Clay Minerals (1983) 18, 127-138
O R I G I N OF B A U X I T E AT E U F A U L A ,
USA
T. C. L U K A S , * : ~
F. C. L O U G H N A N ~
ALABAMA,
AND J. L. E A D E S *
*Dept. of Geology, University of Florida, Gainesville, Florida 32611, USA, and ~fSchool of Applied Geology,
University of NS W, P.O. Box 1, Kensington, New South Wales 2033, Australia
(Received 3 August 1982; revised 29 October 1982)
ABSTRACT: An autochthonous origin for the bauxite deposits of the Eufaula district,
south-eastern Alabama, appears to have received general acceptance but, compared with
younger residual bauxites of the present day tropical regions of the world, the Eufaula deposits
have a number of features that are difficultto reconcile with developmentin situ. In an attempt to
resolve the enigma, a detailed study was undertaken of cores from three drill holes that
intersected a complete succession through one of the Eufaula deposits. Although the results are
not conclusive,it is believedthat much of the observed phenomena can be explainedon the basis
of an essentiallytransported origin for the deposits.
From the time of their discovery in 1922, the bauxite and bauxitic clay deposits of the
Eufaula district, south-eastern Alabama (Fig. 1), have incited interest not only because
they represent an important source of alumina for the refractory and alum industries, but
also because their origin is somewhat enigmatic. In his initial detailed description, Rettger
(1925) assigned the occurrences to the Nanafalia Formation, which in this area is the
lowermost unit of the Eocene Wilcox Group. They are, therefore, coeval or approximately
coeval with similar deposits at Andersonville, Georgia (Shearer, 1917) and also with the
residual and transported bauxites near Little Rock, Arkansas (Gordon et al., 1958).
In considering the origin of the deposits, Rettger (1925) believed the pertinent aspects to
be: (i) their apparent restriction to a zone immediately above an erosion surface that
separates the Nanafalia from the underlying Clayton Limestone (Table 1), (ii) the apparent
lack of sedimentary structures in the bauxite and associated kaolin, and (iii) the evident
downward gradation of the bauxite into kaolin. On the basis of these observations he
concluded that sand and clay detritus derived from weathered crystalline rocks in the
Piedmont to the north (Fig. 1) was transported and deposited 'in depressions such as lakes
and lagoons, or in shallow waters off the coast'. In the on-shore area much of the clay was
segregated to form large, elongate bodies, which during an ensuing regression were
intensely leached of silica, leaving a residue correspondingly enriched in alumina.
Although Rettger's mode of origin for the bauxite has received general acceptance by
subsequent workers, various modifications have been proposed. Thus, MacNeil (1945)
believed that the lenticular form of the bauxite-kaolin bodies resulted from partial collapse
of the Nanafalia into depressions created by karstifieation of the underlying Clayton
Limestone, whereas Clarke (1966, 1972) and Jones (1972) argued that karstification of the
Clayton mostly preceded deposition of the Nanafalia and that leaching of silica from clay
:~Present address: Exxon Production Research Co., P.O. Box 2189, Houston, Texas 77001, U.S.A.
9 1983 The Mineralogical Society
T. C. Lukas et al.
128
oo
Tenn.
E/j~L
R0 CK
/I
~.-,
~.
Miss.
J
I
~"
,,,
i
i ~,k~
/t
i
i
/, ~,NDERSONVILLE
I
,
t. ......
krn
,
DMONT PROVINCE
I
.
/
i
PAL EOZOIC
\\
~
j
BLUE RIDGE ~',~
r
o. ,,,
i
i Ala.
I
I A f\ )
/
1
Ga.
I
1
I
...........
I
,
\
,,
r~
I .~ J
FIG. 1. Sketch map of the south-eastern United States.
TABLE 1. Stratigraphic succession in the Eufaula area,
Alabama.
