Tectonic Setting Discrimination Diagrams

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Sedimentary Geology 17

Research paper

Critical evaluation of six tectonic setting discrimination diagrams

using geochemical data of Neogene sediments from

known tectonic settings

J.S. Armstrong-Altrina,T, Surendra P. Vermaa,b

aCentro de Investigacion en Energıa, Universidad Nacional Autonoma de Mexico, Priv. Xochicalco S/No., Col. Centro,

Apartado Postal 34, Temixco, Morelos 62580, MexicobCIICAp, UAEM, Av. Universidad 1100, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico

Received 26 August 2003; received in revised form 5 February 2005; accepted 18 February 2005

Abstract

An attempt is made to evaluate 6 tectonic setting discrimination diagrams (1 discriminant function and 5 bivariate diagrams)

frequently used by many researchers. For this purpose, an extensive database was established for major element geochemistry

derived from Miocene to Recent sand and sandstone (medium to fine-grained) samples collected from a variety of tectonic

settings including (1) passive margin (PM) setting, (2) active continental margin (ACM) setting, and (3) oceanic island arc

(OIA) setting. Our results suggest that the discrimination fields proposed to infer tectonic settings for six commonly used

discrimination diagrams do not work properly for the analyzed Miocene to Recent sediments. The % success for these diagrams

varies from 0% to about 62%. We therefore recommend that these diagrams be used with prudence.

D 2005 Elsevier B.V. All rights reserved.

Keywords: DSDP; ODP; Sand geochemistry; Mexico; U.S.A.; Papua New Guinea; Japan

1. Introduction

Knowledge of the tectonic setting of an ancient

basin is important for the exploration of petroleum

0037-0738/$ - see front matter D 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.sedgeo.2005.02.004

T Corresponding author. Present address: Centro de Investiga-

ciones en Ciencias de la Tierra, Universidad Autonoma del Estado

de Hidalgo, Ciudad Universitaria, Carretera Pachuca-Tulancingo

km. 4.5, Pachuca, Hidalgo, 42184, Mexico. Tel.: +52

7717172000x6622; fax: +52 7717172133.

E-mail addresses: [email protected],

[email protected] (J.S. Armstrong-Altrin).

and other resources as well as for paleogeography.

Some authors have described the usefulness of major

element geochemistry of sedimentary rocks to infer

tectonic setting based on discrimination diagrams

(e.g., Bhatia, 1983; Roser and Korsch, 1986),

although others have pointed out the difficulties in

using geochemistry to interpret tectonic setting (e.g.,

Van de Kamp and Leake, 1985; Nesbitt and Young,

1989; Milodowski and Zalasiewicz, 1991). The geo-

chemistry of sedimentary rocks is a complex function

of the nature of the source rocks, intensity and

7 (2005) 115–129

J.S. Armstrong-Altrin, S.P. Verma / Sedimentary Geology 177 (2005) 115–129116

duration of weathering, sedimentary recycling, dia-

genesis, and sorting (e.g., Argast and Donnelly, 1987;

McLennan et al., 1993). Furthermore, specific tec-

120o

485

DSDP Leg 65

Pacific Ocean

Active continental marginPassive margin

USA

Mexico

A

40oN

30o

130o 140oE

6000m

582

5841151

583

Korea

KyushuShikoku

Honshu

Hokkaido

Honshu

B5oS

10o

Oceanic island arc

104010411042

ODP Leg 186

DSDP Leg 87

DSDP Leg 87

10o

30oN

Fig. 1. Location map with sample sites. (A) passive and active continental m

island arc setting from Japan; and (C) Oceanic island arc setting from Papua

Leg 96 from Bouma et al. (1986) (number of samples compiled n=58); Ro

n=11); ODP (Ocean Drilling Program) Leg 164 from Paull et al. (2000) (n=

Carranza-Edwards (1995) (star symbol, n=13); Carranza-Edwards et al. (20

a circle, n=3); ODP Leg 205 fromMorris et al. (2003) (n=18); ODP Leg 17

(2003) (n=44); DSDP Leg 87 from Kagami et al. (1986) (n=27); ODP Le

tonic settings do not necessarily produce rocks with

unique geochemical signatures (McLennan et al.,

1990; Bahlburg, 1998). In some instances, sediments

90oW

618619 615

616

DSDP Leg 96

Gulf of MexicoFloridaShelf

ODP Leg 170

ODP Leg 205

ODP Leg 164

New Britain Trench

Trobriand Trough

Solomon Sea

Papua

New Guinea

New Britain

148o 152oE

110811091114

11161115

1118 2000 m

C

Cuba

997

12541255

ODP Leg 180

Oceanic island arc

CentralAmerica

argin settings in U.S.A., Mexico, and Central America; (B) Oceanic

NewGuinea. The data sources are: DSDP (Deep Sea Drilling Project)

sales-Hoz and Carranza-Edwards (1998) (triangle containing a circle,

245); DSDP Leg 65 from Lewis et al. (1983) (n=2); Rosales-Hoz and

01) (plus symbols, n=17); McLennan et al. (1990) (square containing

0 from Kimura et al. (1997) (n=33); ODP Leg 186 from Fujine et al.

g 180 from Robertson and Sharp (2002) (n=53).

