Middleton G.V. (Ed.) Encyclopedia of Sediments and Sedimentary Rocks

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'KOVhNANCE

545

quarlzose

cralonic sand

typical

toreland-bagin

sand suites

uplifted

subductjon

complexes

Figure P14 A Q,,,FL| plot of Hetrilal modes (modified .if'fcr Dickinson,

I 'IH)!l serves bctler as ,i guide J pruvenance rather ihan serving as a

(.lassiiitation

(e,g,,

as in Dickinson,

19851,

climatic inlluence on bodies of sediments derived principally

from similar source rocks. Point-counting methods in these

studies define roek fragments as multi-mineral sand-sized

grains in which at least two sub-grains are larger than

0,0625 mm or no single phase constitutes >90 percent of the

whole grain.

Ptofiertii'sofrockfht^iments. Rock fragments, if identifiable

tiespite alteration suffered through weathering and diagenesis,

are infallible guides to source rocks. Carbonate rock-fragments

may contain identiilable fossils, which may specilicaliy identify

and date a source rock. Particularly informative are fossils in

coeval carbonate fragments derived from shelfal banks in off-

shelf sediments. Overall, the rarity of good preservation and

differential preservation of different rock-types lead to

incomplete and possibly misleading inferenecs. For example,

quartzite rock fragments are far better preserved than schistose

rock fragments. Inference based solely on grain eounts of roek

fragments derived from a sequence of metamorphosed

sedimentary roeks would underestimate the eontribution from

schistose parent rocks. Based on such arguments, Palomares

and Arribas (1993) developed the concept of Sand Generation

lnde,\

(SGI) quaiitilying the proportions of schistose, gneissic.

and granitoid rock fragments expected to be delivered to

daughter sands from identical climatic and geomorphic units,

A follow-up study on sedimentary source roeks confirms

earlier conclusions.

Properiiciof tninerals. Ail minerals suffer different degrees of

alteration and obliteration through proeesses of weathering,

transportation, deposition, and especially diagenesis. Feldspar,

the most abundant mineral in crystalline basement rocks, is

subordinate to quartz in most sandstones. If preserved, types

of fcldspais. their chemical compostions, twinning habits and

zoning, and their structural states are useful guides to parent

rocks.

However, feldspar grains do not survive abrasion and

transportation well. Fragmentation along cleavage planes and

composition planes (of twinned feldspars) may preserve a

biased population in delrital sands. For example, if twinned

(eldspars from igneous source rocks break along composition

planes during transportation, the detrital population may took

like one from metamorphie souree rocks that contain, in

general, fewer twinned feldspars. Moreover, partial to

complete dissolution and albitization render provenance

determination from feldspars prone to substantially inade-

quate interpretation mueh like that from rock-fragments

alone. Hence, degrees of alteration of feldspars cannot be

assigned unequi\ocally to weathering oi' parent rocks to

estimate climatic conditions prevalent in (he provenance

(e.g.. Folk, 1980; after Krynine and the "Dogma of the

Immaeulate Feldspar"").

Many in search of provenance-related properties have

studied quartz beeause it is the most abundant and the most

durable detrital mineral. Additionally, some believe that

"quartz is an ideal mineral to study because many ot them

could be assigned to a definite type of source roek" (Folk.

1980),

Properties of quartz are related to its formation and

subsequent overprinting by geological events. The genelie

classification of quartz types based on optical petrographie

properties as taught by Krynine (in 1940s) and later eneoded

by Folk (p.69 in Folk. 1980) is still valid (but see Quartz,

Detrital. and eaveats below). Principal criteria are extinction

types (straight or undulose). inclusions (vacuoles; mierolites).

idiomorphism and embayment. and nature of sub-grain

boundaries (straight; crenulatcd; wavy) of polycrystalline

grains. Based on these eriteria six genetie lypes of quartz arc

defined: (a) common plutonic quartz, (b) volcanic quartz, (c)

vein quartz, and metamorphie quartz of three principal types,

i.e.. (d) recrystallized, (e) schistose, and (f) stretched. The last

three are polycrystalline quartz grains and the first three are

presumably all monocrystalline. However, local environment

of quartz generation does nol necessarily eorrelate with speeifie

source roek assemblages. For example, vein quartz may come

from quartz-bearing veins in several kinds of rocks from

several tectonic environments. Additionally, not every detrital

quarlz grain in a sedimentary roek can be unequivocally

assigned to a particular genetic type. Folk devised a pragmatie

empirieal classification of quartz types for delrital grain

generally in the size range between O.I5 mm and 0.35 mm

based on the nature and degree of undulose e,xtinction and the

nature and abundanee of inelusitins. An empirical distribution-

diagram of detrital quartz-types from different source rocks is

constructed to infer ihe provenance of sand-sized quartz grains

in a sedimentary rock (p.67 and p.73 in Folk. 1980). Although

neither Krynine nor Folk published data-tables in their

summary reports, their observations (published in various

journal articles) are based on examining numerous thin

sections from numerous roek samples.

Two commentaries on the above remain important.

Detailed quantitative optical petrographic studies of quartz

in modern sand from known source rocks to test the

empiricism of Krynine and Folk showed that: (1) apparent

undulosity of any grain depends on the erystallographic

orientation of the plane of the thin section and fiat-stage

estimates may be random, i.e., not significant; and (2)

polycrystaliine and strained quartz grains (hence undulose)

are selectively destroyed in transportation relative to those

without strain, i.e.. exhibiting straight extinction. This

invalidates much of the empirical approach of Krynine and

Folk, However, beeause strain in quartz under natural stress is

linite and bending ofthe c-axis is possibly limited to not more

than 30 , one would expect a statistically higher proportion

of undulose quartz grains in detritus from metamorphie

sotn'ce rocks. Based on a combination of universal-stage and

546

PROVENANCE

flat-stage measurements of undulosity and polyerystallinity in

medium sand-sized (0,25 ().50mm) quartz grains from igneous

granitic rocks and various grades of regionally metamor-

phosed rocks, .separate provenance fields can be delineated in a

"diamond diagram" that show some overlap between granitic

and gneissic source rocks (Basu etal.. 1975), In summary,

principles espoused by Krynine and Folk arc validated

although some modification of detail has become necessary.

