Middleton G.V. (Ed.) Encyclopedia of Sediments and Sedimentary Rocks
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645
(honora causa) from Syracuse University in 1979. He
advanced through the academic ranks from assistant to
associate professor at the University of Chicago and after
working for the Beach Erosion Board of the US Corp of
Engineers during WWII and a short stint with Gulf Research
and Development Company (1945-1946), joined Northwes-
tern University as a full professor in 1946, later made William
Deering Professor of Geological Sciences, retiring in 1970.
His first papers in 1932 were on the mechanical analysis of
fine-grained sediments and his last was on probabilistic
modeling in 1978. (He was senior author posthumously on,
CORSURF: a Covariance-Matrix Trend Analysis Program,
published in Computers & Geoscienees in 1995.) He explored
sampling, textures, size distribution, diagenesis, transport,
properties, and classification of modern and ancient sediments.
He was one of the early workers to apply quantitative
techniques, including descriptive statistics, Latin square
experiments, regression analysis, Markov chains, and prob-
abilistic modeling, extensively to geological problems.
With introduction of the computer in the mid 1950s, he
transferred his statistical analyzes from the calculator to the
computer; in 1958, he published (with L.L. Sloss) the first
geologically oriented computer program (in SOAP). His last
publications were philosophical in nature as he explored the
directions and influences of quantification on sedimentology.
He had an uncanny analytical mind and could cut through the
extraneous material directly to the problem.
He carefully formulated and presented his ideas in his 130-f
publications including 5 books. His manual with Francis
Pettijohn, Matmal of Sedimentary Petrography (1938), was a
standard text for several decades as was his book with Larry
Sloss on StratigraphyandSedimentation
(1951,
1963). However,
it was his book in collaboration with Frank Graybill in
1965,
An Introduction to Statistical Models, that put him in
the forefront of quantitative sedimentology. Krumbein co-
authored several papers with leading statisticians of the day
including John Tukey, Geoff Watson, Frank Graybill, Ron
Shreve, and Mike Dacey.
He was a founding member of the International Association
for Mathematical Geology (IAMG), was elected the first Past-
President of the Association, and their premier award was
named the William Christian Krumbein Medal in his honor;
these tributes indicate the esteem held for him by his peers.
He was a fellow of GSA, AAAS, and ASA; member of SEPM
(President in 1950), SEG, AAPG, and AGU. He received a
Guggenheim Fellowship, was a Fulbright Lecturer, and a
President's Fellow at Northwestern University.
Daniel F. Merriam
Bibliography
Krumbein, W.C, 1932. A history of the principles and methods of
mechanical analysis. Journal of Sedimentary Petrology, 2 (2): 89-
124.
Krumbein, W.C, 1932. The mechanical analysis of fine-grained
sediments. Journal of Sedimentary Petrology, 2 (3): 140-149.
Krumbein, W.C, 1934. Size frequency distributions of sediments.
Journal of Sedimentary Petrology, 4 (2); 65-77.
Krumbein, W.C, 1937. (and Aberdeen, E.J.). The sediments of
Barataria Bay (La.). Journal of Sedimentary Petrology, 7 (1): 3-17.
Krumbein, W.C, 1953. (and Miller, R.L.). Design of experiments for
statistical analysis of geological data. Journal of
Geology,
6t (6):
510-532.
Krumbein, W.C, 1956. (with Slack, H.A.). Statistical analysis of low-
level radioactivity of Pennsylvanian black fissile shale in Illinois.
Geological
Societyof America Bulletin, 67 (6): 739-762.
Krumbein, W.C, 1958. (and Sloss, L.L.). High-speed digital compu-
ters in stratigraphic and facies analysis, American Association of
Petroleum Geologists Buiietin, 42 (11): 2650-2669.
Krumbein, W.C, I960. The "geological population" as a framework
for analysing numerical data in geology, Liverpool and Manchester
Geology
Journal, 2 (3): 341-368.
Krumbein, W.C, 1962. Open and closed number systems in
stratigraphic mapping. American Association of Petroleum Geolo-
gists Bulletin, 46 (12): 2229-2245.
Krumbein, W.C, 1968. Statistical models in sedimentology. Sedimen-
toiogy, 10 (1): 7-23.
Krumbein, W.C, 1969. (and Daeey, M.F.). Markov chains and
embedded markov chains in geology. Journal of Mathematicai
Geology, 1(1): 79-96.
Krumbein, W.C, 1974. The pattern of quantification in geology.
In Merriam, D.F. (ed.). The Impact of Quantification on Geoiogy.
Syracuse University Geology Contributions. Volume 2, 51-66.
Krumbein, W.C, 1975. Probabilistic modeling in geology.
In Merriam, D.F. (ed.). Random Processes in Geoiogy. Springer-
Verlag, pp. 39-54.
Cross-reference
Statistical Analysis of Sediments and Sedimentary Rocks
PAUL DIMITRI KRYNINE (1902-1964)
Paul D. Krynine was born in Siberia, the son of Dimitri P.
Krynine, an engineer who travelled with his family to
Argentina (1909-1917), then back to Moscow, where Paul
graduated with a BSc in geology in 1924. Paul then emigrated
to the United States, obtained a second bachelor's degree
in geology at Berkeley (1927), and worked for Standard Oil
of California for three years in Mexico. At this time his
father also left Russia and became professor of soils
engineering at Yale: Paul moved to Yale in 1931, and
completed his doctorate there in 1936. He then accepted a
teacliing position at Penn State University where he remained
until his death in 1964.
Krynine's doctoral thesis was a detailed study of the Triassic
of the Connecticut Basin, a study which set new standards for
sedimentary petrographic work in America (publication was
delayed by the Second World War until 1950). Krynine made
use of his experience in Mexico to argue that arkoses were not
necessarily, or even most probably, deposited in arid climates.
Humid climates, combined with active tectonic uplift of
suitably feldspar-rich source rocks, and burial in a rapidly
subsiding basin, was the most probable explanation. He also
noted that red soils, which he considered important in the
deposition of red arkosic beds, were confined to humid
climates (his study of red beds in Mexico was, however,
flawed by inadequate field work). These views started a long
fruitful debate about the relative importance of tectonics,
climate, and diagenesis in controlling the major mineralogy of
sandstones (with most sedimentologists now inclined to the
opinion that Krynine underestimated the importance of
diagenesis).
In Pennsylvania, Krynine produced petrographic studies of
the Third Bradford Sand, a major Devonian oil reservoir, and
646
SEDIMENTOLOGISTS
a sandstone with many "low rank metamorphic" rock
fragments, and the Oriskany Sandstone, a pure quartz
sandstone. Out of these, and other studies came Krynine's
famous "megascopic" classification of sandstones into four
main types: arkoses (with few fine-grained rock fragments),
low and high rank greywackes (rich in fine grained rock
fragments, and either poor—low rank, or rich—high rank, in
feldspar), and the Orthoquartzites that were derived from them
by much sedimentary recycling. Krynine presented these ideas
in 1948 with the aid of the first triangular diagram used in
sedimentary petrology: the classification was designed to be
used for field classification using a hand-lens, so exact
numerical boundaries between petrographic fields were never
specified. This work, and Krynine's earlier ideas about tectonic
control, were presented at meetings but published, if at all,
only in obscure conference proceedings (Folk and Ferm, 1966,
give a complete bibliography, and an exposition of some of his
obscure publications: see also Bates and Griffiths, 1971).
