mineralogical and geochemical indicators of the polygenetic nature of terra rossa in istria, croatia

Ž .Geoderma 91 1999 125–150

Mineralogical and geochemical indicators of thepolygenetic nature of terra rossa in Istria, Croatia

G. Durn a,), F. Ottner b,1, D. Slovenec a

a UniÕersity of Zagreb, Faculty of Mining, Geology and Petroleum engineering, PierottijeÕa 6,HR-10000 Zagreb, Croatia

b UniÕersity of Bodenkultur Vienna, Department of Applied Geology, Peter Jordan Strasse 70,A-1190 Vienna, Austria

Received 11 March 1997; accepted 23 November 1998

Abstract

Terra rossa in Istria is situated on the Jurassic–Cretaceous–Paleogene carbonate plain and isŽconsidered a polygenetic reddish soil which bears typical terra rossa Fe-oxide characteristics e.g.,

.Fe and Fe rFe . The difference in particle size, mineralogy and geochemistry observed betweend d t

terra rossa and the insoluble residue of limestones and dolomites clearly indicates that theadditions of external materials might have diminished the influence of insoluble residue oflimestones and dolomites as the primary parent material of terra rossa in Istria. Terra rossa is clay

Žand silty clay composed of quartz, plagioclase, K-feldspar, micaceous clay minerals illitic. Ž .material and mica , kaolinites Kl and Kl , chlorite, vermiculite, low-charge-vermiculite orD

Ž .high-charge smectite, mixed-layer clay minerals other than illitic material , hematite, goethite andXRD-amorphous inorganic compound. Calcite, dolomite and boehmite are sporadically presentand are of local importance. Kaolinites and illitic material are dominant clay mineral phases in theclay fraction of all terra rossa from Istria. Kaolinite which does not form intercalation compounds

Ž .with dimethylsulfoxide DMSO is the dominant mineral phase in fine clay and is consideredpredominantly authigenic rather then inherited from parent materials. Neither the content andparticle size distribution nor the bulk and clay mineralogy of the insoluble residue of limestoneand dolomite support development of terra rossa entirely by dissolution of carbonate rock. If terrarossa has developed only from the insoluble residue of limestone and dolomite, its clay content,due to weathering should be higher than that in the insoluble residues which is not the case.Plagioclase was found only in one insoluble residue while all terra rossa samples contain this

) Corresponding author. Tel.: q385-1-4836067; Fax: q385-1-4836057; E-mail:[email protected]

1 Tel.: q43-1-47654-5407; Fax: q43-1-47654-5449; E-mail: [email protected]

0016-7061r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved.Ž .PII: S0016-7061 98 00130-X

( )G. Durn et al.rGeoderma 91 1999 125–150126

mineral. Moreover, insoluble residues do not contain vermiculite which was observed in smallŽ . Ž .amounts in clay fraction of all terra rossa samples. Na OrK O =100, ZrrNb and ZrrTi =2 2

1000 ratios in the majority of terra rossa samples are much higher than in the insoluble residue oflimestones and dolomites which also supports external material influence in the genesis of terrarossa. Materials other than the insoluble residue of limestones and dolomites which might havecontributed to terra rossa are loess sediments, whose deposition was very important recurrentprocess in Istria probably since the early Middle Pleistocene, and flysch sediments which extendedmuch more southwards from its present position. Analyses performed indicate that both loessolder than that of the Upper Pleistocene age and flysch might have contributed in the genesis ofterra rossa. q 1999 Elsevier Science B.V. All rights reserved.

Ž .Keywords: terra rossa; parent materials; clay mineralogy; geochemical ratios; polygenetic nature

1. Introduction

Terra rossa is a reddish clayey to silty–clayey soil especially widespread inthe Mediterranean region, which covers limestone and dolomite in the form ofdiscontinuous layer ranging in thickness from a few centimetres to several

Ž .meters. Red colour 5YR to 10R Munsell hues is diagnostic feature of terrarossa and is the result of rubification, i.e., formation of hematite.

Ž .In Soil Taxonomy Soil Survey Staff, 1975 terra rossa is classified asŽ . Ž .Alfisols Haploxeralfs or Rhodoxeralfs , Ultisols, Inceptisols Xerochrepts andŽ . Ž .Mollisols Argixerolls or Haploxerolls . According to FAO system FAO, 1974

Ž . Žterra rossa is recognised as Luvisols Chromic Luvisols , Phaeozems Haplic.Phaeozems or Luvic Phaeozems and Cambisols. The Croatian classification

ˇŽ .puts terra rossa in the class of Cambic soils Skoric, 1986 .´The nature and relationship of terra rossa to underlying carbonates is a

long-standing problem which has resulted in different opinions with respect tothe parent material and origin of terra rossa. The most widely accepted theory isthat terra rossa has developed from the insoluble residue of carbonate rocksŽTucan, 1912; Kispatic, 1912; Kubiena, 1953; Maric, 1964; Plaster and Sher-´ ˇ ´ ¨ ´

ˇwood, 1971; Skoric, 1979, 1987; Bronger et al., 1983; Moresi and Mongelli,´.1988 . However, other authors have emphasised that terra rossa could not have

been formed exclusively from the insoluble residue of carbonate rocks. SoilŽ .geomorphic studies made by Olson et al. 1980 in southern Indiana, USA,

indicate that the terra rossa is mainly debris, derived from erosion of higherlying clastic sedimentary rocks, transported and deposited on pediments cut into

Ž .lower lying limestone. Rapp 1984 suggested that the terra rossa soils ofSouthern Europe might be wind-borne material from Africa. Eolian contribu-tions have also been recognised due to the similarities in clay mineralogy

ˇŽ . ŽBalagh and Runge, 1970 , similarities in heavy mineral fraction Sinkovec,.1974b; Durn et al., 1992; Durn and Aljinovic, 1995 , particle size distribution´

Ž .Macleod, 1980 and the divergence of oxygen isotopic ratios of associated fine

( )G. Durn et al.rGeoderma 91 1999 125–150 127

Ž .quartz Jackson et al., 1982 . Given the fact that the ‘cryptogamic imprint’ onthe rocks can be detected on the rock faces under the present soil surface, Danin

Ž .et al. 1983 concluded that the principal contributor to the formation of theupper soil layer of terra rossa in the studied area in Israel is the eolian source.