Additionally, post-lithification deformation of a sedimentary

unit, for example, sueh as those involved in tight folding,

imparts new strain on detrita! quartz grains modifying their

original characteristics.

Quartz, feldspar, carbonate, and clay minerals are light

constittients (/><2.89g/ee) of detrital sediments and usually

add up to about 99 percent of all sedimentary rocks. Heavy

minerals are rare because eommon mafie minerals are

weathered easily and beeause durable heavy minerals

(e.g.. zircon, tourmaline, rutile) are uncommon in parent

rocks.

However, minerals characteristic of certain rock types,

if preserved, are very useful for provenanee determination. For

example, the simple presence of detrital glaucophane in a

sandstone indicates a high-pressure low-temperature bluesehist

source that, hardly any property of detritai quartz or feldspar

could reveal. Some minerals, such as sillinuttiile. kyanite.

rutile. and most detrital garnet are exelusively metamorphie in

origin. Most olivine and pyroxene, especially those rieh in Fe,

are igneous in origin. Magnetite and ilmenite can be either

igneous or metamorphie. However, intergrowth and oxida-

tion-exsoiution textures controlled by erystallographic proper-

ties and mode of origin (observed with reflected light

microscopy or in backscattered electron images) in detrital

magnetite hemalite-ilmenite may distinguish igneous and

metamorphie source rocks,

A recent and still rudimentary development in provenance

studies is to trace the origin of seemingly inorganic material

and structures to its biological parent. Unlike permineralized

body fossils or impressions, some detrital material may be

biogenie but may not have preserved the morphology of its

biologic precursor. If and when the hiologieal origin of sueh

grains is proven and accepted by the community, their study

would move from the realm of provenance to that of

paleontology. For example. Schiebcr (1996) has discovered

remnants of fossilized algal cysts associated with micron-scale

detrital oval quartz grains that have generally been considered

to be clastic quartz in mudstones, but are possibly silica-

repiacement of the cysts, A debate rages over a string of

nanometer-scale cuhedral magnetite crystals of hexaoctahedral

prismatic morphology, which il" exclusively biogenic, would

support the existence of fossils in a Martian meteorite

(Thomas-Keprta elal.. 2000).

In summary, many properties of minerals are characteristic

of their pedigree. In practice, it is not always easy to isolate

such properties but may be used in conjunction with other

variables for very specific identification of source rocks.

Chemical

Weathering and diagenesis may modify the bulk ehemical

composition of detrital sediments rather severely even if

petrographie identities of constituent grains are preserved.

For example, feldspar grains weathered or altered (into elay)

may still be recognized petrographically as feldspars, but

their chemical composition is close to that of clays. A

quart7-cemented fcldspathic sandstone in which detrital

feldspars might have been silicified shows an anomalously

high SiO: content, Albitization of calcic plagiodases changes

the CaO/Na^O ratio ofthe rock; calcite cementation moves the

bulk composition in the opposite direction, K or Ba

metasomatism during diagenesis may fosler a false sense that

the original dcti'itus might have come from a K or Ba-rich

source rock. However, not all K. even in shales with known K-

metasomatism. results from diagenesis. and it is possible to

identify the proportion of detrital and diagenetic K in some

shales. There may also be cases where the bulk chemieal

composition may actually identify the family of a source rock,

even though it can not be resolved petrographically. This is

more likely in sediment that has lost its porosity very early in

diagenesis and in which subsequent ehemical diagenesis has

been minimal. For example, if a silieielastic rock has a large

proportion of diagenetic matrix Uf. pseudomatrix. epimatrix).

its ehemical composition may tell if the precursor parent grains

were volcanic (generally Fe-Mg-rieh) or metamorphie (gen-

erally Ai-rich) rock fragments. Completely argillized rock-

fragments may not be readily identifiable in a thin seetion yet

plug porosity and reduee the ease with which diagenetie fiuids

can permeate a roek. Thus, although weathering, transport,

and depositional processes fractionate elemental abundances

and ratios between souree rocks and detritus in a basin, further

fractionation during diagenesis is minimized in material of low

porosity.

Bulk

rock.-^.

No element is absolutely immobile in the

sedimentary system. Some are less mobile than others (e.g..

Ta, Th, Zr, Se. Co. Ti, V. Nb, Y, Th, some REE) and many

pairs of these elements (e,g,, Th/U. 7r/Y. La/Sm, Ti/Zr)

maintain the same ratio relative to other pairs, as parent rocks

are converted to sediments and sedimentary rocks. Most of

these elements occur in very small quantities in the bulk of

sedimentary rocks; most reside in minor and rare minerals.

especially in heavy minerals (i:/,v,) and in or on clay minerals

{(/.v,).

Beeause the distribution of heavy minerals, especially

those rieh in trace elements and rare earth elements, between

samples of coarser detrital sediments may not be uniform,

most informative data come from siltstones and shales.

Provenance interpretation of TF and REE distribution in

shales and siltstones is now common.

Mud and mudstones or graywackes comprised of significant

argillaceous or argillized rock fragments derived from a large

hinterland, transported by large rivers, and deposited on

platforms or in large turbidite units, have large-seate prove-

nanees. such as the continental shield and the nmuntain chains

beyond. Mudstones and graywaekes with such large prove-

nances, representing different time-slices of Earth-history, and

collecled from aiound the world, have been analyzed to

monitor the temporal changes in the distribution of trace and

rare earth elements in Farth's crust (Taylor and McLennan.