Nevertheless, Krynine's ideas were very influential, focused
attention on refined petrographic interpretation of the major
(light) constituents of sandstones (not just the heavy minerals,
which were the focus of much attention in earlier decades),
and set off many other attempts at sandstone classification.
Krynine did not neglect heavy minerals, either and was one of
the first since Sorby to expose the wealth of information
that can be obtained by studying the compositional and
textural varieties of key minerals, particularly stable minerals
such as quartz and tourmaline. His basic concepts were
extended by Robert L. Folk (one of his doctoral students) to
produce the first generally accepted classification of
limestones.
Krynine was an eccentric personality, no field geologist (he
was almost blind), but a highly perceptive petrologist and an
extraordinarily effective teacher. His teaching style and
influence have been amply documented by his students (Folk,
Ferm, Williams) and contemporaries (Griffiths, van Houten):
together he and Griffiths made Penn State one of the three
major schools for sedimentology in America in the 1940s and
1950s (the others were Chicago, with Pettijohn and Krumbein,
and Northwestern with Dapples, Sloss, and Krumbein after he
left Chicago). These were the decades when sedimentology
came to maturity in the United States.
Gerard V. Middleton
Bibliography
Bates,
T.F., and Griffiths, J.C, 1971. Memorial of Paul Dimitri
Krynine. American Mineralogist, 56: 690-698.
Folk, R.L., and Ferm, J.C, 1966. A protrait of Paul D. Krynine.
Journalof Sedimentary Petrology, 36: 851-863.
Van Houlen, F.B., 1989. Krynine, Pettijohn, and sedimentary
petrology. Journalof
Geological
Education, 37: 241-242.
Williams, E.G., 1965. Memorial to Paul D. Krynine (1901-1964).
Proceedings of the Geological Society of America, 1965,
P63-P67.
Cross-references
Sedimentology, History
Sedimentologists: Robert L. Folk, Francis J. Pettijohn
PHILIP HENRY KUENEN (1902-1976)
Philip Kuenen was born in Scotland. His father was a Dutch
physicist and his mother was English: they moved to Leiden in
1907,
where Kuenen received all his education (including his
doctorate in economic geology in 1925). He served as geologist
on the Snellius expedition in 1929-1930. In 1934 he was
appointed lecturer in Groningen, and remained there until his
retirement in 1972.
Kuenen made major contributions in three main areas:
experimental geology, marine geology, and sedimentology. In
experimental geology, his main studies of sedimentological
interest were: (1) a long series of experiments on the attrition of
grains by sediment transport both in air (using a wind-tunnel)
and in water, using a horizontal "racetrack" flume with the
flow driven by a paddle wheel; (2) experiments on sedimentary
structures, including ripples, plane lamination, and load
structures ("pseudonodules"); and (3) studies of turbidity
currents and their deposits (see below).
His paper of 1965 defends the experimental approach, and
gives a summary of many of the results. He was himself an
excellent experimentalist, with a fine physical intuition, but
with almost no knowledge of mathematics or theoretical
mechanics. His studies on attrition established that aqueous
transport, even for long distances, was incapable of producing
major changes in the size and shape of resistant mineral sand
grains, such as quartz: thus well-rounded quartz grains must
have undergone at least one cycle of wind transport. Earlier
studies, using tumbling mills, did not duplicate natural
processes, and so gave an exaggerated estimate of the attrition
resulting from transport in water.
Kuenen's interest in marine geology dated from his
experience as geologist on the Snellius expedition and included
studies of coral reefs, eustatic changes of sea level, and
calculations of the total mass of sediments in the oceans based
on geological-geochemical cycles. His views were summarized
in his influential textbook Marine Geology, published in 1950.
Later he collaborated with his colleague L.M.J.U. van
Straaten in series of studies of sediment transport and
deposition on Dutch tidal flats (see Seditnent transport by
Tides).
Kuenen is undoubtedly best known for his development of
the turbidity current theory for the origin of graded sand beds.
The studies began as an experimental attempt (1937) to test
Daly's hypothesis that muddy density flows were responsible
for the erosion of submarine canyons. Experimental work
continued during the war, while Kuenen was confined to the
laboratory. The emphasis soon changed to the ability of
turbidity currents (a term suggested by Johnson) to transport
and deposit sand in deep water. The results were first presented
at the International Geological Congress in London in 1948,
and led immediately to collaborative papers with Migliorini,
who had been studying graded beds in the field in the
Apennines, and with Natland, a micropaleontologist who had
faunal evidence that many of the sands and conglomerates in
the Cenozoic Ventura Basin in California had been deposited
in deep water. Natland organized a symposium at the SEPM
meeting in Chicago in 1950, and he and Kuenen carried out
field work together in California. The symposium volume was
published in 1951. A detailed history of the period has been
SEDIMENTOLOCISTS
647
given by Walker (1973). Kuenen's work, together with that of
coworkers and that of Heezen and other marine geologists at
Lamont undoubtedly changed the way that geologists inter-
preted thick series of graded beds, previously thought to
have been deposited somehow in shallow water, even though
they did not display many of the structures (e.g., cross-
bedding) thought to be typical for sands deposited in shallow
environments.
Following the war, Kuenen was a strong advocate of
turbidity currents and conducted field studies in many different
regions. He recognized, described and explained many of the
structures typical of such deposits, and helped to develop the
growing field of paleoeurrent studies in the 1960s and 1970s.
One result from these studies was the discovery that in many
sedimentary basins, sediment derived from the sides or end of
the basin was transported mainly longitudinally, along the
basin fioor.
Gerard V. Middleton
Bibliography
Bourgeois, J., 1981. Kuenen, Philip Henry. In Gillispie, C.C. (ed.).
Dictionary of Scientific Biography. Supplement II Vol. t7:
pp.
509-514.
Walker, R.G., 1973. Mopping up the turbidite mess. In Ginsburg,
R.N. (ed.). Evolving Concepts in Sedimentology. Baltimore: Johns
Hopkins University Press, pp. 1-37.
Cross-references
Attrition (Abrasion), Fluvial
Attrition (Abrasion), Marine
Ball-and-Pillow (Pillow) Structure
Grading, Graded Bedding
Load Structures
Sedimentology, History
Turbidites
JOHN MURRAY (1841-1914) AND THE
CHALLENGER EXPEDITION
The voyage of HMS Challenger (1872-1876) was a major
event in the history of oceanography and in the knowledge of
the deep sea. It was initiated and led by C. Wyville Thomson,
but after his stroke he was forced to resign the Directorship,
and turn over the publication of the results to John Murray.
Murray oversaw the publication of 50 volumes in the years
from 1880 to 1895: five of the volumes he coauthored
himself,
including one on the Deep-sea Deposits (1891).
John Murray was born in Cobourg, Ontario and attended
school there until 1868, when he moved to Scotland, living
with his grandfather, and attending Stirling High School, and
then the University of Edinburgh. Though it was originally
intended that he should become a medical doctor, he followed
an irregular course of study, earning himself a reputation as a
"chronic student," and never graduated. Besides some medical
courses, he studied physics with Tait, and geology with Geikie.
He also participated in a voyage to Spitsbergen, when he
became interested in marine biology. By chance, one of the
assistant naturalists appointed to the Challenger expedition
was forced to resign, and, at Tait's recommendation, Thomson
appointed Murray to replace him.
