Great Neapolitan Earthquake of 1857/Appendix to Part I
APPENDIX TO PART I.
No. (I.)
OF THE NEPTUNIAN ROCKS THROUGH WHICH THE VOLCANOES OF VULTURE FORCED THEIR WAY.
The ancient fires of the region of Vulture opened a road for themselves through the neptunian rocks, which are not materially different from those which surround the other volcanic districts of Campania. The examination which we have made of the neptunian rocks of our kingdom from Balzorano, in the southern limits of Abruzzi, to Tarentum in Puglia, and Pizzo in Calabria, has proved to us that the same rocks occur everywhere in the same order, and with nearly the same topographical conditions. Geologists who have visited these countries have met with no slight difficulty in establishing a division in these sedimentary rocks, according to the order in which they have been deposited; and the difficulty has not been diminished by comparing them with rocks of determined epoch, which might be contemporary with ours. For us, who have not had the advantage of seeing in their natural position any of the various sedimentary formations (except those of the kingdom of Naples), the difficulty has been still greater, nor can we flatter ourselves that we have surmounted it. Meanwhile, without entering into discussions which would be foreign to the principal aim of our work, but keeping to what appears to us to agree with our observations, we prefer to divide our neptunian rocks into three series, that is, three distinct formations. In the first series we shall include all those calcareous rocks which are particularly characterized by Nummulites, Nerineæ, and those organic forms of which we have no example in the fauna of the present epoch, and which paleontologists, uncertain of their real nature, have denominated rudimentary. (Rudisti.) The greater part of our Apennine mountains being formed of this calcareous rock, we shall retain for it exclusively the name of (Calcarea Apennina) Apennine limestone. The rocks of the second series, very varied in their mineralogical composition, agree in being distinctly stratified, in being almost entirely destitute of animal fossils, and in sometimes containing a great quantity of vegetable fossils of the Fucoid order. Although it is not easy to find Fuciform impressions everywhere in rocks of this formation, nothing better indicates their character than the presence of these plants; for the absence or extreme rarity of animal fossils is a negative characteristic which in exceptional cases may be affirmed of every species of rock. The last series comprehends marls, limestone, and sandstone, abounding in marine fossils, the greater number of which belong to species which now exist in our seas. To these rocks we shall confine the name sub-Apennine, although others elsewhere have designated some of the rocks of the preceding series with this denomination. They undoubtedly belong to the supercretaceous period; and if the igneous phenomena of Epomeo in the Phlegrean region, as we have shown elsewhere,[1] have preceded some nearly supercretaceous deposits; yet in the Vulture district, where the order of position between the neptunian and volcanic rocks is in several places very easily seen, I have never found the igneous rocks, lying beneath any of the various rocks of the third series; so that we may maintain that the emergence from the sea of the sub-Apennine deposits, took place previously to the first fires of the Vulture. There are also in this same volcanic region frequent and extensive fresh-water formations; but, contrary to what has been observed of the marine deposits, they lie invariably above the rocks of igneous origin, and closely resemble the sedimentary deposits which are in process of deposition in our own days, under very restricted conditions, in like places abounding in water. Pursuing a chronological order, we shall briefly speak of these when we have concluded our remarks on the volcanoes of the Vulture district.
First Series.—Apennine Limestone.
