John Almon.

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with Zeuglodon bones, Laganum Bogcrai and Scuttlla LyeUi. More-
over, the oyster occurring on top of the Jackson beds, as stated
in a previous paper is not 0. Oeorgiana^ but a Gryphaea every-
where accompanying the Zeuglodon; but also occurring in the
Vicksburg marl and limestone. Nowhere in Mississippi has
a single Orbitoid been found associated with either the Zeuglo-
don, or any of the characteristic fo.<«sils of the Jackson group.
It is quite possible that in Alabama, Zeuglodon bones may have
been picked up in company with Orbitoids, equally as well as
with arift pebbles. There, the same ravine often cuts into the
strata of both groups, and of course commingles their fossils.
In Mississippi, I have found this direct superposition only in a
single instance; elsewhere, the regions in which the several
groups crop out are so far separated geographically, (in conse-
quence of the intercalation of lignittc strata,) as to leave the ob-
server no legitimate chance of error in reference to fossils.

Notwithstanding the defectiveness of his materials, Conrad
assigned to the Jackson group its proper place, between that rep-
resented by the Claiborne sands and the Orbitoides limestone.
He still, however (/. c.) thought it most probable that the Zeu-
glodon was referable to the same age as the latter.

A great deal of the obscurity in which the relative age of the
Southwestern Tertiary has been involved, is owing to too great
a reliance placed by most observers on lithological characters,

* It is impossible to RToid erroneoas infeneiices (mm the examination of foaaila
aent fur determination by amateurs, and rarely collected with a view ti> onroplete-
neis, or general results. From the collecti<m of Jackson fossils submitted to Mr.
Connid, any one would infer that this rich fauna had been totally extinguished by
some ctitaclysm. beft>re the deposition of the Vicksburg strata; whereas in fact»
pri>bably more than one-fifth of the former fauna is n^presented in the latter.

The same has happened with reference to the superior Cretaceous of Mississippi
ftnd Alhliama, the Kipley ^roup of Conrad, whose fossils as described by him from a
seUcted collection forwarded to him, would seem to constitute an isoUted group,
almost unconnected specifically, with the lower members of the Cretaceous of tha
Southwest and elsewhere ; whereas in reality it shares the leading fossils of the lat-
ter, and is ctmnected with the Rotten Limestone group especially, by transitions
both lithological and paleootological, as ascertained by myself a year prerioua,
(Mist. Rep., pp. 19, 84.)



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oj Mississippi and Alabama. 31

difierencea as well bb resemblancea. The '' white limestone of
Alabama" has so long been quoted as the matrix of the Zmtjh-
don as well as of the Orbitoides, that no one seemed to question
their being contemporaries. Yet in examining all the records
of the occurrence of Zeuglodon bones which I have been able to
collect^ I have no where found a distinct statement that the Or-
bitoids have been found associated with them in situ/ The Or-
bitoides limestone is mentioned as forming knolls, hill-tops —
the Ztuglodon as being found in level fields, or in ravines.

The true position of the Zeuglodon bed did not, however,
escape the glance of Lyell (On the Nummulite Limestone of
Alabama; this Jour. [2], vol. iv) ; for he distinctly identifies
the upper "Rotten limestone" bed of the Claiborne bluff with
that which, at Bettis' Hill, contains Aturm Alahamensis and Zeu*
glodon^ and underlies the Orbitoides rock. The only other ob-
server who seems to have recognized the same fact, is C. S. Hale
(this Jour., [2] vol. vi, p. 854). Tuomey, otherwise so accurate
in his field observations, ignores it, and speaks only of the " white
lim^tone " in general.

Nowhere has the geologist more need of divesting himself of
reliance upon lithcAogical characters, than in the study of the
Mi.ssi8sippi Eocene, Not only do the materials of the different

f roups often bear a most extraordinary resemblance to each other,
ut their character varies incessantly in one and the same stratum^
within short distances. Hale (/. c.) remarks that in Mississippi,
the Orbitoides limestone seems to be represented by blue marl-
stone, and so it is — sometimes. But while on the one hand we
see the hard limestone of the Yicksburg bluff passing into blue
marl (Byram, Marshall's quarry), we on the other hand find it

Eassing equally into a rock undistinguishable froni that of St.
tephens (Brandon, Wayne county); the varied fossils described
by Conrad disappearing almost entirely, to be replaced by mil-
lions of Orbitoids imbedded in a semi-indurate mass of carbonate
of lime, interspersed at times with similarly constituted conglom-
eratic masses of Pecten Poulsoni,

I cannot therefore, with the lights before me, agree to the pro-
priety of distinguishing as separate divisions the Orbitoides lime-
stone and the Vicksburg group of fossils. Even the occurrence
of a different species of Orbitoides (0. nupera Con.) at Vicksburg
cannot alter the case, for the undoubted 0. ManttlU occurs there
also, in the solid rock. And there are few of the characteristic
fossils of the Vicksburg profile, which I have not on some occa-
sions found side by side with the 0, ManteUi and its companions,
the Pecten Poulsoni and Ostrea Vicksburgensis.