Murray's interests remained very broad, but on the Chal-
lenger he was assigned the bottom sediments as his main
responsibility. A preliminary report, sent to the Royal Society
from Valparaiso, and published in the Proceedings in 1875,
already recognized "Shore deposits," "Globigerina ooze,"
"Radiolarian ooze," "Diatomaceous ooze," and "Red and
Green clays." The Challenger travelled 110,000 km in the
Atlantic and Pacific Oceans, and took soundings, dredgings,
and bottom samples at 362 stations, thus achieving a major
advance in knowledge of the biology and sediments of the deep
sea. The final report, written with the Abbe Alphonse Renard,
of the Brussels Museum, was not restricted to the Challenger
samples, but also used comparative material from many otiier
sources. It provided, for the first time, a classification and
detailed description of deep-sea sediments (including also
"Pteropod ooze" and iron-manganese nodules), which could
be compared with sediments in the geological record.
The shallow-water nature of most sedimentary rocks was
rarely questioned in America, but many European authors
believed that some geosynclinal sediments, notably radiolarian
cherts were deposited in the deep sea (e.g., Neumayer in 1876;
Haug in 1900; and Steinmann in 1905). Though this
interpretation remains controversial, plate tectonics suggests
that some radiolarian sediments, associated with ophiolites,
may in fact have been deposited at great depths. At first the
Cretaceous chalks of Europe were compared with Globigerina
ooze,
but more detailed comparison with the Challenger
samples soon showed significant differences. Undoubted
deep-sea deposits were, however, described by Gregory in
1889 from Barbados and by Guppy in 1892 from Trinidad.
Besides his work on deep-sea sediments, Murray became a
leading authority on coral reefs, opposing Darwin's subsidence
theory of atolls and barrier reefs. The controversy was in part
responsible for the drillings (1896-1898) on Funafuti commis-
sioned by the Royal Society. The results, reported in 1904,
remained inconclusive. After discovering a sample of phos-
phate rock from Christmas Island (in the Indian Ocean) in
collections made for comparison with Challenger material,
Murray first persuaded the British Government to annex this
uninhabited island, and then organized a company to explore
and ultimately exploit this resource. The population reached
1,500 inhabitants, and Murray claimed that the government
received much more in royalties and taxes than the entire cost
of the Challenger expedition! He used his own profits to
finance further oceanographic research.
Late in life, Murray participated in several other expedi-
tions,
including investigations of Scottish tjords and lochs, and
a four-month cruise (1905) of the Norwegian ship Michael
Sars, together with Johan Hjort. The results were later
included in their book The Depths of the Ocean (1912). Three
years later Murray published a popular book on oceanogra-
phy. He remained active until he died in 1914 as a result of an
automobile accident.
Gerard V. Middleton
Bibliography
Burstyn, H.L., 1981. Murray, John. In Gillispie, C.C. (ed.). Dictionary
of Scientific Biography. New York: Charles Scribner's Sons,
Volume 9, pp. 588-590.
Herdman, Sir, W.A., 1923. Pounders of Oceanography and Their
PVork.
New York: Longman, Green.
648
SEDIMENTOLOGISTS
Linklater, E., 1972. The Voyage of the Challenger. London: John
Murray.
Cross-references
Oceanic Sediments
Sedimentology, History
FRANCIS J. PETTIJOHN (1904-1999)
His life, 1904-1999, spatined most of the 20th century and he
influenced many. By the time he finished high school, Francis
Pettijohn knew he wanted to be a geologist. All his academic
training was at the University of Minnesota (BA, 1924; MA,
1925;
and PhD, 1930), where Professor Grout was his advisor
and the Precambrian of Minnesota was the great center of
geologic interest, which was studied through fieldwork, thin
sections, and a few wet chemical analyzes. He taught briefly as
a graduate student at nearby Macalester College, but spent
1925-1927 at Oberlin College in Ohio. His article "Geology at
Oberlin a Half Century Ago," published in the Oberlin alumni
magazine in 1980, is a tine insight to a small Midwestern
geology department in the late 192O's. Francis developed his
teaching skills and studied the beaches of Lake Erie, but he
spent some of his summers in the North Woods. In 1927-1928
he was a Fellow at the University of California, where he
became acquainted with Andrew E. Lawson from whom he
learned much.
In 1929, Francis moved to the University of Chicago and
started a program in sedimentary rocks with two sedimentol-
ogy courses. He and W. C. Krumbein published A Manual
of
Sedimentary Petrology in 1938, a landmark book that was
recently reprinted, and Sedimentary Rocks (1949), which
established his reputation worldwide. His most famous paper
at that time was "Archean Sedimentation" published in the
GSA Bulletin in 1943. During these Chicago years he spent
nearly every summer in field studies in the Lake Superior
region for the Michigan and US Geological Surveys and the
Geological Survey of Canada. During these prewar Chicago
years he was active with the National Research Council in
Washington, the forerunner of today's National Science
Foundation, and often commented on how stimulating these
small meetings were. Someone would bring along a puzzling
rock and a wild discussion would break out. Later he edited
the Journal of Geology for six years and traveled abroad,
mostly to international meetings.
When he was 48 years old, Francis moved to The John
Hopkins University in Baltimore in 1952, where he remained
for the rest of his life, becoming emeritus in 1973. He left
Chicago because fleldwork was considered old fashioned. At
Johns Hopkins, Francis discovered the Appalachians, had new
colleagues and had the most productive part of his career. He
published Paleoeurrents and Basin Analysis (1963) and Sand
and Sandstone (1972), later translated into Russian and
Chinese, and he revised Sedimentary Rocks (1976) for the
third time. He also published Atlas and Glossary of Sedimentary
Structures (1964) and Metnoirsofan Unrepentant Field Geologist
(1988),
and helped edit Studies of Appalachian
Geology,
Central
and Southern (1970), and wrote A Century of
Geology,
1884-
7984,
at the Johns Hopkins University (1988). While at Johns
Hopkins, he received many foreign visiting geologists who
came to the United States at the invitation of the US
Geological Survey. With all of these activities, Francis had
time to be a Councilor of the Geological Society of America
and to serve on several advisory boards.
The following special qualities and viewpoints were typical
of Francis and served him well throughout a spectacularly
successful, long life. He had sufficient self-confidence that he
could fully appreciate and easily work with talented people
and learn from them. He had the ability to read an article
critically (thanks to Andrew Lawson). He persuaded with
good observations, rationality, and tact. Conversely, even
though
Prof.
Pettijohn had some strong opinions, he was
conservative in his expression of them. Francis followed the
rule,
"Clarity of expression is best achieved by simplicity of
expression." His favorite short and simple rule was, "Only
outcrops keep geologists honest," which goes far to explain the
common-sense attitudes seen in his writing.
Francis's influence on the profession was great and extended
worldwide. Even as late as 1998, 25 years after he retired, his
publications were cited 57 times; from 1990 to 1998, they were
cited 497 times. His influence was transmitted through his
books, his key articles, and his many students and visitors.
Many of his students became prominent in the US geological
and Canadian Geological Surveys, the petroleum industry, and
university teaching. Many people had the opportunity to work
with him and watch how he approached and resolved geologic
problems—by asking questions that could be answered by the
direct logical study of rocks or sediments rather than questions
based on broad physical, chemical, or geological principles.
Right or wrong, his analysis of a problem always employed a
strong internal logical consistence and a full review of the prior
literature.