J.S. Armstrong-Altrin, S.P. Verma / Sedimentary Geology 177 (2005) 115–129 117

are transported from one tectonic setting into a

sedimentary basin in a different tectonic environment

(McLennan et al., 1990). In spite of these difficulties,

the geochemistry of sedimentary rocks has been used

to infer the tectonic setting of ancient sedimentary

basins (e.g., McCann, 1998; Kasper-Zubillaga et al.,

1999; Burnett and Quirk, 2001; Faundez et al., 2002;

Gu et al., 2002).

Bhatia (1983) proposed major element geochem-

ical criteria to discriminate plate tectonic settings of

sedimentary basins from identification of well-

defined sandstone suites. Roser and Korsch (1986)

proposed tectonic setting discrimination fields cen-

tered primarily on sandstone–mudstone geochemical

data from known tectonic settings. The tie lines

between the sandstone–mudstone geochemical data

were considered to be characteristic of specific

source types.

Several studies have found that the tectonic settings

inferred from these geochemical discrimination dia-

grams are inconsistent with those inferred from plate

tectonic reconstructions of ancient terranes (Valloni

and Maynard, 1981; Maynard et al., 1982; Van de

Kamp and Leake, 1985; Haughton, 1988; Winchester

andMax, 1989; Holail andMoghazi, 1998; Toulkeridis

et al., 1999; Shao et al., 2001). Winchester and Max

(1989) suggested that these discrimination diagrams

should be evaluated by using recent sediments from

known tectonic settings. In this respect, Van de Kamp

and Leake (1985) observed discrepancies in tectonic

settings inferred from the fields proposed by Bhatia

(1983). They recommended using individual analyses

instead of the average values suggested by Bhatia

(1983) to draw conclusions concerning the tectonic

discrimination fields. To our knowledge, no attempt

has yet been made to test these discrimination diagrams

using Neogene sediments with similar grain sizes

(medium to fine-grained) from known tectonic settings.

We attempt to evaluate six commonly used discrim-

ination diagrams by using major element geochemistry

of Miocene to Recent sands and sandstones from (1) the

passive margin (PM) setting of the Gulf of Mexico, (2)

the active continental margin (ACM) setting of the

southwestern coast ofMexico, and (3) the oceanic island

arc (OIA) settings of Japan and Papua NewGuinea (Fig.

1). Since it is difficult to gather a statistically significant

number of sandstone samples of Recent age, we decided

to test these discrimination diagrams by using Miocene

to Recent sands and sandstones from these different

tectonic settings. This is the first systematic attempt to

evaluate the functioning of these diagrams based on a

b% successQ parameter.

2. Sample description

We have established an extensive database on

major element geochemistry of sand and sandstone

samples from different tectonic settings around

Mexico, Central America, and U.S.A. (ACM and

PM; Fig. 1A); Japan (OIA; Fig. 1B); and Papua New

Guinea (OIA; Fig. 1C). The geochemical data and

lithologic descriptions for sand and sandstone (Mio-

cene to Recent; medium to fine-grained) samples are

from: (i) reports of the Deep Sea Drilling Project

(DSDP) Legs 96 (Bouma et al., 1986), 65 (Lewis et

al., 1983), and 87 (Kagami et al., 1986); (ii) Ocean

Drilling Program (ODP) results from Legs 164 (Paull

et al., 2000), 205 (Morris et al., 2003), 170 (Kimura

et al., 1997), 186 (Fujine et al., 2003), and 180

(Robertson and Sharp, 2002); and (iii) other pub-

lished literature on Mexico (McLennan et al., 1990;

Rosales-Hoz and Carranza-Edwards, 1995, 1998;

Carranza-Edwards et al., 2001). The number of

samples and averages compiled for each tectonic

setting, lithology, age, and grain-size details are

given in Table 1. General description about sample

lithology, and locations are provided below.

2.1. Passive margin sediments

The geochemical data for passive margin sediments

were collected from four sites (sites 615, 616, 618, and

619; Table 1) of DSDPLeg 96, drilled in themiddle and

lower Mississippi Fan in the Gulf of Mexico (Fig. 1A;

Pickering and Stow, 1986). These sediments, predom-

inantly deposited during late Wisconsin glacial time,

provide an excellent opportunity to examine the geo-

chemical characteristics of deep-ocean sediments

derived from re-deposited continental sources. Fifty-

eight fine-grained sand samples (Late Pleistocene)

were selected from various sites of Leg 96 (Fig. 1A;

Table 1).