1995) and to model the growth of Earth's crust. The ability to

infer the "big picture" in space and time through studies of

muddy sediments is a consequence of using trace and rare

earth elements (TE and REE) as the principal indicators. A

pronounced inerease in REE content takes place in sediments

across the Archean Proterozoic boundary, indicating a rapid

growth of continental crust at that time.

Distribution and partitioning of TE and RF.F in igneous

and metamorphie proeesses are far better known than in

sedimentary processes. Inverse modeling to back-calculate

the source composition of sediments is not possible yet.

PROVENANCE

547

Additionally, minerals rieh in TF and REE (eg., apatite.

monazite. garnet, zircon) may not be homogeneously dis-

tribLited through different grain size fraetions of sediments;

some may be suseeptible to diagenetic alteration (e.g.. apatite)

and others may be so durable (e.g,, zireon) that they can

recycle not only through many sedimentary cycles but also

through one or more plutonic eyelcs. Therefore, application of

TF and REE studies lo provenance analysis on a regional or a

smaller seale is limited. Interpreting of the ultimate origin of

the crystalline rocks (e.g., depleted or enriched mantle; crustal

melting) from which sediments of a basin have been derived is

more readily done than figuring out the nature and the identity

ofthe immediate source rock.

The grain size effect can be offset by analyzing only the

<2Mm fraction of sediments, uhich however excludes

eontribution of minerats that do not normally alter or

disintegrate into the <2f.im fraction. Diagenetie effects in

the distribution of TE and REE in shales, and by extrapolation

in the <2\im fraction, are now well documented. Never-

theless, studies at smaller scales and in conjunction with

petrographic data are gradually defining and constraining the

use of TE and RFF as provenance indicators (Cullers. 2000).

Beeause TE and REE analyzes can be made on small samples

of <2|.mi fractions, provenance and sediment dispersal

patterns of carbonate sediments may also be traced using the

small amounts of detrital clayey material dispersed in such

rocks.

At present, however. TE and RFF characteristics are

mostly useful for identifying arc-derived sediments including

eolian dust.

.Single niitierals. Detrital sediments are but a mechanical

collection of many single mineral grains each of v\hich may

retain a chemical memory of its origin. The more complex the

eomposition of a mineral the higher is the probability of TE

and RFF substitutions in its crystal strueture, which are

sensitive to modes of formation of the mineral. Thus low

quart7 (SiO^) does not allow much substitution in its lattiee,

but feldspar ((Ca. Na. K, Ba) [AN xSi^.xPn) provides ample

opportunities for substitution. Of particular interest is the

easy ability of F.u" ' to enter the plagioclase strueture relative

to other RFH, The extent of Eu anomaly in a collection of

consanguineous detrital plagioelase determined by instrumen-

tal neutron activation analysis (INAA), or determined o\)

individual detrital grains by ion mieroprobes (SIMS; second-

ary ion mass spectrometer) indicates if their parental erystal-

line rock was derived from a source enriched or depleted in

REE, Mueh less abundant detrital minerals, i.e., the

lie;uy minerals, may have definitive chemical signatures of

iheir origin, which can be determined by eleetron probe

microanalysis or using analytical SEMs (scanning electron

microscopes),

Liiminesivnee. including iaihadohttmnesceme (CL;

q.w)

and

ihennolamine.scence (TL) are physical properties of minerals,

Hoth depend on a combination of the distribution of minor

(and trace) elements and erystallographic properties and it is

rarely possible to separate the physieal from the chemical

causes of luminescence. CL depends on the distribution of

exciter and inhibitei' ions that usually reside in minor to trace

quantities in minerals, and on crystal defects sueh as vacancy

in the oxygen site, CL of detrital silicate grains may be

diagnostie with some unusual spectrum or fabric and may

identify a specific source rock (Seyedolali elal.. 1997), More

importantly. CL is commonly used to identify populations of

zircons for ion microprobe age-dating of single grains. It is

eommon to find igneous eores (CL-bright) of zircon with

metamorphie overgrowths (CL-dull). and to date the core and

overgrowths separately. In addition, specific identification of

CL spectra of particular source roek, for example, marble with

a characteristic stress-history may identity the source-quarry of

an ancient statue (e.g., Lapuente

etaf.

2000); or. identical CL

spectra of two diamonds may identify the jewels to be from a

single raw stone (Sunagawa elal.. 1998). TItermolumine.scence

(TL) can be used, under favorable circumstances to age-date

bodies of mostly Holocene sediments. Relative degrees of

weathering and exposure to the atmospheres affect TL

properties of sediments. Thus. TL is a good guide in

identifying the origin and in tracing movements of coastal

sands,

sand dunes, and loess.

Isotnpic

Stable

isotopes.

Principles and constraints that apply to the use

of TF and RFF in provenance analysis also apply to ratios of

stable isotopes and radioisotopes. Robust stable isotopie

signatures of source rocks are commonly preserved in selected

mineral and rock fragments. Large sand grains seem to be less

attecled by diagenetic proeesses than smaller elay-sized grains

and are the preferred material for analyzes. Ratios of "*O/"'O

and '^C/''C in carbonate detritus, sueh as foraminiferal tests

or nodules in silieielastic sediments, may uniquely identify the

source, isotopic identification of provenanee of iceberg-rafted

detritus, e.g.. for Heinrich events or to track recycling of

carbonate dusts is now routine. Isotopic ratios of carbon in

organic matter are routinely used to trace the source of

petroleum, as are certain organic molecules. Combined

moleeular-isotopic tracing of organic particles is indeed an

extremely discriminating parameter. Oxygen isotopic ratios of

detrital quartz and fluid inclusions therein may indieate their

temperature of formation. For example. ()"^O/"'O of quartz

from very high temperature rhyolilJc tephra and low-tempera-

ture authigenie products are different although both types of

grains may reside in a single body of sediment. Preservation of

high temperature isotopic signature, however, may depend on

the degree and selectivity of diagenetie reactions, which in the

extreme may homogenize all (j"*O/"'O values of detrital

quartz. The uniformity of oxygen isotopic ratios may also

indicate recycling of sedimeniary material such as in Vendian

and Cambrian shales in Spain.