The rocks of which the oldest formations of aqueous origin in the kingdom of Naples are composed, are almost exclusively calcareous, and include many varieties, which seldom constitute an essential difference. The most frequent of these varieties is the compact, with conchoidal fracture, of a white, or clear smoke-gray colour. Another variety, somewhat less abundant, has a granular texture more or less distinct, in which oftener than in the preceding, small cavities lined with crystals of the same substance are found. Passing over several varieties of minor importance, we shall enumerate four others. The first has a brecciated structure, enlivened by gay colours, and is capable of receiving a beautiful polish. Of this we have magnificent specimens in the marbles of Vitulano, and Mondragone, in Terra di Lavoro. The second is of a beautiful white colour, and pulverizes easily at a touch. It may be seen between Piedimonte di Alife and S. Potito at the foot of Matese in the district of Melfi, after the 77th milestone on the road from Valva, and in many other places. The third variety, not very different from the preceding in appearance, is that which geologists denominate chalk, and which, so far as we know, is only found at Monte Gargano.[2] The fourth is bituminous, and is met with in many places, particularly in those which abound with Ichthyolitic fossils. Quartz or Firestone (Piromaco) is so frequently found in limestone of this series, that it may be considered characteristic of it. Sometimes it appears in veins at the junction of the thicker calcareous strata, but more frequently it is imbedded in them, assuming various figures, among which the spherical is remarkably perfect. Astonishment at the perfection of the globular figure of these Rognoni di Piromaco[3] has occasionally given rise to the foolish supposition that they are areolites. The manner in which this variety of quartz is found in the limestone clearly proves it to have had the same origin as the rock which contains it; and this is corroborated by the frequent cases in which it partly or entirely takes the place of the carbonate of lime, of which the fossils enclosed in the same rock were originally formed. In such cases it is worthy of note, that the other variety of crystallized quartz is occasionally united to the Piromaco. With our present chemical knowledge, we can easily understand that silex, as well as carbonate of lime, may have been held in solution in the water by which they were deposited. But we cannot, with the same facility, account for the silex being precipitated in the state of Piromaco, or as crystallized quartz, whilst we know that silex is naturally deposited by some mineral springs, or artificially by solution in concentrated waters, with the qualities proper to Gieserite, or hydrate of silex. Perhaps arguing from the frequency with which fossils are found converted into Piromaco, we may attribute its presence to organic substances, as Becquerel observed that organic substances in a state of putrefaction, deposit crystals of pyrites in a solution of sulphate of iron.
Carbonate of magnesia, in widely-varying proportions, is always united to carbonated Apennine limestone. The large quantity which is occasionally found, we think, must be attributed to the facility with which, in some places more than others, this rock undergoes great changes, caused by the continual influence of the weather (meteori). One of the most surprising examples of this kind of decay may be observed in the upper part of the valley of Tramonti, in the province of Salerno, where the phenomenon extends over a large tract of ground. In some places, as in the vicinity of Amalfi, the magnesian limestone presents the characteristics of Dolomite, having a granular texture, and dissolving slowly in acids. However, we cannot subscribe to the opinion of those who attribute the presence of magnesia to the action of internal plutonic masses, which have given to the sedimentary limestone rocks the characteristics of Dolomite. There is no ground for refutation of the opinion, that true Dolomite is of neptunian origin, and therefore its presence is insufficient to prove that the change has been occasioned by plutonic rocks. And the reasons which prevent our applying the theory of dolomization to our Apennine mountains are—1st. The absence of plutonic rocks in their vicinity, which might occasion the phenomenon. 2nd. The rare occurrence of true Dolomite, and the fact that it is confusedly mixed with magnesian limestone, which does not possess the distinctive characteristics of Dolomite. And, lastly, the organic forms of well-preserved fossils in those rocks which most manifest dolomitic qualities. The last is one of the best arguments against the maintenance of the Dolomite theory in reference to our magnesian limestones, but of it we do not find many examples. We might conclude that the presence in great quantity of carbonate of magnesia is adverse to the propagation of marine animals, or that it has contributed to the destruction of the shells of the ancient fauna. In the Dolomite of Amalfi, where we found several well-preserved casts of Terrebratulæ and Ammonites, this opinion is still further strengthened; for in all the examples