Eocene
Paleocene
Cretaceous
WflcoxGroup
Hatchetigbee Formation
Tuscahoma Sand
Nanafalia Formation
Disconformity
Clayton Limestone
MidwayGroup
Unconformity
Providence Sand
SelmaGroup
Ripley Formation
infilling these sink holes and depressions was the principal factor contributing to
development of the bauxite. Burst (1974), on the other hand, could find little evidence to
support the sink-hole origin of Clarke and Jones. Rather, he envisaged the Nanafalia in the
Eufaula area as representing deposition of elastics in an extensive, near-shore, freshwater
swamp and the bauxite-kaolin bodies as 'meander fills in an ancient tidal fiat or barrier
island'. Leaching of these meander-fills was believed to have resulted in discrete lensshaped accumulations with a gibbsitic core surrounded by zones of bauxitic kaolin, kaolin
and sandy kaolin (Fig. 2).
Inherent in all these proposals is the concept of selectivity by the bauxitization processes,
whereby the somewhat impermeable clay lenses were stripped of a high proportion of their
silica content while the enclosing, much more permeable, micaceous quartz sands remained
virtually unaffected. However, selectivity to such a marked degree is not apparent in
younger residual bauxites, e.g. those of western India and northern Australia, where,
despite development from a wide array of rock types including basalt, granite, shale and
Origin of Eufaula bauxite
129
KAOLIN
SAND
SANDY KAOLIN
~]
~
BAUXITIC KAOLIN
BAUXITE
FIG. 2. Zonal structureof a typicalbauxitedepositin the Eufaulaarea9After Burst (1974).
V/I//)
9
(~'0~
1 . /i
1,1
il
/I
"('3//, " P z / , ,
I
~/
,i/)~/~ij],/i/I///
I~
/0/~ / / 1
EufOula
4;//D?. :,
PROSPECT
";17~':( ,--
--
FIG. 3. Geologicalmap of the Eufaula bauxite district. Modified from Clarke (1972). Dots
represent workedareas.
kaolinitic quartz sands, they persist as thick, continuous, blanket-like crusts over extensive
areas.
Therefore, to gain a better understanding of the origin of the bauxitic clays of Eufaula
and, in particular, to examine the validity of Rettger's concept, a study was undertaken of
the vertical variations in mineral and chemical composition through one of these
bauxite-kaolin bodies. Complete cores were obtained, through the courtesy of A. P.
Green Refractories, from three drill sites designated A, B and C at McLeod Prospect (Fig.
3) in Barbour County, situated about 5 km south of Baker Hill.
GEOLOGICAL
SETTING
The oldest rocks in the Eufaula area are of late Cretaceous age and comprise sands, silts
and clays of the Ripley Formation and Providence Sand (Table 1). An unconformity
separates the Providence Sand from the Palaeocene Midway Group, which in this area is
represented by the Clayton Limestone. The Clayton is variable in both thickness and
composition in that it ranges up to 45 m (Warren & Clark, 1965) but in places is absent
and, whereas fossiliferous limestone is the dominant rock type, locally the unit grades into
chert, sandstone and conglomerate. The Wilcox Group, which disconformably overlies
the Clayton Limestone, is of Eocene age and has been subdivided into the Nanafalia
130
T.C. Lukas et al.
Formation at the base, this being succeeded by the Tuscahoma Sand and the Hatchetigbee
Formation.
South of Fort Gaines, the Nanafalia consists of marine strata, mostly quartz and
glauconitic sands with some limestone, termed the Ostrea thirsae beds by Warren &
Clark (1965). To the north, however, it is represented by the Gravel Creek Sand Member,
a continental facies with a thickness between 18 and 36 m. The Gravel Creek Sand is
characterized by cross-bedded, fine- to coarse-grained, micaceous quartz sand with
lenticular to irregular shaped clay bodies that range from less than a metre to several km
across. The smaller bodies are generally composed of kaolinite with or without quartz,
whereas the larger ones commonly comprise a gibbsite-rich core that grades outward
through envelopes of kaolinite and sandy kaolin into the surrounding, micaceous quartz
sand. Nevertheless, gibbsite-rich lenses virtually devoid of kaolinitic envelopes have been
encountered (Clarke, 1972). Sporadic, lenticular beds of lignite are evident in the Gravel
Creek Sand and these may occur above, below or within the bauxite-kaolin bodies.
The succeeding Tuscahoma Sand marks a return to marine conditions throughout the
entire area. According to Warren & Clark (1965), this unit consists of four distinct facies
with either a white sandy clay or red sand at the base, succeeded by a glauconitic sand, a
light grey to green shale and a fine-grained sandstone at the top. Clarke (1972) recorded
the presence of clay balls in the basal sand and concluded that these were derived from
erosion of the clay bodies in the Nanafalia Formation.