Radioi,sotopes. Preeise radiometric age-dates perhaps con-

nect detrital grains to source roeks most definitively. For

example, from a U Pb eoncordia. a 422 million year old

granite ciast in a Devonian conglomerate is uniquely tied to a

specific Silurian granite the original source-terrain

ot"

which is

identified to be 2445 million years old. Because weathering and

diageneiic alterations may disturb the original isotope

systematics. the precision in dating is often compromised. If

souree roeks had suffered retrograde events then some of the

isotope systems might have been reset complicating the direct

tie-in with daughter sediments. Sedimentary differentiation

may preferentially concentrate certain minerals in differenl size

fractions such that analyzes of size separates produce pseudo-

isochrons. for example ofthe Rb Sr system. Understanding of

radioisotope systematics in sedimentary systems has increased

substantially in the last 25 years and many of these

methodological and natural artifacts have beeome known.

Determination of radioisotope systematics (mostly Sm Nd.

Rb Sr. -"'Ar "'Ar. Pb Pb. and U Th disequilibria) and

548

PROVENANCF

dating Quaternary dust have immensely improved ihe under-

standing of its origin, movement, and its relation to

geomorphologic changes and climatic conditiotis through

time.

For example. Innocent I'lul. (2000) traec the silt fraction

in dccp-se;t sediments to riverine contribution and ihe move-

ment ofthe <

(.1111

fraction lo ocean bottom currents through

Nd-isotopic measuremctils: Grousset iial. (1998) and Walter

elal. (2000) recognize specific dust plumes produced during

glacial and intcrglacial periods and deposited as discrete units

from Sr and Nd isotopie studies; and. Aleinikoff c/^/. (1999)

trace the sources of loess in Colorado using the Pb isotopic

eompositions of K-feldspars.

Ancient lithihed sediments are commonly far too removed

from their sources and their distribution systems {e.g.. rivers,

wind pattern) are mostly obliterated. Therefore, the origin and

modes of movements of ancient sediments arc much more

difficult to trace than those of their Recent counterparts. If

relatively unaltered large polymineralic rock fragments such as

pebbles and boulders arc present, it is possible lo obtain

mineral-separates for determining an isoehron and estimating

the age of the clast for provenance. However, polymineralic

pebbles and boulders are not abundant in the sedimentary

record nor are they necessarily unaltered. Disaggregation.

mineral-separation, and age-dating many pebbles in one

conglomerate may be much too time-consuming and perhaps

not cost-effective. Populations of

detrital mineral if free from

substantial weathering and diagenetic modificiition of the

radioisotope system of interest may produce reliable isochrons

and ages (Faure. 1986). Such populations could be separated

by grain size (e.g.. for feldspars) or color and shape (e.g.. for

zircon) to obtain appropriate isochrons and concordia for

detrital minerals. Improvements in measurement techniques,

such as secondary ion mass spcctrometty (SIMS), laser

ablation microprobe-inductively coupled plasma-mass spcctro-

nictry (LAM-ICP-MS). and thermal ionization mass speetro-

metry (TIMS) now allow age-dating individual detrital grains

(especially zircon). The potential of such analyzes in prove-

nance studies is immense. As SIMS becomes more readily

available, one may expect to obtain age-dates of several

individual grains from all samples oi interest and truly collect

representative and comprehensive range of ages of source

rocks represented In a Formation. Much of current isotopic

investigations of bulk sediments and single grains only provide

an average provenance age of a sedimentary unit. This is

because many detrital grains in clastic sediments arc recycled

and several source rocks commonly contribute to a single

sedimentary unit. However, very ancient age of some detrilal

zircons indicates the existence of an early crusi ofthe earth and

is an important contribtition by

itself.

Fission Hacks in apatite and zircon are robust indicators of

ages of thermal events, which are commonly related to

unroofing and cooling histories. Thus, apart from identifying

source rocks under limited conditions, they provide good

evidence for tectonic events especially about the exhumation

history of an orogen. Fission track data contribute, albeit

somewhat indirectly, to a necessary correction of U-Pb dating

oi detrital zircons that have endured post-deposition heating

and cooling (Carter and Moss. 1999).

Purpose and future

The purpose of any provenance study dictates the choice of

methods and the scope of the investigation. For example.

diverse approaches with varied samples are necessary to

address a segment of the kinematics of Himalayan orogeny

(e.g.. DeCelles etui.. 1998) whereas a single confirmatory test

can identify two fragments of a single diamond (Sunagawa

cl al.. 1998). For most geologieal problems, application of

more than one method decreases the degree of uncertainty in

the results. Part ofthe uncertainty is attributable to not only to

the variability inherent in nature but also to the uncertainties

associated with the methods themselves. It is necessary to be

cognizant of both.

Very few provenance studies have attempted to quantita-

tively estimate the relative contribution of diiTerent rock units

or tectonic units to a body of detrital sediments. For a more

complete paleogeologic reeonstruction o\' the earth through

time,

and estimating rates of relevant geologic processes, such

quantitative analysis may be the future of provenance studies

(Valloni and Basu. 2003).

Abhijit Basu

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15: 1469 1493.

Morton, A.C. Todd,

S,P.. and

Haughton. P.D.W. (eds.). 1991. /JciW-

opmenis

Sedinieimtry Provenance Sniilifs. Geological Society

Special Publication,

57^

370p.