which we examined their shells were entirely destroyed. The preceding considerations, however adverse to the phenomenon of dolomization in the rocks of our Apennines, do not exclude the internal plutonic forces, by which they were disturbed from their primitive position, and raised to their present height; nor the phenomenon of metamorphosis, which is clearly manifested in some particular districts, where limestone is found at a short distance from crystalline rocks of igneous origin. In the district of Castrovillari, perhaps more than anywhere else, frequent examples of metamorphosed Apennine limestone are met with. It acquires a granular crystalline texture, not unlike statuary marble, and contains passing through it some thin veins of quartz, with chlorite, many crystals of pyrites, and sometimes cinnabar, and the traces of fossils are very nearly obliterated. There are yet more evident proofs of metamorphosis in the rocks of the succeeding series, which are changed into Quartzite, Stannite, Talc, and schistose argil, all of which are found in the limestone of the region. The Apennine limestone has generally been reported poor in organic remains, which might furnish paleontologists with determined characteristics. Our researches lead us to a contrary opinion; but as we cannot, without deviating from the design of our work, enter into an examination of the different species of fossils which we have found, it must suffice to say, that the number of species, and the quantity of each kind, are such as to give us a correct idea of the abundant fauna of the sea, in whose depths our highest mountains were formed. Any who wish for a convincing proof of this assertion may find it in the rich collections which, within the last few years, have been deposited in the Mineralogical Museum of the Royal University of Naples. The most frequent and abundant organic forms which we have found belong to the Rudisti, and of these we may say, that there is no place in which we cannot discern their trace; and in some spots, whether owing to the nature of the rock in which the fossils are preserved, or from the habits of those animals to live in myriads in a small space, the quantity is so enormous, that the entire rock appears to be composed of them. Monte Gargano, Monte Lesule, in Matese, the brown limestone of Il Ponto Consolazione, near Lauria, in Basilicata, present striking examples. Although they are usually so completely petrified, and identified with the rock itself, so as to render the determination of the species difficult, yet by attentive examination we can distinguish a difference between those found in places not very distant from each other. The large species of Nummulites next claim our attention; and while, like the Rudisti, or even more strikingly, they are found united together in myriads in one place, they are not, like them, distributed over a large district. In many extensive districts they are in vain sought for. Besides, in Monte Gargano, and the neighbouring islands of Tremiti, renowned for fossils of this kind, no contemptible deposits are found in the vicinity of Lama, in Abruzzi, near Casalbone, and not far from Ariano, in the province of Avellino, and in the territory of Benevento (Olivella di Pacca), where they are disseminated through limestone and Piromaco. The nerinæa, another kind of mollusc, which deserves our attention, usually accompanies the Rudisti, and is found in many places; several species, differing in size and form, being recognizable. Besides these three groups of fossils—to mention but a few examples of a long series, containing many species, some of which probably ought to constitute new genera—we must record, in the province of Terra di Lavoro, the spiral shells of the Lumachelle of Monte Casino and Vitulano, the Diceratiti of Monte Licinio, near Cerreto, and some shells, allied to the Natiche, of Monte Lesule, in Matese. In Monte Gargano there are also some remarkable impressions of plants, probably of the family of the conifers, two gigantic specimens of Bulle, a Pirula, and Ammonites Rothemagensis; and in this same mountain, as well as in the vicinity of Amalfi, and near Castelgrande, in the district of Melfi, different species of zoophytes are not scarce. As to our ichthyolites, of which but few species were known before the recent works of Costa (Costa, 'Paleontology of the Kingdom of Naples, 1850'), we are now acquainted with a great many in the mountains of Pietraroia, Giffuni, and Castellamare; and by the discoveries also of Professor Costa, of which as yet only a brief account has been published (Costa, 'Hints relative to the Discoveries of the Paleontology of this Kingdom made in the year 1851'), we have made out at Pietraroia, in the icthyolitic limestone, some species of reptiles. From the brief account we have given of the fossils found in the Apennine limestone, it is easy enough to infer that all, or at least the greater part of them, belong to the great Chalk formation. But from such observations as have hitherto been made, although we cannot say that they are sufficiently numerous, it is not equally easy to establish any division among them; nor can we decide with any certainty whether some of them may not belong to still more