Previous statements imply polygenetic nature of terra rossa. In some isolatedkarst terrain it may have formed exclusively from insoluble residue of limestoneand dolomite but much more often it comprises a span of parent materials whichderived on carbonate terrain via different transport mechanisms. For example,

Ž .Yaalon 1997 concluded that practically all terrestrial soils in the Mediterraneanregion were influenced by the addition of eolian dust. Erosion and depositionprocesses which are superimposed on karst terrains and induced both by climaticchanges and tectonic movements might be responsible for thick colluvial terrarossa accumulations in uvala and dolina type of karst depressions. In this casewe can consider terra rossa as a pedo-sedimentary complex.

Ž .Boero and Schwertmann 1989 concluded that as long as the generalpedoenvironment remains essentially suitable for the formation of terra rossa itis of little relevance for the process of rubification whether the primary Fesources are autochthonous or allochthonous.

The mineral composition of terra rossa in the Mediterranean area may be veryŽ .different. Macleod 1980 found that the clay fraction of terra rossa from Epirus

Ž .Greece consists of kaolinite, micaceous minerals, vermiculite, quartz andŽ .Fe-oxides. According to Moresi and Mongelli 1988 terra rossa from Apulia

Ž .Italy is composed of kaolinite, illite, Fe-oxides, quartz, feldspar, mica, Al-oxides and hydroxides, and Ti-oxides. The clay fraction of terra rossa fromSpain contains kaolinite, illite, vermiculite, montmorillonite, interstratified clay

Ž .minerals and goethite Garcia-Gonzales and Recio, 1988 . Chief constituents ofclay fraction of terra rossa from Sardinia are illite and kaolinite, while hydroxy-

Ž .interlayered vermiculite is the dominant phase in NE Italy Boero et al., 1992 .Ž .Bronger and Bruhn-Lobin 1997 found considerable to extensive formation of

clay minerals, mainly kaolinites in terra rossa from NW Morocco.Red soil on hard carbonatic rock commonly referred as terra rossa is the most

extensive soil type in Istria and was considered polygenetic paleosol or pedo-Ž .sedimentary colluvial complex Durn, 1996 . In this paper terra rossa refers to

Ž .reddish soils 5YR to 10R dry Munsell colors overlying hard and permeablelimestone and dolomite.

Additions of external materials might have strongly diminished the influenceof insoluble residue of limestone and dolomite as the primary parent material ofterra rossa in Istria. Namely, since the early Middle Pleistocene on, loesssedimentation was very important recurrent process in Northern and Central

Ž .Italy which also effected Istria and Dalmatian Archipelago Cremaschi, 1990a .The aim of this paper is to show to what extent mineral, especially clay

mineral assemblage and chemical composition can be used as indicators of thepolygenetic nature of terra rossa in Istria.


2. Study area

The Istrian peninsula is composed of Upper Jurassic and Cretaceous shallowwater carbonate-rocks, Paleogene carbonate and clastic rocks, and Neogene and

Ž .Quaternary sediments Fig. 1 . It belongs to the NW part of the AdriaticŽ . Ž .Carbonate platform. Velic et al. 1995 distinguish: 1 Jurassic–Cretaceous–´

Ž .Paleogene carbonate plain of southern and western Istria, 2 Cretaceous–Paleogene carbonate-clastic zone characterised by overthrusting structures in

Ž .eastern and north-eastern Istria, and 3 Paleogene flysch basin of central Istria.According to the same authors, four sedimentary units or megasequencesbounded by important emersions of different duration can be separated in Istria:Ž . Ž . Ž .1 Bathonian–Lower Kimmeridgian, 2 Upper Tithonian–Upper Aptian, 3

Ž .Upper Albian–Lower Campanian, and 4 Paleocene–Eocene. The Bathonian–Lower Kimmeridgian megasequence is characterised dominantly by different

ŽFig. 1. Simplified geological map of Istria modified from Geological map of SFRJ 1:500000,. Ž . Ž . Ž . Ž .1970 . 1 Upper Jurassic limestones and dolomites . 2 Cretaceous limestones and dolomites .

Ž . Ž . Ž . Ž . Ž . Ž . Ž .3 Paleocene–Eocene mainly limestones . 4 Eocene flysch . 5 Quaternary loess . 6 FaultsŽ . Ž . Ž .normal and reverse . 7 Location of rock samples limestone, dolomite, loess and flysch .


types of shallow-water limestones and a regressive trend which is expressed bythe appearance of regressive breccia and clayey bauxite in the uppermost part of

Ž .the unit Velic and Tisljar, 1988 . The main constituent of bauxite is boehmite´ ˇˇŽ .Sinkovec, 1974a . The Upper Tithonian–Upper Aptian megasequence is domi-

nated by carbonates deposited in peritidal environment with subordinated emer-sional breccia, early- and late-diagenetic dolomites and grainstones. UpperAptian deposits are characterised by relatively rapid shallowing which resultedin extensive emersion during the late Aptian and early Albian. Shallow-waterplatform carbonate system was re-established at the beginning of late Albian.The Upper Albian–Lower Campanian megasequence is characterised with veryvariable facies successions. As the result of Laramian movements which startedin the late Senonian, the uplifted carbonate rocks were exposed to weatheringand a network of deeply karstified and intensely eroded landforms opened along

Ž .extension joints Marincic and Maticec, 1991 . Due to subaerial exposure,ˇ ´ ˇ ´bauxites of dominantly boehmite composition were formed, which fill a tectoni-cally controlled relief of shallow-water carbonates of Albian to Senonian in ageˇŽ .Sinkovec et al., 1994 . The Paleocene–Eocene unit which unconformably

overlies paleorelief developed on carbonate rocks is variable, both in a lateraland vertical sense. It consists of carbonate and clastic rocks and can, in general,be divided into Liburnian deposits, Foraminifera limestones, Transitional bedsand Flysch. The most widespread sediments in this unit are flysch depositswhich are characterised by an alternation of marl and carbonate sandstone beds.

Since that time the surface has been affected by karst processes and weather-ing which has led to the development of both surficial and underground features.Different types of sediments, polygenetic paleosols and soils have been formed.

ˇThe oldest Quaternary sediments were discovered in Sandalja cave near Pulaand are represented by red breccia with fauna remains of Early Pleistocene ageŽ .Malez, 1981 . Climatic and biotic factors have changed during Late Tertiaryand Quaternary but the pedoenvironment on hard carbonate rocks of Jurassic–Cretaceous–Paleogene carbonate plain of southern and western Istria generally

Ž .remained suitable for rubification after Boero and Schwertmann, 1989 . As aresult of this process, paleosols formed on hard and permeable limestone anddolomite have characteristic reddish color. Terra rossa is found on the Jurassic–

ŽCretaceous–Paleogene carbonate plain of southern and western Istria Figs. 1.and 2 . It fills cracks and sinkholes, and forms a discontinuous surface layer up

Ž .to 2.5 m thick. Thick up to 14 m accumulations of terra rossa like material arefound in karst depressions in the form of pedo-sedimentary colluvial complexes.The mechanism responsible for the origin of this accumulations was at leastpartly induced by both vertical and horizontal neotectonic movements which, invariable intensities and directions, occurred from the Pliocene until recent times

Ž . Ž .in the region Prelogovic et al., 1981 . Benac and Durn 1997 showed the´importance of tectonic activity during the Quaternary on the recent position andthickness of terra rossa in the Kvarner area.


