety of ages. Examples
of successful application of the technique include the following:
- Dating of
well characterized Archean tonalites in greenstone belts and Au-molybdenite
deposits in
- The
discovery of similar ages (1,800 to 1,822 m.y.) in molybdenite ores in western
- The dating
of Cu-Molybdenite ores in Lithuanian Proterozoic granites, and
- Dating of
310 m.y. Au-Molybdenite veins in 330 m.y. host granites in the
Reproducible
dates have also been determined for Au-Molybdenite-bearing granites,
W-Molybdenite skarns, Paleozoic shear zones, Molybdenite-carbonate veins and
the Tertiary Climax-type deposits in
Questions
were asked by David Applegate (American Geological Institute), Robert Hatcher (
Eirik J. Krogstad,
The goal of
thermochronometry is to determine the time that a particular rock passed
through a temperature threshold. The additional
thermal information is critical to the interpretation of cooling rates and
correspondingly the tectonic styles associated with the formation of the rocks
from distinct structural units. Coupled
with knowledge of the evolving phase chemistry of metamorphic rocks,
geochronometers can be used to determine the pressure-time-temperature paths of
tectonic units.
A review of
the history of age dating indicates that in the 1950s and 1960s emphasis was
placed on the ages provided by K/Ar dating schemes. In the 1970s and 1980s many new systems were
available with U/Pb dating of zircons and Ar/Ar schemes being most successful. Current emphasis is on multiple dating
schemes with multiple minerals to extract both age and other intensive
parameters.
In the
future new methods will permutate a number of isotopic schemes, from a number
of different minerals with different cooling characteristics, in different
phase assemblages, from different petrologic and tectonic settings, to give
considerably enhanced insights to understanding the significance of the radioactive “age” of a rock.
As an
illustration, the range of potential minerals, with their corresponding range
of closing temperatures that depend on the composition of the minerals and vary
in single minerals for different isotopic systems, include
- Sphene : 550 to
650 degrees Centigrade
- Monazite : 650 to
750 degrees Centigrade
- Garnet :
greater than 800 degrees Centigrade for U/Pb systems, and about 650 degrees centigrade
for Sm/Nd systems
- Apatite : 560 to
620 degrees Centigrade
- Zircon : 800
degrees Centigrade
Other
promising minerals using U/Pb dating schemes are Staurolite, Kyanite, Allanite
and the Columbite-tantalite solid solution series.
Coupled with
the field work is considerable experimental work to calibrate the cooling
characteristics of different minerals.
As new experimental data on closure temperatures become available we may
expect significant improvements in the interpretation of the age-history
relationships of rocks.
Examples
where thermochronolgy has been applied include an understanding of the thermal
evolution of the Kola schist belt in the southern Indian Peninsular, and the
use of apatites and garnets to differentiate the separate cooling paths of the
rocks from the
Questions were
asked by Jane Hammarstrom, James Sparkwalk and David Stewart (U.S.G.S.)
Respectfully
submitted:
(Ian D.
MacGregor)
Minutes of
the 1,273rd meeting of the
Geological
Society of
Wednesday,
January 24, 1996
The 1,273rd
meeting that started at 8:06 p.m., was attended by 91 people and adjourned at
10:10 p.m..
Guests who attended were
- Karen James (
- Sarel Weal (City Planner,
- Margaret Oliver (
Announcements
President Helz announced
that George Erickson, Link Page and Hank Coulter had recently passed away.
Welcome to New Members
Full members
- P. Patrick Leahy
(U.S.G.S.)
- Jean Weaver (U.S.G.S.)
- Katrin D. Kral (
- John D. Powell (U.S.G.S.)
Society Business
1. Chris King announced the schedule for local schools’ science fairs and encouraged volunteers to register.
2. Members were again asked to provide their email addresses and
indicate whether they would prefer to receive program announcements by email or
not. At subsequent meetings the process will continue.
3. Jane Hammarstrom announced that GSW is setting up a home
page. Any ideas or help would be
welcome.
4. The President announced that Cy Galvin would be holding a field trip.
INFORMAL COMMUNICATIONS
E-an Zen (U.S.G.S.), “Low Tech Observations of the Flood of
1996”
Visiting
Great Falls and the gorge of the Potomac two days (1/23/96) after the peak flow
of 21st January E-an noticed that the water levels had dropped by 40 feet at
the main cataract and 25 feet at the downstream end of the gorge. Reconstructing the high water marks, at
maximum flood, at a number of locations he was able to show that the
longitudinal slope of the flow down the gorge was 0.6% while for the shorter
distance adjacent to the main cataract it was closer to 0.3%. The higher slopes observed in the gorge are
comparable to those measured for the biggest flood ever recorded in 1936.
E-an
ascribed the difference in the slopes to the abrupt right angle turn that the
gorge takes just below the cataract. The
net effect is that the bend acts somewhat like a dam and the momentum of the
water, which is flowing at a rate from 4 to 5 meters per second, raises the
mean level at that location by approximately 1 meter.
Presentations
Rhea L. Graham (
Ms. Graham complimented the Society for the recognition of African women during African American month. However, there is much additional work to be
done particularly at this time when the role of men and women geologists are under
considerable scrutiny. However, she saw
this critical time as one of opportunity for geologists for despite the fact
that the populace is becoming much less appreciative of the contributions of
science many of the new problems we now face require the skills of a geologist.