Paul E. Potter
RUDOLF RICHTER (1881-1957), AND THE
SENCKENBERG LABORATORY
Rudolf Richter (Figure S20(A)) was born on November 7,
1881 at Glatz in Silesia and studied at the Universities of
Munich and Marburg. Richter worked under the tutelage of
Emanuel Kayser and completed his doctorate at Marburg in
1909,
his doctoral dissertation was published under the title
"Beitraege zur Kenntnis devonischer Trilobiten aus dem
Rheinischen Schiefergebirge" (Contributions to the knowledge
of Devonian trilobites from the Rheinische Schiefergebirge).
Richter is generally regarded as having been one of the most
influential geologists of his time, his influence reaching far
beyond the boundaries of Germany. Biographical works
include Stubblefield (1957), Kegel (1957), Schmidt (1982),
and Burghard Flemming (personal communication) provided
insights on both Richter and the Senckenberg Laboratory.
After leaving Marburg Richter earned his living as a high
school teacher in Frankfurt, his scientific work being carried
out in his spare time. In 1908 he joined the Senckenberische
SEDIMENTOLOGISTS
649
Figure S20 The Kichtt'rs; (A) Rudolf Rithter 1801-1957; and (Bl
Fmm.i Rkhler 18H8-19.S6. (Photographs courtesy of the University nf
Fr.inkfurl.l
Nalurforschende Gesellschait and in 1919 he launched the
journal
Senef<etihergiana
to mark the centenary of the soeiety.
Richter maintained the editorship of ihat journal unlil his
death in 1957, He also founded and edited its popular
maga/ine Natur und Museum. In 1920 Richter was appointed
Privat Dozent in Geology and Paleontology at the Johann
Wolfgang Goethe University in Frankfurt: in 1925 he became
Extraordinary professor, and in 1934 Ordinary Professor and
Director of the Geologieal and Pateontological Institute a
position he held until his retirement in 1949. In 1932 Richter
took control of the Society and in 1933 was named "Leiter"
and also took over the directorship of ihe Natur-Museum at
I
Yankfurl.
Riehler married Emma Hiithcr (Kigure S20(B)) in 1913 and
they enjoyed a remarkable collaboration. Emma was a skilled
artist and was invaluable in their joint work on trilobites and
the series of ichnologieal papers. The papers on animal-
sediment relationships were fundamental in establishing basic
principles on how organisms affect the substrate. Their
iehnologieal work also established the zoological affinities of
many traee fossils and beeame the corner stone for ftirther
work in aetuopaleontology and aetuoichnology. Emma died
on Novetnber 15, i9.S(i.
In 1929 with ihe support of the Senekenberg Society and the
Ciertnan Navy Riehter established the Senckenberg
Vorschtingstclle fur Meeresgeologie und Meerespalaontologie
at Wilhelmshaven which was subsequently known as "Senek-
enberg am Mecr" (Senckenberg by the Sea). The institute is
presently housed in a btiilding named after him. the "Rudolf
Riehter llaus". Riehter's interest in the modern marine
environment was documented as early as 1920 when he gave
an inaugural lecture at I rankfurt LIniversity entitled "Die
Erscheinungen des Wattenmeers in ihrer Bedeutung fur die
Geologie" (The manifestations of the Wadden Sea and their
significance for geology). The station was founded with the
specific aim of studying animal-sediment relationships in ihe
interiidal environment in the Wadden Sea. It was ihe first
institution founded with the specific aitii of actively applying
the aciualistic concepts of Charles Lyell. following the
principle "the present is the key to the past". The Wadden
Sea has been the enormously successful hunting grounds of
well-known Senckenbergian researchers such as Watther
Hantzschcl. Wilhelm Schitfer, and Hans-Erich Reincck. It
was instrumental in establishing Germany as the home of
ichnologieal research and shallow water marine sedimenlol-
ogy. The Senekenberg Lab has been used as the model for
other facilities around the world including the Sapcio Island
Marine Institute in Georgia, In fact these two institutes had
very elose ties in the 1970s and did joint work on the
sedimentology and animal-sediment relationships of modern
shoreface and estuarine enviromnenis (see Howard
etaf.
1972
and Howard and Frey, 1975). Today the station houses the
Marine Science Division of the Senckenberg Institute and the
legaey of cxccllenee left by Richter, Hiintzsehel. Schafer and
Reineek continues.
Richter received many honors including honorary member-
ship in the Societe beige de Geologie. Paleontologie et
d'Hydrogeologic. the Paliiontologische Gesellschaft and the
Paleontology Society of Ameriea. He was also the recipient of
the Gold Medal of the Palaontologischc Gesellsehaft and the
Hans Stille Medal given by the Deutsehe Geologische
Gesellschaft. To celebrate his seventieth birthday fortiier
students and friends put together a special Festschrift volume
published by the Senekenbergisehe Naturforschende
Gesellschaft. Rudolf Riclner passed ;iwiiy at Frankfurt on
January 5, 1957.
S. George Pemberton
Bibliography
Howard, J.D.. Krey, R.W., and Reincck. H.-E.. 1972. Georgia coastal
rcfiioii, Sapelo Island, USA: sodimentology and biology. Setukcn-
hergiana Maritinta. 4. .1-222.
Howard, J.D., and l-"rcy. R.W.. 1975. tistiiaritrs of llie Georgia coast.
USA: scdimenlology and biolouy. Seiuketiheniiatut \taritiina. 7.
I .105.
Kegel, W., 1957. Sachruf fur Rudolf Ri(liter Emma Richier. Zeits-
ehrift Deulsehe
Geologische
Gesellschaft. Volume 110: f)37-642.
Schmidt. H., 19S2. Rtidolf Riclitcr (1881 1957) in scinen Wortctt.
Aufsi'itze Reiieii Senckenhcrgische Natitrfotseheiide
Ge.sell.schafi.
32.
I ')5.
Stiihhlclield,
C".J.,
1957. RtidolT Richter. Proceediti^.sGeolo^iccdSociety
•
•f
London. 1554,
1.17-I.^S.
HENRY CLrFTON SORBY (1826-1908)
Henry Clifton Sorby lived all his life in Sheffield. Ettgland. He
never married, and inherited enough money from his father to
pursue a life of independent seholarship and scientific research.
He made major contributions to microscopy applying the
newly discovered polari/ed light technique to ihe study of
rocks,
meteorites and melals, earning the titles "Father of
Petrography" and "Founder of Metallograph\'". Later he
worked on spectrum analysis, and coastal marine biology,
using his own 35-ton vessel.
Sorby never attended university; his tnain forum for the
exchange of ideas was the local Literary and Philosophical
Soeiety. though from the beginning of his active research
career (in 1851) he presented papers to the Geological Society
of London, the British Association for the Advancement of
650
SEDIMENTOLOGISTS
Science, and other well-known societies. Later in life he helped
found the Royal Microscopical Society (1874) and the
Mineralogieal Society (1876: he was the tirst president), and
was active in the Geological Society, becoming president in
1878-1880.
