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OCR for page 6
-- 6
Erh; bit _
PROPOSED COt.iPIL~:ON OF LIZ}; DATE OF S;EDI~TTS
W. C. ~nbein
University of Chicago, Chicago, Illinois
Prelirun~ar~r ~n~x~coment of the Sub-Cor~.aittee for the
Compilation of Statistical Data on Sediments
Tntroducti on
~_
The Sub-Comn~ittoo for Lee Co~pilaho:n cf Statistical Into of Sed~-
ments was appointed by Park or D. Tras}<, Chin of the Comrnittes on
Sedimontation of the National Pcso~rch Council, for tho purpose of making
available in convenicat form the qu~titc.tive do.ta on sed~mc~ts which in
now widely scatt˘rod through the geologic literature.
personnel of the Sub-Committee is as follows:
W. M. Cogen, Shell OF Comply, Houston, Te:~s
W. O. ~7(rumbe~n, University of Chicago, Chairman
G. H. Otto, Soil Conservation Service, Pasadena'
A. C. Tester, F~iv~sity of Iowa
The present
Calif Ortega
The Sub-Co~ttee has not met as ~ body, but the Printer has
conferred with Trask and With individual members of the sub-comm~ttee
rogard~ng some of the problems ~,rol~red In the co~ttea's work. ~ a
result of these conforonces it was docidod to start the work of tho
committee on mLoch.~?~.~1 analysis data, both because of the large number
of such c.nalyses av=~1~' arm becmso of the grouter ~ed~to USE which
may be made of s' ze data in the corupax~so:~ and interpretation of
sent. Several practical difficulties arise even here, however, in
the mere task of oc~mpiling the data. Some analyses are Comply, due
usually to techniques which do not include the finer sizes; other o:nalys˘s
were made with so few class contorts that inadequato crate arc a~ra~lablo
for significant sumr~ies; and some papers include over ~1 graphs or
condensed Barrios of statistical Bruce, enrich lordly precut further
analysis of the original size distribution.
In wow of the unsatist`~tory state of many earlier Ed some
contemporary Ales, it socked ad~ris~ble to issue a prey state-
mcnt indicating the ,:E`~:ro ~d scope of the ocmm~tto~'s Work, 'as wo11
as to suggest more suitable procod-~res for th& publication of sedimontar~r
data, to avoid d~ticult~ as in the Rapture.
interested readers an opportunity of expressing their Mews about the
work, as well as to pert the =~-co~ittee itself to crystallize its
Ah? ~ report W~ 1~ als o =~ford
OCR for page 7
Exhibit ~
aims and metho d o ~ at track .
Scone and Purpose cat
~ Co:.nmittee's
Qu~titat~e intonation on sediments includes ~ wide variety of
analytical data. NQt 00~; size distributions Qua sediments, but shape and
roundness distributions, mineralog~c~ studies, pet,~otabric Saudi es, and
the investigation of such mass properties as porosity ard pe~cabil~ty,
are frequently encauntcrod in the litera~ro. It is ob~ou sly beyond
the soopc of any single c~nittoo to attest a compilation of this vast
field. The present committee is cornmi rosined with the Glucose of co~'l-
ing size data pr~r~ly, with ~ possible e=ens~or~ to other characteristics
such as shape and roundness. Parallel work on other aspects of sediments,,
especially heavy ~Li:aerals, may well ocei;py a similar committee it the
present venture i s rmso~bly successful.
.
. . . . . .
Sedirae~tary petrologists who- wish to c~pare their f~nd~x~gs. =~ the
results of earlier studies arc forced to search c,= over-i:acroasing
l~teraturo. Goneral goolo~sts Ache wish to gain a co~reLcnsi~c p3CtUrO
of the characteristics of any group of sediments bind few quantitative data
in tows or rofor˘nce books.