ancient formations. Yet, not knowing of any instance in which Rudisti have been found in those rocks which contain the fossil fish at Giffuni, Pietraroia, and Castellamare, we are inclined to think that they ought to be placed in the Jurassic group. Meanwhile we consider it better to refrain from putting forward ill-grounded opinions, and to defer the solution of this question until a future day shall bring more decided facts to light; for at present, so far as our knowledge extends, ichthyolitic limestone has not undoubtedly been found either above or below that which contains Rudisti, nor have any of our species of fossil fish been recognized in rocks of a well-determined epoch, although some species have been found in the chalk formation of Monte Gargano. The topographical character of mountains formed of Apennine limestone enables us to distinguish them at a great distance: their long narrow summits, the lesser ramifications branching off from their sides, and dipping down till they end in an acute ridge, their slope not unfrequently broken by majestic steps, against which the inferior rocks lean, as if against a firm vertical wall, the strata of which they are composed appearing gradually to tilt up, as if they would touch with their ends the high acclivities, and even the most elevated ridges, form so characteristic an aspect, that they are easily distinguished from neighbouring mountains and hill of a different nature. Admitting a few unimportant exceptions to this general order of topographical configuration, the fact of greatest significance to which it is necessary to direct attention is, that the same Apennine limestone which is visibly displayed to a great extent in the provinces of Capitanata, Bari, and Lecce, there assumes a completely different aspect. We find low hills, commonly called Murge, in the province of Bari, extending in various directions, and sloping down to a vast plain, which with the mountainous region forms a winding line from north-west to south-east, almost parallel with the coast of the Adriatic, that extends from the Gulf of Manfredonia to Brindisi. To the characteristic outline essential to the Murge we must add the no less important character apparent in the arrangement of the strata, which, besides being more distinct than is usually observed in mountains, is generally horizontal, or somewhat inclined to the horizon. These differences between the perpendicular strata of the mountainous regions, and the horizontal strata of the low hills, sufficiently prove the elevation, or at least the great displacement, to which the former were subjected; while the latter have preserved the same position in which they were originally deposited, relatively at least to the horizon, if not to their distance from the centre of the earth. It might be thought that the limestone of the Murge, the stratification of which is so different from that of the mountains, was deposited at a later period; and this would appear to verify the opinions of these geologists who, unacquainted with the fossils it contains, considered it to belong to the super-cretaceous period. But the frequent occurrence of Hippurites in it contradicts his opinion, and as we find it agrees in paleontological characteristics with the limestone of the Apennines, we are compelled to hold them contemporary. Nor can we find any other reason for the difference of stratification except that now mentioned, viz., that the first was not subjected to the internal plutonic forces of our planet.
Second Series.—Rocks with Fucoids, or the Macigno Formation.
Generally speaking, their topographical aspect sufficiently distinguishes the rocks of this series from those of the preceding; and, although they are often found in the elevated regions of the Apennines, yet they never form great chains of mountains. Their usual appearance is that of small mountains or hills, with rounded and depressed summits, and in a few cases, where the strata are unusually thick, and greatly elevated, they assume the appearance of limestone mountains. The old summit on which the city of Monteverde is built, and which rises much above the lesser prominences which surround it, furnishes us with a most striking example of this effect; and even here, though the developed form of the mountain is an exception to the general rule, yet its height does not equal that of the ordinary limestone mountain masses. The different species of rocks which compose this formation are remarkable for the manner in which they are stratified, frequently alternating with each other, and presenting the most beautiful appearance of regularly disposed strata, the one kind surprisingly distinct from the other. The ordinary thickness of the strata varies from a decimeter to half a meter. Instances of great thickness are less frequent, and occasionally the layers are very thin. The most important point observable in these rocks is their strange position, so highly inclined to the horizon. The distinct development of the strata enables us to determine their degree of inclination and direction with great accuracy; yet as to their direction we have not been able to ascertain towards what point they are generally elevated, the direction of their inclination being found