The study of Geology is such that it greatly helps to
understand the behavior of natural forces and its grasp of evolutionary principles
helps evaluate the significance of change. Geology’s strength derives from the
application of basic sciences such as physics, chemistry and mathematics to
practical problems. In its application
we must emphasize the outcomes for society not the outputs of specific investigations. Because of the emphasis on outputs rather
than outcomes, the public does not fully comprehend the contributions of
geologists which may partially account for the difficult budget situation now
facing the science. The new emphasis on
outcomes is epitomized by the new Government Performance and Review Act (GPRA)
which will be used to evaluate the performance of government agencies.
As examples
of outcomes valuable to society she told of the case of Joe Holmes who pointed
out the adverse health effects of coal dust and the application of engineering
geology to the mitigation of earthquake hazards. A new area that may well have exciting
potential is in understanding the study of the role of microbes in shallow
crustal processes.
In the
future we need to adapt by bringing in new ideas and new disciplines. Rather than a stagnation of the field, what
is needed is an infusion of new minds, skills and ideas to deal with the dynamically
changing needs of society.
Three
principles for managing the future of geology are, building a foundation on the
pure sciences, helping society to understand and embrace new knowledge and
improving efficiency.
Questions were asked by Margaret Johnson (Bureau of Mines), Gene
Robertson (U.S.G.S.), George Helz (
Peter F. Folger (GSA Congressional Science Fellow): 222Rn
Variation in a Fractured Crystalline Rock Aquifer and Impacts to Indoor Air: An
Example from
With
apologies to Peter
Little bubbles
Causing troubles,
In fractured rock
An aquifer courses
To subtly change your future choices
How much inhalation
Will change your station,
Or what level of ingestion
Is still much of a question.
Lets pass regulations,
Exaggerate the doses.
Who’ll care what’ll be
The final prognosis ?
Se la vie its all osmosis.
Radioactive radon an alpha releases
For some it troubles
For others it
pleases;
The picoCuries come by the litre
At what levels do we trust the meter ?
Experimental tests
Show that it is best
Don’t build a house on
No architect should ever plan it.
With logging truck and televiewer
Heat pulse and gamma show flow less pure
Associated with a uranium sewer
Down
Changing residents status
quos.
For steady state at equilibrium
There’s constant radon in the system;
The size of fractures fight each other
From large to small its vice versa.
Pumping can affect the outcome
Its iron oxide that one must shun;
Uranium minerals will not leach
So get the water that is deep
The shoaler part dump in the street.
The motto of the story goes,
Drink the water
But don’t use your nose,
Restrict the laundry, showers reduce,
Flush seldom to escape the noose.
Just heed these truths while you’re growing
And in your grave you’ll not be glowing.
Questions were asked by Malcolm Ross (U.S.G.S.), Brooks Hanson,
Murray Hintzman and Christopher King.
Questions when rhymed:
Malcolm posed that
radioactivity
In small doses: no harmful
proclivity
But instead,
Got many patients out of
bed.
Murray’s puzzle
Effects of hot springs ?
Peter’s answer; just not his
thing.
But King topped all
Eschew Cashew nuts !
Charles D. Cunningham (U.S. Geological Survey, Reston): Age and
Thermal History of Cerro Rico de Pososi, Bolivia: the World’s Largest Silver
Deposit
Cunningham’s
friend and co-author, George Erickson passed away after 50 years with the
U.S.G.S. He will be fondly remembered by
Presidents he counseled, young geologists he taught and colleagues he
inspired.
The Miocene
to Recent volcanic field that forms the crest of the central Andes hosts many
ore deposits. One of the most famous is Cerro Rico de Potosi, the world’s
largest silver deposit. The deposit has
been mined since 1545 and in the 16th and 17th century the adjacent city had a
population that exceeded 500,000.
The ore
systems are concentrated in a dacite, mushroom shaped, body with a keel like
feeder pipe intruded into a brecciated phyllite overlain by a ring shaped tuff
deposit. The dacite is highly altered to
a quartz-alunite-kaolinite matrix characteristic of acid-sulfate leached
systems. The ore body is zoned with a
tin-rich core, composed of a cassiterite-wolframite-bismuthinite-arsenopyrite
assemblage, surrounded and overprinted by base metal assemblages with galena,
sphalerite, Ag-bearing minerals and Pb-sulfosalts that were deposited at lower
temperatures. Mineralization is
dominated by reactivation of a magmatic system that follows a decreasing
temperature trend paralleled by changes in salinity and mineralization.
U/Pb dating
of zircons from the dacite give 13.8 m.y. rims and Precambrian cores (1.7 b.y.). Sericite and alunite from alteration zones
using K/40Ar and 40Ar/39Ar schemes give
similar ages showing that major mineralization was followed closely by
sericitization and both are part of the same evolving magma-hydrothermal system. However younger ages from some alunite veins
that range from 11 m.y. to 6 to 9 m.y. coincide with age of the adjacent Los
Frailes volcanic field.
The Cerro
Rico deposit lies within a north-south belt of tin deposits associated with
peraluminous rocks ranging in age from the Triassic batholiths to late Tertiary
volcanic centers. The source for the tin
is complex and probably comes from Brazilian Precambrian crust complexly mixed
with the more closely associated Ordovician black phyllites.