~_. ~. ~
An cutout to offset this d~˘ulty was
made in 1931 by Wont~orth, v~hc published nearly a thousand histc'~;raTn.~ of
common sodimonts. This oxcollont sundry is widely used, a~ Ingests
the desirability of preparing ~ fairly complete compilation of ~11 available
data. ~o NATO task of compute on Is prodigious, inasmuch as shore must
be thousands of mechanical analyses in print. Such an undertak~ir~ can
only be assumed by co-operative Short, and the present ccqr~iaittee has for
its purpose at least aL.preliminary e~lorat~on at the field.
~ The speci:~c purpose of the co~ittee's work is to assemble into
convenient fc~ the availab] e data on mochameal analysis, so that workers
may have an easily accessible summary of the observed characters sties of
sed~m~ts. In the.decade which followed Wentworth's work shore has been
increased emphasis on the statistics troatmondt of tnech~ic~ analysis
data. This wider recognition of tho goonotrica1 meaning of statistics
parameters, =.nd their greater use in the intax~prct~t'-n of the data,
suggests that the co~ttoe's su~=y may co=~niontly be published as
statistical data rather than is ~st<3gr~ or cumulativo cunos.
involved in two cost of publication a3Lso.fca~c~r this solution.
:E?actors
Present plans are accordingly to a=?~nge sed=~n=,ts into various
croup a. such as beach sat ~ dune sand" river gravel , etc., and to compute
the statistical measures of each sample. These data will be summarized
in tables, giving ~11 information regarding; the source of the original
data. For those sedimentary types in Mice; su:eficiont analyses are
available, the tabular data will be ~rther strived in teems of the
general statist3;ca1 cha:mcterist' as of the sects. . Thus any work cr who
wishes to compare his own data on pa:rticul~r sot with previous Priorly
may }.eadily do so by noting whether tho general characteristics of hi ~
~, ~, ~_ _ a,
OCR for page 8
Exhibit A
.,. _
supers Ogre with tho lo~r cavorages obtained from tho overlies data.
Similarly, the characteristics of ancient sediments may be compared with
the data given in the tables to see whether the unknown samples fit Alto
any recognizable geIl~a1 group.
In order to facilitate groping the sediments, it lo preferable to
confine the data in the tables to xc3cont sediments collected from know
on~rom~nonts. The ~nclus~c,~ of ancient sediments Which mar have been
interproted as belonging to particular genetic titles woul d introduce
inferential data into what should be a strictly facial picture.
It is generally recognized that wide variations hong sediments
from the sane environment render it doubtful whether in the average case
it =11 to possible to identify unknots sediments from their size
charactoristics aloe. It is partly for this reason that the corm, ttee
hopes ultimately to extend its work to other properties o* sediments. It
is not unlikely that if Qu~t~tat~ve data on several other ch~.racter~stics
of seas Arch as shape a~ roundness) were av=1 able in summarized
form, ~ given sediment might heave characte:rist~cs common to several types
in terms of size, a~ yot be di~erontiated in respect to some other
characteristic. -4mong Widely dx~orent -sod1montary- rows it is possible
that size chare~te:rist~cs along may be helpful In Pontification.
Chow ~ of Stat! sti Cal T`teasures
. . . . .
Rocent increased emphasis on statistical state of moch~ic~l
analyst delta carries witch it ct roast ho disadvantages. ~e first is
that workors uso ~ ;~ e Amity of statistica1 norametors, 50 that direct
comparison With the Gore of others is frequently difficult. l.~Q~eov=,
there is ~ ~ncreas~x~'g tendency to publish only the statistical ~x~naries,
rather than the complete analytical data, so that oth~ workers cannot
recompute the data into other measures. One solution which suggests
itself ~ s that all workers adopt the same statistical dewees, but such
a solution Is probably premature. Experience in other scimees which
use statistical methods has $~0~ tot 000 cannot predict, ~ pr~ori'
which at several stat' stical approaches is the most significant for a
given set of aeta. IJntil analytic al theories of the factors contrdlli~
the statistical parameters of sed~:acnts are developed, it seers safer to
use several approaches.
Sorae choice must be mad o among the many statistical approaches,
however, to avoid an in:fin~t~ set of p~;~m˘~rs Ace each sample. Within
the past decade stati$tica:1L methods based on co~vontiona1 met hermetical
theory have tondcd to supc~sede mp~r~cal or unconditional methods,
but such specks methods are still rathe3: widely used by European workers.