Palomares.

M.. and

Arribas,

J.. 1993.

Modern stream sands IVom

compound crystalline sources; compo.sitioii

and

sand generation

index.

Johnsson,

M.J.. and

Basu.

(eds.I.

Processes

Conlrollbii^

theConijiosilionolClaslicSediments. Cjcological Society

America

Special Paper.

284.

pp.313

322.

Pearce.

T.J,.

Besly.

B.M..

Wray.

D.S.. and

Wriglit.

D.K.. 1999.

Chemostratigraphv:

method

improve inierwei! correlation

barren sequences;

case study using onshore Duckmantian/

Stephanian sequences (West Midlands.

UK.).

Seilt'menkiry Gcol-

of-y. 124:

197 220.

Schieber.

J.. 1996.

Early diagenetic silica deposition

algal cysts

and

spores:

source

sand

black shales.' .lonriial

Sedimeniary

Research.

ee\

I7.V-I83.

Seyedolali.

A..

Krinsley,

D.H.,

Boggs.

S. Jr.

O'Hara.

P.K..

Dypvik.

H,.

and Coles.

G.G.. 1997.

Provenance inierprctation

qtiart/

scanning electron microscope eathodokiminescence labric analysis.

Geolof;y.

25: 787 790,

Sunagawa.

I..

Yasuda.

T.. and

Fukushinia.

II..

199K. Fingerprinting

ol'

two diamonds

cut

IVom

the

same roimh. Gems

und

Gemokn-y.

34:

270

28(1.

Taylor.

S.R.. and

McLennan,

S.M..

1995.

The

geochemical evolution

the

coniinentai crtisl. Reviews of Geophysics.

33: 241 26?.

^homa^-Keprta. K..L.. Ba/yiinski.

O.A,.

Kirschvink. .I.L.. Clemett,

S.J.. McKay. D.S,. Weiilwoith.

S.J..

Vali.

H..

Gibson.

E.K. Jr. and

Romanek,

C.S..

2t)()t). Elongated prismatic magnetite crysials

ALH84()0! carbonate globtiles: potential Martian magnetolossiis.

Geochiinicdcl

Cosoclittiiicu

Aita.

64:

41)49-4081.

Valloni.

R.. and

Basu.

(eds.).

2t)(l3.

Qiianiilaiiye Provenance Slitdies

inllaly. Roma: Memorie Descrittive della

arta Geologicii d'ltalia

(in press).

Walter.

H.J..

Hegner,

E..

Diekmann.

B..

Kuim.

Ci.. and

Rutgers.

L.M.M

2000. Provenanee

and

transport

terrigenous sediment

the

South Atlantic Ocean

and

their relations

glacial

and

inlerglacial cycle.s;

Nd and Sr

isoiopic evidence. Geodiiinieci

Cosmochimica.icui.

64: 3X13

3827.

ZulTa,

G,G.

ted.).

1985.

Provenance

Arctiiies. Dordrechi. Reidel:

NATO-ASI. Series

148: 4()8pp.

Cross-references

rathodoltiininejicence

Climatie Control

Sedimentalion

Extraterrestrial Material

Sedimenls

Eeatiires Indicating Impact

and

Shock Meiamorphism

Feldspars

Sedimentary Rocks

Fluid Inclusions

Heavy Minerals

Isolopic Methods

Sedimentology

Oi'art/. Detrital

Sand

and

Sandstone

Tectonic Controls

Sedimentation

PSEUDONODULES

Definition

and

description

PscLidoiiodttlcs

arc a

.soll-scdimcnt dctbrmalioii structure

comprising rotinded masses

clastic sediment

set in

similar

or tincr-jrrained matri.x.

The

terminology

pseiidonodulcs

and ball-and-pillow strueture ((/.v.)

highly confusing.

It is

proposed here that pseudonodules

can

refer both

individual

rounded niasse.s.

and to

horizons comprising

single

row oi

masses. Pseudonodiile horizons

can be

subdivided into

attached pseudonodules.

which

the

upper suri'aces

of the

pseudonodules

are

level vtith

the

upper surface o\'

the

matrix

(Figure PI5(A).(IJ)).

and

detached pseudonodules that

are

overlain,

well

surrounded

matrix (Figure PI5(F),(G)).

Pseudonodtiies

are

usually eomposed

sand

sandstone.

or occasionally gravel

clastic limestone.

The

matrix

usually mud, mudstone

shale, although

it may be

sandstone,

and

may

differ little

lithology from

the

pseudonodules

(Figure PI5(B)).

which case

the

strtieture

may

resemble

convolute laminiition

((/,

r.). Pseudonodules

are

usiiaHy semi-

circular, oval

kidney-s)iaped. although some

arc

contorted

into zigzags

spirals. They range

length from

a few

centimeters

several meters,

and in

thickness from

a few

centimeters

to a

meter

so. Their outer surfaees

may

preserve

structures such

ripple marks. Lamination within pseudo-

nodules typieally conforms

their outer margins,

but may

become more contorted toward

the

center. Lamination

may be

contorted

in the

matrix. There

may be a

lateral passage from

pseudonodules

""normal" load easts affeeting only

the

base

a bed.

Pseudonodtiies

are

partieularly common

shallow

marine

and

deltaic deposits,

but

oecur

most depositional

environments,

and

similar structures

are

known IVom volea-

nielastic

and

intrusive igneous rocks. Some periglacial involu-

tions (cryoturbation structures) resemble pseudonodtiies.

Although psetidonodtiles resemble chemically formed

di-

agenetie concretions

or the

products

spheroidal ueatheruig.

the presence

detbrmed laminae shows that they form

by Ihe

physical disttirbance

tinconsolidated sediment. They

are a

type

o\'

load structure

((/.

v.).

formed

by the

foundering

sediment into

its

substrate,

but

whereas "'normal"" load casts

affect

the

base

of a

laterally eontinuoiis

bed,

pseudonodtiies

seem

represent more extreme loading that

led

either

to the

detachment

sinking masses from

the

base

bed or to the

puncttiring

of a bed by

rising plumes

buoyant sedimenl.