very various even in places separated by short distances. The angle of inclination also is very uncertain, varying often between 25 and 50 degrees; nor are instances rare in which it attains to 70 or more degrees, and in some places the strata might be called vertical. In no other of our sedimentary rocks have we better evidence of the great displacement which must have occurred, than in that which the great inclination of these strata presents, as it is impossible to conceive how they could have been deposited as they now appear. Yet it is in rocks of this series that we find the greatest difficulty in assigning the true cause of this fact. First of all, finding several strata of clay which crumble easily, on account of the softness which they acquire from the absorption of water, and the limestone and sandstone strata having, on account of their thinness, but little resistance, we are justly inclined to think that the elevation of the strata is the effect of the rents occasioned by the continual mining of subterranean water. Admitting the possibility of this reason, and maintaining that it may have in some measure effected the change of the primitive situation of the stratified rocks of this series, it is not probable that it alone, could have produced such great effects, and often in an uniform manner over a great space, as observation has made known to us. In many places it is entirely impossible that any other cause than that of plutonic forces, having their seat at a great depth beneath the terrestrial surface, could have, so strangely and throughout entire regions, elevated the enormous stratified masses, and thus discovered their internal structure; but for which we should never have been conveniently enabled to examine them, and perhaps might still have remained in ignorance. And now, for a clear explanation how catastrophes of a like nature appear to us to have happened, it is necessary to declare, that if, by relating facts as they first appear to sense, we have attributed the actual position of strata inclined to the horizon to elevation, this does not exclude the idea of undermining operations. And since, whether they have been elevated or whether they have been undermined, we should always find their primitive horizontal position deranged in the same manner, it is not easy to decide which of the two conditions has rendered the region mountainous, or, if both were in operation, which of the two has had the greater influence. For if we consider the general physical property of matter to diminish in volume by the decrease of its temperature, the theory at present held by all, of the primitive state of igneous fusion of our planet, leads us to the necessary consequence, that in cooling it must have diminished in size, and the forces which have acted on its consolidated crust must induce it to approach the centre. In the district occupied by the volcanoes of the Vulture, other particular considerations present themselves to the mind of the geologist who contemplates the strata of the neptunian rocks, here, perhaps, more elevated than elsewhere. As we shall presently state, these volcanoes are surrounded on every side by hills, formed of rocks of the second and third series, which must have felt the effects of the disturbing volcanic eruptions, and therefore it is easy to attribute their elevation to the same eruptions. In the east side of the base of Mount Vulture, along the line occupied by the cities of Melfi, Rapolla, Barili, and Rionero, in many places it is easy to observe the strata of limestone and red marl beneath the lavas and volcanic conglomerates, with the ordinary character of elevation proper to this formation. Half way on the road between Rionero and Barili, on the left-hand side going from Rionero, in the place denominated the Valle del Salice, a long series of the outcrops of stratified rocks, which form the bed of a brook which flows over them, is seen. The average of their inclination, though variable, is about 70 degrees, and they are elevated from the side turned towards the east and south-east. It is enough to say that they are inclined in a contrary direction to the slope of the Vulture, to prove it impossible to attribute their elevation to an internal force, whose centre of action should coincide with the central part of the volcano. The same thing may be observed in many places on the same road, so that this arrangement of strata is invariable for upwards of a mile. And to this fact surely Fonseca alludes, when he says that between Rionero and Barili the limestone strata are inclined almost at right angles to the declivity of the mountain. (Fonseca, 'Geognostic Observations on the Vulture.') Along a brook which runs near Barili, from the north-west side, the same strata of limestone and marl on the right bank are elevated towards the west 44 degrees, and on the left bank, towards the north, 31 degrees; and, one being almost opposite the other, their displacement cannot be referred to the action of the Vulture. In a valley situated to the north of Rapolla, the waters which run through it pass over limestone strata; and in one place where these are very apparent we have found them elevated 55 degrees towards the north-east, not to mention