Altho~g:h no prediction ~ r be made of the exact form of the most s~ti-
cant parameters, e~erimce in other bells has ~;o,~n that those'`neasures
whim integrate Dim the great body of probability theory are generally
OCR for page 9
Inhibit h
~ _
__ ~ __
most ~=ccess~ll:r applied to analysis. Among such measles are the
quartile and moment measures, expressed either in d~mneter terms directly,
. . . .. . .
or as their corresponding geometric and logar~tb~nic transformations. In
addition, certain positions values, such as the modal diameters, axe
useful amok distributions ~chhave more then ore ''max~mum,'t
In general it may be said that sedimentary experience has shown that
geometric and ~ oga-rit1~m; c misuses are more useful ~n interpreting
sediments thy arithmetic mea=res, t,ecause tho former lair the size
tractors in m~ measures as sorting and duress. Arthur, the geometric
am logarithmic measures may be Preformed comparatively easily, so
. . .
that both are readily available for comparative p~OSQSe Peso factors
suggest that the data of sediments be summarized in tams of geometric
and aog,~rithmic measures expressed in both the quartile and moment
notation. This approach incIndas specifically the following measures:
1 ~ Median diameter An mm. Lois averse grain size represents the
middlemost diameter of the distribution.
. . . .
. . .
2) Geometric mean d~neter in ran. lhis average size iB it's
antilog of the ce=~of gravity (first moment) of the
Sari thmi c di stribution-.
3) Modal di~eter ~n mm. .
The modo represents the highest
point of the frequency curve. TYhm several modes are
present they may be rm::re si~it~cant for summarizing the
di stribu~on then aver single mean bad up.
4) "Sorting coefficient, " Go, (flask) of the so . Tha s
is a nea sure of flue geometric spread of the c ontraJ half
of the d' stribut~on.
5) me logarithmic standard donation' 0~' This is based on
the second Comet of the logarithmic distribution, and it
measures the average spread of the distribution.
6) Tho quartile ~kow:}ess (Trask) of the sediment. The log
of this measure to the baso 10 e~esscs the asy~etr~r
of the central :~f of the distribution.
7) The logarithmic skewness of the sediment, Ski, This is
based on the third moment of the logarithmic distribution
,
and it measles the asymmetry of the distribution.
Detai ls of the measures: ~ described above, and suitabI e m ethods for
computing them may be found in Trask (1932) ~ Erumbein (1936), and l;tumbein
~ Petti30hn (1938' chapters 8 am 9~. The graphic deto=aination of
moment measures is described by Otto (19593.
OCR for page 10
- - lo - -
Tllu$tra~ve E~ples
Stat~stica:L Sullies
~ib~t A
_
It Is believed that the following data are essential for the tabulated
summaries:
1) A committee retere3ace number for all sappiest Reich will
serve in subsequent quotations by wetters who use the data.
~,
23 Ihe source of the data, with the original autI~or's reference
numb er .
5) Lee geographic location of the sample.
4) Me nat=e of the sect.
5) The completeness of the original data' in tens of the
Thumbs of size grades used in the analysis, a~ whether or
not a full report of the analysis is given by the author.
6) The method of analysis used.
7) Me several statistical values, together with some indica-
t~on whether they wore given by flee original author or
Were computed by the sub-co~ittee,
Scruples of tables whith she' this ~ntorr~ation are included here to
illustrate the method of presentation.
O my,
lye s ~ exam? es are t ent ative
once due suo-cor.~ee urges ~nrerestod readers to offer criticisms
and suggestions which will ~ the compilations more U$~] . For the
examples three kinds of sediments wero chosen, largely because the data
were a~r~lable in files at i;~˘ University of Chic~o. Table ED-T shows
a number of beach suds, table PS-T includes Alluvia sands, and table
GT-I covers ~ number of Glacial tills.