Historical development

The term pseudonodule

(as

"pseudo-nodule")

was

introduced

by Macar (1948).

who

recognized that contorted laminae

within rounded sandstone masses encased

mudstone

demonstrated that

the

struetures

had

fomied through defor-

mation prior

lithifleatlon. There

are few

signliicant

differences between

the

struetures described

Maear (1948)

and those di:scribed

Smith (I91(>)

and

Potier

and

Pettijohn

(1963)

bail-and-pillow strticttire.

and

most authors have

subsequently considered

the

terms ball structure (Smith. 1916),

pillow-form structure (Smith. 1916), psetidonoduie

pseudo-

nodule (Maear,

1948) and

bail-and-pillow strueture (Potter

and Pettijohn. 1963)

to be

synonymous. Other synonyms that

have been introduced inelude: bal!ed-up structtire. crtmipied

ball, droplets, llow-fold. tlow layer, tlou rolls.

How

structure,

force-aparts, hassock strticttire, intra-stratal Howage. kneaded

sandstone, mammillary strueture, sand rolls, sandstone balls,

sandstone

How.

slump balls, snowball strtielure

and

storm

rollers.

Various criteria have been used

other authors

differentiate between pseudonodules

and

ball-and-pillow

strtieture, ineluding:

the

reeognition

of a

source layer

for

ball-and-pillow strueture;

the

oeeurrenee

psetidonotlules

550

PSFUnONODULES

Attached pseudonodules

Detached pseudonodules

Figure P15 Dflinition and interpretdtiun of pseudonodules. See text for yxpLinjtion. B shows attached pseudonurlules (arrowed) from

Upper Cirboniffrtius Helta mouth bar s^indstones at Amroth, west Wales, tJK. The pseudonodules and their matrix are of similar lithology.

The illustrated seclinn is 1.5 m thick. G shows detached psoudonodules (arrowed) and load casts on the base of a tuff berl from the Ordovician

of Kamsey Island, west Wales, UK. Scale bar (bottom right) is

cm.

a single row, as opposed to vertically stacked masses in

ball-

and-pillow structure: the use of pseudonodule to describe a

single mass and ball-and-pillow strtieture for a horizon of

pseudonodules; or a difference in the inferred origin. What

seems clear is that soft-sediment deforrnation structures com-

prising rounded masses isolated in matrix are sufficiently

distinct from load casts to merit a separate name, and that

sufficient variation exists to define several structures in a

continuum from load casts to pseudonodules and ball-and-

pillow structure. The definitions presented here combine

several of the above criteria in an easily applied, objective

scheme.

Interpretation

Some early workers interpreted psendonodnles as the products

of lateral movements on slopes, but experiments by Kuenen

(1958) demonstrated that most pseudonodules are a type of

load structure

{c/.v.),

in whieh vertical displacements are driven

by variations in gravitational potential energy. Most load

structures develop where denser sediment overlies less dense,

but similar deformation results from the foundering of an

unevenly distributed load

(e.g.,

bedform relief). Deformation

can occur in a system in which potential energy is not at a

minimum if

lower layer becomes liquidized

(i.e.,

undergoes a

temporary reduction in strength). This allows the upper layer

to founder and the lower to rise buoyantly. Several mechan-

isms of liquidization are associated with the expulsion of

exeess

pore

fluid,

and some load structures represent a type of fluid

escape structure

{(/.

v.).

Examples of deformation pathways that can lead to

pseudonodules are shown in Figure P15. These can operate

in eombination, and the end products may be further

eomplicated through the action of lateral forces related to

slopes or currents, giving an asymmetry to the pseudonodules.

The morphology ol'pseudonodules is influenced by the relative

\iscosity of the sediment layers (Anketell

(•/(//.,

1970), and

sinking pseudonodules can deform if they encounter an

obstrtiction, such as non-liquidized sediment.

Methods by which attached pseudonodules can form

include: the puneturing of an upper layer by rising buoyant

plumes (Figure Pt5(C); cf. experiments described by Owen,

1996); the foundering of an unevenly distributed load

(Figure P15(D)); or erosion of load easts (Figure P15(E)).

Detached pseudonodules ean form by: detachment of masses

sinking from the base of an upper layer (Figure P15(H));

complete disruption and foundering of a denser layer (ef

experiments by Kuenen, 1958): continued sinking of an

unevenly distributed load (particularly if the load is denser

than its substrate: e.g., loading of sand ripples into mud as

in Figure PI5(1)): certain cross-sections of load casts

(Figure P15(J)): or isolated slump folds.

'SEUDONOL^LiLES

.551

Significance of pseudonodules

Pseudonodules record the post-depositional disturbance of

sedimenl by loading processes driven by gravitationally

tiiistabie density gradients or by unevenly distributed sediment

load.

Their presence has implications for the physical state of

sediment shortly after deposition, which may relate to

depositional processes (Rijsdijk, 2001).

Several factors may favor the formation of pseudonodules

over load casts confined to the base of a continuous layer.

These include: (a) a driving force of high magnitude

(e.g..

unusually large density contrast): (b) a combination of driving

forces

(e.g.,

sand bedforms on a mud substrate); (c) a lower

layer of very low stretigth

(e.g..

deposition of sand onto

freshly-deposited mud); or (d) prolonged deformation

(e.g..

very thick or fine-grained lower layer, since for some

liquidization meehanisnis the time needed for strength to be

restored is proportional to layer thickness and inversely

proportional to grain-size).