some which are even nearer to the vertical position. Lastly, omitting other facts of a similar nature which are less conspicuous, along the little river which runs round the hill of Melfi in the north-west side, some strata of grey argil are seen, which have the same inclination as the hill; and in the west side, not very distant from the bridge, commonly called Gaetaniello, there are some strata of red marl, containing fucoids, inclined 70 degrees towards the north-east. Their elevation cannot be attributed to the principal volcanoes of the Vulture; nor does it agree with the centre of action of the volcano of Melfi, as then they would have been inclined to the east. From these facts it is natural to conclude that the displacements observable in the neptunian rocks of the volcanic region of Vulture were not occasioned by the same forces which gave rise to the volcanoes, but rather that they occurred previously to their eruptions. This opinion is strengthened by the fact, that they present the same appearances as have been observed in other places, where the distance from the Vulture and the particular manner of dislocation prove that the eruptive volcanic force could not have occasioned such displacements. We shall select, from many instances which we might quote, that of the lofty eminence which we recently mentioned, on which the city of Monteverde is built. It lies to the north-west, distant in a direct line little more than four miles from the lakes of Monticchio. It is chiefly composed of large strata of Macigno, some of which are upwards of four metres in diameter; and in the southern summit, called Sierra della Croce, the strata being laid bare by several hollows, show an inclination of 47 degrees; and from this side rises another opposite summit, having the same inclination, from which we may conjecture that the Sierra della Croce has been separated from it. Therefore, even supposing we admit that the internal impulse accompanying the fires of the Vulture, having its centre in the neighbouring lakes of Monticchio, may have extended to a great distance, it is impossible that the actual arrangement of stratification of the Macigno of Monteverde could have been occasioned by it: an order not essentially different from that of the stratified rocks which are displayed from Melfi to Rionero.
In the district of the Vulture, much better than in any other volcanic region of our kingdom, we can observe the manner in which the volcanic rocks interstratify with the neptunian; and, comparing them with the observations here collected, we cannot reconcile them with the idea that volcanic forces could have had so extensive a field of action near the terrestrial surface. On the contrary, we are led to the opposite opinion, namely, that the space is very limited in which volcanic explosions can occasion elevations or other perturbations of ground, and that the first convulsions are almost always concocted under the materials which are subsequently ejected. As we must return to this argument in another part of our work, what we have already said is sufficient to testify, that in our opinion the volcanoes of the Vulture have had no part in the elevation of the rocks of the second series, in which they have appeared.
The relation of arrangement between these rocks and the Apennine limestone presents another field of inquiry, in which it is not easy to see clearly. Is it beyond a doubt that the former belong to a period subsequent to the latter? Are the elevations of the first cotemporary with the elevation of the second? Have they been once or oftener convulsed? What difference of conditions results from the difference of composition between the rocks of the first and second series? These are the principal questions which the geologist is compelled to discuss. We shall speak of the last when we have given the necessary mineralogical description of the numerous fucoidal rocks. As to the first question, we must admit that, throughout Campania and the greater part of the Principatas, we cannot, generally speaking, perceive with sufficient clearness the super-position of one system of rocks above the other. Not so in Lucania: there the super-position of the fucoid strata above the Apennine limestone is very evident, and their conditions are notably different. These observations have induced us to maintain, not only that the former were laid down at a subsequent period to the latter, but also, what is still more important, that they belong to two distinct formations. Perhaps the most suitable place for examining these conditions is the Valva Road, along which, from Oliveto to within a few miles of Atella, we never lose sight of the line of contact between the hill of the second series and the mountains of the first. The latter appear to come out from under the hills which lie round their bases; and in some places, as at Fontana della Rose, between Laviano and Muro, the order of the strata which form the hill is clearly seen to rest upon the Apennine limestone. At the same time we can observe the difference of direction and inclination of the strata belonging to the two systems: a discordance which is also manifested in the different topographical aspect of which we have already spoken, and