Sorby's first petrographie study was of a "Calcareous Grit,"
and he went on to make major diseoveries about the nature of
calcareous rocks and their diagenesis: many of these were
summarized in his Presidential Address to the Geological
Society (1879). He distinguished the different types of grains
making up limestones, and described the mineralogy and
textures of bioclasts, and their infiuenee on resistance to
mechanical attrition and chemical alteration. He demonstrated
the original ealcitic nature of Paleozoic corals, as opposed to
the aragonitie nature of most later corals. He described oolites,
and proposed a mechanical "snowball" origin, followed by
recrystallization, and recognized that some ancient oolites
were originally aragonitie, while others were ealcitic. His
petrographie studies were soon extended to minerals found in
other rocks, particularly sandstones (1877, 1880), and he paid
particular attention to the mineral and fluid inclusions found
within mineral grains (1858), showing experimentally how fluid
inclusions could be used to deduce the temperature and
pressure at which the minerals had originally formed. His
combination of microscopic and experimental studies also
provided the first clear evidence that slaty eleavage was formed
by deformation under anisotropic stress (1853).
Sorby was also interested in the hydraulies of sediment
transport and structure formation. He observed in a small
stream how ripples formed soon after sediment began to move,
but were washed away leaving a plane bed at higher flow
intensities. He observed ripple cross-lamination and attributed
it to "ripple drift" and described climbing sets (1859). He
proposed that cross-bedding ("drift bedding") formed by
migration of mierodeltas. He also systematically recorded the
orientation of ripples and cross-bedding and proposed that
they be used to study paleoeurrents, long before this became
standard practice.
In retrospect it seems strange that Sorby's work did not
inspire similar studies by his eontemporaries. The work on
limestones lay fallow (with rare exceptions, such as Cullis'
study of the Funafuti cores, and Cayeux's work in France)
until the revival of carbonate petrology in the 1950s. The
textural and mineralogieal study of sands fared better, but the
main emphasis was on the "heavy minerals" and on mineral
inelusions. Sorby's work on ripples and cross-bedding
remained largely unknown, even after the revival of interest
in America, due to the work of Gilbert, Kindle, and Bueher,
until rediscovered in the 1960s. Paleocurrent teehniques were
developed in Germany (Brinkmann and others) and America,
before being taken up again in Sorby's homeland.
Gerard V. Middleton
Bibliography
Allen, J.R.L., 1993. Sedimentary structures: Sorby and the last decade.
Journal of the
Geological
Society of London, 150: 417-425.
Folk, R.L., 1965. Henry Clifton Sorby (1826-1908), the founder of
petrography. Journai of
Geoiogicai
Education, 13: 43-47.
Sellwood, B.W., 1993. Structure and origin of limestones. Journai of
tlie
Geoiogicai
Societyof London, 150: 801-809.
Smith, C.S., 1975. Sorby, Henry Clifton. In Gillispie, C.C. (ed.), Dic-
tionaryof Scientific Biography. New York: Charles Scribner's Sons,
Volume 12, pp. 542-546.
Summerson, C.H., (ed.), 1976. Sorby on Sedimentology: A
Collection
of
Papers from
1851 to 1908
by Henry Clifton Sorby. Miami: Comparative
Sedimentology Laboratory, Geological Milestones I.
Cross-references
Carbonate Diagenesis and Microfacies
Sedimentology, History
WILLIAM H. TWENHOFEL (1875-1957)
William H. Twenhofel was prominent in the emergence during
the 1920s-1930s of a new specialty called sedimentation, which
became known as sedimentology during the 1950s. He was
born on a northern Kentucky farm to German immigrant
parents. Twenhofel's formal education began in public country
schools and a private secondary school. For eight years, he
taught grade sehool and studied at a normal (teachers) college
until he qualified for a position at East Texas Normal College.
After three years at Commerce, Texas, he entered Yale
University at the age of 32, where he earned AB, MA, and
PhD degrees within four years. He had intended to pursue
mathematies, which he had been teaching, but an emergency
assignment to teach geology showed him his true calling. At
Yale,
Professor Charles Schuchert suggested a dissertation on
fossils of the Ordovician-Silurian boundary in Maritime
Canada, which became the foundation for his first career,
paleontology and stratigraphy. But also at Yale, Joseph
Barrell had planted interests in weathering, erosion and
sedimentation, which would blossom into Twenhofel's later
and more famous sedimentation career. In his presidential
address to the Paleontological Society in 1931, Twenhofel
blended the two with a talk about the importance of
sedimentary environments to paleoecology.
After six years at the University of Kansas, Twenhofel
joined the University of Wisconsin in 1916. His sedimentolo-
gical career began in 1919 with appointment to the National
Research Council's Committee on Sedimentation. As chair of
the Committee (1923-1931), he was the principal author of
A
Treatise on
Sedimentation, a 661 page synthesis published in
1926,
whieh defined the new specialty. In that same year, he
was also a co-founder of the Society of Economic Paleontol-
ogists and Mineralogists (SEPM), the first professional society
for sedimentology. From 1933 to 1946, he was editor of the
first journal in the discipline. The Journal of Sedimentary Pet-
rology, which was published by SEPM. After the Treatise
appeared, the National Research Council capitalized upon
his unusual talents by enlisting him to organize a Committee
on Stratigraphy and another on Paleoecology.
Like many sedimentary geologists of his day, Twenhofel's
early publications were chiefly on stratigraphy and paleontol-
ogy. Later he contributed papers on a very wide range of
sedimentary topics, which included the origin of blaek shales,
Cambrian glauconitic greensands and their potential as a
source of potash fertilizer, marine conglomerates and un-
conformities, deep-sea sediments, reefs, and blaek beach sands.
SEDIMENTOLOCISTS
651
In 1939 Twenhofel published the important text book. Princi-
ples of Sedimentation. He is also remembered for emphasizing
the environments of deposition and paleoecology of sediments,
for pioneering the study of temperate lake sediments, and for
stressing the geology of soils and the importance of soil
conservation.
As an educator, Twenhofel inspired countless introductory
geology students as well as many post-graduate students; he
was also active in publie outreach. Twenhofel's importance to
sedimentology was recognized by the creation in 1973 of the
Twenhofel Medal as SEPM's highest honor. Other recogni-
tions included an honorary doctorate from Belgium's
University of Louvain awarded to him in 1947.
Robert H. Dott, Jr.
Bibliography
Dunbar, CO., 1960. Memorial to William Henry Twenhofel. In Pro-
ceedings
Volume
of the Geoiogicai Society of America Annual Report
for I960, pp. 151-156.
Shrock, R.R., 1981. William Henry Twenhofel. In Dictionaryof
Scien-
tific Biography, Volume 6, pp. 518-519.
Twenhofel, W.H., 1926. A Treatise on Sedimentation. Baltimore:
Williams and Wilkins.
Twenhofel, W.H., 1931. Environments in sedimentation and strati-
graphy. Buiietin of the
Geoiogicai
Society of America, 42: 407-424.
Twenhofel, W.H., 1939.
Principles
of Sedimentation. McGraw-Hill.
Twenhofel, W.H., and Tyler, S.A., 1941. Methods of Study of Sedi-
ments. McGraw-Hill.