Several liquidi/ation mechanisms arc initiated by the action

of a triggering agent, and pseudonodule horizons have been

used as evidence of paleoseismicity. although load structures

can readily be triggered by other agents such as the rapid

deposition of sediment. The eommon association of pseudo-

nodules with shallow marine deposits may point to storm

aeti\ity as a common trigger.

Bibliography

Allen.

J,R,L.. 19S2

Phy<ieitl BasI

Geraint Owen

Seilinientary Slrucliircs: Their Charmler and

Ankctcil.

J.M., Cegla, J.. ;ind Dztilynski. S.. 1970. On the deforma-

tiotial structures in systems wit)i reversed densily gradients.

.initales di- III Societif Geolo^iqiic (le Polofine. 40: 3 }•{).

Kuenen.

Ph.H..

I95f<. E.xperiments in geology. Tran.'ntctions of the

Gfoloi^iiid Society of Gktsgow. 23: I 28.

Macitr, P.. 194S. Les pseudo-nodules du Famcnnien ct leur origine.

.Annales

de la Sociele Geokifiitjuede lieli-iijiie. 72B: 47 74,

OwL-n.

G.. 1996. Experimental sott-sedinient durormation: structures

tbrmed by the liquefaction of unconsolidated sands and some

ancient examples. .Sedimcniology. 43: 279 29.1,

Potter, P.E.. and Pettijohn, F.J.. 1963, P<deoctirrenis and Basin Analy-

sis. Springer-Verlitg.

Rijsdijk, K.I-"., 2t)t)l. Density-driven deformation structures in

glacigeiiic consolidated diamicts: examples from Traelli y MvvnI.

Cardiganshire, Wiiles. I'K. .lournal of Seditnentary Re.search. 71:

122-135.

Smith.

B.. 1916. Ball or pillow-form structures in sandstones. Geokigi-

calMam-ine.SV. 146 156.

Cross-references

Ball-and-Pillow (Pillow) Structure

Beddinj:

and Internal Structures

Convolute Lamination

Deformation of Sediments

Fluid Escape Siruciures

Liquefaction and Fkndi7alion

Load Structures

QUARTZ, DETRITAL

Detrital quartz forms about 35 percent ofthe mineral grains in

sedimentary rocks, an amount subequalty divided between

sandstones and mudroeks. Because of its abundance its

internal features, grain size, and shape have been the topic of

thousands of journal articles since the 1850s. However, despite

this extraordinary effort the amount of information that can

be obtained from the mineral is not large.

Internal structure

Many investigations of detrital quartz have concerned its

internal structure, particularly the degree of crystal deforma-

tion and the character of the crystals in polycrystalline grains

(pure quartz rock fragments). Results reveal that nearly all

quartz crystals are visibly plastically deformed, a property

described in thin section as undulatory extinction. Polycrystal-

line quartz grains contain crystals that may be elongated or

equant, erystallographieally aligned or not, unimodal or

bimodal in size, and the crystals may have smooth contacts

with their neighbors or be interpenetrating (sutured). Elon-

gated and/or aligned crystals and bimodal crystal size

distribution indicate recrystallization and, therefore, deriva-

tion from a metamorphic rock. Undulatory extinction in

crystals and variable types of crystal contacts are common in

both metamorphic and igneous rocks.

As the total amount of kinetic energy applied to quartz

grains during their sedimentary life increases, polycrystalline

grains and grains with undulatory extinction are preferentially

destroyed (Figure Ql). Polycrystalline grains fracture along

crystal boundaries to produce smaller single crystals of quartz.

Crystals with undulatory extinction are destroyed more easily

than crystals without undulatory extinction so that pure quartz

sandstones are preferentially enriched in nonundulatory

grains. The average pure quartz sandstone contains about 40

percent nonundulatory grains, compared to 15 percent to 20

percent in the igneous and metamorphic rocks from which the

grains were derived.

Quartz crystals in porphyritie volcanic rocks are generally

not plastically deformed and, therefore, are abundant in

volcaniclastic sandstones. But in most sandstones quartz

grains from porphyritie volcanic rocks are trivial in abundance

compared to quartz grains from granites, gneisses, and schists.

Mineral inclusions

Most detrital quartz grains lack mineral inclusions but a wide

variety of these inclusions have been described from detrital

grains. Commonly the inclusions are too small to be identified

with certainty in thin section using only a polarizing

microscope. Any mineral found in igneous and metamorphic

rocks can be found in detrital quartz. Insofar as the mineral is

diagnostic of a specific type of rock it can be useful in

provenance determinations. Although there have been numer-

ous studies of mineral inclusions in crystalline rocks, only one

investigator (Tyler, 1936) has used inclusions in sandstones for

provenance determination. Unfortunately, the sandstone was

the St. Peter (Cambrian, Wisconsin), now known to be

composed largely of recycled grains from a wide variety of

crystalline rocks so that there can be no check on Tyler's

conclusions regarding the accuracy of mineral inclusions as an

indicator of provenance.

Grain size

Detrital quartz grains vary in size from cobbles to clay. Cobble

and pebble size grains are derived largely from either

metaquartzites or hydrothermal veins. Those from hydrother-

mal veins commonly are milky or white in color, an effect

produced by inclusions of water bubbles. As grain size

decreases into the granule and coarse sand sizes, the

proportion of quartz grains derived from granitoid rocks and

gneisses increases. In finer sizes the proportion of quartz grains

from schists increases. In granule and coarse sand sizes the

grains are mostly polycrystalline but in fine sand sizes single

crystals dominate. In silt sizes polycrystalline grains are rare.

QUARTZ, DETRITAL

553

•I 100

•S 80

I I

-I..

o °'

Average ^ I •

- granite • I •

and gneiss

Average

I schist

' '

°8

Less than

40%

quartz

J I

Average rhyolite 0

10 120 30 40 50 60 70 80

X Percetitage of nonundulatory quartz in total quartz

90 100

Figure Ql Relationship between percentage of quartz in crystalline rocks and sandstones and percentage of that quartz that has undulatory

extinction (Blatt and Christie, 1963).