Of course, the coral had its favorite haunts — the mollusks
theirs. There is nothing surprising in the fact that where the
one.abounds the others are usually scarce, or vice versd.



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82 £• W. Hilgard on the Tertiary formations

The Bed Bluff group.^n a late paper, above referred to, Con-
rad proposed to diistingiiish the lowe8t fossil iferous stratum ordi*
narily visible at Vicksburg, and subsequently studied by him
(No. 4 of roy Vicksburg section, ut supra), as a separate group,
which he considers as chtiracterized by the occurrence of Oslrea
Oeorgiana^ and for which he proposes tlie name of Shell Bluflf
group. I have elsewhere (this Jour., July, 1866) explained my
reasons for dissenting from Conrad as to the position between
the Claiborne and Jackson groups, which he assigns to this new
division. To the propriety of distinguishing it, however, as a
sub-group of the v icksburg age, I fully agree, though doubting
that of giving it the name of a loc^ility from which, as Conrad
remarks, but one coincident fossil is known — 0, Geoj'giana —
while another also occurring there — 0. sellfe/ormis — in Missis-
sippi and Alabama is confined to the Claiborne group. In a pro-
me of 80 feet, as occurring at Shell BlufiP, loose data like those
extant regarding this locality, cannot fairly be made a ground
of conclusions contrary to the order elsewhere elaborately ob-
served. For aught that is on record, the whole Jackson group
may be represented between the beds in which 0. Oeorgiana
and 0. sellixformis respectively occur at that'pluce, if (as seems
probable from its non-occurrence in the Jackson group of Missis-
sippi and Alabama) the former shell should be so restricted in
its range as Conrad supposes.

I believe the white limestone (No. 1 of my Vicksburg section)
which underlies the lignite at Vicksburg, but is visible only at
extraordinarily low stages of water, to be of the Jackson age, both
from its stratigraphical position and the lithological character of
the specimens I liave seen. But whether it is or not, there can
be no reasonable doubt that the usual Jackson strata, which are
larj^ely developed on the Yazoo above Vicksburg, underlie at
Vicksburg, as well as on Pearl river and Chickasaw hay, the Vicks-
.burg group.

The Georgiana bed at Vicksburg is preeminently the habitat
of a shell common to the Jack.son and Vicksburg stages, but most
abundant in the former, viz., Merelrix Subrina Con. ; of the two
Madrepores described by Conrad, and of Fulfjoraria Mississip.,
all occurring, more or less, in the Vicksburg stage proper. Of
the fossil first mentioned, I have afler a freshet found hundreds
washed out, mingled with numerous masses of Madrepores,
sometimes of several pounds weight, with Fulgoraria^ Natlca f
Vicksburgensis, Ostrea Oeorgiana^ etc. The bed has therefore af-
finities both above and below, and moreover occupies precisely
the stratigraphical position of the bed at Red Bluff (Miss. Bept.,
p. 185). Here the fossils are much more numerous and the afHni-
ties in both directions are therefore better expressed. Character-
istic and abundant above all, however, is a Plagiostoma, whioh I



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of Mississippi and Alabama. 83

cannot distinguish from figures and descriptions of P, dumosum^
but hesitate to refer to that species, since it has not been found
in the underlying Jackson strata. Lyell mentions the occurrence
of P. dumosum in the lower portion of the Orbi(oides limestone
at Bettis' Hill ; the same is mentioned by Tuomey, moreover, as
occupying a corresponding position in the St. Stephens profile,
associated with Orbitoids, and even his description of the litho-
logical character of the bed tallies with that of the Eed Bluflf de-
posit. Hale, likewise, mentions P, dumosum as one of the prom-
inent fossils of the "white limestone."

The Eed Bluflf bed seems, therefore, to be more or less coex-
tensive with the Vicksburg group, and regularly associated with
it as a subordinate feature. Its inconsiderable thickness readily
explains its entire absence at many points where, stratigraph-
ically, it ought to appear. Unfortunately, the fossils accom-
panying 0, Georgianasit the only locality, other than Vicksburg,
where it has been found in Mississippi, have not been observed.