Questions were
asked by Murray Hitzman, E-an Zen (University of Maryland), John ?, ? Hemley
(U.S.G.S.) and Craig Schiffries (NAS/NRC)
Respectfully
submitted:
(Ian D.
MacGregor)
The
Geological Society of Washington
Minutes of
the 1274th Meeting, 28 February 1996,
Cosmos Club
Auditorium, Washington, D.C.
President
George Helz called the meeting to order at 8:02 pm. The minutes of the 1273rd meeting were read
by the Council Secretary, who took the liberty of rearranging them so that the
“Ode to Radon, with apologies to Peter Folger” was read last. Folger, who had been tipped off by an
anonymous source that the permanent record of his talk might contain more than
a few bad rhymes and irregular meters, immediately took to the podium, and
added a few more verses which did little to improve the overall literary merits
of this exercise. The minutes were then
approved as amended.
Two guests
were announced: Shelly Oles of Canada, and John Rice of Nevada.
Cy Galvin
briefly described the field trip he is leading down Pohick Creek to see the
Occoquan granite. The President then
called on Dan Milton to explain to the audience what was meant by “the sea mills of Cephalonia,” in a talk
given 100 years ago. And, John Jens was still searching for science fair
judges.
Ken Towe
gave an informal communication on the “Vinland Map,” which had recently been
re-declared as authentic in articles in the New York Times and Washington
Post. In work that Towe and others had
done 20 years ago, it was found that the pigments on this supposedly mid-15th
Century map contained anatase, and must have been made by modern
processes. The document was certainly a
fake. In spite of a lack of any new data
at all, a press release was recently issued by parties with a clear financial
conflict of interest, declaring that there was now sufficient evidence to doubt
earlier results and that the Vinland Map was really pre-Columbus in age. Towe
seemed to be somewhat disappointed by this example of “science by assertion.” There were questions by Brett Leslie, Bill
Back, John Slack, Ray Rye, E-an Zen and Gene Robertson. [7.5 minutes]
Sean Smith
of the Maryland Dept. of Natural Resources gave the first formal talk of the
evening on “Changes in the hydraulic characteristics of a relocated stream
channel.” Human re-engineering of stream
channels in urban areas has been happening in the US for hundreds of years,
usually to enhance the stability of the banks.
The recent trend has been to engineer the channels in such a way as to
have a minimum effect on habitats, but this exercise is not always so
easy. Heavily used literature data on
meander wavelength vs. channel width relationships may not be completely
trustworthy. In a redesigned stream
channel in suburban Maryland, engineers managed to reduce and homogenize the
bankfull area and hydraulic radius, change the discharge vs. u/u* slope, not to
mention the d/d84 vs. u/u* and discharge vs. T/Tc relationships, while
preserving the discharge vs. shear stress trend. Needless to say, this is not a more stable configuration. A flood in January, 1996, was particularly
damaging due to the clearing of surrounding vegetation. We should be careful of
engineering solutions that incur large repair costs every time the water
rises. Cy Galvin and John Fanzel asked
questions. [27.5 minutes]
Mark McBride
of Groundwater Metrics, Silver Spring, Md., spoke next on “My short career as a
geo-journalist, and some lessons from it.”
After spending years as a hydrogeologist in the public and private sectors,
with the USGS and Dames and Moore, the speaker was “downsized” and out on the
street looking for work in the D.C. area.
He found temporary relief by editing a newsletter called Groundwater Monitor, which boasts of a subscription list of about
100 parties, mostly environmental remediators, lawyers, and a few others, who
are willing to pay $500/year for 6 homemade issues. Newsletters are nontechnical in nature, and
can quickly get ideas out to people interested in making a profit. Editing such a publication is time-consuming,
and may require moving around furniture in one’s home, and aggravating other
family members who want to use the computer.
Scientists should be more diligent in writing press releases, as these
are fodder for newsletter and newspaper editors. This is a good way to get
one’s results out to the public. McBride
strongly recommended a career in newsletter editing to young scientists, especially
those whose brains are turning to mush due to the presence of small
children. There were questions and
comments by Mave Boland, Brett Leslie, Barbara am Ende, Paul Thomacek, E-an
Zen, Janet Crampton, and Rama Kotra, and one from Bruce Lipin, who noted that
press releases from a certain nameless federal agency in northern Virginia may
be as old as the Vinland map by the time they get distributed. [16 minutes]
Miriam
Baltuck of NASA then swept onto the stage. As she tried frantically to get
organized, she managed to accuse the President of stealing her drink, mumbled
something about former boyfriends, possibly including Mick Jagger, and scattered
visual aids across the podium, table, floor and projectors. After three minutes, Baltuck suddenly remembered
that she was up there to give a talk on “Synthetic aperture radar applications
in natural disaster reduction,” and began a formal presentation. SAR bounces electromagnetic waves off a surface,
producing an image of surface roughness.
It penetrates through clouds, but the signal is affected by water on the
ground. This method has been used to
see through dense Amazon jungles to find flood waters, to visualize levee
breaches after floods on the Missouri River, to obtain images of soil moisture
in Oklahoma, and to measure the water content of mountain snows in
California. SAR has the potential for
looking at mud slides in real time during tropical storms. Radar interferometry is a new method that can
show crustal movements during earthquakes.