All units have a shallow dip to the south, the average being ~ 1.5 ~
ANALYTICAL
PROCEDURES
From preliminary examination in the laboratory it was apparent that the cores from the
three drill holes were similar and that each was readily divisible into a number of zones.
The core from drill hole B was selected for detailed chemical and mineralogical analysis.
COMPOSITION CUMULATIVE %
I0
20
30
40 50 60 70
80
90
DNES
IO
ID
12
IC
20
I-~
KAOLINITE ~
mMICA
GIBBSITE
~
~
QUARTZ
OTHERS
FIG. 4. Mineralcompositionin relationto depth in drill hole B, McLeodProspect.
Origin of Eufaula bauxite
131
Determination of major elements was carried out by a combination of techniques,
including X-ray fluorescence spectrometry, atomic adsorption spectrophotometry and
gravimetric means. Moreover, since according to Adams & Weaver (1958) and Adams &
Richardson (1960) the relative concentrations of thorium and uranium can be used as a
measure of the extent of leaching to which a rock sequence has been subjected, analyses for
these dements were made on kilogram core samples by means of a gamma ray
spectrometer with counting times of 5400 s. The mineralogical analyses shown in Fig. 4 are
based primarily on the X-ray diffraction results, although the chemical data were also used
to supplement these. In addition, selected samples of the cores were examined with a
scanning electron microscope in order to determine the textural relationships of the various
mineral constituents.
MINERALOGICAL
AND
TEXTURAL
VARIATIONS
Zone I
Sediments at the base of the drill holes generally had a mottled appearance and consisted
of argillaceous sand in which medium- to coarse-grained angular quartz was disseminated
in an abundant matrix of disordered kaolinite. Small amounts of mica were also present.
The rock generally broke with a conchoidal fracture and developed plasticity on wetting.
Zone H
The kaolinitic sand of zone I passed upwards into a dense, relatively pure clay composed
almost entirely of b-axis disordered kaolinite. A few flakes of mica were observed in some
samples from this zone and a reflection at 3.51 A, attributable to anatase, could be detected
on most X-ray diffraction traces. The clay was frequently mottled and fine limonitic
banding was evident in places. Gordon et al. (1958) described similar ferruginous banding
in the transported bauxites of Arkansas and attributed the phenomenon to fluctuations in
groundwater level.
Zone I I I
The boundary between zones II and III at the 18.3 m level was marked by a change in
the crystal structure of the kaolinite from disordered below to predominantly well-ordered
above. Throughout zone III gibbsite was almost invariably associated with the wdl-ordered
kaolinite and frequently formed the dominant mineral constituent. In the core from drill
hole B, gibbsite was generally fine-grained and disseminated but in drill hole A it was
present also as nodules and oolites. Within zone III several distinct breaks in the
mineralogical trend were apparent and, on the basis of these, division into subzones
designated A, B, C and D, from the base upwards, was made.
Ferruginous banding was common towards the lower part of subzone IliA where
well-ordered kaolinite predominated. Higher in the succession, however, gibbsite was also
present and the clay showed a distinct mottled appearance. Toward the top of this subzone,
mottling gave way to an overall maroon colour and gibbsite was almost as prevalent as
kaolinite. Several of the samples contained scattered flakes of muscovite mica and in one
from the 17.38 m level a granule of quartz was found. A scanning electron micrograph of a
kaolinite 'book' from this subzone is shown in Fig. 5(a).
132
T.C. Lukas et al.
FIG. 5. Scanning electron micrographs: (a) kaolinite 'book' in zone IIID, drill hole B; (b)
gibbsite 'book' from interior of pisolite, zone III, drill hole A; (c) gibbsite crystals in a pisolite
from zone III, drill hole A; (d) botryoidal kaolinite from zone IV, drill hole 13.
Subzone 11113 was characterized by the presence of mica in addition to kaolinite and
gibbsite. The mica content rarely exceeded a few per cent of the total mineral constituents,
but in the sample from the 16-3 m level up to 15% was present. At the equivalent interval
in drill hole A, much of the gibbsite was present either as 'books' (Fig. 5b), or euhedral
crystals (Fig. 5c) contained within coarse-grained oolites.