The Cluibome group proper. — That the beds of blue marl and
white marlstone, which in my Beport I have designated as the
" Calcareous Claiborne " group, are strictly equivalent to the typ-
ical fossiliferous sand at Claiborne, with underlying limestone
bed, is probable both from their stratigraphical position and the
correspondence of all the fossils thus far observed; though from
the indiflferent state of preservation in which the latter are found
. in the Mississippi stratum, these are few in number. Ostrea sellce-
Jormis Con. and O.divaricata Lea, are the leading shells; I have
also recognized Corbula gibbosa Lea and Volula petrosa Con. These
beds possess fewer good exposures in Mississippi than either of
the preceding groups, and may possess many unooserved features.
Since publishing my Beport, I have received evidence that it
extends somewhat farther westward, between the territory of
the Jackson and Siliceous Claiborne groups, than it appears on
the map. Nor is the division between it and latter groups very
well defined, inasmuch as the transition from siliceous to calca-
reous materials is a gradual one, through strata often very rich
in Soutella Lyelb\ Pecten Lyelli, Oslrea diuaricata and 0. Alahamen-
sis Tuo.? I am not aware of the existence of any lignite bed
in the dark colored clays which immediately underlie the blue
marl.

Siliceous Olaibome, or Buhrstone group. — The precise Alaba-
mian equivalents of ray "Siliceous Claiborne" group are not
nearly so obvious. The extreme variability of its strata both
in Mississippi and Alabama (see Tuomey's first Beport, and C. S.
Hale, I. c), which it seems natural should carry with it a corres-
ponding variation at least in the predominance of fossils, and
the comparative scarcity and ill preservation of the latter, render
its study doubly diflicult. I think that, as Tuomey intimates
Am. Jour. Sci.— Second Ssriis, Vol. XLIII, No. 137.-^ an., 1867.

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34 E, W. Hilgard on the Tertiary formations

(ibid., p. 146) and Conrad more decidedly avers (this Jour., Sept
1865, p. 266), there is a lower division to be distinguished, which
represents the fauna of the Great Lignite epoch, while the upper
one seems clearly to be the equivalent of the Buhrstone forma-
tion of Georgia and South Carolina. That here as elsewhere
in the Mississippi Eocene, lignitic beds should intervene where
there is a direct superposition in Alabama, need not surprise us.

Since publishing my Report, I have had some opportunity of
examining more closely the southern portion of Newton and
Lauderdale counties. I have ascertained that the facies of the
white siliceous claystone, so remarkable for its lightness (Miss.
Rep., p. 124), is much more extensively developed than I had
anticipated; that though often showing lithological transitions
into chert and sandstone, it is on the whole characteristic of the
superior part of the siliceous division, whose lower portion is
represented by the soft yellow sandstone of South Neshoba and
North Newton, its lowest probably by the hard, buhrptone-like
rock with chalcedonized shells, of the Marion ridge. (Ibid., I c.)
All this tallies very closely with Tuomey's observations in Ala-
bama where the " chalk hills " are also a matter of popular re-
mark.

Lower Lignite — Oreat Lignite group? — The fauna of the lower
division, which has never been studied as yet, I conceive to be
represented in the small fossiliferous sandstone deposits skirting
the Cretaceous in Tippah and Pontotoc (Miss. Rep., pp. 109-112) ; -
in the isohited patch of ferruginous green sand of Shongalo, in
Carroll, Holmes, Attala and Choctaw counties, Miss., which seems
to have been struck again at 415 feet in the bored well at Jackson.
(Ibid., pp. 121-123.) As regards this deposit, I will call attentioa
to the lact that it contains Aturea Alabamtnsis^ claimed by Con-
rad as a leading fossil of the Great Lignite, and moreover closely
resembles in its lithological characters, the Shark river beds de-
scribed by Meek and Havden.

Finally, in Alabama, this era, as Conrad observes, is probably
represented in the Bashia creek section of Tuomey's first Report ;
which, since it is said to contain abundance of well preserved
fossils, is well worthy of especial study.

But from this point, Conrad, Hale and others have been led
by lithological appearances to extend the limits of the Great Lig-
nite to the southward and westward, to deposits far above it,
and even, probably, beyond the limits of the Tertiary.