which cannot exclusively depend on difference in mineralogical composition of the rocks. As the strata of clays, sandstones, and limestones with fucoids, in the northern provinces, do not possess any notable difference of composition from those in the southern, nor are the paleontological characteristics at all different, arguing from analogy, we consider them all to belong to the same formation, and are confirmed in this opinion by never having met with any fact which could clearly contradict it. From this difference between the Apennine limestone and the rocks of the second series we are led to infer, as a necessary consequence, that the former must have been displaced before the latter were deposited; and again, these latter rocks being so much inclined is the proof of a second period of elevation. The manner in which the rocks of both series interstratify with each other appears to us sufficiently to declare that the more ancient formations cannot of necessity have been exempt from the disturbing force which displaced the more recent. Of these general conjectures relative to the convulsions to which our sedimentary rocks have been subjected we find satisfactory proofs in the southern regions; whilst, on the contrary, in the northern, as we have already observed, the relation of arrangement between the rocks of both systems is not manifested with sufficient clearness, nor can we support the theory that the same phenomena have everywhere occurred. Having already observed that the Apennine limestone may be divided into two distinct regions, the one mountainous, the other almost level, called Murge, a fact of no slight importance appeals to our consideration, relative to the distribution of rocks of the second series in connection with this division, viz., that they only occur in the mountainous region. It was not without surprise that we traversed the province of Bari, and the neighbouring districts of the provinces of Lecce and Capitanata, seeking diligently, without success, for rocks of the second series, of which we never found a trace. We must confess that we cannot clearly account for this circumstance. Where the mountains formed of Apennine limestone rise, there must certainly have been during the epoch in which the rocks of the second series were deposited, a topographical condition completely different from the level plains. Ought this topographical difference to be considered sufficient to prescribe the limits within which such rocks can be formed? Now, as we shall presently show, among the components of these rocks, there are some which have very probably been transported from the granite mountains of Calabria, and in general consist of materials which may have come from distant places. Ought we to regard the direction in which their elements were transported as the cause of their being found in certain regions, and being wanting in others? The mineralogical composition of the fucoidal rocks is extremely varied. We may divide them into five different species, viz., limestone, marl, sandstone, limonite, and gypsum; and each of these admits of being subdivided into many varieties, of which we shall only record the principal. The varieties of most frequent occurrence in the limestone are the marly, of various colours, sometimes with those beautiful appearances which take the designs of ruined buildings (calcarea ruiniforme). Another, less frequent, but not less characteristic, is a breccia, of very minute fragments, with rose-coloured cement, sometimes intense, and again diffused, bearing a great resemblance to red porphyry, consequently of lovely effect in workmanship. The most beautiful specimens of the calcarea ruiniforme are to be found in the neighbourhood of Gesualdo and Frigento, in the province of Avellino, and the second variety is more common in the district of Melfi than anywhere else. If the limestone of this series contains almost invariably some clay, the clays, on the other hand, are always mixed with some proportion of carbonate of lime, which gives them a marly character. They are sometimes compact (amorphous), but more frequently divided into thin laminæ, without losing the property of forming with water a ductile paste. They are usually of a gray sky colour, and in Lucania are not unfrequently red. These rocks on one side pass by imperceptible degrees into limestone; on the other beginning to contain minute particles of mica and small grains of sand, the latter gradually becoming more abundant, they change into sandstone. The sandstone itself, owing to the size of the grains of quartz, and their abundance or scarcity, and also to their varying degree of tenacity, present innumerable differences, which are of no importance. They possess, for the most part, the characteristics of true Macigno; in some cases are good for sharpening edged tools, and in others may be used with advantage for making bricks or crucibles capable of bearing a high temperature. The Limonite is seldom found pure, and its deposits are so scarce, that they can with difficulty be profitably used for the extraction of iron; nevertheless, mixed with carbonate of lime, it is rather frequently found in each of the three preceding kinds of rocks, especially in the limestones and marls.