JOHAN AUGUST UDDEN (1859-1932)
Johan August Udden was the "father of sedimentology" in
North America, although during his 49-year career he made
contributions in stratigraphy, areal geology, eolian processes,
till in the upper Mississippi valley, and other topics. He was
born at Lekasa, Sweden, March 19, 1859, and in 1861 moved
with his parents to Carver, Minnesota. He attended Augustana
College in Rock Island, Illinois, and received a bachelor's
degree in 1881, a master's degree in 1889, an honorary PhD
degree in 1900, and an honorary Doctor of Laws in 1929. He
taught natural science and other courses at Bethany College,
Lindsborg, Kansas, from 1881 to 1888 as the first teacher of an
institution established to enhance the education of Swedish
emigrants to Kansas. Udden returned to Augustana College as
the Oscar II Professor of Geology and Natural History and
taught geology, botany, zoology, meteorology, astronomy,
physiology between 1888 and 1911. Even with this crushing
teaehing load he published 46 papers. In 1911, Udden joined
the Bureau of Economic Geology and Teehnology of the
University of Texas and served as its director from 1915 until
his death. Prior to moving to Texas he worked short periods
for the Iowa Geological Survey, University of Texas Mineral
Survey, and US Geological Survey.
Udden is best remembered as the originator of the Udden
grain-size scale for sediments published in 1898 and 1914.
In order to document the eolian origin of loess, which
influential geologists, including J.D. Dana disputed, he
collected till, glacial outwash, and wind-blown sediment
around the Mississippi River valley and analyzed their grain
size distributions. He rejected a partially geometric scale used
by soil scientists in favor of a totally geometric scale. He
devised sieves to determine grain size distributions for gravel
and sand to 0.06 mm and laboriously measured the diameter of
tiner particles, which he called dust, down to 4
^tm
under the
microscope. He used histograms to help visualize his data.
Chester Wentworth later changed some of the grain-size terms
to establish the Udden-Wentworth scale that we use today.
Udden was inventive in collecting eolian sediment. In addition
to cylindrical sediment traps, he used glycerin-coated cloth
attached to flagpoles, collected dust from melted snow, and
swept sediment from the clothes of train passengers and from
tree and corn leaves. After years of colleeting sediment from
various environments, in 1914 he published the tirst sediment
grain-size database of 337 samples.
Udden's contributions extend far beyond grain-size ana-
lyzes.
In 1905, he flew a model helicopter of his design. Using a
horse, he studied the geology within 30 miles of Rock Island in
great detail. He eompiled a detailed picture of the artesian
groundwater system in the area and used well cuttings and
driller's logs to establish the subsurface stratigraphy. He
recognized the potential value of well cuttings in a variety of
geological endeavors and demonstrated this to the oil industry
by establishing the first subsurface geology laboratory when he
assumed directorship of the Texas Bureau of Economic
Geology. In 1914, from a study of cuttings from a deep well
in West Texas, he demonstrated the occurrence of extensive
deposits of potash salts in the Permian basin. In 1916, on the
basis of theoretical reasons and fieldwork done years
previously, Udden advised the regents of the University of
Texas of the likely occurrence of oil and gas on university
lands in Reagan County, Texas. This led to the discovery of
the first deep giant oil field in Texas and led to the development
of the West Texas and eastern New Mexico oil province. Oil
and gas revenues from university lands generated the
permanent endowment of the Texas state university system.
Udden's early work on the Permian in the Glass Mountains led
to the establishment of that area as the type marine Permian of
the world.
According to Charles Laurence Baker, a colleague of Udden
in Texas, Udden's success can be attributed to his mastery of
the basic natural sciences chiefiy through his teaching, his
ingenuity, and his ability to rely on his own powers of
observation and reasoning. His ingenuity is exemplified by his
invention of one of the earliest successful adding machines,
and his ability to accomplish important results with cheap and
simple devices. Udden early came to the conclusion that the
best contributions he could make, given the limited opportu-
nities available to him, was in fields neglected by others. In
1911,
Udden was awarded the Swedish Order of the North
Star by the king of Sweden.
Earle F. McBride
Bibliography
Baker, C.L., 1933. Memorial of Johan August Udden. Geoiogicai
Society of America Buiietin, 44: 402-413.
Heiman, Monica, 1963. A Pioneer Geologist: Johan August Udden—a
Biography. Texas: Privately published, Kerrville.
Sellards, E.H., 1932. Memorial to Dr. Johan August Udden. University
of
Texas,
Bureau of Economic
Geology,
Bulletin 3201, pp. 8-12.
652
SEDIMENTOLOCISTS
Udden, J.A., 1898. The Mechanical Composition of Wind Deposits.
Augustana Library Publications No. 1, Rock Island, Lutheran
Augustana Book Concern.
Udden, J.A., 1914. Mechanical composition ofclastic sediments. Geo-
logical
Societyof America Bulletin, 25: 655-744.
T. WAYLAND VAUGHAN (1870-1952)
Thomas Wayland Vaughan, (born Jonesville, Texas,
September 20, 1870—died Bethesda, Maryland, January 16,
1952) entered Tulane University in 1885, receiving a BS in
Physical Sciences in 1889. From 1889 to 1892 he taught physics
and chemistry at Mount Lebanon, Louisiana, where he
encountered Eocene fossils, and became especially interested
in corals. In 1892, Vaughan published his first two scientific
papers (his bibliography lists about 350 titles until his last
paper in 1946). The same year he enrolled in Harvard
University and received a BA (1893) and a MA (1894). His
PhD (1903) thesis was on Eocene and Oligocene corals.
Vaughan was a US Geological Survey, Assistant Geologist,
1894-1903;
1907-1923 he was geologist in charge of the
Coastal Plain Subsection. Attending the 1897 International
Geological Congress allowed him to examine European fossil
coral collections and meeting Sir John Murray sparked his
interest in oceanography. Two major Federal projects,
resulting in more than 100 papers, occupied him between
1901 and 1923. First was Carribean geologic and paleontologie
studies. Vaughan assisted in Cuba in 1901, and in 1911 worked
in the Panama Canal Zone. In 1914 he led an expedition to
islands north of Guadalupe and west of Puerto Rico. In 1919
he examined strata in the Virgin Islands and eastern Puerto
Rico.
From 1919 to 1921 he directed reconnaissance geological
studies in Dominica and Haiti. His second major effort
concerned Atlantic and Gulf Coast coastal plain investiga-
tions,
ranging from Mexico north to Cape Cod. In addition to
these duties, with support from the Carnegie Institution of
Washington, Vaughan studied recent and fossil corals and
coral reefs in the Florida Keys and in the Bahamas from 1908
to 1915. He is reputed to have published more papers on corals
than any of his predecessors or contemporaries. In 1922 he
also began the study of larger Foraminifera, which subse-
quently became particularly important for stratigraphic dating
in the Pacitic Islands.
During his early days, stratigraphy and paleontology for
correlation were mainstays of the geologic community. The
first world war and the need for petroleum began to focus
attention on rocks as such and sedimentation started to
develop as a discrete discipline. The formation of the National
Research Council in 1915 and its subsequent war efforts,
served as a national focus for comprehensive geological
investigations. Vaughan was member of the NRC, Division
of Geology and Geography, 1919-1926 and chairman of the
Committee on Sedimentation, 1919-1923. This committee laid
the foundation for the classic "Treatise on Sedimentation"
complied by W. H. Twenholfel (1926). Vaughan wrote few
papers directly on sedimentation, but it was his vision which
led this work. He then went on to organize the Committee on
Submarine Configuration and was its chairman, 1992-1932.
Prior to the advent of the second world war, this committee
stimulated what little American investigation there was of the
oceanic sedimentation.
February I, 1924, Vaughan moved to California, though he
continued as a nominal member of the USGS, with the title of
senior geologist (1924-1928) and principal scientist (1928-
1939).