ˇŽ . Ž .Fig. 2. Distribution of terra rossa in Istria modified after Skoric, 1987 . 1 Terra rossa,´Ž . Ž .calcocambiosol, eutric cambiosol, rigosol from terra rossa area of terra rossa)70% . 2 Terra

Ž . Ž .rossa, calcocambiosol, eutric cambiosol area of terra rossa is 50–70% . 3 Eutric cambisol onŽ . Ž .loess, luvisol on loess, rigosol from luvic and eutric cambiosol 40:30:30 . 4 Location of terra

rossa samples.

ŽThe Upper Pleistocene loess is situated only in the southern part Premantura. Ž .and Mrlera and in the north-western part of Istria Fig. 1 . In the latter, it is up

to 4-m thick and covers terra rossa. When thinner, loess is not easily recognis-ˇŽ .able because it may be mixed with terra rossa Skoric, 1979; Durn, 1996 .´

3. Materials and methods

Forty two terra rossa samples from B horizons on limestone and dolomite ofŽ .Jurassic and Cretaceous age were taken at 16 localities in Istria Fig. 2 .

Samples of the limestone or the dolomite were collected under 6 terra rossaŽ .profiles and at 3 distant sites Fig. 1 . Although terra rossa may not longer be

found in its original positions, the hard carbonate rock situated immediatelybeneath terra rossa, should have a genetic relationship because soils are sub-


Ž . Ž .jected to rubification Boero and Schwertmann, 1989 . Three flysch marl andŽ .five loess samples were also taken as reference Fig. 1 .

Terra rossa samples were air-dried after crushing the aggregates by hand andsieved through a 2 mm sieve. Particle size analysis was determined on the -2mm fraction after dispersion in water and ultrasonic treatment. Fractions )45mm were obtained by wet sieving. The -2 mm and 2–10 mm fractions wereseparated by sedimentation in cylinders and quantitatively obtained after theappropriate settling time. What remained in cylinders was calculated as the10–45 mm fraction.

Rock samples of limestone, dolomite and marl were carefully crushed to passthrough a 4 mm sieve. To remove carbonates, samples of loess and crushed

Ž .fragments of limestone, dolomite and marl 2–4 mm were treated with a 1 MŽNaOAc solution buffered at pH 5 with HOAc Jackson, 1979; Tassier et al.,

.1979 . The particle size analysis of the insoluble residues was determined asdescribed above.

In order to characterize chemically insoluble residues of carbonate rocks andcompare them with terra rossa, marl and loess, we used elements with a highionic potential which are considered relatively immobile in soil environments

Ž .and suitable for geochemical ‘fingerprinting’ Muhs et al., 1987, 1990 andelements with low ionic potential which are considered relatively mobile in soilenvironments. We chose elements Ti, Nb and Zr from the first group and Naand K from the second group. The reason for taking later into consideration is

Ž .direct relation of this elements to plagioclase Na , and micaceous clay mineralsŽ . Ž .illitic material and mica and K-feldspar K . These elements were measured in

Ž .insoluble residues of carbonate rocks four samples , -2 mm fraction of terraŽ . Ž . Žrossa three profiles, twelve samples , marl three samples and loess five. Ž .samples with an XRF spectrometer Philips PW 1404 using pressed powder

pellets. Analytical results are given in Appendix A. For evaluation, ratios ofelements were used instead of concentrations of individual elements which are

Ždirectly influenced by changes of concentration in other constituents Nesbitt et.al., 1980 .

Ž .Total iron Fe was measured in -2 mm fraction of terra rossa samples withtŽ .an XRF spectrometer Philips PW 1404 using pressed powder pellets. Iron

Ž .extractable with Na dithionite–citrate bicarbonate Fe was extracted after thedŽ . Žmethod of Mehra and Jackson 1960 modified after U. Schwertmann letter

. Ž .communication , and measured with AAS Pye-Unicam SP9 .The mineral composition of -2 mm and -2 mm fractions of terra rossa

Ž .and rocks and their insoluble residues was determined by X-ray powderŽ . Ždiffraction XRD using a Philips diffractometer graphite monochromator, Cu

.Ka radiation, proportional counter . Before the analysis of the clay fraction,humic materials and iron oxides were removed according to Tributh and LagalyŽ . Ž . Ž .1986 and Tributh 1991 . Coarse and medium clay 2–0.2 mm and fine clayŽ .-0.2 mm from selected terra rossa and loess samples were also X-rayed after


Table 1Ž .Particle size analysis, total, and dithionite extractable iron in terra rossa samples wt.%

Ž .Sample Depth cm Color Clay Silt Sand Fe Fe Fe rFe Soil Surveyt d t dŽ .Staff 1975

Profile Sjenokosaˇ1 20–35 5YR4r8 41.1 58.3 0.6 4.20 2.78 0.66 silty clay2 35–100 5YR5r6 47.5 51.2 1.4 4.44 2.96 0.67 silty clay3 100–145 5YR5r6 49.4 49.1 1.5 4.60 2.89 0.63 silty clay4 145–200 5YR5r6 51.8 46.0 2.2 4.68 2.84 0.61 silty clay5 200–225 5YR5r6 54.2 45.3 0.5 5.12 3.22 0.63 silty clay6 225–265 5YR5r6 53.0 46.1 0.9 4.90 3.34 0.68 silty clay7 265–300 5YR5r6 57.1 42.6 0.2 5.29 3.22 0.61 silty clay8 300–325 5YR4r6 61.1 38.6 0.3 5.75 3.78 0.66 clay9 325–335 5YR4r6 59.8 40.1 0.1 5.45 3.80 0.70 silty clay

10 335–360 5YR4r6 71.7 28.3 0.1 5.92 3.57 0.60 clay11 360–400 5YR5r6 59.9 39.8 0.3 4.91 3.43 0.70 silty clay12 400–450 2.5YR4r6 60.1 39.4 0.4 4.97 3.94 0.79 clay13 450–550 2.5YR4r6 63.1 36.4 0.5 5.22 3.39 0.65 clay14 550–650 2.5YR4r6 64.6 34.8 0.6 5.51 3.79 0.69 clay15 650–750 2.5YR5r8 66.4 32.7 0.9 5.51 3.96 0.72 clay16 750–850 2.5YR4r6 62.9 36.2 0.8 5.41 4.00 0.74 clay