The succeeding subzone IIIC was 4.73 m thick and comprised mostly fine-grained
gibbsite with well-ordered kaolinite, together with small amounts of anatase and
disseminated iron oxide. The iron oxide imparted a red colour to the material. At the
13.8 m level, pisolites of hematite and lepidocrocite were encountered.
In subzone I I I D gibbsite was subordinate to kaolinite. The clay had an earthy
appearance and was, in places, heavily stained by iron oxides.
Despite the relative abundance of gibbsite in zone III, boehmite was not found in any of
the samples and, indeed, has not been recorded from the Eufaula area generally.
Zone I V
In composition and texture this zone did not differ appreciably from zone II in that it
was composed essentially of kaolinite. However, the kaolinite was well-ordered and mostly
present as plates, although botryoidal masses (Fig. 5d) were also observed.
Origin of Eufaula bauxite
133
Zone V
The upper part of the succession exposed in drill hole B was composed of fine-grained to
pebble-size, angular to rounded quartz with minor amounts of mica, ferruginous concretions, root remains and wood fragments, all embedded in a predominantly kaolinite
matrix. The kaolinite gradually changed from predominantly well-ordered at the base to
disordered at the top of the zone and, in places, was accompanied by minor amounts of
mixed-layer clay minerals, gibbsite and gorceixite.
CHEMICAL
VARIATIONS
S i O 2, A1203 and Fe203
In Fig. 6 the values for SiO2,A1203and Fe203 have been plotted relative to depth of the
sample for the interval between 7.1 and 21.3 m. The curves reflect the variations in mineral
composition shown in Fig. 4. Alumina attains maximum development and silica is
correspondingly depleted in zone III where gibbsite is abundant, whereas in zones II and
IV free-alumina minerals are absent and the relative abundance of the two oxides is
reversed.
Compared with younger, residual bauxite deposits developed on kaolinitic quartz sands,
e.g. at Weipa, Queensland (Loughnan & Bayliss, 1961; Jepsen & Schellmann, 1974), the
iron content in the Eufaula deposit is unusually low. This is probably due to
post-depositional reduction and dissolution of the element and, as discussed later, there is
evidence that the Eufaula bauxites accumulated, at least partly, in a reducing environment.
However, much of the iron is now present in the form of hematite, although lepidocrocite is
also abundant at the 13.84 m level.
TiO2/Al20 a relationships
Titanium and aluminium form hydrolyzate ions (Goldschmidt, 1954) and as such should
be concentrated to much the same degree in weathered sequences developed on a relatively
homogeneous parent rock. Consequently, if the Eufaula bauxite formed in situ through
%
IO
i
20
i
COMPOSITION
3,0
40
I
i
ZONES
50
I
60
I
8,
IOE]'~.
"1B..~14-
~.~---. . . .
t6.
Iiia
IlIA
18-
Fe203
20-
_..s.Lo2
1
1
I
i
i
I
I
FIo. 6. SiO2, AI203and Fc203 contentsrelativeto depth in drill hole B.
134
T. C. Lukas et al.
TiOz x10 3
20
30
4o
l
I
AI203
50
60
I
I
7o
ZONES
[
8
IV
IO
IIICI
I
12
E 14
I
16
IIIB
e-~ 18
IliA
i
I
I
i
i
i
i
i
i
I
I
i
FIG. 7. TiO2/A1203 ratio against depth in drill hole B.
intense leaching of clay material, as Rettger (1925), MacNeil (1945), Clarke (1972), Burst
(1974) and others have proposed, the TiO2/A1203 values plotted relative to depth of the
sample should yield a straight line. Fig. 7 shows that this is not the case for the Eufaula
samples; there is, however, a tendency for low values in the gibbsite-rich rocks. Possibly the
composition of the parent material varied markedly or, alternatively, the gibbsite and
associated minerals are of transported origin and represent the accumulation of detritus
derived from contrasting source areas.