His new position was Director of the Scripps Institution
for Biological Research which shortly became the Institution
of Oceanography. Vaughan made the place into a world leader
in the growing field of ocean investigations, and remained its
head until 1936. Biological work continued, but Vaughan
instituted programs in dynamic and physical oceanography, as
well as chemical and geological oceanography. As a member of
the National Academy of Sciences, in 1927 Vaughan was
appointed to the Committee on Oceanography. In large
measure this committee was responsible for the
{"ounding
of
Woods Hole Oceanographic Institution and the Oceano-
graphic Laboratories of the University of Washington. The
1926 Pan-Pacific Congress formed an International Committee
on Oceanography of the Pacific. Vaughan served as its
chairman for a decade. Thus, a significant portion of our
present understanding of the oceans can be traced to his
infiuenee; his 1924 paper on oceanography is noteworthy.
Simultaneously with his directorship, Vaughan was Professor
of Oceanography; upon his retirement in 1936, he was
appointed professor emeritus.
In retirement, Vaughan returned to the Natural History
Museum in Washington. He continued his studies of Cenozoic
fossil corals and foraminifers until 1947 when pneumonia led
to failing eyesight which curtailed his scientific efforts. "His
interest remained unabated to the end, and his circle of close
friends kept him in close contact with current developments in
his many fields of interest to the day of his death on January
16,
1952" (Wells, 1952, p.l495).
Just as Vaughan fused his combined interests in stratigraphy
and paleontology into formalizing sedimentation at the NRC,
he also sparked studies of the allied discipline of paleoecology.
Indeed drawing a sharp hne between these two may be
difficult. The efforts of the Committee on Ecology and
Paleoecology took longer to erystalize than did that on
Sedimentation. It is sufficient to note that both volumes of
"Treatise on Ecology and Paleoecology" (Geological Society
of Ameriea Memoir, 67) are dedieated to him.
Vaughan's outstanding efforts were reeognized by his peers
and in 1915 he was president of the Geological Society of
America, among other organizations. He was awarded the
Agassiz Medal (1935) and the Mary Clark Thompson Medal
(1945) of the National Academy of Sciences, and the Penrose
Medal (1946) of the Geological Society of America, along with
many honorary memberships, degrees, and other honors. In
the last year of his life, Scripps Institution dedieated a new
building to him in appreciation of his manifold activities.
Ellis L. Yochelson
Bibliography
Thompson, T.C., 1958. Thomas Wayland Vaughan: September 20,
1870-January 16, 1952. Memorial
Volumes
of the National Academy
of Sciences, 32: 398-437 [with photograph and bibliography].
Vaughan, T.W., 1947. Response [to receipt of Penrose medal].
Proceedings
Volume
of the
Geoiogicai
Society of America, Annual Re-
port for
1946,
70-75 [with photograph].
Wells,
J.W., 1952. Memorial—Thomas Wayland Vaughan (1870-
1952).
Bulletin of the American Association of
Petroieum
Geologists,
36:
1495-1497 [photograph].
SEDIMENTS PRODUCED BY IMPACT
653
JOHANNES WALTHER (1860-1937)
of salt deposits in desert basins stands against Ochsenius' bar
theory.
Biographical data
Johannes Walther was one of the pioneers in sedimentology
combining lithological and ecological aspects. He was born
July 20, 1860 in Neustadt/Orla, Germany and died May 4,
1937 in Hofgastein. After his studies of zoology in Jena (PhD
1882) he studied geology more intensely in Leipzig and
Munich. In 1886, he became lecturer in Jena; in 1894 associate
"Haeckel-Professor" and from 1906 until his retirement
1928 he held the post of director of the Geological Institute
in Halle. He received honorary degrees in Perth and
Melbourne (1914!) and in 1928 he was guest professor at the
John Hopkins University; from 1924 to 1931 he served as
president of the Academy "Leopoldina" in Halle, (for
biography and bibliography, see I. Seibold, 1992).
At the time when Walther wrote his principal works,
paleontology, stratigraphy and tectonics played a leading role
in geology. Walther took little interest in them but followed his
line of "dynamic geology". His scientific thinking was deeply
influenced by the famous zoologist Ernst Haeckel, the German
apostle for Darwin whose thoughts thus shaped Walther's
view on geology. He looked at the processes causing the
formation of rocks and not only at their characteristics. He
wanted to revive Lyell's uniformitarianism, but he showed
critically that some phenomena of the past are not occurring
today. On his travels he tried to study as many different
geological conditions as possible. His topics were:
Shallow marine sediments
In 1884, 1885 and 1910, Walther went to the Zoological
Station in Naples to carry out investigations of the recent
seabottom. The 1910 study on the sediments of the "Tauben-
bank", a shoal in the Gulf of Naples, became classic for its
quantitative and experimental approaches to sedimentology
(e.g., ashes of Mt. Vesuvius) and biogeology (e.g., bioturba-
tion).
For instance, he kept crawiisch together with mussels in
an aquarium to find out how long the former would need to
work the shells into detritus.
Reefs
In the Sinai Peninsula (1886), Walther studied recent and fossil
coral reefs, their growth, subsidence, tectonic uplift and
diagenetic processes. He completed his investigations 1888 in
India (see R.N. Ginsburg et al., 1994, for commented
translations).
Deserts
His main desert voyages in the Sinai and Egypt (1886), USA
(1891) and Central Asia (1897) revealed to him the importance
of the eolian erosion, which had hitherto found less recogni-
tion. After a first publication in 1892, his desert book of 1900
went through four editions (English edition by E. Gischler and
K.W. Glennie, 1997) and made him widely known as the
"Desert-Walther". Besides a vast material of observations
about erosion and sedimentation he dealt also with fossil
deserts and the shift of climatic zones. His theory of the origin
Lithogenesis
Finally, his name became worldwide linked with the "Law of
the Facies" originally expressed by A. Gressly (1839) but
explained in detail in volume til ("Lithogenesis of the
present") of Walther's principal work "Einleitung in die
Geologie als historische Wissenschaft" (1893/94). Historical
geology had previously been treated almost exclusively under
its paleontological aspects. He pointed to the priority of
lithological research in connection, of course, with paleonto-
logical Undings. One can regret that he published only few case
studies to illustrate his ideas, tn his time, this inspiring work
received only limitited attention in Anglo-American circles,
though Amadeus Grabau welcomed it with enthusiasm (1913).
Yet Walther's impact on Russian geology (including transla-
tions of his main works) was remarkable.
Since the 1970s his work found renewed attention by the
facies research in the oil industry. Middleton (1973), dealt with
the Law of facies. The recent English translations of his works
will make him better known as a forerunner of modern
biogeology.
Eugen and Use Seibold
Bibliography
Ginsburg, R.N., Gischler, E., and Schlager, W. (eds.), 1994. Johannes
Walther
on Reefs. University of Miami, Geological Milestones II,
140pp.
Gischler, E., and Glennie, K.W. (eds.), 1992. Johannes
Watther:
The
Law of Desert Pormation—Present and Past. University of Miami,
Geological Milestones IV, 273pp.
Grabau, A.W., 1913.
Principles
of Stratigraphy, 2, Dover.
Middleton, G.V., 1973. Johannes Walther's law of the correlation of
facies.
Bulletin ofthe
Geological
Society of America, 84: 979-988.
Seibold, I., 1992. DerWegzurBiogeoiogie—JohannesWaither. Springer.
Walther, J., 1893/94. Einleitung in die Geologie ais historische
Wissenschaft, Volume 3, Jena: Fischer.