Profile Kamnik19 10–25 5YR4r6 32.5 65.1 2.4 3.37 1.86 0.55 silty clay loam19A 25–50 5YR4r6 35.7 61.9 2.4 3.40 2.03 0.60 silty clay loam

Profile Pomer22 18–30 5YR5r6 45.1 52.7 2.2 3.74 2.42 0.65 silty clay23 30–62 2.5YR4r8 64.2 34.0 1.9 6.20 4.15 0.67 clay24 62–105 2.5YR4r8 71.1 28.0 0.9 6.03 4.11 0.68 clay25 105–130 10R4r8 70.2 28.7 1.1 5.60 3.91 0.70 clay

Profile Porec53 15–35 5YR4r6 59.4 39.5 1.1 6.10 4.01 0.66 clay55 35–50 2.5YR5r6 74.1 25.2 0.8 4.70 3.19 0.68 silty clay

Profile Mondolako60 12–30 2.5YR5r6 61.3 36.0 2.7 6.57 5.20 0.79 clay61 30–60 2.5YR5r6 67.7 30.8 1.5 6.70 5.11 0.76 clay

Profile NoÕigrad131 9–20 5YR4r6 55.7 43.2 1.1 4.04 3.19 0.79 silty clay132 20–42 5YR4r6 60.3 38.6 1.2 412 3.64 0.88 clay133 42–63 2.5YR4r6 70.1 29.0 1.0 6.07 4.61 0.76 clay134 63–80 2.5YR4r6 73.1 26.0 0.9 6.12 4.62 0.75 clay135 80–112 2.5YR4r6 73.5 25.4 1.1 6.20 4.71 0.76 clay136 112–150 2.5YR4r6 77.2 21.9 0.9 6.51 4.90 0.75 clay

Profile SaÕudrija47 400–420 2.5YR5r8 32.1 55.4 12.6 n.d. n.d. n.d. silty clay loam


Ž .Table 1 continued

Ž .Sample Depth cm Color Clay Silt Sand Fe Fe Fe rFe Soil Surveyt d t dŽ .Staff 1975

Single samples42 5–15 5YR5r6 46.8 47.9 5.3 4.06 2.67 0.66 silty clay52 10–30 2.5YR4r8 42.1 55.3 2.5 5.47 3.76 0.69 silty clay100 10–25 2.5YR4r8 72.1 26.8 1.1 6.67 5.24 0.79 clay101 10–25 2.5YR5r8 73.8 25.4 0.8 7.06 5.74 0.81 clay234 5–15 5YR4r8 35.8 61.1 3.1 3.38 2.30 0.68 silty clay235 5–10 2.5YR4r6 35.1 63.9 1.0 4.13 3.53 0.85 silty clay236 5–10 2.5YR4r6 42.1 57.3 0.6 4.33 3.31 0.76 silty clay237 5–10 2.5YR4r6 59.1 40.4 0.5 5.45 3.99 0.73 silty clay96 5–10 0.5YR5r6 55.1 38.1 6.8 n.d. n.d. n.d. silty clay

Ž . Ž . Ž . Ž .Color dry after Munsell Soil Color Charts 1994 . Clay -2 mm , silt 2–63 mm and sandŽ .)63 mm .

quantitative separation from -2 mm fraction. XRD patterns of non-orien-Ž .ted samples were taken after the following treatments: a air-drying and

Ž . Ž .b dissolution in HCl 1:1 . XRD patterns of oriented samples were taken afterŽ . Ž . Ž .the following treatments: a air drying, b glycol solvation, c Mg-saturation,

Ž . Ž . Ž .d K-saturation, e Mg-saturation and glycol solvation, f Mg-saturation andŽ . Ž .glycerol solvation, g K-saturation and DMSO solvation, and h heating to

5508C.The identification of clay minerals was generally based on the methods

Ž . Ž .outlined by Brown 1961 , Brindley and Brown 1980 , and Moore and Reynolds´Ž . Ž .1989 . The term ‘illitic material’ was used as defined by Srodon 1984 and´

´ Ž .Srodon and Eberl 1984 . The term ‘low-charge vermiculite or high-charge´smectite’ refers to clay mineral which was found only in the -0.2 mm fraction

Žand has some typical properties of both smectites and vermiculites Ruhlicke¨.and Niederbudde, 1985; Douglas, 1989 . The DMSO-treatment enabled the

differentiation of kaolinites which form intercalation compounds with DMSOŽ . Ž . ŽKl from kaolinites which do not intercalate with DMSO Kl Range et al.,D

.1969 .By means of semiquantitative XRD analysis the amounts of quartz, plagio-

clase, K-feldspar, calcite, dolomite and boehmite were determined in selectedbulk samples. An external standard was applied, by measuring relative intensi-ties of characteristic diffraction lines. Estimation of iron oxide percentages wasbased on the content of iron extractable with Na dithionite–citrate bicarbonate.The term ‘iron oxide’ embraces oxides, oxyhydroxides, and hydrated oxides

Ž .according to Schwertmann and Taylor 1989 . Semiquantitative estimates ofclay minerals in the 2–0.2 mm and -0.2 mm fractions were based on theintensities of characteristic X-ray peaks following the method of Johns et al.Ž . Ž .1954 and using multiplication factors given by Riedmuller 1978 .¨


IR absorption spectra of selected terra rossa were recorded on a Perkin–ElmerSpectrum 1000 spectrometer over the range 4000 to 200 cmy1 using 13 mmdiameter KBr pressed disks containing 1 mg sample.

4. Results

( )4.1. Total iron Fe and iron extractable with Na dithionite–citrate bicarbonatet( )Fe in terra rossad

The rather limited variation of selected Fe-oxide characteristics in 40 terraŽrossa samples from Istria Tables 1 and 2; especially average and 95% C.I

.values of Fe and Fe rFe are very similar to those of Boero and Schwertmannd d tŽ .1989 , who analysed 48 terra rossa samples from various locations around the

Ž . Žworld. While Fe in 45 terra rossa samples averaged 3.5% "0.3 Boero andd. Ž .Schwertmann, 1989 , in 40 samples from Istria Fe averaged 3.68% "0.28 .d

The arithmetic means of the two sets of data are not significantly different at theŽ .0.05 level t-test . We can conclude that the two populations are indistinguish-

able at the 0.05 level, i.e., two arithmetic means represent two independentŽ .estimates of the same population Fe in terra rossa . This supports Boero andd

Ž .Schwertmann 1989 conclusion, that the rather limited extent of variation ofselected Fe-oxide characteristics may indicate a specific pedoenvironment inwhich terra rossa is formed.