Etch table has an index number,
end within each table the samples are numbered serially. Thus for
reference purposes one May cite the table and sample numbers. Me
principal items of intonation are given in separate columns, and
under "Mark" are symbols which-Wish data on the less ir~nediately-
used information. ~ bibliography of source material accompanies the
tables; a list of the symbc>Is used Is given below.
OCR for page 11
OCR for page 12
OCR for page 13
OCR for page 14
OCR for page 15
OCR for page 16
OCR for page 17
OCR for page 18
OCR for page 20
Representative terms from entire chapter:
analytical data
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bible
, ~_
As extensions of each table are published, the serial numbers
(column 13 mill be merely continued under each tabular head. The source
of the data, given in colors 2, include the initials and first two letters
of the authorts ~e, the it - r of publication, and the author's original
sample number. Thus J=a-14-65 refers to sample 65 of a paper by Udden
In 1914. The full reference is given In an alphabetical bibliography,
arranged according to the key letters themselves. The third column of
the tabs e indicates the location of the sample. In the United States
it is expressed by state; elsewhere by country.
Condemns 4 to 10 list the statistical parameters of the samples.
Because of the wide variation in methods of analysis, am particularly in
the n~a~bsr of size grades used' it is necessary to distinguish among the
parameters in te~s of the w reliability as numerical data. ~ beach sand
analyzed with three silo grades cmnot Gove ~ close an approbation to
the true paromoters as the same sand analyzed in seven or eight ambler
size grades. In order to include such analyses, however, the following
arbitrary plan is proposed:
a) When the number of size grades used is three, the data
will be given ~Q the first signi~c~t file only.
b) When four to six size grades are used, the data will genoral-
ly be given to two significant figurer.
c) ~n seven or more size grades ~Q USED the data mill
generally be given to three sig~lticant figures.
a) The data Fill never be given to more than three decimal
pla ces.
me te~ "size grade" as used here refers to the anthor's original
data, whether it is expressed in ~ex~tworth Grades, Comrades, or any
other system, and regardless of the frecuency in anger grade. The
quartile data may be read from data based on irregular ct ass intervals,
but th e moment notati on i a; facilitated by regular ,~comotri c interval ~
in the size grades. 3uro~u of Soils grades, for ex~plo, wound have
to be reconverted into an equivalent number of YVer:~worth or ]'2-grades,
depending upon the ori~;ina1 number of grades reported. At present it
sews unlikely chat analyses reported merely as "sand, silt, arm clay"
can be adapted to statistical computations or graphed. this may
intcrfore wash the use of some a=1ysos b`ased on tho hydrometer method,
for example.
The above -ply is subject to the tollowi~ restrictions:
All; bit A
.
_ - 15 -
When the data have "open ends I' (i.e., when an appreciable
p=t of the distribution is not included in the analysis, as
mom t~ne-grained sediments) the number of significant figures
is generally reduced by one. In such instances also the
skewness values will generally not be included because of Thor
fictitious value in such cases.
When the data are polynodal (i.e., in&Ye more than one
maxims In the distributions the sign: ficant figures arc general-
ly xeducod by one, and tho Lowness values are not computed.
In connection mththemodos, the tO1iQ=~= p~codurc is Accosted:
Tho principal rude is dctinod as tic geometric mid-point
of that class harm the largest percontage frequency. Secondary
Rhodes arc considered sigr~hcant if they arc prcs˘nt among
classes having ~o per cont or more of tho distribute on. Open
onds of distributions ~o not considered to bo nodos. Ihe
order of listing the Diodes Is the principal r.~od˘ first and
secondary Modes in order of frequcacy In the modal classes.
Son c secondary modes may occur In the open ends, but these
cannot be detected in such cases.
The "Remarks" column includes a number of it's which may prove of
value for reference Osmoses. These symbol s are arranged in their
positional groups separated by semicolons. The following list
indicates the symbols used in the current examples:
The first position in the column indicates the grade scale
used, and the number of grades, where that ~nfox~ation is giver.
For example, the symbol W-7 means that seven Wer~two~rth grades
were used. The symbols for flee grade scales are:
. . .