Additional samples are from Ocean Drilling

Program (ODP) Leg 164 drilled on the Blake Ridge

(Paull et al., 2000; Fig. 1A). The Blake Ridge is a

Table 1

Data source and sample descriptions used in this study to evaluate the discrimination diagrams proposed by Bhatia (1983) and Roser and Korsch

(1986)

Tectonic

setting

Location/Leg Site ns na Lithology Grain-size Age Ref. Figure #

PM DSDP 96 615 21 1 sand fine L. Pleistocene (1) Fig. 1A

616 24 1 sand fine

618 7 1 sand fine

619 6 1 sand fine

PM* 18808VN 94830VW – 11 1 sand med Recent (2) Fig. 1A triangle

containing a circle

PM ODP 164 997A 108 4 sand med to fine Plio to Pleist (3) Fig. 1A

997B 137 2 sand med to fine L. Mio to E. Plio

ACM DSDP 65 485 2 1 sst med Quaternary (4) Fig. 1A

ACM* 17830VN 101815VW – 13 1 sand med to fine Recent (5) Fig. 1A star

symbol

ACM* 308N 1128W–108N 858W – 17 1 sand med to fine Quaternary (6) Fig. 1A plus

symbols

ACM Lamont D. Piston core – 3 1 sand med to fine Recent (7) Fig. 1A square

containing a circle

ACM ODP 205 1254A 15 1 sand fine Pleistocene (8) Fig. 1A

1255A 3 1 sand fine Pliocene

ACM ODP 170 1040B 7 1 sand fine Plio to Pleist (9) Fig. 1A

1040C 12 1 sand fine Plio to Pleist

1041A 4 1 sand fine L. Pliocene

1041B 4 1 sand fine L. Mio to E. Plio

1041C 1 1 sst med to fine L. Miocene

1042A 4 1 sand fine L. Mio to L. Plio

1042B 1 1 sand fine L. Miocene

OIA ODP 186 1151C 44 1 sand fine Pleistocene (10) Fig. 1B

OIA DSDP 87 582B 8 1 sand fine Quaternary (11) Fig. 1B

583 4 1 sand fine Quaternary

583F 3 1 sand fine Quaternary

583G 2 1 sand fine Quaternary

584 10 1 sand fine M. to L. Plio

OIA ODP 180 1108 4 1 sst fine L. Plio to Pleist (12) Fig. 1C

1109 13 1 sst fine E. Plio to Pleist

1114 5 1 sst fine L. Plio to Pleist

1115 16 1 sst fine E. Plio to Pleist



PM=Passive margin; ACM=Active Continental Margin; OIA=Oceanic Island Arc; DSDP=Deep Sea Drilling Project; ODP=Ocean Drilling

Program.

*=surface samples; ns=number of samples; na=number of averages taken according to similar tectonic setting, age, and site; L.=Late; M.=Middle;

E.=Early; Mio=Miocene; Plio=Pliocene; Pleist=Pleistocene; med=medium; c=coarse; sst=sandstone; Ref.=reference; Fm.=Formation.

(1)=Bouma et al., 1986; (2)=Rosales-Hoz and Carranza-Edwards, 1998; (3)=Paull et al., 2000; (4)=Lewis et al., 1983; (5)=Rosales-Hoz and

Carranza-Edwards, 1995; (6)=Carranza-Edwards et al., 2001; (7)=McLennan et al., 1990; (8)=Morris et al., 2003; (9)=Kimura et al., 1997;

(10)=Fujine et al., 2003; (11)=Kagami et al., 1986; (12)=Robertson and Sharp, 2002.


continental rise deposit perpendicular to the general

trend of the eastern U.S. continental margin

(Mountain and Tucholke, 1985). Most of the sedi-

ments recovered during Leg 164 accumulated

during the Pliocene and Miocene. The sediments

were deposited by the south-flowing western boun-

dary undercurrent that sweeps southward along the

Atlantic margin (Gradstein and Sheridan, 1983). The

stratigraphic sequence is composed of lithologically

rather homogeneous nannofossil-rich clays and clay-

stones and variable amounts of medium to fine-

grained sand. For this study, two hundred and forty-


five medium to fine-grained sand samples (late

Miocene to Pleistocene) were selected from two

sites (Fig. 1A; Table 1).

In addition, eleven medium-grained surface sand

samples (Recent, triangle containing a circle in Fig.

1A; Rosales-Hoz and Carranza-Edwards, 1998; Table

1) were also included in our compilation.

2.2. Active continental margin sediments

Sediments derived from an active continental

margin setting include DSDP Leg 65 (site 485;

Kurnosov et al., 1983; Fig. 1A). Site 485 (Leg 65)

is located near the continental slope of mainland

Mexico, and is characterized by an extremely high

sedimentation rate of about 625 m/m.y. (Kurnosov

et al., 1983). Several layers of lower Quaternary

sediments were recovered intercalated with basalts

in the depth interval from 160 to 330 m sub-

bottom, including lithified clayey siltstones, sand-

stones, and claystones. Geochemical data for two

sandstones (Quaternary) were selected from this site

(Table 1).

In addition, thirteen medium- to fine-grained sand

samples (Recent) from the Pacific coast of Mexico

(Rosales-Hoz and Carranza-Edwards, 1995; star

symbol in Fig. 1A; Table 1) also were included.

Similarly, major element data for 17 medium- to fine-

grained sand samples (Quaternary) analyzed from the

beaches of the Pacific coast of Mexico (plus symbols

in Fig. 1A) were also included in our compilation

(Carranza-Edwards et al., 2001; Table 1).

The geochemical results of the samples (three

medium- to fine-grained sands of Recent age)

collected from three locations near DSDP Site 485

(McLennan et al., 1990; square containing a circle in

Fig. 1A; Table 1) were also included.