4.2. Particle size analysis

Ž . Ž .Terra rossa is composed predominantly of clay -2 mm and silt 2–63 mmŽ . Žsized particles, with sand )63 mm particles forming less than 4 wt.% Table

.1, Fig. 3 . Higher content of sand sized particles is present in samples 47, 42 and96. Sample 47 represents B horizon of terra rossa buried by 4-m thick UpperPleistocene loess complex. Higher content of sand sized particles in this sampleis attributed to rhizoconcretions which formed in terra rossa as the result of

Žpaleopedological processes which post-date terra rossa formation recalcification

Table 2Basic statistics for total and dithionite extractable iron in terra rossa samples

Ž .n x s CV % 0.95 C.I.

Fe 40 5.19 0.99 19.07 4.88–5.51t

Fe 40 3.68 0.89 24.18 3.40–3.96d

Fe rFe 40 0.70 0.07 10.00 0.68–0.72d t

Ž .nsNumber of samples, xsarithmetic mean, ssstandard deviation, CV % scoefficient ofvariation, 0.95 C.I.sconfidence interval.


Fig. 3. Particle size analysis of terra rossa.

.of terra rossa following its burial . Higher sand content in samples which areŽ .situated in the vicinity of flysch samples 42 and 96 is attributed to the recent

colluvial additions of flysch.Ž .Generally, the clay content increases with depth in profiles Table 1 . An

exception is Sjenokosa, a colluvial terra rossa complex composed of superim-ˇposed features of colluviation and pedogenesis, where clay content increases

Ž .with depth within the each superimposed cycle Durn, 1996 .The insoluble residue content of limestone and dolomite samples ranges from

Ž .0.08 to 2.23 wt.% Table 3, Fig. 4 and is dominated by clay sized particles.Ž .The insoluble residues of analysed marls are clayey silts samples 88 and 94

Ž . Ž .and silty clay sample 88 , respectively Table 3, Fig. 4 The insoluble residuesof loess from Savudrija are also clayey silts but are enriched in silt and sand size

Ž .fractions compared to the marl insolubles Table 3, Fig. 4 . The Premanturaloess is considerably different from the Savudrija loess because of the high sandsize fraction content.

4.3. Bulk and clay mineralogy

Istrian terra rossa is composed of quartz, plagioclase, K-feldspar, micaceousŽ . Ž .clay minerals illitic material and mica , kaolinites Kl and Kl , chlorite,D

vermiculite, low-charge-vermiculite or high-charge smectite, mixed-layer clayŽ .minerals other than illitic material , hematite, goethite and XRD-amorphous

inorganic compound. Based on broadening of the 110 reflection of hematite inŽ .terra rossa samples from Istria, Durn 1996 concluded that the size of hematite


Table 3Ž .Particle size analysis of the insoluble residues of limestone and dolomite, marl, and loess wt.%

Sample Ir Clay Silt Sand

Limestone and dolomite17 0.43 71.8 24.1 4.120 0.08 – – –50 0.48 85.2 14.8 –56 0.58 84.7 15.3 –63 2.19 87.5 11.9 0.675 0.59 – – –79 2.23 80.5 19.3 0.285 0.32 86.3 13.7 –130 0.86 63.8 33.6 2.6

Marl87 57.59 51.0 46.4 2.688 58.82 35.4 64.6 –94 52.76 49.0 50.5 0.5

Loess18 87.41 17.1 46.0 36.944 74.61 29.3 64.6 6.145 78.45 27.6 62.9 9.546 69.23 21.6 67.0 12.448 50.73 23.2 68.1 8.7

Ž .IrsContent of the insoluble residue wt.% .Ž . Ž . Ž .Clay -2 mm , silt 2–63 mm and sand )63 mm .

crystals is lower than 50 mm. Calcite and dolomite were found in terra rossawith rhizoconcretions and in terra rossa with recent colluvial additions of flysch.Boehmite bearing terra rossa are those situated in the vicinity of bauxites ofJurassic and Paleogene age. The results of semiquantitative phase analysis ofselected terra rossa samples are given in Table 4.

Dominant mineral phases in the clay fraction of all terra rossa from Istria areŽ .kaolinites Kl and Kl , illitic material, Fe-oxides and XRD amorphous inor-D

ganic compounds, while vermiculite, low-charge-vermiculite or high-chargesmectite, chlorite, mixed-layer clay minerals and quartz are present in subordi-

Ž .nate amounts Fig. 5 . The clay fraction of terra rossa also contains boehmiteŽonly those samples which were taken in the vicinity of bauxites of Jurassic and

.Paleogene age . The results of XRD analysis of the clay fraction separated fromselected terra rossa samples are presented in Table 5. In all terra rossa samplesthe content of kaolinite which does not form intercalation compounds with

Ž .DMSO Kl is higher than that of kaolinite which intercalates with DMSOŽ .Kl . An example can be seen in Fig. 5c showing a part of the diffractionD

Ž .pattern of sample 52 -2 mm fraction treated with DMSO; the diffraction lineŽ .of Kl is stronger than the one of Kl . Fine clay -0.2 mm fraction containsD


Ž . Ž . Ž .Fig. 4. Particle size analysis of: 1 Insoluble residues of limestone and dolomite. 2 Loess. 3Marl.

Ž .only kaolinite which does not form intercalation compounds with DMSO KlŽ .Table 6 . This mineral is the dominant mineral phase in fine clay. Coarse and

Ž .medium clay 2–0.2 mm fraction contains both kaolinite which does not formŽ .intercalation compounds with DMSO Kl and kaolinite which intercalates with

Ž . Ž .DMSO Kl , the former being more abundant Table 6 . Low-charge vermi-D

culite or high-charge smectite was detected only in the fine clay of samples 47Ž .and 52 Table 6 .

Table 4Ž .Mineral composition of the -2 mm fraction of terra rossa wt.% . Phyllos.qam.sPhyllosilicates

and amorphous inorganic compound

Sample Quartz Plagioclase K-feldspar Hematiteq Phyllos.q Calcite Dolomite BoehmiteGoethite am.