A shuttle mission to produce a topographic map covering 80% of the
Earth’s land surface using interferometry is nearing approval, and may fly near
the end of the century. Baltuck finished
by offering NASA freebies to the audience.
There were questions by Dallas Peck, Bill Houser, and President Helz. [27
minutes]
The meeting
was adjourned at 10:05 pm; attendance was 81 [20 women].
Respectfully
submitted,
Jeffrey N.
Grossman (Council Secretary)
for Ian MacGregor
Minutes of
the 1,275th meeting of the
Geological
Society of Washington
Wednesday,
March 13, 1996
The 1,275th
meeting that started at 8:04 p.m., was attended by 88 people and adjourned at
10:05 p.m..
Guests who attended were
- Erik Wright (University of S. Florida)
- Tanya Atwater (UCSB)
- Guan Yang Peng (Smithsonian Institution)
Announcements
President Helz announced a field trip that will be run by Norrie
Robbins on “Red Slime, Black Coats and Oily Films” at Huntley Meadows. Should be a great attraction for all kids,
old and young.
Informal Communication
John Slack gave a short communication on “Sedimentary Exhalative
Pb-Zn Deposits” (SEDEX). The SEDEX-type
deposits occur world-wide and are largely concentrated in Proterozoic sediments. In
addition, a few deposits are of Paleozoic age and associated with sediments
deposited in anoxic marine conditions.
Examples are the 1,690 m.y., Broken Hill and Mount Isa deposits in
Australia. By using geochemical
tracers such as Th, La, Nb, Sc and Ti it
is possible to show that the ore deposits are derived from sedimentary hosts
whose chemical characteristics reflect a provenance from Proterozoic, A-type,
anorogenic granites.
Presentations
John C. Lassiter (Department
of Terrestrial Magnetism, Carnegie Institution of Washington): How do flood
basalts form? Geologic and chemical evidence from the Wrangellia Terrane of
North America
The 230 m.y.
old Wrangellia flood basalt province may be used to test the hypothesis that
major flood basalt provinces are temporally and spatially related to the partial melting of deep mantle plumes as they
first impinge on the base of the local lithosphere.
Model
predictions confirmed by the Wrangellia sedimentary and volcanic sequence show
1) that the
Wrangellia Terrane was rapidly uplifted by about 1 Km approximately 5 m.y.
prior to the extrusion of approximately 106 Km3 of basalt
in a few (2 to 6) million years, and that the Terrane rapidly subsided back
below sea level after volcanism and passage of the plume,
2) that the
basalts have εNd (T), 87Sr/86Sr(initial)
and 206Pb/ 204Pb(initial) that show a
plume signature that was mixed with lithospheric material early in the eruption
sequence, and
3) that the
major and rare earth element chemistry show that the Wrangellia basalts are
derived by low degrees of partial melting of a plume source at depths, of
approximately 80 km, within the garnet peridotite stability field beneath a thick
lithospheric lid.
Questions
were asked by Bill ? (USGS), Brooks Hanson (AAAS), Dan Stanley (Smithsonian
Institution) and E-an Zen (University of Maryland).
William S. Logan (George Washington University): Late Quaternary
sea level changes through the eyes of a coastal plain aquifer
In order to
resolve the problems of salt water intrusion into the groundwater reservoirs of
the city of La Plata, Brazil it is necessary to understand the hydrologic
history of the flat lying coastal plain sediments. The reservoir resides in an aquifer, the
Puelche sands, that lies above silts of the Parana sequence and beneath an
aquitard of impermeable wind blown loess (Pampeano formation) overlain by
Neogene silts and muds. Quaternary sea
level changes result in exposure of the Puelche sands by erosion along the Rio
de la Plata allowing seawater incursions into the aquifer. Though much of the seawater has been flushed
out by the circulation of fresh rainwater since the last 3,000 year sea level
incursion, pockets of saline brines remain that cause problems for the
city. Models that include the 3,000 year
seawater incursion into the aquifer with the subsequent freshwater flushing
have trouble explaining the observed present day distribution of saline brines
in the coastal plain sediments. One ad hoc hypothesis confirmed by D versus
Cl chemistry of the unexplained brine pockets indicates that the anomalies may
be the result of enhanced evapotranspiration along selected zones.
Questions by
Dave Stewart (USGS), Dan Milton (USGS), Cy Galvin, Dan Stanley (Smithsonian
Institution) and Bevin French (NASA).
Christopher G. Newhall (U.S. Geological Survey): Old man lahar -
he just keeps on flowing: An update from Pinatubo Volcano, Philippines
Old man
Chris just kept on overflowing with impressive image after image of lahar after
lahar.
Although the
primary Pinatubo eruption of 5 km3 of debris and the associated
caldera collapse caused considerable initial disruption it was the
remobilization of the newly draped ash by heavy rains into erosive lahars that
has caused most of the more enduring damage and human suffering. Over 31/2 Km3
of the original debris has been remobilized by lahar-like erosion in the last 5
years. The lahars materialize from heavy
rains whose runoff undercut and erode the unconsolidated ash mixing it into a
mobile cement-like mass that gravitationally slurps over confining riverbanks
burying the surrounding fields and exposed villages. The erosive power of this process is powered
by the 2,000 mm to 4,000 mm of annual rainfall on the eastern and western
slopes of Mount Pinatubo, respectively.