Additional samples are from lower trench slope

of the Costa Rica forearc (Fig. 1A; Table 1) drilled

during ODP Leg 205 (Morris et al., 2003) and ODP

Leg 170 (Kimura et al., 1997). Sites 1254 and 1255

are located (~ 1.5 km and ~ 0.4 km, respectively)

arcward from the deformation front at a water depth

of 4183 m, close to the holes drilled during Leg

170 (Kimura et al., 1997; Fig. 1A). The section

recovered at sites 1254 and 1255 largely comprises

fine sand, massive dark gray claystones, and silty

claystones. For this study, we selected eighteen fine-

grained sand samples (Fig. 1A; Table 1). ODP Leg

170 drilling of the Costa Rica margin retrieved

good quality cores and successfully penetrated the

decollement, providing excellent opportunities for

understanding the processes associated with plate

convergence (Ibaraki, 2000). The general lithology

retrieved includes silty sand, fine-grained sand, silty

claystone, fine-grained sandstone, and sandy silt-

stone. Our data compilation includes thirty-two fine-

grained sand samples and one medium- to fine-

grained sandstone sample from different sites of

ODP Leg 170 (Table 1).

2.3. Oceanic island arc sediments

2.3.1. Japan

The Japan area is probably the best investigated

arc–trench system on the planet. Ocean Drilling

Program (ODP) Leg 186 on the eastern edge of the

forearc basin (site 1151; Fig. 1B), was located at a

water depth of 2182 m in the deep-sea terrace ~ 100

km west of the Japan Trench (Fujine et al., 2003).

At this site, middle Miocene to Holocene sedimen-

tary sections were recovered that were over a

kilometer thick. A sedimentary record spanning the

past 1 m.y. is preserved in the upper 100 m of the

section, in which multiple holes have been cored

(Sacks et al., 2000). The sediments are homoge-

neous, consisting mostly of diatomaceous claystones

and oozes interbedded with sandy layers. The site

also receives a relatively high flux of detrital

materials from riverine input from Honshu Island.

For this study, forty-four fine-grained sand samples

were selected (Table 1).

Previous drilling in the forearc area took place

during the Deep Sea Drilling Project (DSDP) Leg 87

(site 584; Fig. 1B), which transected the Japan

Trench at ~ 39.88N–40.78N (Kagami et al., 1986).

Site 584 is on the landward slope of the Japan

Trench off Sanriku, northeastern Japan. A 954-m

sediment column composed of thin layers of sand

with intercalated mudstone was recovered from this

site (Kagami et al., 1986). Two other sites (582 and

583) situated in the southern Nankai trough, about

135 km southeast of Shikoku were also drilled

during DSDP Leg 87 (Fig. 1B). The general

lithology of stratigraphic section recovered includes

sand, silty sand, silty claystone, hemipelagic mud,

Fig. 2. Critical evaluation of discrimination diagrams of tectonic settings, for the individual samples compiled from passive margin (PM) setting

with discrimination fields after Bhatia (1983) and Roser and Korsch (1986). Fe2O3* represents total Fe expressed as Fe2O3. (A): Fe2O3*+MgO–

TiO2 (Bhatia, 1983); (B): Fe2O3*+MgO–K2O/Na2O (Bhatia, 1983); (C): Fe2O3*+MgO–Al2O3/SiO2 (Bhatia, 1983); (D): Fe2O3*+MgO–Al2O3/

(CaO+Na2O) (Bhatia, 1983); (E): Discriminant function diagram (Bhatia, 1983) and the discriminant functions are: Discriminant Function 1=

(� 0.0447 d SiO2)+(� 0.972 d TiO2)+(0.008 d Al2O3)+(� 0.267 d Fe2O3)+(0.208 d FeO)+(� 3.082 d MnO)+(0.140 d MgO)+(0.195

d CaO)+(0.719 d Na2O)+(� 0.032 d K2O)+(7.510 d P2O5); Discriminant Function 2=(� 0.421 d SiO2)+(1.988 d TiO2)+(� 0.526

d Al2O3)+(� 0.551 d Fe2O3)+(� 1.610 d FeO)+(2.720 d MnO)+(0.881 d MgO)+(� 0.907 d CaO)+(� 0.177 d Na2O)+(� 1.840

d K2O)+(7.244 d P2O5); and (F): SiO2–log(K2O/Na2O) (Roser and Korsch, 1986).


Fig. 3. Critical evaluation of discrimination diagrams of tectonic settings, for the individual samples compiled from active continental margin

(ACM) setting, with discrimination fields after Bhatia (1983) and Roser and Korsch (1986). Fe2O3* represents total Fe expressed as Fe2O3.

Explanation and major element parameters used for panels A–F are the same as in Fig. 2A–F.


Fig. 4. Critical evaluation of discrimination diagrams of tectonic settings, for the individual samples compiled from oceanic island arc (OIA)

setting, with discrimination fields after Bhatia (1983) and Roser and Korsch (1986). Fe2O3* represents total Fe expressed as Fe2O3. Explanation

and major element parameters used for panels A–F are the same as in Fig. 2A–F.



and mudstone. We included major element geo-

chemical data for twenty-seven selected fine-grained

sand samples from Leg 87 sites (Fig. 1B; Table 1).