SEDIMENTS PRODUCED BY IMPACT
Impact cratering is now recognized to be a very important (if
not the most important) surface-modifying process in the
planetary system. The reason for this becomes clear if one
takes a look at the Moon, or peruses spacecraft images ofthe
surfaces of Mercury, Venus, Mars, the asteroids, and the
moons of the outer gas planets. On Earth, the situation seems
to be different. Lunar-like craters are not an obvious or
common landform, and impact cratering is not described as an
important process in textbooks on terrestrial geology. There
are a number of reasons for this deficiency, as impacts happen
on Earth just as they do on other planets, but endogenic forces
cover or obliterate their traces. This would explain why impact
cratering, on first glance, does not seem to be a particularly
important geological process on Earth and why it has been
ignored by generations of earth scientists.
654
SEDIMENT5 PRODUCED BY IMPACT
One of the most important driving forces for impact
research in the past decades was the study of roeks from the
Cretaceous-Tertiary (K
-T)
houtuiary. At the beginning of this
important development was a serendipitous discovery. Alvarez
and colleagues were trying to use the concentration of the
extraterrestrial tracer element iriditim (!r) as a proxy for the
sedimentation rate of CretaceoLis and Tertiary age limestones
in Italy. It turned out that Ir was not useful as such a tracer
because the abundanees were too low. but they found that the
concentrations of the rare platinum group elements (PGEs;
Ru.
Rh, Pd. Os, Ir. and Pt) and of other siderophile elements
(e.g..
Co, Ni) in the thin clay layer that marks the K-T
boundary are considerably enriched compared to those found
in adjacent Cretaceous and Tertiary rocks. These significant
enrichtnents (up to four orders of magnitude) and the
characteristic interelement ratios were interpreted by Alvarez
['/(//.
(1980) to be the result of
a
large asteroid or comet impact,
which also caused extreme environmental stress. There are
several excellent overviews of this discovery and its implica-
tions for the earth sciences
(e.g..
Glen, 1994; Alvarez, 1997;
Powell,
1998). Subsequently, shock-metatTiorphosed minerals
(quartz, feldspar, etc.) were found in K T boundary layer
samples from all over the world
(e.g..
Bohor
etaf,
1984. 1987),
which confirmed the impact origin ofthe K T boundary layer
and.
thus, that a large-scale impact event was responsible for
the end-Cretaeeous mass extinctions. Details on shock
metamorphism can be found in Features Indicating Impact
and Shock Metamorphism, and other reviews
(e.g.,
Melosh.
1989;
Stoffler and Eangenhorst. 1994; Grieve ci al.. 1996;
Erench,
1998; Montanari and Koeberl. 2000; Koeberl. 2001).
An itnportant result of K-T boundary studies is the
demonstration how the various types of distal ejecta can be
correlated with proxintal ejecta and. eventually, an impact
structure. The determination of the enrichment in the
concentration of the element iridium, a specific marker of
extraterrestrial material, in the sedirnents from the K. T
boundary provided the first direct evidence for a large impact
event at the end of the Cretaceous. This led, in
turn,
to the
theory that the mass extinction of the end of the Cretaceous
was caused by a huge asteroid or comet impact. Studies of the
K T boundary event provided data that helped with the
understanding ofthe origin and signilicance of other, possibly
impact-related,
boundaries and exotic layers in the strati-
graphie record (cf. Montanari and Koeberl, 2000; Peuckcr-
Ehrenbrink and Schniitz. 2001). As such, K-T boundary
research played several important roles: to increase the
visibility and aeeeptance of impact research, and to provide
applications for decades of impact-related research.
An important basic concept is the definition of pro.xititaland
di.\tal
ejecta.
Proximal ejecta are those that are found in the
immediate vicinity of an impact crater, within <5 crater radii
from the rim. In contrast, distal ejecta are those ejecta that
occur at considerable distances from the source crater (>5
crater radii from the crater rim; see, e.g.. Melosh, 1989). Distal
ejeeta commonly consist of (usually fine-grained) roek and
mineral fragments or of glassy spherules or fragments.
Whereas it is often not possible to right away recognize their
connection to a specific impact structure, distal ejecta can act
as a guide to major impact events and even lead to the
discovery of large itnpact structures. During crater formation,
at the end of the excavation stage, about 90 percent of all
material ejected (excavated) from the crater is deposited as
proximal ejecta. This conclusion has been obtained from
impact experiments, simulation calculations, and comparison
with nuclear and chemical explosions. The mass ofthe ejecta
decreases outward; about half of the ejected material can be
found within about one crater radius frotn the
ritn.
At greater
distances the ejeeta blankets become increasingly thinner and
discontinuous. The presence of an atmosphere significantly
influences the ejection and distribution mechanisrns. On an
airless planet, ejecta will be emplaced ballistically. Calculations
and experiments show that not only the total ejecta mass
decreases with increasing distance from the crater, but also the
average particle size. Ejection of material from a crater is a
complicated,
multistage process. Some material is ejected early
on during the contact and cotiipression stage at very high
velocities, but tnost material is ejected during the excavation
phase.
The material seems to be ejected at relatively low angles,
with very little material being thrown out at angles of more
than 45' (Oberbeek, 1975). On Earth (or another planet with
an atmosphere), ejecta near the crater can also be deposited in
a base surge, which is a gravity-driven density current
(composed of air and dust entrained by the fireball) that flows
down (and outward) from the expanding mushroom-shaped
cloud.
Material launched early in the crater formation will still be
in flight after the crater is completely excavated and after the
more massive local ejecta have been deposited to form the
continuous deposits around the crater (Oberbeek, 1975). Eate
during the erater formation (when the shock wave has already
decayed somewhat), material is ejected at lower velocities and
will be deposited close to the crater rim, whereas material that
was ejected early and at higher velocities is deposited at greater
distances from the crater. The low velocity ejecta deposited at
the crater rim often preserve the initial stratigraphic relation-
ship,
which leads to the inverted stratigraphy (the overturned
ilap) at the crater rim (because material from greater depth at
the target is deposited last on the rim). This can well be seen in
the field at, for example, the famous Meteor Crater in Arizona,
in general, material from greater stratigraphic depth at a crater
location is, thus, deposited closer to the crater compared to
distal ejecta, which more commonly consist of the uppermost
stratigraphic layers of the target. The higher energies available
early in the crater formation sequence make it also more likely
that the earliest ejecta are molten or at least strongly shocked,
while the later ejecta may only be slightly shocked or not at all.
Examples of molten distal ejecta include tektites (see below).
On Earth the interaction with the atmosphere complicates
matters somewhat. Early ejecta may also be entrained in the
rapidly expanding fireball and. if the event is large enough,
they will be ejected outside of the atmosphere, leading to a
global distribution. Size sorting will result in larger particles
settling out lirst and liner dust being deposited later.
There are several empirically derived equations that describe
the thickness of ejeeta blankets with distance from the crater
(ef. Melosh. 1989, p. 90). One ofthe most commonly used ones
gives a power law for the ejecta blanket thickness t as a
function of distance r from the crater center:
forr>
R
(Eq.
where R is the radius of the transient eavity and dimensions
are in meters. The exact values for the function of R are
debated,
and Melosh (1989) proposed a more general version
in which the term 0.14/? is replaced by f(R}. a poorly
defined function that depends on a variety of parameters.