Although
there is no fully effective way to escape the inevitable damage done by the
lahars, mitigating actions include the making of hazard maps with associated networks
of rain gauges and acoustic flow meters to provide short term warnings, and engineered
barriers, that are seldom fully successful, to stem the flows. Alternately, the Philippine authorities are
forced to evacuate threatened villages and towns into temporary communities
where 200,000 displaced people now reside.
Questions
were asked by Will ?, David Stewart (USGS),
Raymond Rye, CY Galvin, John Jeans (USGS), Motto Sao (retired USGS),
Peter Stifel (U. of Maryland), Brooks Hanson (AAAS) and Dyer Rubbing (USGS).
Respectfully
submitted: …………………………………..
(Ian D.
MacGregor)
The
Geological Society of Washington
Minutes of
the 1276th Meeting, 10 April 1996,
Cosmos Club
Auditorium, Washington, D.C.
With the
Secretary and President both missing, first vice-president Bruce “on-the-dot”
Lipin nervously called the meeting to order at 8:00 pm. The minutes of the
1275th meeting were read and approved after the audience filled in a few, but
not all of the blanks.
The three
guests were Tong Bo-Lin, Wang Ching-Chen, from China, and Ruth Tsong of
Stanford University.
There were
two new members:
W.
Alexander Merrill, Madison, Wisconsin
Alfred
Friendly, Washington, DC.
John Jens
made his biweekly appeal for science fair judges.
There were no informal communications.
First
vice-president Bruce “no monkey business” Lipin sped on to the formal program,
even before the beer in anyone’s glass could get as warm as the coke that was
provided straight up by the Cosmos Club.
Michael J.
Kunk of the USGS, Reston, spoke on “The timing of intrusive igneous activity
and K-feldspar cementation in Mesozoic basins of eastern North America.” These basins record the early history of the
breakup of Pangaea, and sediments deposited in them may provide information of
climate change in the Jurassic. The
sediments are intruded by diabases and basalts which, except for one study, are
poorly dated. Kunk then set out on an
veritable isotopic travelogue, presenting endless vistas of majestic plateaus,
each giving an Ar-Ar date of unsurpassed splendor...196.7, 196.4, 197.7, 196.6,
and 196.3 Ma for “HTQ” intrusives of the
Gettysburg and Culpeper Basins, and for sanidine in rhyolite dikes in no
particular basin in southern Virginia.
The journey continued on to the rugged argon high-country of the
sedimentary rocks, inhabited by void-filling cements rich in potassium. Here are found more plateaus of nearly the
same elevation, at 196.2 and 196.6 Ma, but also quite a few badlands where the
speaker dared not tread. Fluid flow
during the emplacement of the igneous rocks was probably related to the
cementing of the younger sediments.
There were questions by Dallas Peck, Gene Robertson, Bevan French and
Moto Sato. [24 mins]
John Farrell
of Joint Oceanographic Institutions, Inc., followed with “Glacial-interglacial
changes in nutrient utilization in the Pacific Ocean.” A hush fell over the audience, but that was
only because First Vice President Bruce “iron fist” Lipin was in the back of
the hall threatening people who were chatting.
Nutrient-rich waters cause zones of intense bioactivity, especially near
the equator in zones of upwelling. CO2
degasses in these regions, whereas at the poles CO2 is taken up by
the ocean. Nitrogen isotopes can be used as a tracer for oceanic productivity,
as the light isotope is taken up during photosynthesis. Off western South America, nutrients are high
in upwelling zones, and d15N in
suspended particles is inversely correlated with the nitrate concentration of
water, as expected. Surface sediments
show the same relationship with nitrate, but are shifted to heavier d15N values,
possibly due to diagenetic effects. During the ice age around 20 Ka ago, d15N was
very low, and there was abundant organic carbon in the sediments. Glacial periods are thus marked by higher
productivity, and so there must have been higher CO2 efflux and more
upwelling. Questions were asked by Bevan
French, J.K. Bohlke, Moto Sato, and E-an Zen.
[22 mins]
The last
talk was by Steve Bohlen of the USGS, Reston, on "the role of mineral
reactions in continental dynamics."
Mineral reactions can control the density of rocks, and are key to understanding
the gravity-driven vertical movements of continents. Bohlen uses 1960's vintage piston-cylinder
devices to study reactions relevant to basaltic rocks formed by ponding of
magma at the base of the continental crust.
Whether or not such rocks undergo the eclogite transition may control
whether delamination occurs, and thus affects heat flow, basin formation and
uplift. Kinetic controls on such reactions may be important, as evidenced by
the survival of pyroxene in Adirondack rocks at least 3.5 kbars into the garnet
field. The albite®jadeite+quartz reaction was studied in the lab, and found to have
significant kinetic barriers. The
presence of water greatly facilitates the reaction, but there are kinetic
barriers even in wet experiments.
Experiments on the reaction of plagioclase with pyroxene to form garnet
were exceedingly sluggish, even 10 kbar above the reaction curve at 1100°C. This implies
that basalts may not change to eclogites at the base of the crust, helping keep
the crust buoyant, and enhancing erosional uplift to expose lower crustal
rocks. In the lab, coesite was found to
quickly invert back to quartz transition, presenting a mystery as to how
coesite ever survives to reach the surface.