Fig. 5. Critical evaluation of discrimination diagrams of tectonic settings us

fields after Bhatia (1983) and Roser and Korsch (1986). Fe2O3* represents

similar tectonic setting, age, and site. The number of samples used to calcu

and major element parameters used for panels A–F are the same as in Fig

2.3.2. Papua New Guinea

DuringOceanDrilling Program (ODP) Leg 180 (Fig.

1C) a nearly north–south transect of six holes, with good

ing average values computed from our database, with discrimination

total Fe expressed as Fe2O3. Number of averages taken according to

late one average value is the same as given in Table 1. Explanation

. 2A–F.


recovery, was drilled across theWoodlark Basin near the

Papua New Guinea arc–trench system (Robertson and

Sharp, 2002). The lithology of core sections includes

sandstone, siltstone, claystone, and conglomerate. The

sandstones deposited during this period are composed

dominantly of silicic volcanic detritus, probably derived

from the Amphlett Islands and surrounding areas where

island arc volcanic rocks of Pliocene–Pleistocene age

occur. During this time, terrigenous and metamorphic

detritus derived from the Papua New Guinea mainland

reached theWoodlark rift basin as fine-grained turbiditic

sediments (Sharp and Robertson, 2002). Modal analysis

of middle Miocene to Pleistocene volcaniclastic sands

and sandstones indicates a complex source history for

sand-sized detritus deposited within the basin. Fifty-

three fine-grained sandstone samples were selected from

various sites of ODP Leg 180 (Fig. 1C; Table 1).

Table 2

Critical evaluation of the tectonic setting discrimination diagrams propose

values compiled from localities around U.S.A., Mexico, Central America

This study Inferred tectoni

Figure # Known tectonic

setting

# of

samples

PM AC

# of samples p

Fig. 2A PM 314 0 1

Fig. 2B PM 314 0

Fig. 2C PM 314 5

Fig. 2D PM 314 1

Fig. 2E PM 314 45 19

# of samples p

Fig. 2F PM 314 162 14

# of samples p

Fig. 3A ACM 86 0

Fig. 3B ACM 86 2

Fig. 3C ACM 86 0

Fig. 3D ACM 86 5 1

Fig. 3E ACM 86 71 1

# of samples p

Fig. 3F ACM 86 13 4

# of samples p

Fig. 4A OIA 124 0

Fig. 4B OIA 124 0

Fig. 4C OIA 124 0

Fig. 4D OIA 124 0

Fig. 4E OIA 124 85

# of samples p

Fig. 4F OIA 124 42 4

PM=passive margin; ACM=active continental margin; CIA=continental

The data sources are the same as in Table 1.

The numbers in bold are the total number of samples used for evaluation,

Percent success=100d (number of samples falling in the expected field/ t

3. Results

Bhatia (1983) considered the tectonic setting of

sandstones that he studied to have been (1) oceanic

island arc (OIA), (2) continental island arc (CIA), (3)

active continental margin (ACM), and (4) passive

margin (PM). He compiled the average chemical

compositions of medium- to fine-grained sandstones

(e.g., arkose, greywacke, lithic arenite, and quartz

arenite) and modern sands from various regions of the

world and used these average values (9 average

compositions to represent each of the OIA, CIA, and

PM tectonic settings and 7 for the ACM setting; see

Tables 5 to 8 and Fig. 6 in Bhatia, 1983) to propose

discrimination diagrams. The discriminating parameters

used are (Fe2O3* represents total iron as Fe2O3): (i)

Fe2O3*+MgO and TiO2 (Figs. 2A, 3A, 4A, and 5A); (ii)

d by Bhatia (1983) and Roser and Korsch (1986) using individual

, Japan, and Papua New Guinea

c setting

M CIA OIA Outside

any field

Percent (%)

success

lotting in a given field (defined by Bhatia, 1983)

1 8 239 56 0

8 3 0 303 0

3 0 103 203 1.6

2 3 199 109 0.32

9 68 2 0 14.3

lotting in a given field (defined by Roser and Korsch, 1986)

8 – 4 0 51.6

lotting in a given field (defined by Bhatia (1983)

4 4 48 30 4.6

8 4 4 68 9.3

6 4 42 34 7.0

2 1 7 61 13.9

3 2 0 0 15.1


5 – 28 0 52.3

lotting in a given field (defined by Bhatia, 1983)

2 22 19 81 15.3

3 4 3 114 2.4

2 3 28 91 22.6

2 1 11 110 8.9

3 15 21 0 16.9


3 – 39 0 31.5

island arc; OIA=oceanic island arc.

and also signify that the samples fall in the correct (expected) field.

otal number of samples evaluated for a given tectonic setting).