Conrad (this Jour,, Sept., 1865) inclines to refer to this group
the buried forest containing tree palnw (Miss. Rep», 153), observed
jointly by Harper and myself in 1855. The "Nipadites and
Cycadites" of tnat locality, so far as any determination of speci-
mens goes, were "all in the eye" of one of the observers. At
all events, the bed lies above the Orbitoides limestone, and with-



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of Mississippi and Alabama^ 85

in the Grand Gulf group of my Beport ; and the " large oygter"
overlying marl and limestone, mentioned in the same place, is
not 0. Oeorgiano^ but the Oryphcea repeatedly referred to. As
for the Yickaburg lignite, it is but one of the many lignitic
seams constantly found intercalated between the marine stages
of the Mississippi Tertiary. Finally the Port Hudson strata,
observed by Carpenter and Lyell, are either the highest of the
Grand Gulf group, or form part of the (probably Post-pliocene)
formation underlying the Mississippi delta — the *' Coast Plio"
cene " of my Report.

Hale (this Jour., [2], vol. vi, p. 356) goes so far as to identify
with the Bashia creek lignite, beds occurring near Natchitoches,
and on the Trinity, Colorado and Brazos rivers, in Texas.

I shall not here reiterate the reasons and data given in my
Beport (p. 109) in support of my opinion that the whole of my
"Northern Lignitic" is of the lowest Eocene age, having noth-
ing new to add to what is said there on the subject, and by Dana,
(Manual of Geology, p. 610.) In a late letter, Lesquereux informs
rae that according to the specimens he has examined, there must
be a considerable difference of age between the Winston strata
marked c in my general section (Miss. Bep., p. 108) and those
marked a in Tippah, and that the former appear to be newer,
probably Pliocene. Had the conclusion been the reverse, it
might have been more readily reconciled with stratigraphical
evidence. Winston county adjoins Neshoba, where, as in Lau-
deniale, the Lignitic unequivocally dips beneath the siliceous
Claiborne strata, and the locality c is on the same parallel with
the marine outlier of the Claiborne age, in Carol! and Attala.
Between locality c and the edge of the siliceous Claiborne strata
in Neshoba and Lauderdale, the outcrops continue in unbroken
succession and uniformity of character; there is nothing to indi-
cate the superimposiiion of a limited Pliocene basin upon the
most ancient Eocene, here, any more than between loc. a in Tip-
pah and b in Lafayette county, which latter Lesquereux is also
inclined to consider of later age.

I hope to be able, hereafter, to submit to the experienced
hands of Lesquereux more complete sets of specimens from these
and other localities situated nearer to the recognized Eocene,
with a view to the solution of the interesting problem regarding
the correspondence of ancient and modern floras on the two
continents.

It is the continuation of these lowest lignite beds of Lauder*
dale which, in the map accompanying Tuomey's first Alabama
Beport, is intended to be represented by a narrow band of brown
lint, skirting the Cretaceous on the south, across the state. Tuo-
mey was not certain of its eastward limit, and it would appear
from the notes of Mr. Thornton, appended to Tuomey's second



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36 E. W. Hilgard on the Tertiary formations

Beport, that on the line between the Cretaceous and Tertiary in
BarlKJur county, Ala., no similar strata occur.

Straiigraphical cojtformatwn of the Tertiary, — I now turn to
the consideration of some of the general stratigraphical phenom-
ena of the Mississippi and Alabama Tertiary, which have given
rise to misapprehensions regarding its dip and general arrange-
ment.

I have stated (Miss. Kept, p. 107) that the general dip of the
Tertiary strata of Mississippi seems to conform lo that of the Cre-
taceous strata — westward in the northern part of the state, and
southward, or nearly so, in the southern. The westward dip of
the old Lignitic does not appear to be much greater than the fall
of the rivers, from the fact that on the waters of tlie Tallahatchie
and Yallabusha, the same strata appear in the beds of streams
for miles, before giving place to higher ones. I do not think the
dip can exceed four or five feet per mile; but the variability of
materials and small extentof outcrops (which often exhibit local
dislocations^ render direct observations extremely difficult. As
we approacn the region of southward dip, however, the inclina-
tion becomes more aecided and can be observed even in limited
outcrops, on streams or railroad cuts trending southward. On
Pearl river below Jackson, and on the Chickasaw hay, there is
no difficulty in recognizing the fact; but yet it is by no means
«asy to determine correctly the amount of dip, unless by reg-
ular leveling operations; the variability of the materials and
thickness of the strata, as well as their irregular surface, render-
ing all the usual pocket instruments unreliable. According to
the best observations I have been able to make by reference to
the river level, the dip of the Vicksburg strata at Byram (Miss.
Bep., p. 146) and of the Jackson strata near Trotter's plantation
(ibid^ p. 135) amounts to from 10 to 12 feet per mile, S. by W.
But this is by no means the maximum or minimum observed,
but refers to points where the great regularity of succession for a
considerable distance seemed to indicate a normal configuration.