There were questions by Jane Hammarstrom, Bevan French, Moto Sato and
Gene Robertson.
First
vice-president Bruce "early to bed" Lipin adjourned the meeting at
9:46 pm; attendance was a disappointing 65 [16 women], including only two
non-retired USGS people recognized by the Secretary who were not councilors,
committee chairs, or speakers.
Respectfully
submitted,
Jeffrey N.
Grossman (Council Secretary)
for Ian MacGregor
Minutes of
the 1,277th meeting of the
Geological
Society of Washington
Wednesday,
April 24, 1996
The 1,277th
meeting that started at 8:06 p.m., was attended by 59 people and adjourned at
10:11 p.m..
New Members
- Susan Krosky Nangonten (Coastal Environment Inc., Richmond,
VA)
Guests who attended were
- Robert Reuter (University of Maryland)
- Melanie Rock (University of Maryland)
- Jordan Adelson (University of Maryland)
- Bhatke Petigera (University of Maryland)
- Pierre Glynn
- Tyler Copeland
Announcements
President Helz announced a field trip that will be run by Norrie
Robbins on “Red Slime, Black Coats and
Oily Films” at Huntley Meadows. Should
be a great attraction for all kids, old and young.
Jane
Hammarstrom discussed the continued activity to prepare a GSW Home Page. Anyone interested in helping was invited.
Informal
Communication
Cy Galvin
examined the issue of how to monitor average annual temperatures as a measure
of climate change. Past climates are usually
monitored through proxies that reflect temperatures in the water column rather
than the atmospheres. In order to
evaluate the difference in these two measurements he looked at monthly averages
of air temperature at airports and records kept at nearby river gauges. Using 1993 as a base, he found that in three
the cases examined monthly averages tracked fairly well and were usually within
1 to 2 degrees centigrade of each other.
Water temperatures were slightly higher except in the spring. As expected, annual variations greatly
exceeded the long term averages that would reflect any global change.
Presentations
Barbara Anne am Ende (Consultant, Gaithersburg): The use of
glauconite for environmental and dating studies: An example from the modern sea floor
In submarine
dives, at 400m depth, off the Florida-Hatteras continental slope, the Johnson
Sealink submersible was used to collect samples of glauconite filled, foraminifera
tests from sediments in a Barchan dune that overlay Miocene bedrock. The foraminifera are Quaternary species whose
carbonate tests gave ages ranging from a minimum of 30,000 to 40,000 years from
14C dating to 2 to 3 million years from 87/86Sr evolution
techniques. 87/86Sr dates of
the enclosed glauconite which varied as a function of color and potassium
content of the glauconite. The lightest
grains gave the oldest ages of approximately 13 m.y., intermediate colored
grains gave the youngest ages at 3 to 5 m.y. and the darkest greens slightly
higher at approximately 7 m.y. It is not
possible to unambiguously interpret the age relationships since the glauconite
ages may result from mixtures of diagenetic and mixed detrital Miocene
glauconite and other clay minerals.
Textural studies show that the glauconite is diagenetic, replacing calcite
in multiple generations. The diagenetic
replacement is probably the result of freshwater discharge from Eocene aquifers
that are connected to the Miocene horizons through fracture systems. However, the chemistry of the freshwaters and
seawater leave unresolved the question of what is the source of the iron in the
glauconites.
Questions
were asked by Sorena Sorensen (Smithsonian Institution), John Bohlke (USGS),
Moto Sato, Kurt Sellers (USGS), Blair Jones (USGS) and Owen Birker.
Warren Wood (U.S. Geological Survey): Ground water and the
coastal sabkhas of Abu Dhabi: An
alternative model for dolomitization
By looking
at the formation of Recent dolomites it is possible to exploit the premise that
“the present is the key to the past” and get some insights into processes that
control the ubiquitous formation of dolomite in ancient limestones. One accepted model for recent dolomitization
in the Arabian Gulf, developed by David Kinsman, is that dolomitization results
from the percolation of densified seawater brines through coastal sabkha formations. The densification results from the mixing of
the groundwater solutes with evaporated seawater blown onto the limestone
deposits. An alternate model, examined
in this talk, is that the dolomitization results from the circulation of
Mg-rich ground waters. In Abu Dhabi
ground water flowing through the regional El Ain aquifer passes through the
coastal sabkhas as they exit to the Gulf.
Careful study along a single flow line of the El Ain aquifer shows that
the groundwater in the aquifer is a mixture of fluids from precipitation of
rainwater in the Oman highlands at the eastern limit of the aquifer and saline
ground water from Permian salt and anhydrite horizons. The Oman highlands and detrital sediments of
the El Ain aquifer are unusual in that they are made up almost solely of the
olivine-rich harzburgites of the Oman ophiolite so that the entrained
groundwater solutes are unusually high in Mg.
Flow balances show that at the outflow in the Gulf the groundwater is
composed of approximately 20% rain water and 80% of intermixed Permian
brines. Only 10% of the El Ain aquifer
discharges into the Gulf the balance being evaporated through the coastal
sabkhas. Evaporation and precipitation of gypsum and anhydrite significantly
increases the total Mg content and Mg/Ca ratio of the groundwater leading to
dolomitization of the host sabkhas. Confirmation
of the hypothesis comes from the chemistry of groundwaters, collected from a
traverse of shallow pits across the sabkhas, which show that the Se, Cr and Br
content of the groundwaters cannot result from circulating seawater but
reflects the changing chemistry of the El Ain aquifer.