Fe2O3*+MgO and K2O/Na2O (Figs. 2B, 3B, 4B, and

5B); (iii) Fe2O3*+MgO and Al2O3/SiO2 (Figs. 2C, 3C,

4C, and 5C); and (iv) Fe2O3*+MgO and Al2O3/(CaO+

Na2O) (Figs. 2D, 3D, 4D, and 5D). The geochemical

concept behind these discrimination diagrams (Fig. 6A–

D in Bhatia, 1983) was based on a general decrease in

Fe2O3*+MgO, TiO2, andAl2O3/SiO2 and an increase in

K2O/Na2O and Al2O3/(CaO+Na2O) as the tectonic

setting changes in the sequence OIA-CIA-ACM-PM.

Bhatia (1983) used these diagrams to infer the

tectonic settings of five Palaeozoic sandstone suites of

eastern Australia. He then proposed discriminant

functions (Functions 1 and 2) by using 11 major

element oxides as discriminant variables to construct a

territorial map for the tectonic classification of sand-

stones. Discriminant scores of Functions 1 and 2

(Bhatia, 1983) were calculated from the unstandar-

dized function coefficient and the actual abundance of

element oxides in the average (not on volatile free

basis; Bhatia, 1985; Figs. 2E, 3E, 4E, and 5E).

Table 3

Critical evaluation of the tectonic setting discrimination diagrams proposed

compiled from localities around U.S.A., Mexico, Central America, Japan,

This study Inferred tectonic s

Figure # Known tectonic

setting

# of

averages

PM ACM

# of averages plot

Fig. 5A PM 11 0 0

ACM 13 0 1

OIA 12 0 0

Fig. 5B PM 11 0 0

ACM 13 0 1

OIA 12 0 0

Fig. 5C PM 11 0 1

ACM 13 0 1

OIA 12 0 0

Fig. 5D PM 11 0 0

ACM 13 0 1

OIA 12 0 0

Fig. 5E PM 11 1 6

ACM 13 9 2

OIA 12 9 0

# of averages plot

Fig. 5F PM 11 6 5

ACM 13 1 8

OIA 12 2 4

PM=passive margin; ACM=active continental margin; CIA=continental

The data sources and the number of samples used to calculate one averag

The numbers in bold are the total number of averages used for evaluation,

Percent success=100d (number of averages falling in the expected field/

Roser and Korsch (1986) differentiated the sedi-

ments derived from oceanic island arc (ARC accord-

ing to the original authors), active continental margin

(ACM), and passive continental margin (PM) using

SiO2 and K2O/Na2O ratio (Figs. 2F, 3F, 4F, and 5F).

Roser and Korsch (1986) further stated that associated

with subduction zones, ARC-derived material is

typical of fore-arc, back-arc, and inter-arc basins

formed on oceanic crust, whereas ACM-derived

material occurs in similar settings but on continental

crust. PM sediments are derived from stable con-

tinental areas and deposited in intra-cratonic basins or

on passive continental margins.

Our study to evaluate these discrimination dia-

grams includes geochemical data for 314 samples

from a passive margin setting, 86 samples from an

active continental margin setting, and 124 samples

from an oceanic island arc setting (Tables 1–3). These

compiled samples are sand and sandstones, all of

Neogene age (see Table 1 for grain-size details). We

by Bhatia (1983) and Roser and Korsch (1986) using average values

and Papua New Guinea

etting

CIA OIA Outside any field Percent (%)

success

ting in a given field (defined by Bhatia, 1983)

1 6 4 0

2 9 1 7.7

1 2 9 16.7

0 0 11 0

1 0 11 7.7

0 0 12 0

0 3 7 0

1 9 2 7.7

0 7 5 58.3

0 8 3 0

1 0 11 7.7

0 3 9 25

4 0 0 9.1

1 0 1 15.4

0 3 0 25

ting in a given field (defined by Roser and Korsch, 1986)

– 0 0 54.5

– 4 0 61.5

– 6 0 50

island arc; OIA=oceanic island arc.

e are the same as in Table 1.

and also signify that the averages fall in the correct (expected) field.

total number of averages evaluated for a given tectonic setting).


omitted diatomaceous ooze, silty clay, glauconite,

iron-rich, coarse- and very fine-grained samples from

all DSDP and ODP sites because we wanted to use

only similar rock types and grain sizes to those used

for proposing the discrimination diagrams under

evaluation.

3.1. Evaluation of discrimination diagrams using

individual geochemical data

The actual individual analyses from our database

were used to evaluate the discrimination diagrams as

follows. The results are given in Table 2 and in Fig.

2A–F (for passive margin setting samples), Fig. 3A–F

(for active continental margin setting samples), and

Fig. 4A–F (for oceanic island arc setting samples).

3.1.1. Fe2O3*+MgO–TiO2 plot (Figs. 2A, 3A, and 4A)

In the Fe2O3*+MgO–TiO2 plot (Fig. 2A; Table

2), none of the 314 samples selected from the

passive margin setting plot in the expected field of

PM (~ 0% success), although 11 samples plot in the

ACM field and 8 samples plot in the CIA field.

Most of the samples plot in the OIA field (n=239)

and the remaining 56 samples plot outside of any

field.

With the exception of 4 samples (Fig. 3A; Table 2),

all other samples compiled from the active continental

margin setting (n=86) plot outside the expected field

of ACM (only ~ 5% success).