Th/U values
From examination of the thorium and uranium contents of a wide array of sedimentary
rocks including bauxites, Adams & Weaver (1958) concluded that the relative abundance
of the two elements is primarily a function of (i) the degree of oxidation and leaching to
which the parent material has been subjected during the weathering stage and (ii) the redox
potential prevailing in the depositional environment. Under oxidizing conditions uranium is
readily lost to the leaching solutions during weathering, whereas immobile thorium tends to
be concentrated in the residuum. Hence, products of intense weathering such as bauxite
should have high Th/U values (>7 according to Adams & Weaver (1958)). On the other
hand, relatively low values (< 2) are to be expected in sediments deposited in a reducing
environment, due to the uptake of uranium from the associated waters through either
fixation in organic complexes or adsorption by clay minerals. These authors also contended
that sedimentary rocks with intermediate Th/U values (2-7) either comprise incompletely
weathered products or represent mixtures of materials derived 'from low- and high-ratio
environments'. If these proposals are correct, it follows that the Th/U values could furnish
a suitable method for differentiating allochthonous bauxites from those formed in situ.
Origin of Eufaula bauxite
135
Th/U
I
2,
3,
ZONES
i
5
V
I0
IIID
I
12
o
IIIC
E 14-
~ 16-
IIIB
IliA
~ 18-
II
20
I
I
i
I
I
I..2_,,-
FIG. 8. T h / U ratio against depth in drill hole B.
In Fig. 8, the Th/U values for sections of the core from drill hole B at McLeod Prospect
are plotted relative to depth. However, the results are the reverse of those anticipated if the
bauxite is essentially autochthonous. Thus, in the kaolinite-rich, gibbsite-deficient zones II
and IV the values range from 2-3 to 4.9, corresponding to the intermediate geochemical
facies of Adams & Weaver (1958), but in zone III, which is characterized by the presence
of gibbsite (and therefore should represent the most intensely weathered material), the
values are generally <2. An exception to this trend is in the sample from the
16.03-16.22 m interval where a value of 2.9 was recorded, but, as evident in Fig. 4, the
gibbsite content of this core section is very low.
DISCUSSION
Bauxitization is essentially a process of dissolution and leaching of mobile constituents,
including silica, from a parent rock and the concomitant enrichment in alumina, which is
mainly in the form of gibbsite. Critical to the process are the silica content and pH of the
leaching solutions--for as Gardner (1970) has shown, gibbsite does not develop where the
silica concentration exceeds 1.5 ppm, while at pH < 4 . 2 the mineral tends to pass into
solution. For bauxitization to proceed, therefore, silica must be flushed from the system as
rapidly as it is released from the parent minerals and thus infiltration of copious quantities
of fresh water is an essential prerequisite. It follows also that the process is inhibited by the
presence of organic matter since the intense leaching necessary to maintain such an
unusually low concentration of silica in the groundwater leads to the conversion of organic
matter to humic and other acids, resulting in podsolization (depletion of alumina) rather
than bauxitization (concentration of alumina). The specific requirements for bauxite
development are a permeable parent rock containing aluminium, a well-drained site, a high
rainfall and an environment facilitating rapid oxidation of organic matter.
Since bauxite and bauxitic kaolin occur within the Wilcox Group at locations as far
afield as Arkansas (Gordon et al., 1958) and Georgia (Shearer, 1917), there seems little
doubt that a climate conducive to bauxite accumulation prevailed over much of the
south-eastern United States, including the Eufaula area, during the early Eocene. It does
not necessarily follow, however, that the Eufaula deposits developed in situ. Indeed, when
comparison is made with residual bauxite occurrences of the present day tropical regions of
136
T . C . L u k a s et al.
the world, such as those of western India (Balasubramaniam, 1978) and northern Australia
(Loughnan & Bayliss, 1961; Grubb, 1970; Somm, 1975), it is evident that the Eufaula
deposits have a number of features that are difficult to reconcile with autochthonous
development.
Thus, unlike the younger residual bauxites, the Eufaula deposits occur as isolated masses
within a sequence of micaceous, quartz sands. Consequently, if as Rettger (1925) and
others have contended, the deposits formed in situ through intense leaching of segregated
clay bodies, it would be anticipated that the much more permeable sands encompassing
these bauxite-clay bodies would also have been affected by the percolating solutions, at
least to the extent of breakdown of the mica. However, not only does the mica in the sands
persist in a virtually unaltered state but, furthermore, flakes of the mineral can be found
within the bauxite zone.