15 23 2 1 6 6822 33 5 2 3 5725 21 2 1 6 7047 32 4 1 3 52 5 352 29 1 1 5 6460 18 3 1 7 62 9

100 13 2 8 67 10131 25 3 1 5 66136 15 1 1 7 76


Ž .Fig. 5. Characteristic parts of XRD patterns of terra rossa sample 52 -2 mm fraction afterŽ . Ž . Ž . Ž .removal of Fe-oxides oriented preparations : a Mg-saturated. b K-saturated. c K-saturatedŽ .and DMSO solvated. d Heated for 1 h at 5508C. V: Vermiculite. MC: mixed-layer clay mineral.

I: Illitic material. Kl : Kaolinite which intercalates with DMSO. Kl: Kaolinite which does notD

intercalate with DMSO. Q: Quartz.

In general, it was not possible to perform XRD identification of illiticmaterial because quartz was present in most of the clay fractions. However, in

Ž .the clay fraction of sample 6 Fig. 6 quartz was not identified, which enabled´ Ž .XRD identification of illitic material according to Srodon 1984 . The positions´

of the 002 and 003 reflections of glycolated sample lies in the illite field´Ž .Srodon, 1984; Fig. 2 . Nevertheless, the intensity ratio of the 001 and 003´

Ž .reflections of the air-dried and glycolated sample Ir equals 1.8, which points toan admixture of expandable material. The join breadth of 001 illite and adjacentillitersmectite reflection, measured in 2Q8 from where the tails of the peak join

´Ž . Ž .the X-ray background BB1 is smaller than 4. According to Srodon 1984 ,´illitic material in sample 6 is a mixture of illite and ISII-ordered illitersmectitewith less than 15% smectite layers. Moreover, a small inflection at 2Q;58 on

´Ž . Ž .the pattern of glycolated sample Fig. 6 indicates, according to Srodon 1984 a´transition from IS to random interstratification with about 40–50% smectite.

IR spectra of the clay fraction of selected terra rossa show the characteristicŽ .absorption bands corresponding to kaolinite and illitic material Fig. 7 . Accord-

Ž . y1ing to Russel 1987 , the 3669 and 3652 cm doublet in well-crystallisedkaolinites is replaced by a single broad band at 3653 cmy1 in disordered


Table 5Mineral composition of the -2 mm fraction of terra rossa after the removal of carbonates, humicmaterials and iron-oxides

Sample Illitic Kl Kl Vermiculite L.c. Chlorite Mc Quartz BoehmiteD

material vermiculite

15 q q q q q q22 q q q q q ChrV q25 q q q q q q47 q q q q x q q q52 q q q q x q q q60 q q q q q q q q

100 q q q q q q q q131 q q q q q q136 q q q q q q

Kl sKaolinite which forms intercalation compounds with DMSO, KlsKaolinite which doesD

not intercalate with DMSO, L.c. vermiculitesLow-charge vermiculite or high-charge smectite,McsMixed-layer clay mineral, ChrVschloritervermiculite, x smineral present only in the-0.2 mm fraction.

y1 Ž .kaolinites. In terra rossa we have detected only 3653 cm line Fig. 7 whichpoints to the predominance of disordered kaolinites.

Table 6Semiquantitative clay mineral composition of the -0.2 mm and 2–0.2 mm fractions of terrarossa after the removal of carbonates, humic materials and iron-oxides

Sample Illitic Kl Kl Vermiculite L.c. Chlorite Mc BoehmiteD


-0.2 mm15 25 75 tr. q22 45 55 tr. q25 30 70 tr. q47 23 63 tr. 14 q52 10 77 tr. 13 q60 32 60 8 tr. q q

100 15 81 4 tr. q q131 22 78 tr. q136 19 78 3 q

2 – 0.2 mm25 44 12 35 9 q52 50 12 33 5 tr. q

Kl sKaolinite which forms intercalation compounds with DMSO, KlsKaolinite which doesD

not intercalate with DMSO, L.c. vermiculitesLow-charge vermiculite or high-charge smectite,Mc sMixed-layer clay mineral, ChrVschloritervermiculite, Illitic materialqKl qKlqD

VermiculiteqL.c. vermiculiteqchlorites100 wt.%.


Ž .Fig. 6. Characteristic parts of XRD patterns of terra rossa sample 6 -2 mm fraction afterŽ . Ž . Ž . Ž .removal of Fe-oxides oriented preparations : a Air dried. b Ethylene glycol solvated. c

Heated for 1 h at 5508C. I: Illitic material. Kl: Kaolinite.

The insoluble residues of limestone and dolomite are greyish-brown in colorŽ .and contain quartz, micaceous clay minerals illitic material and mica , mixed-

layer clay minerals, goethite and amorphous organic and inorganic compounds.Ž .K-feldspar was identified in four samples 130, 56, 63, 75 . Kaolinite which

Žforms intercalation compounds with DMSO was detected in three samples 17,.75 and 79 . Plagioclase was found in sample 17 and chlorite in sample 56. The

dominant mineral phase of the clay fraction of the insoluble residues is illiticmaterial. The results of semiquantitative phase analysis of selected insolubleresidues are shown in Table 7. The results of XRD analysis of related clayfraction, based on the patterns of oriented samples, are given in Table 8.

Marls are composed of calcite, quartz, plagioclase, micaceous clay mineralsŽ . Ž .illitic material and mica , chlorite and smectite Tables 7 and 8 . Vermiculitewas identified only in sample 87. The clay fraction of marl is dominated byillitic material and smectite.

Ž .The Upper Pleistocene loess from north-west Istria Savudrija containscalcite, dolomite, quartz, plagioclase, K-feldspar, goethite, micaceous clay min-

Ž .erals illitic material and mica , chlorite, vermiculite, low-charge vermiculite or


Ž . y1Fig. 7. IR spectra of terra rossa sample 25 -2 mm fraction . Enlarged is 3700 to 3600 cmregion.

high-charge smectite, chloritervermiculite and both kaolinite which does notŽ .form intercalation compounds with DMSO Kl and kaolinite which intercalates

Ž . Ž . Ž .with DMSO Kl Tables 7 and 8 . Fine clay -0.2 mm fraction of sample 48D

Table 7Mineral composition of insoluble residues of limestone and dolomite and mineral composition of

Ž .bulk samples of marl and loess wt.%

Sample Quartz Plagioclase K-feldspar Goethite Phyllos.qam. Calcite Dolomite

Ir of limestone and dolomite56 6 6 4 8463 8 6 4 8275 14 2 6 7879 15 4 8085 8 4 88

130 17 4 2 77

Marl94 15 2 36 47

Loess48 17 4 1 1 31 21 25

Phyllos.qam.sPhyllosilicates and amorphous inorganic compound.