Nineteen samples out of 124 compiled from the

oceanic island arc setting (Fig. 4A) are correctly

discriminated amounting to ~ 15% success. Others

show a wide scatter: 2 samples plot in ACM field, 22

in the CIA field, and remaining 81 samples outside the

designated fields (Table 2).

3.1.2. Fe2O3*+MgO–K2O/Na2O plot

(Figs. 2B, 3B, and 4B)

In the Fe2O3*+MgO–K2O/Na2O plot (Fig. 2B;

Table 2), none of the samples from passive margin

(n=314) plots in the PM field (~ 0% success) nor in

the OIA; in fact, most of the samples (n=303) fall

outside any pre-defined field of Bhatia (1983). Only 8

samples plot in ACM field and 3 in CIA.

Only 8 out of 86 samples compiled from the active

continental margin setting (Fig. 3B; Table 2) plot in

the correct ACM field, amounting to ~ 9% success.

With the exception of 3 samples, all other samples

(121) from the oceanic island arc setting (Fig. 4B) plot

in other fields (3 samples plot in ACM and 4 in CIA)

and mostly outside any field (114; Table 2), although

they were expected to plot in the OIA field (only ~ 2%

success).

3.1.3. Fe2O3*+MgO–Al2O3/SiO2 plot

(Figs. 2C, 3C, and 4C)

In the Fe2O3*+MgO–Al2O3/SiO2 plot (Fig. 2C;

Table 2), only 5 samples out of 314 plot in the

expected PM field (~ 2% success). Most of the

samples (n=103) plot in the OIA field except 3

samples, which plot in ACM field. The remaining 203

samples plot outside any field.

Eighty-six samples from active continental margin

setting (Fig. 3C) show a wide scatter; six of these

samples plot in the expected ACM field (~ 7%

success; Table 2).

Concerning the oceanic island arc setting (Fig. 4C),

of the 124 samples compiled in our database, 28 plot

in the expected OIA field, 2 in ACM, 3 in CIA, and

91 outside any field, amounting to ~ 23% success

(Table 2).

3.1.4. Fe2O3*+MgO–Al2O3/(CaO+Na2O) plot

(Figs. 2D, 3D, and 4D)

In the Fe2O3*+MgO–Al2O3/(CaO+Na2O) plot

(Fig. 2D; Table 2), only 1 sample out of 314 compiled

from passive margin setting plot in the PM field,

amounting to ~ 0.3% success. The other samples were

wrongly discriminated, e.g. 2 samples plot in ACM

field, 3 in CIA, and 199 in OIA. The remaining 109

samples plot outside of any field.

This plot (Fig. 3D) works with about ~ 14%

success for the 86 samples compiled from the active

continental margin setting (Table 2).

Also, this plot (Fig. 4D) shows ~ 9% success for

the samples from oceanic island arc setting. Except 3

samples most of these plot outside any field (n=110;

Table 2).

3.1.5. Discriminant function diagram

(Figs. 2E, 3E, and 4E)

On the basis of discriminant functions given by

Bhatia (1983), the discriminant functions 1 and 2 are

plotted in Figs. 2E, 3E, and 4E and are listed in Table

2. Forty-five samples out of 314 compiled from


passive margin setting plot in the correct field (~ 14%

success). This diagram fails to discriminate the

remaining samples correctly.

When considering the samples from active con-

tinental margin setting (Fig. 3E), this plot correctly

discriminates 13 samples out of 86 (~ 15% success),

and most of the samples plot in the PM field (n=71;

Table 2).

Among the 124 samples compiled from the oceanic

island arc setting (Fig. 4E), 21 samples plot in the

expected OIA field (~ 17% success), with the

remaining samples plotting mostly in the PM

(n=85) and other fields (Table 2).

3.1.6. SiO2–log(K2O/Na2O) plot (Figs. 2F, 3F, and

4F)

In the SiO2–log(K2O/Na2O) plot (Fig. 2F; Table 2;

Roser and Korsch, 1986), 162 samples out of 314

compiled from the passive margin setting plot in the

expected PM field, amounting to ~ 52% success. The

remaining 148 samples plot in the ACM field except 4

samples, which plot in the OIA.

Forty-five samples out of 86 compiled from active

continental margin setting (Fig. 3F) plot in the

expected ACM field (~ 52% success); others plot in

the PM and OIA fields (Table 2).

Moreover, 39 samples out of 124 compiled from

oceanic island arc setting (Fig. 4F) are correctly

discriminated (~ 32% success; Table 2).

3.2. Evaluation of discrimination diagrams using

average geochemical data

The average values for each site were also used to

evaluate the discrimination diagrams. The average

values were calculated with respect to similar ages

and Leg sites. The number of averages (na) for

different tectonic settings is listed in Table 1. Eleven

average compositions for passive margin, 13 for

active continental margin, and 12 for oceanic island

arc settings were calculated (Table 1) to evaluate the

discrimination diagrams. The results are summarized

in Table 3, as well as in Fig. 5A–F. The % success of

these discrimination diagrams are summarized as

follows.