This indicates that chert is not an important source of

quartz silt.

Part of the change in internal character of quartz with

decreasing grain size results from the disintegration of

polycrystalline grains during soil formation, impacts during

stream transport, and high velocity impacts in environments of

deposition such as beaches, marine sand bars, and desert

dunes.

More important as an explanation, however, is the

source rock of most silt size quartz grains. Isotopic evidence

indicates that the bulk of detrital silt size quartz grains are

generated by disintegration of low-grade metamorphic rocks

such as slates, phyllites, and low-grade schists (Figure Q2).

These source rocks contain quartz crystals mostly of silt size,

which are released into the sedimentary environment as the

rocks decay and the grains are eroded. Most silt size detrital

quartz grains are not produced by abrasion of coarser quartz

particles released from granites and gneisses and coarse

grained schists. This fact refiects the hardness of quartz, lack

cleavage,

chemical stability, and the fact that quartz sand is

transported in streams by saltation, in which impacts with

other quartz grains are limited. Apparently, disintegration of

polycrystalline quartz grains produces fine quartz sand but

little silt.

Detrital quartz is rare in sizes smaller than about two

micrometers.

Depositional environment

Detrital quartz tends to be more abundant in some deposi-

tional environments than in others. This reflects the fact that

feldspars and polymineralic rock fragments are more easily

disintegrated than quartz in environments of high kinetic

energy. Hence, beaciies, marine sand bars, and desert dunes

tend to be richer in quartz than are rivers and alluvial fans. But

exceptions are common. The amount of quartz in a

sedimentary rock is not a reliable environmental indicator.

^°'^20

—

•—

- 1

t2.5

—

35.2

28.1

23.9

\t9.i

12.5

9.3

r/a,

19.

LLJ

-o

(Yeh and Souin, 19771

dept*

iing

19.6

t&l

27.4

25.7

22.8

depth

179 I

ept

•o

ing

Figure Q2 Range in

b^'^O

values in quartz from sedimentary rocks and

various types of coarse grained source rocks. Quartz in the few slates

and phyllites that have been analyzed (not shown) have b^^O values

that average 19 (Blatt, 1987).

Quartz cobbles and pebbles travel in streams by rolling and

hence are nearly always rounded. The degree of roundness of

quartz sand has been used as an indicator of depositional

environment but this also is not reliable. Quartz sand grains

554

QUARTZ, DETRITAL

can be rounded only in environments of high kinetic energy

(not in rivers) but such rounded grains can be subsequently

incorporated into environments of low kinetic energy follow-

ing burial, uplift, and erosion. Recycling is a common

phenomenon but the percentage of recycled quartz in

sedimentary rocks is unknown. Probably it is quite liigh.

The percentage and grain size of detrital quartz have been

used as an indicator of distance from shore in shallow marine

mudroeks. As distance increases, quartz grain size decreases,

as does the quartz/clay mineral ratio. Alignment of elongate

quartz grains can reveal dominant current directions but

directions are more easily deciphered using cross-bedding or

other sedimentary structures.

Harvey Blatt

Bibliography

Blatt,

H.,

1963. Original characteristics

clastic quartz grains. Jour-

nalof Sedimentary

Petrology,

37: 401-424.

Blatt,

H.,

1987. Oxygen isotopes

and the

origin

quartz. Journalof

Sedimentary

Petrology,

57;

373-377.

Blatt, H.,

and

Christie, J.M., 1963. Undulatory extinction

quartz

igneous

and

metamorphic rocks

and its

significance

provenance

studies

sedimentary rocks. Journal of Sedimentary

Petrology,

33,

559-579.

Blatt,

H., and

Schultz,

D.J., 1976.

Size distribution

quartz

mudroeks. Sedimentotogy, 23:

pp.

857-866.

Blatt,

H., and

Totten, M.W., 1981. Detrital quartz

as an

indicator

distance from shore

marine mudroeks. Journal

Sedimentary

Petrology, 51: 1259-1266.

Chandler,

F.W., 1988.

Quartz arenites: review

and

interpretation.

Sedimentary Geology, 58: 105-126.

Gotze,

J., and

Zimmerle,

W.,

2000. QuartiandSilicaasGuidestoPro-

venance in Sediments and Sedimentary Rocks. Stuttgart:

Schwei-

zerbart'sche Verlagsbuchhandlung,

91pp.

Kennedy,

S.K., and

Arikan,

F.,

1990. Spalled quartz overgrowths

a potential source

silt. Journal

Sedimentary Petrology,

60:

38-44.

Lechak,

P., and

Ferrell,

R.E. Jr.,

1988. Morphologies

suspended

clay-sized quartz particles

in the

Mississippi River

and

their

relation

sedimentary sources. Geology, 16: 334-336.

Suttner,

L.J.,

Basu,

A., and

Mack,

G.H.,

1981. Climate

and the

origin

quartz arenites. Journal

Sedimentary Petrology,

51:

1235-1246.

Suttner,

L.J., and

Leininger,

R.K., 1972.

Comparison

of the

trace

element content

plutonic, volcanic,

and

metamorphic quartz

from southwestern Montana. Geological Society of America Bulletin,

83:

1855-1862.

Tyler,

S.A., 1936.

Heavy minerals

of the St.

Peter Sandstone

Wisconsin. Journatof Sedimentary Petrology,

55-84.

Cross-references

Classification

Sediments

and

Sedimentary Rocks

Diagenesis

Isotopic Methods

Sedimentology

Mudroeks

Provenance

Sands, Gravels,

and

their Lithified Equivalents

Weathering, Soils,

and

Paleosols