Again, if the zones enveloping the gibbsite-rich core represent intermediate stages in the
transition of clay to bauxite, leaching must have attained maximum intensity at the core
and declined in effectiveness outwards. A mechanism by which this was achieved is difficult
to envisage.
Moreover, as Clarke (1972) observed, in places lignite beds up to several metres thick
are intimately associated with the bauxite and, therefore, swampy conditions prevailed over
at least part of the area, an environment that would seem least likely to promote intense
leaching.
The alternative proposal, that the Eufaula bauxite deposits are essentially allochthonous,
does not appear to have received serious consideration to date. Yet, the concept could
furnish an explanation for much of the observed phenomena, including not only the
lenticular and zoned structure of the individual deposits, and the intimate association of
lignite and mica with gibbsite, but also the vertical variations in A1203, TiO2, Th and U
contents, as well as the relatively low iron content and the absence of boehmite. A suitable
but probably oversimplified model in this respect is that of a meandering stream (or
streams) draining residual, blanket-like bauxite in the Piedmont to the north and dropping
its load both on-shore and off-shore. That deposited off-shore in the area south of Fort
Gaines probably intermingled with sediments of diverse source areas and lost its diagnostic
characteristics, whereas on-shore, intermittent stream flooding could have carried much of
the fine-grained material and occasionally coarser fragments into backswamps that
approximately paralleled the stream course. The well-ordered kaolinite found within and
above the gibbsite core at McLeod Prospect possibly resulted from reaction of gibbsite with
silica-charged waters diffusing from the surrounding sands and, pertinent in this respect,
De Kimpe et al. (1964) have shown that gibbsite, 'under suitable acid conditions favouring
breakdown to boehmite' reacts with depolymerized silica solutions to yield kaolinite. This
mechanism could also account for the absence of boehmite from the Eufaula deposits
inasmuch that development of the mineral would be inhibited by the conversion of all
available reactive alumina to kaolinite. Conceivably these processes are continuing at the
present time.
The kaolinite in zone II below the gibbsite core at McLeod Prospect has a disordered
structure and may represent original detrital material derived from a kaolinitic rather than
bauxitic source area.
ACKNOWLEDGMENTS
We are indebted to Messrs J. F. Westcott and F. C. Heivilin of A. P. Green Refractories for permission to
Origin o f E u f a u l a bauxite
137
study the cores, to M. C. Walker of the University of New South Wales for the elemental analyses, and to Dr
Paul Mueller of the University of Florida for advice on the thorium and uranium determinations.
REFERENCES
ADAMS J.A.S. & RICHARDSON K.A. (1960) Thorium, uranium and zirconium concentrations in bauxite. Econ.
Geol. 55, 1653-1675.
ADAMS J.A.S. & WEAVER C.E. (1958) Thorium-to-uranium ratios as indicators of sedimentary processes:
example of the concept of geochemical facies. Bull. Am. Ass. Petrol. Geol. 42, 387-430.
BALASUBRAMANIAM K.S. (1978) Mineralogy, geochemistry and genesis of bauxites of certain profiles of
western India. Proc. 4th Congress. Bauxites, Athens !, 35-76.
BURST J.F. (1965) Genetic relationship of the Andersonville, Georgia, and Eufaula, Alabama, bauxite-kaolin
areas. Am. Inst. Mining Eng. Trans. 256, 137-143.
CLARKE O.M. (1966) The formation of bauxite on karst topography in Eufaula district, Alabama, and
Jamaica, West Indies. Econ. Geol. 61,903-916.
CLARKE O.M. (1972) Bauxite and kaolin in the Eufaula District. Geol. Surv. AIa. BuR. 100, 89 pp.
DE KIMPE C., GASTUCHE M.C. & BRINDLEY G.W. (1964) Low temperature synthesis of kaolin minerals. Am.
Miner. 49, 1-16.
GARDNER L.R. (1970) A chemical model for the origin of gibbsite from kaolinite. A m. Miner. 55, 1380-1399.
GOLDSCHMIDT V.M. (1954) Geochemistry. Clarendon Press Oxford.
GORDON M., TRACY J.I. & ELLIS M.W. (1958) Geology of the Arkansas bauxite region. U.S. Geol. Surv. Prof.