Fig. 5A (Fe2O3*+MgO–TiO2) shows only ~ 8%

success for the average values from active continental

margin setting, with other setting PM being wrongly

discriminated (~ 0% success). This figure shows ~ 17%

success for the OIA settings. Fig. 5B (Fe2O3*+MgO–

K2O/Na2O), on the other hand, completely fails to infer

the tectonic setting for any of the average values

compiled from PM and OIA settings (~ 0% success)

and ~ 8% success for the ACM setting. Fig. 5C

(Fe2O3*+MgO–Al2O3/SiO2) shows ~ 58% success

for the average values of oceanic island arc, but fails

for PM setting (~ 0% success) and shows only ~ 8%

success for active continental margin setting. Fig. 5D

(Fe2O3*+MgO–Al2O3/(CaO+Na2O)) completely

fails (~ 0% success) for average values compiled

from PM but shows ~ 8% success for ACM setting

and ~ 25% success for OIA setting.

The discriminant functions 1 and 2 (Bhatia,

1983) calculated using average values are plotted

in Fig. 5E (Table 3). This discrimination diagram

works with ~ 15% success for the average values

compiled from active continental margin setting and

~ 9% success for the average values compiled from

passive margin. Twelve average values computed

for OIA margin show ~ 25% success (Table 3).

In SiO2–log(K2O/Na2O) diagram (Fig. 5F; Table 3;

Roser and Korsch, 1986) about 50% of the average

values compiled from oceanic island arc plots in the

correct field (~ 50% success). This plot shows ~ 62%

success for the average values compiled from active

continental margin and ~ 54% success for the average

values compiled from passive margin setting (Table 3).

4. Discussion

A close examination of these diagrams (Figs. 2–5)

shows that the geochemical parameters might be useful

for such discrimination diagrams but the proposed

fields do not seem to correctly work for sand and

sandstone samples compiled in our database. There

may be several reasons for this failure; some of them

are: (1) the discrimination based on average values

(Bhatia, 1983) is not a suitable approach because, as

pointed out by Roser and Korsch (1985) and Van de

Kamp and Leake (1985), this approach eliminates the

possibility of detection of geochemical variations

within a single suite; (2) the average analyses from

different suites used by Bhatia to propose the discrim-

ination fields are not representative of the particular

tectonic settings, for example, he included greywacke


(Pettijohn, 1963) in the CIA setting, but the analyses

that Pettijohn (1963) used to derive his average value

came from different tectonic settings (OIA, CIA, and

PM; e.g., Roser and Korsch, 1985); (3) the distinction

between CIA and ACM settings proposed by Bhatia

(1983, see his Table 9) is not clear, for example, why

bTyee, OregonQ and bFranciscan, CaliforniaQ samples

are classified as CIA whereas bSanta Inez, CaliforniaQand bSalton Basin Sand, CaliforniaQ as ACM; (4) the

method of proposing the discrimination fields in these

diagrams is also not acceptable, e.g., Bhatia (1983)

used 9 average values to draw a field for passive

margin setting but he defined the fields by using only 4

average values (only 44% of the whole data set) for

Fe2O3*+MgO–TiO2 and Fe2O3*+MgO–Al2O3/

(CaO+Na2O) plots and 5 average values (only 56%

of the whole data set) for Fe2O3*+MgO–K2O/Na2O

and Fe2O3*+MgO–Al2O3/SiO2 plots. Similarly, the

approximate field designated for CIA is not the

representative field for samples exclusively from CIA

setting, because in all discrimination diagrams (Figs. 6

to 7 in Bhatia, 1983) the CIA field includes one

average value of PM and ACM settings.

Roser and Korsch’s (1986) SiO2–log(K2O/Na2O)

diagram seems to work somewhat better (~ 32–62%

success; Tables 2 and 3) than Bhatia’s diagrams (0–

58% success). The relatively low % success of the

Roser and Korsch (1986) diagram may be due to the

fact that the database used by these authors may not

be fully representative of worldwide rocks, for

example, they used only California to represent active

continental margin setting of the world.

Therefore, a worldwide representative database

should be established for modern sand and sandstones

and proper statistical methods should be used in the

future to propose new discrimination diagrams that

could result in a higher % success for inferring

tectonic settings of modern and ancient basins.

5. Conclusions

This study suggests that the tectonic setting

discrimination fields proposed to differentiate the

fields in six different discrimination diagrams are not

working properly. Therefore, these diagrams must

not be used to infer tectonic setting of ancient

basins. There is still an urgent need of new and

efficient discrimination diagrams in sedimentary

geochemistry.

Acknowledgements

We are grateful to the reviewers Gary H. Girty and

Salvatore Critelli and Editor Keith A.W. Crook and

Associate Editor Frans Koning for numerous helpful

comments to improve our paper. The first author

(JSA) wishes to express his gratefulness to Otilio

Arturo Acevedo Sandoval and Kinardo Flores, Centro

de Investigaciones en Ciencias de la Tierra, Universi-

dad Autonoma del Estado de Hidalgo (UAEH), and to

SEP-PROMEP (Programa de Mejoramiento del Pro-

fesorado; Grant No: UAEHGO-PTC-280)-CONA-

CYT (Consejo Nacional de Ciencia y Tecnologıa),

Mexico, for financial support.

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