Table 8Mineral composition of the -2 mm fraction of insoluble residues of limestone and dolomite,marl and loess after the removal of humic materials and iron oxides

Sample Illitic Kl Kl Vermiculite L.c. Chlorite Smectite Mc QuartzD


Limestone and dolomite56 q q ChrV q63 q q q75 q q q q79 q q q q85 q q q130 q q q

Marl94 q q q q q

Loess48 q q q q x q ChrV q-0.2 mm 29 36 tr. 35 tr. q2–0.2 mm 53 10 12 9 16 ChrV

Semiquantitative clay mineral composition of -0.2 mm and 2–0.2 mm fractions of loess sample48 are also presented. Kl skaolinite which forms intercalation compounds with DMSO,D

Klskaolinite which does not intercalate with DMSO, L.c. vermiculitesLow-charge vermiculiteor high-charge smectite, McsMixed-layer clay mineral, ChrVschloritervermiculite, x smineral present only in the -0.2 mm fractionqs identified mineral. Illitic materialqKl qKlD

qVermiculiteqL.c. vermiculiteqchlorites100 wt.%.

contains only kaolinite which does not form intercalation compounds withŽ . Ž . Ž .DMSO Kl Table 8 . Coarse and medium clay 2–0.2 mm fraction contains

both kaolinites in similar amounts. Low-charge vermiculite or high-chargeŽ .smectite is quite abundant in the fine clay of loess sample Table 8 . In the

Ž .Fig. 8. Molar ratios of Na OrK O =100 in terra rossa, loess and marl. Two horizontal lines2 2

represent minimum and maximum values for this ratio in the insoluble residues of limestone anddolomite.


Fig. 9. Ratios of ZrrNb in terra rossa, loess and marl. Two horizontal lines represent minimumand maximum values for this ratio in the insoluble residues of limestone and dolomite.

coarse grained loess from Premantura, amphibole and epidote were also de-tected.

4.4. Geochemistry

Ž .Na OrK O =100 ratios in the insoluble residue of limestones and2 2

dolomites ranges from 2 to 4.3 and are much lower than ratios in terra rossa,Ž .loess and marl Fig. 8 . This, together with the results of bulk mineralogy

Ž .Tables 4 and 7 indicates that terra rossa, loess and marl are enriched inplagioclase compared to the insoluble residue of limestones and dolomites.ZrrNb ratios in the insoluble residue of limestones and dolomites are alsosignificantly lower than ratios in loess, marl and majority of terra rossa samplesŽ . Ž .Fig. 9 . This is also partly valid for ZrrTi =1000 ratios although there isobvious overlapping of profile Mondolako and lower part of profile Novigrad

Ž .with the insoluble residue field Fig. 10 .

Ž .Fig. 10. Ratios of ZrrTi =1000 in terra rossa, loess and marl. Two horizontal lines representminimum and maximum values for this ratio in the insoluble residues of limestone and dolomite.


5. Discussion and conclusions

The content of the insoluble residue indicates that an excessive thickness oflimestone and dolomite must have been dissolved to form terra rossa, and thatthe extent of the preservation of that residue through Quaternary must have beenunusually high. Neither the insoluble residue content of limestone and dolomitenor its particle size distribution is compatible with the development of terra

Ž .rossa entirely by dissolution of carbonate rock Tables 1 and 3, Figs. 3 and 4 .Specifically, if terra rossa has developed only from the insoluble residue oflimestone or dolomite, its clay content, due to weathering, should be higher than

Žthat in the insoluble residues which is not the case Tables 1 and 3, Figs. 3 and.4 .

The bulk and clay mineral assemblage in the insoluble residue of limestonesand dolomites also does not support development of terra rossa entirely bydissolution of carbonate rock. The dominant mineral phase in the insolubleresidues is illitic material, they do not contain kaolinite which intercalates withDMSO, and kaolinite which forms intercalation compounds with DMSO was

Ž .detected only in three samples 17, 75 and 79 . Plagioclase was found only inŽ . Ž .one sample 17 while all terra rossa samples contain this mineral Table 4 . The

insoluble residues do not contain vermiculite which was observed in smallamounts in clay fraction of all terra rossa samples. Vermiculite is an unstable

Žmineral in pedogenic environment Barnhisel and Bertsch, 1989; Douglas,. Ž .1989 . Boero et al. 1992 suggest formation of hydroxy-interlayered vermiculite

on the expense of 2:1 silicates in terra rossa of the moist environment of NEItaly. We postulate that the appearance of vermiculite in terra rossa from Istriacan be related to some parent material other then insoluble residue of limestoneand dolomite.

Geochemical ratios also support external material influence in the genesis ofŽ .terra rossa Figs. 8–10 . If we consider Zr, Nb, and Ti relatively immobile in

soil, than parent materials other than the insoluble residue of limestones andŽ .dolomites may have influenced terra rossa composition. Na OrK O =1002 2

Ž . Ž .ratios Fig. 8 and results of bulk mineralogy Tables 4 and 7 indicate that terrarossa, loess and marl are enriched in plagioclase compared to the insolubleresidue of limestones and dolomites.

The difference in particle size, mineralogy and geochemistry observed be-tween terra rossa and the insoluble residue of limestones and dolomites clearlyindicates that the additions of external materials might have diminished theinfluence of insoluble residue of limestones and dolomites as the primary parentmaterial of terra rossa in Istria. Unfortunately, the contribution of the insolubleresidue of limestones and dolomites to terra rossa is not easy to estimate becauseof its very low content and the variability in the rock itself.

ŽMaterials other than the insoluble residue of limestones and dolomites and.related karst bauxite where present which might have contributed to terra rossa


are flysch sediments, which extended much more southwards from its presentŽ .position Polsak, 1970; Fig. 1 and loess, whose deposition was very importantˇ

recurrent process in Northern and Central Italy since the early Middle Pleis-Ž .tocene which also effected Istria and Dalmatian Archipelago Cremaschi, 1990a .

The particle size distribution of insoluble residues of marls is similar to thatŽ .of terra rossa Tables 1 and 3; Figs. 3 and 4 . The clay fraction of marls is

dominated by illitic material and smectite. These minerals are also reported to bemain clay minerals in 50 flysch samples from Istria and Kvarner area which also

Ž .contain chlorite, vermiculite and chloritervermiculite mixed-layer Durn, 1996 .Ž .However, kaolinite was also detected in flysch from Istria Bonazzi et al., 1996 .