A - Atterberg scale
B _ Bureau of Soils scale
:B - Mesh scale (onginooring practice)
- Forth root scale
I - Other scale
~ _ Square root scale
W _ Wentworth scale
reported.
The nm~be~followir~ the grace scale symbol is the number of grades
The second position in the column indicates the con:plote-
ness of the reported data. Here arc i no? udod the following
symbols:
-- 16 --
c
f
H
o
Q
author gives cumulative curios
author Eves complete finale cal data
author gives frequency curves
author gives his togr~s
author gives moment data
author gives nc, analytical details
author's data includes open ends
author gives quartin ~ data
Exhibit ~
The third position in the column indicates the method of
analysis used. The symbols are:
~ - elutriation
h _ hydrometer
m = microscopic method
o = other meted based on Oden theory
p = pipette
s = scat
Classification of Sediments
a..
One of the p~robleans befom the committee is the choice of a Citable
classification of sediments which may be used as ~ basis for the tabular
subparts. A detailed class~ticat~on would sewn desirable so chat
shades of distinction may be-drawn between sediments, but practically
this is impossible at ~resent. Many authors describe their sediments in
broad environmental terms. and too bide a distinction. not based on sound
T.t scat s~cst
as ~ first approach to use a broad classification based .~r~mar~ly on
gonesi`$ and socond~ar~ly on Bean size. X~nhofo] (1939, p. 51) gives
the following classification of on~nrorments:
theory, mail lead to over-~Phas~s of minor differences.
.
Conti nonfatal
Torrestri=1
Des ort
Glacial
Aqueous
Pluv~a~
Pi odr~ont
V£~11oy flat
P3;Luda1
L=~e sweeps
Rivers swamps
Flat-land 5W0I2p 5
tie sweeps
X~nhof o3
=hibit A
-- 17 ~-
cu:;tr~e
Prosh
Salt
Sp clears ~ cave ~
taxed co:~tine:atal and unrig
Li ttoral
3)e] ta
Marginal lagoon
Study
Marine
Neriti c
~thyal
Abyssal
Twenhofel's classification may be considered at ultimate end in the
c~pilaticn of $edim~tary data, but for present purposes it seems neces-
sary to condense the classification somewhat because of the l=ge amount
of data which may not fit Erect sely into the individual groups, owing
either to incomplete data from the authors, or because the samples are
classifi ed on some other basis. As ~ first approach, th~afo:re, the
f o l ~ on ng br eakdown i s su gg e st ad:
Wind deposits
Dano sand
Loes ~
Wired lays
Glacial deposits
Glacial ti 11
Glacial ollfwash
Fluwal sediment s
Channel deposits
Flood plain deposits
Swamp deposits (fresh water)
lacustrine deposits
Fresh filter lakes
S`~]Lt la:
Shore deposits (beaches without distinction)
Delta deposits
-- 18 ~-
.
. . . .
. [agc~onal deposits? including b.ays and estuaries
~ · ,.
. Iv~rino Bottom deposits
. . Moderate depth (~s than 100 fathoms)
Deep water (greater than 100 fathoms)
Icon by ~ ~
I . - _.
. . · · . . .
The list roughly parallels Twenhotel's classification, although some
of the distinctions are less sharp. :Efor exam., beaches usually consist
of sand or coarser material, and as a first appro:~:i~tion it seems safe
to merge the deposits of lake and sea beached Tt sems unlikely that the
difference :between salt a~ fresh water would mate:~ially affect the
physical behavior of sand~or pebbles along ~ beach. It is not sate to
Wage lake and marine Mud, however, because of the possible coagulating
oft'ect of.~ons.~n sm water.. Sir.lilar1y, outrun met elicit Smalley train
and outwash plain deposits) are ~ separate group because Virile fundamentally
they axe;wnning water ds~?osits, sorae wor1i.
Exhibit ~
-
-- 19 --
indi~du-1 sappy es of a ~n sod~=t vary about their okra
mums. For example, it seens likely that the curve of several
hundred dune sands will yield a distribution of means having a
lesser spread than the some number of outwash sands. The relative
homogeneity of various sedim~ta~r Ados cold thus be brought out.