Paper 299, 117 pp.
GRUBS P.L.C. (1970) Mineralogy, geochemistry and genesis of the bauxite deposits on the Gove and Mitchell
Plateaux, northern Australia. Mineral. Depostta 5, 248-272.
JEPSEN K. & SCHELLMANN W. (1974) Uber don stoffestand und die bildungsbcdingungen der bauxitlager
statte, Weipa, Australien. Geol. Jb., Hanover 7, 19-106.
JONES G.P. (1972) Origin, diagenesis and structure of bauxite deposits of southeastern Alabama. Proc. 7th.
Forum Geol. lndust. Minerals. Spec. Publ., Florida Bur. Geol. 7, 23-28.
LOUGI-INAN F.C. & BAYLISS P. (1961) The mineralogy of the bauxite deposits near Weipa, Queensland. Am.
Miner. 45, 209-217.
MACNEIL F.S. (1945) The Midway and Wilcox stratigraphy of Alabama and Mississippi. US Geol. Surv.
Strategic Minerals Inv., Prelim. Map 3-195.
RETTGER R.E. (1925) The bauxite deposits of southeastern Alabama. Econ. Geol. 20, 671-686.
SHEARER H.K. (1917) A report on the bauxite and fuller's earth deposits of the coastal plain of Georgia.
Georgia Geol. Suv. Bull. 31,340 pp.
SOMM A.F. (1975) Gore bauxite deposits, Northern Territory. Aust. Inst. Min. & Metall., Mono. $, 964-968.
WARREN W.C. & CLAng. L.D. (1965) Bauxite deposits of the Eufaula district, Alabama. US Geol. Surv. Bull.
1199-E, 310 pp.
K U R Z R E F E R A T : Allgemein wird angenommen, dab die Bauxit-Lagerst/itten des EufaulaDistrikts, Siidost-Alabama, autochthonen Ursprungs sind. Verglichen mit jiingeren residualen
Bauxiten der heutigen tropischen Regionen der Welt haben die Eufaula-Lagerst/itten jedoch
eine Anzahl yon Merkmalen, die sich nur schwer mit einer Entwicklung in Situ vereinbaren
lassen. Zur KI/irung dieses Sachverhalts wfirden drei Bohrkerne mit der kompletten Abfolge
einer der Eufaula-Lagerst/itten untersucht. Obwohl entg/iltige Schlul3folgerungen noch nicht
gezogen werden k6nnen, lassen sich die meisten der beobachteten Ph/inomene auf der Basis eines
in wesentlichen transportierten Ausgangsmaterials der Lagerst/itte erkl/iren.
R E S U M E N : Se ha aceptado generalmente el origen aut6ctono de los dep6sitos de bauxita
del distrito de Eufaula, al sureste de Alabama. Sin embargo, comparando con las bauxitas
residuales m~is recientes de las actuales regiones tropicales del mundo, los depositos de Eufaula
presentan una serie de caracteristicas que son diflciles de reeonciliar con su desarrollo in situ.
En un intento de resolver este enigma, se ha realizado un detaUado estudio sobre muestras
procedentes de tres perforaciones que atraviesan una serie completa en uno de los dep6sitos
de Eufaula. Aunque los resultados no son concluyentes, creemos que muchos de los fendmenos
138
Origin of Eufaula bauxite
observados pueden explicarse suponiendo que los dep6sitos se forman esencialmente por arrastre
del mineral.
R E S U M E: Une origine autochtone est g6n6ralement admise pour les gisements de bauxite du
district d'Eufaula dans le Sud-Est de l'Alabama. Cependant, compar6s ~ des bauxites r6siduaires
plus r6cents issues de r6gions actuellement tropicales, les gisements d'Eufaula pr6sentent un
certain nombre d'aspects difficilement conciliables avec une formation in situ. Dans le but de
r6soudre cette 6nigme, une &ude d6taill6es des carottes de trois forages effectu6s ~ travers un
gisement entier d'Eufala a &6 entreprise. Bien que les r6sultats ne soient pas concluants, il est
vraisemblable que la plupart des ph&mm6nes observ6s peuvent &re expliqu6s en admettant
une origine essentiellement due au transport des s6diments.