Questions
were asked by Sorena Sorensen (Smithsonian Institution), Moto Sato (USGS),
Sandy Neuzil, Blair Jones, Barbara am Ende, E-an Zen (USGS) and George Helz
(University of Maryland).
Shaun K. Frappe (University of Waterloo, Ontario): Uses of stable
chlorine isotopes in tracing the origin and migration of saline waters in
sedimentary and crystalline environments
We learnt
from this talk of a novel way to get a beer break midway during the sessions -
have a bulb failure in the projector.
This is a procedure we could use more effectively in the future.
At zero fractionation the ratio of the stable isotopes
of chlorine, 37Cl and 35Cl, is unusually high at
0.31978. The unusually high ratio means
that, unlike other isotopes such as oxygen (1), a significantly larger number
of Cl atoms (138) must be fractionated to give a one per mil change. Despite the insensitivity to fractionation
significant variations are observed in nature.
Variations in the 37/35Cl ratio are measured relative to
Standard Mean Ocean Chlorine (SMOC) - kept in a bottle but never found in the
oceans! Examination of groundwaters from
the Finnish and Canadian shields indicate very different histories. The heavy Cl, old groundwaters of the
Canadian shield are derived from in situ
metamorphic and magmatic reactions without much further mixing. In contrast the Finnish shield groundwaters
fall along mixing lines that show three components. Light Cl from the rift-related eruption of
large Permian volcanic fields, waters from the Baltic Sea and weathering of
glacially redistributed, Permian Zechstein salt deposits.
Questions
were asked by Richard Walker, Brooks Hanson (AAAS), William Logan and George
Helz.
Respectfully
submitted: …………………………………..
(Ian D.
MacGregor)
Minutes of
the 1,278th meeting of the
Geological
Society of Washington
Wednesday,
September 11, 1996
The 1,278th
meeting that started at 8:08 p.m., was attended by 69 people and adjourned at
10:06 p.m..
Guests who attended were
Rex Hanger (George Washington University),
and 13 other unnamed
undergraduate and graduate students
Announcements
- President Helz announced
the deaths of Dick Sheldon and Walt Ketterer
Informal Communication
Greg Sohn revived from the depths of a micropaleontologist’s retirement was delighted to see the apparent imprint
of a fossil dinosaur in the back of a bench at the Federal Center Metro Station. Harnessing the limited resources of the
Smithsonian Institution he was able to show that the image was made primarily
of quartz and plagioclase with minor K-spar and biotite. Could it be
metamorphic or ingenious ? The puzzle
remains, but a name is the game, so now we have “Microthermosaurus”. A field trip will be announced at the next
meeting.
Presentations
Glenn MacPherson (Smithsonian Institution) Unraveling the first
few million years of Solar System history
Visual
images of the protoplanetary discs around stars and star-forming regions of the
Orion nebula by the Hubble telescope support models of the early solar system
by condensation of material from a dispersed gaseous solar halo. The earliest record of this process is locked
in the 4.5 billion year plus chondritic
meteorites. These relicts of early solar
processes are made up of aggregates of planetary grains as accretion breccias. Amongst the primary constituents are a
variety of spherical chondrules. The
most common are made up of skeletal olivine, but Ca-Al-Ti rich inclusion with
oxide mineralogies and glass spherules are also found. The chondrules seemed to have formed by the
rapid cooling of molten glass droplets.
Examination
of the Al and Mg isotopic chemistry of the Ca-Al-Ti inclusions shows systematic
variations that confirm the early existence of 26Al, a radioactive
isotope that decays to 26Mg with a half life of 0.75 million
years. Fossil isochrons from this decay
scheme show that these meteorites formed in the first 2 to 5 million years of
the early solar system and that the heat from 26Al decay is adequate
to melt 10 to 20 kilometer diameter planetisimals.
Questions
were asked by Sorena Sorensen (Smithsonian Institution), John Robertson (USGS),
Richard Walker, Robin Brett (USGS) and Bill?. (USGS).
Stephen J. Schaefer (NASA Goddard Space Flight Center) Remote
measurements of sulfur dioxide from volcanic eruptions: Lessons from Nevado del
Ruiz and Rabaul volcanoes.
The flux of
SO2 from volcanic emissions is measured by a variety of
techniques. These include the use of
satellite observations with ultraviolet ozone spectrometers with the TOMS and
ADEOS satellites, air-borne COSPEC and IR spectrometers and direct sampling
coupled with simultaneous observations of the vertical wind profiles that
disperses the volcanic clouds. Measurements
of different volcanoes show different SO2 emission characteristics.
For example,
the Nevado del Ruiz , 1985, eruption was preceded by significant SO2
degassing, large emissions during the eruption and degassing rates remained at
comparable levels for about 13 years after the eruption. The total emissions over that time period amounted to 10 million tons of
sulfur. In contrast, the Mount Tavurvur
and Mount Vulcan eruptions in Rabaul, Indonesia, had significantly lower SO2
eruption rates that rapidly decreased after the eruption. Variations in the emission characteristics
from each volcano showed that the different eruptions tapped parts of a
subvolcanic magma chamber. The observations
may be explained by considering the variable stages of the cooling, fractionation and degassing of
subvolcanic magma chambers.