. 3) A worker with ancient sadists may wish to dotermirle whether one
of his samples may be interpreted as a dune mad. By comparers
: the parameters of his scruple with the group averages' it will be
possible to detente whether the ~3ivea~: simple lies within the
rave of values solo by the group. Under some conditions it
my be.possible to apply probability theory directly to this
prob fem.
·4) It Sufficient data on other segmentary characteristics (such as
shape, roundness, mineral content, and the like) are obtained, it
may be possible ~n some instances to identify ancient sodim=ts
in terms of the s=aultancous agreement among several sets of
paramotcrs, prodding any one parameter is not su£fic~rrt for
the purpose.
5) Iho dovelopment of analytical theories of cede trm~partat~on
and deposition may be -tided by such compiled. data. For o:xamplo,
If it wore find their boach sand in general Ad ~ negligible
skis, it would bc possible to simplify the thooretical condi
- ticks :~ecossary for the deposition of dune sad. Moreover, the
absence of a skewness term In the sent would permit the direct
application cuff probability theory and the use: of standout probabil
ity integral tables in hauling the data.
. . . .
An increasing recognition Within :recent years of the variations of
sediments during transport (Russell 1939) suggests that as work progresses
it mar be des1:rabic for cmsidor sits in tows not Any of their
environment of deposition' but as wo11 in terms of their distance =om
source, if the latter call be dote~inod. Thore so~s to be little doubt
that sodimontary cbaractorishcs- vary, more or less systematically with
dist~co from source, Ad such canes Will be merged into the general
group a~rorages of the prosont scheme of classit~cat~o;~. lIowover, once
the data care assembled and available, it ma~y bo possible to red Mine
the original lit Pratt in forms of transportation flaws, =~ to r~
assemble the par~etors into such secac.da^= groups. This compIexity
. . .
probably will not influcacc tho co~.:i ttec ' s Work in the near .tuture .
General Conclusions
On the ass~qptnon that the cornp~lat~ons antic~pc.ted by the
co~ittec's work Viral prove of Ague to geologists, it scams desirable
chit Floors co-opo~to In the ~tu:r˘ c~pilot~on of such data by taking
cognizance of several features Chill greatly reduce the burden of
--- 20 ~
Gore: in~rolvod in comb long the lo tc:raturo for data.
appear to bo in ordor:
33~hi~b~t
r ~ J _ _
... . .
Tho fo~lo;ang sug~cstions
1) iVhenovor possible tho author s'~ould:tncludo Pueblos of his ori
Whit it ~
.~1 ~
-- 21
Why
Erumbein, W. C., (1936) Applicat~on-of logarithmic moments to
si he frequency do stributi ons of s ed~ment s: Joker . - Sed .
Petrol. ~ vol. 6, Up . -35_a=7, 1936.
T`~:rumtein, ~. 0. Id Pettijohr~, :E?. i., (1938) Equal of sedimentary
,, , , _
Petrography, New York, 1938.
Otto, G. H., (1939) A modified logarithmic probability graph for
the interpretation of mechanical analyses of sediments:
Jaw. Sed ~ Pet:co1., vol. 9, pp . 62-76, 1939.
. ~ . .
Rouse, H.,{1939) An analysis of sedun£~t transportation in the light
of fluid turbulence: IT. S. Depth Sari culture, Sedimentation
,
Division, ~ 1939, p. 20.
:Etussel1, P`. :D., (1939) Erects of transportation on sedimentary
particles: Symposium on Roget Scdimonts, Tulsa, 1939,
in. 32-47.
Trask, P. D., (193-2)
Orion n and onvi~~omnc~Lt of source sediments
of Petroleum, Cousin, Texas, 1932.
Twonhofo1, W. E., (~939) Principles of sedimentation, Ned York, 1939*
iVentworth, C. K., (1929) The mechanical conpo,sit~on of sediments
in graphic form: U:niv. Toga Studies in Nat. Bristol Sol. 14,
ear_ ~. . ., ~ . ,
~ 931.