If tWs estimate be correct (and I do not believe it will here-
After be found to differ materially from the truth), it would go
to prove that the upheaval which caused this dip as well as that
of the Cretaceous system in Mississippi and Alabama, was a slow
one. For the artesian borings on the territory of the former
formation, have shown the dip to be about double the above, or
25 feet per mile^ in Monroe and Lowndes counties. Miss., and
the adjoining portions of Alabama. On the other hand, ,the
strata of the formation overlying the marine Tertiary in south
Mississippi possess so slight a dip as, at first, to render its very
existence doubtful.

In the general (north and south) section accompanying Tuo*
fney's geological maps of Alabama, the Tertiary strata are rep-



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of litississippi and Alabama. 37

resented as dipping southward, conformably with those of the
Cretaceous. Nevertheless, in tlie section from Baker's bluff to
the lower Salt Works on the Tombigby, he finds the white lime**
stone (= Jackson and Vicksburg groups) occupying "a trough-
like depression in the Buhrstone formation." In conversations
with me, a few months prior to his death, he expressed his belief
that such was the general disposition of the Tertiary strata, and
that on clase examination it would turn out that the strata passed
over in going southward from the bordtT of the Cretaceous,
would be again passed over iu reversed order, still farther south.
My report of the existence in Mississippi, of a lignitiferous for-
mation (the Grand Gulf group) southward of the marine Ter-
tiary, seemed to confirm this view.

My subsequent examination of the Mississippi Tertiary has
proved that in Mississippi at least, the disposition is such as first
conceived by Tuoiney, and laid down on his map; affording a
strong presumption that the same is the case in Alabama But
at the same time I found, in two different meridians, a similar
anomalous reappearance of older strata which had sunk out of
view farther northward.

One of these cases is noticed in my Beport (p. 128). From
Jackson to Canton, a distance of twenty -five miles N. and S., the
same clay marl stratum with Zenglodon bones and Oryphcea con-
tinues on the surface, overlying conformably, as it seems, the lig-
uitic strata, which appear in the bed of Pearl river, just above
Jackson, overlaid by the shelUbed. But thence they sink out of
view rapidly, and are followed in regular succession by the Jack-
son and Vicksburg strata. It will be remarked that here there
is a singular elbow interrupting the regular E. by S. course of
the strike.

The other case occurs on the Chickasawhay, contrary to the
statement in my Report (I, c), in making which I overlooked
some specimens and notes of 1855, then mislaid.

I find that on the very southern edge of the Vicksburff terri-
tory in Wayne county, at Dr. E. A. Miller's (p. 146), I collected
Oaslrtdum vetiutum^ Morio Petersoni^ Laganum Rogersi and other
Jackson fossils, from a blue sandy marl directly underlying
the Sl Stephens limestone teeming with Orbitoids. North of
this locality, the Vicksburg strata alone are seen outcropping un«
til we reach Red Bluff* where the Jackson strata disappear be-
neath those of the Red Bluff group. Within this distance of
about ten miles, not only have the Jackson strata "dipped up"
again, but the Red Bluff group, with its concomitant green clays
and stiff clay marls (nearly a 100 feet in thickness altogether) has
vanished from between them and the Vicksburg strata proper.
It might therefore be suspected that the whole formation was
here tninning out, and that we were near the edge of a basin.



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38 E, W. Hilgard on the Tertian/ formatiom

So far, I have been unable to observe the marine Tertiary iq
juxtaposition with the Grand Gulf group on the Chickasawhaj,
and cannot positively assert that the former dips under the lat<
ter at all. In Hinds, fiankin and Smith counties, their relative
age is clearly exhibited, but it is possible that they do not over-
lap very far, so that, were a portion of the superior formation
removed by denudatiou, the edge of the marine basin might be
laid bare. Yet from the fact that at the very locality mentioned,
the Yicksburg strata proper possess approximately the same ag-
gregate thickness as elsewhere observea, we should notoonclude
that the stratum is about to run out Nor is it easy to reconcile
such a supposition with the grand scale on which these marine
strata are developed in the direction of their strike, through the
states of Alabama, Mississippi and Arkansas, and their relations
to the Great Lignite. It would seem more natural to suppose
that they form part of the deposits of a tertiary Gulf of Mexico,
and now (either themselves or their deep sea equivalents) under-
lie that gulf. Under this point of view, they might possibly be



Online LibraryJohn AlmonThe American journal of science and arts → online text (page 5 of 102)