ŽThe fact that smectite is not present in terra rossa except low-charge vermiculiteor high-charge smectite which were detected in the fine clay of samples 47 and

.52 does not necessarily exclude marls as a potential contributor to terra rossa.ŽSpecifically, smectite is an unstable mineral under intense weathering Borchardt,

. Ž .1989 . Morgan et al. 1979 found that under intense weathering and gooddrainage smectite can be directly transformed to kaolinite. This process isaccompanied by the formation of Fe-oxides. Geochemical ratios also does notexclude marls as a potential contributor to terra rossa.

Low-charge vermiculite or high-charge smectite was detected in the -0.2Ž . Ž .mm fraction of terra rossa samples which are situated bellow 47 or near 52

Ž .Upper Pleistocene loess Table 6, Fig. 1 . The presence of this mineral in thosesamples may indicate its eolian origin because it was detected as one of main

Žmineral phases in fine clay of the Upper Pleistocene loess in Savudrija Table.8 . The Upper Pleistocene loess post-dated terra rossa formation, but it indicates

that during terra rossa formation, similar external materials might have con-tributed to terra rossa. This is especially important when we bear in mind thatsince the early Middle Pleistocene loess deposition effected Istria and Dalmatian

Ž .Archipelago Cremaschi, 1990a . The clay fraction of loess from Northern andŽCentral Italy mainly consists of vermiculite, illite and kaolinite Cremaschi,

.1987 . According to the same author, Alpine loess contains more illite andkaolinite while Apennine loess contains more vermiculite. In addition to theseminerals, the clay fraction from the Upper Pleistocene loess in Savudrija alsocomprise chlorite, low-charge vermiculite or high-charge smectite and mixed-

Ž .layer clay minerals mainly chloritervermiculite . The content of the clayfraction in the highly weathered loess from Northern and Central Italy ranges

Žfrom 58 to 75 wt.% and that of the sand fraction from 1 to 3 wt.% Cremaschi,.1990a; Fig. 1 . These results are very similar to the results obtained for terra

Ž .rossa Table 1, Fig. 3 . This, together with the similarity in clay mineralassemblage and geochemical ratios for the Upper Pleistocene loess may indicatethat loess, older than that of the Upper Pleistocene age might have considerablycontributed as a parent material for terra rossa. This is also supported by thecharacteristic heavy mineral assemblage in terra rossa from Istria which is very

Ž .similar to that of the Upper Pleistocene loess Durn, 1996 .


Although there are no data about older loess deposits in Istria, they wererecognised on the Susak island. They are situated below the Upper Pleistoceneloess and have reddish alfisol developed on their top which is supposed to have

Ž .formed in the Riss-Wurm interglacial Cremaschi, 1990b .¨Kaolinites, along with illitic material and XRD amorphous inorganic com-

pounds, are dominant clay mineral phases in the clay fraction of all terra rossafrom Istria. They are scattered constituents in the clay fraction of insolubleresidues of limestone and dolomite, and minor constituents of Upper Pleistoceneloess. They were not detected in flysch. Kaolinite which does not form

Ž .intercalation compounds with DMSO Kl is dominant mineral phase in fineclay of terra rossa. The ability of kaolinite to intercalate is generally related to

Ž .particle size and crystallinity Jackson and Abdel-Kader, 1978 . PedogenicŽkaolinites seem to have thinner particles broader line width for the basal

˚ . Ž .reflections at 7.15 and 3.57 A and generally poor crystallinity Calvert, 1984 .Ž .Coarse kaolinite particles 0.2–2 mm generally intercalate more readily than

Ž . Ž .fine kaolinite particles -0.2 mm Jackson and Abdel-Kader, 1978 . This mayindicate that the kaolinite which does not intercalate with DMSO is pedogenickaolinite, i.e., authigenic mineral in terra rossa, while kaolinite which interca-lates with DMSO is inherited from kaolinite containing parent material whichmeans it is of a lithogenic origin. However, kaolinite which does not formintercalation compounds with DMSO was also detected in fine clay of loessŽ .Table 8 . Moreover, kaolinite crystals can easily be altered structurally through

Ž .grinding Hayes, 1963 because their structure is mechanically weak. Althoughsoil kaolinite would frequently rank among the most disordered kaolinitesŽ .Dixon, 1989 , this does not necessarily mean they are authigenic in soil.Tentative explanation would be that their particle size and disorder is the resultof mechanically destroyed kaolinites inherited from parent materials. In the caseof terra rossa this is quite probable because superimposed processes of erosionand deposition on karst terrain might have considerably effected its constituents.However, we postulate that kaolinite in fine clay of terra rossa is predominantly

Ž .authigenic pedogenic rather than inherited from parent materials. The possibleŽ .sources of pedogenic kaolinite are feldspars plagioclase and K-feldspar , kaolin-

ite, muscovite, vermiculite, chlorite and smectite. This is in accordance withŽ .Bronger and Bruhn-Lobin 1997 who found considerable to extensive formation

of clay minerals, mainly kaolinites in terra rossa from NW Morocco.Istria is an example of a non-isolated karst terrain which was effected with

Ž .karst processes, neo tectonic activity and external material contributions sincelate Tertiary. It is not easy to estimate to what extent materials other than theinsoluble residue of limestones and dolomites have contributed in the genesis of

Žterra rossa. However, further studies in Istria which are in progress micromor-.phology, heavy mineral studies, REE should give more answers to this contro-

versial topic.


( )Appendix A. Concentrations of Na O, K O and Ti wt.% , and Nb and Zr2 2( )ppm in terra rossa, insoluble residue of limestone and dolomite, marl andloess

Sample Na O K O Ti Nb Zr2 2

Terra rossa

Profile Pomer22 0.93 2.04 0.64 26 36523 0.50 2.25 0.65 32 24924 0.70 2.18 0.58 32 24525 0.93 2.19 0.67 29 253

Profile Mondolako60 0.23 1.57 0.83 35 22761 0.23 1.64 0.91 36 232

Profile NoÕigrad131 0.40 1.61 0.77 32 276132 0.38 1.58 0.76 33 287133 0.26 1.65 0.64 28 206134 0.26 1.65 0.65 30 171135 0.23 1.63 0.65 30 183136 0.18 1.55 0.61 29 122

Insoluble residue of limestone and dolomite50 0.11 3.89 0.46 14 6063 0.07 5.18 0.5 21 9075 0.08 3.00 0.35 21 9779 0.09 3.82 0.41 24 113

Loess18 2.28 1.39 0.41 9 26644 0.66 1.75 0.45 14 16145 0.62 1.71 0.46 14 21546 0.63 1.54 0.44 13 15948 0.61 1.46 0.34 9 125

Marl87 0.44 1.59 0.33 8 9288 0.50 1.84 0.34 9 9094 0.34 1.72 0.32 7 116


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