Questions
were asked by Sorena Sorensen (Smithsonian Institution), Robin Brett (USGS),
Gene Robertson (USGS), Sandy Nouzell (USGS) and E-an Zen (retired).
Michael P. Ryan (USGS) Double-porosity hydrothermal convection
systems
Fluid flow
in Neovolcanic zones in Iceland is controlled by flow regimes with variable
permeability. In the case of the Krafla
volcano fluid flow is dominated by two systems.
The first, are large vertical fractures that are separated by about 500m
to 1000m and extend to depths of a approximately 2000 m, and the second, at smaller scales of a few
centimeters, controlled by thermal cracking such as that seen in columnar
jointing and aa lava flows. Finite
element models using coupled fluid and thermal flow equations showed time
dependent flow and thermal fields in such systems. The same models may be applied to examples in
Oahu, Hawaii where parts of the Wainae and Koolau volcanoes are dominated by
dike and sill swarms and associated fracture systems that intersect at very
high angles to give a boxwork structure to the permeability variability. Permeabilities of the different blocks may
vary from 10-4 to 10-20, giving very complex flow and
thermal patterns to the evolving flow regimes.
Such flow
models when applied to volcanoes in the Pacific Cascades help to identify such
features as structural decoullements, and zones of high pore pressure and
variable fluid chemistry which have implications for identifying zones of high
seismogenic hazard.
Questions
were asked by Chris Nouzel (USGS), E-an Zen (retired) and Dallas Peck (USGS)
Respectfully
submitted: …………………………………..
(Ian D.
MacGregor)
Minutes Of
the 1279th Meeting of the
Geological
Society of Washington
September
25, 1996
President
George Helz convened the meeting at 8:05 p.m. Second Vice President Jane
Hammarstrom filled in for absent Meetings Secretary Ian MacGregor, having
already filled in from 4 to 6 that afternoon for absent Council Secretary Jeff
Grossman leading her to conclude that second vice president was not quite the
fluff job that last year's nominating; committee had led her to believe! Minutes of the September 11 meeting were read
and technically approved although 2 members thought up corrections during the
meeting which they conveyed later on over beer - does that count?
Our distinguished
group of guests included
Peter
Barnes, new Chief Scientist for the Coastal Program at the USGS in Reston,
three State
Geologists
Charles
Gardiner of North Carolina,
John
Steinmetz of Montana,
and
John Price Of Nevada,
and Tamara Nameraff,
GSA Congressional Follow.
E-an Zen
announced the publication of the Hutton Symposium volume as an issue of
Transactions of the Royal Society of Edinburgh.
GSW was a cosponsor of the 1995 Third Hutton on the Origin of
Granite. The volume will be reprinted as
a GSA Special Paper.
Jane
Hammarstrom announced that the GSW web site was established and solicited
suggestions for additions or changes in content. The site lists the upcoming program and
provides link to contact the President, Membership Committee, and Program
Committees as well access to the list of local area employers.
Reto Giere of the Carnegie Institution of Washington and the
University of Basel kicked off the formal program with a talk on “Metamorphism
of tourmaline-rich metapelites from the Swiss Central Alps". Reto demonstrated that tourmalines are not just pretty stones, but minerals that can provide
constraints on metamorphic history. He described
chemical and isotopic zoning in tourmaline that has never been demonstrated
before. In metapelites of the Italian
Alps, traces of 3 deformation events are recorded in 1 to 3 cm long tourmalines
which display cracks, boudinage, and color zoning that documents 3 growth
stages. In long sections, one can see
green cores, outer rims and outermost olive colored rims. The outermost rim material occupies cracks
across the entire crystal documenting a post-deformation growth stage. Zoned garnet inclusions in tourmalines allow
a correlation of the chemical evolution of both minerals. Iron decreases from core to rim, with a sharp
boundary between core and innermost rim and an irregular boundary between inner
rim and outermost rim, recording a major corrosion event. The tourmaline zones were separated and
analyzed for oxygen isotopes which showed higher 18O values for the
outermost rim (+6 versus +5 for inner rims and cores). Tourmalines exhibit chemical polarity, and
perhaps isotopic polarity. Oxygen
isotope measurements on muscovite, biotite and quartz indicate temperatures of
620 to 630, outer rim-quartz suggests 600 for isotope lock-in. Thermodynamic analysis of the mineral
assemblage indicates about 630 at 7.5 kbar, in good agreement with
fractionation technique. Tourmaline
zoning records a clear and pronounced event that is seen in chemical and isotopic
changes and could reflect infiltration of fluids.
Questions by
Slack, Zen, Schiffries, Farquahr, and Robinson.
Ron Litwin, USGS Reston, spoke on “Middle to Late Pleistocene climate change in the southwestern United States: Owens lake, California". Land-based records of climate change are scarce, but the complete pollen record for Holocene and Pleistocene climate change preserved in Owens Lake drill core from SE California provides a unique opportunity to obtain an independent chronology for comparison with the marine record. The 323 meter laminated core was sampled at 2 meter intervals, and 300 pollen specimens per sample were counted to compare core with modem pollen. The most useful pollen for documenting climate history in the core are the pac-man shaped juniper pollen, oak, desert scrub, the mickey-mouse eared pine pollen, and most importantly spruce - southernmost occurrence in the SW.