Ferruginous sandstones, occasionally mixed with deposits of Limonite, are not scarce in the district of the Vulture, and it is requisite to take care not to confuse them with volcanic productions. When the limonite unites with marl, it occasions such strange forms, that the naturalist no less than the uninitiated must regard them with astonishment. Besides what I have said relative to these Eagle stones, of which beautiful specimens are to be found in the district of Gerace, there are some remarkable varieties in the Fucino district near Pietraroia, which, from their resemblance to pieces of petrified serpents, have been denominated serpentini. To these kinds of configuration we may add the spheroidical masses with laminated concentric structure, found in the vicinity of Alberona, in Capitanata, and the prismatic forms of the valley of Ansanto, outwardly composed of large crusts of Limonite with Siderosa, and filled interiorly with marl, and often with pieces of the same Limonite. In the sandstone, besides the minute grains and rounded pebbles (pezzetti rotolati) of quartz, of which it is essentially composed, pebbles of rock crystal are sometimes found in great abundance. For the most part they belong to the granite, quartzite, or porphyry, and vary greatly in size, increasing from that of a filbert to about two decimeters in diameter. In occasional instances they are found of a surprising magnitude; but these, as well as the smaller specimens, have a rounded surface. We may instance one, which was found above Monte Vergine, near Avellino, more than five decimeters in diameter; and another, in the region called Fontana delle Rose, not far from Muro, whose greatest diameter was sixty-three centimeters. This last region, made known by the published works of Tenore and Gussone,[4] ought to be visited in preference to any other, by those who desire to examine the great rolled masses of granite which exist in our Apennines. On the road from Laviano to Atella, a little past the seventy-first milestone, we met on the right-hand side, a path leading to a spacious valley, through which the waters of the Fontana delle Rose run. Along this rough path we often meet with large granite boulders, and in the valley following the course of the stream, several large isolated ones may be found. Of these last there can be no doubt, that, like those still imbedded in the sandstone, they too were inclosed in the rock, and when it was disintegrated they remained scattered as we see them through the valley. Many such rolled masses of granite, and of another kind of crystalline rock, are found along the River Olivento, commencing at the source under Ripa Candida, and extending to its junction with the torrent of Macera; similar rocks are also found in other places surrounding the volcanic region of Vulture, or on the Vulture itself. We have seen some at the Bosco di Gaudianella. When we have explained the relation of arrangements between the neptunian rocks of the third series and the volcanic, it will not be difficult to understand how they came there. Lastly, among the districts in which numerous pebbles of rock crystal are observed, we must enumerate the vicinity of Pietraroia, remarkable for the great variety which is found there. Before we had observed the granites enclosed in the limestone of the Fontana delle Rose, we referred the blocks of the same kind found at Monte Vergine, and Pietraroia to the doubtful series of masses of similar rocks, sometimes of enormous size, called by geologists (erratici massi) erratic blocks.[5] We now class them in another group of rocks, and assert that their origin is not at all different from that of the minute grains of quartz, of which the Macigno of the fucoidal rocks is composed; the grains as well as the spangles of mica which are frequently seen in clay, being minute particles of granite, or of some other crystalline rock. The greater number if not all the varieties of granite found in isolated blocks among the sedimentary rocks of the Apennines, resemble, in the most minute particulars of their sensible properties, the rocks of the same kind which we observed in their primitive arrangement in Calabria. If this is sufficient to assure to us that they owe their origin to the granitic mountains of Calabria, it will follow, that we must hold, that at least the greater part of the materials which form these rocks of the second series, was derived from these mountains; for, it is indubitable that the elements of which they are formed, must have been transported from regions many miles distant from the places where they are deposited, and the mountains of Calabria from which they might have been taken, are the nearest. As to the inquiry into the origin of such impetuous and extensive torrents of water, possessing the force necessary for carrying down so large a quantity of waste material, this, we must admit, is a difficult question, and perhaps the consideration of the manner in which this transport was effected is still more difficult.
Allowing every one to conceive the events of such remote epochs, according to his own measures of probability, and trusting to future researches to reveal to us the ancient history of the earth we tread, we shall confine ourselves to a few considerations relative to the manner in which the rocks we have undertaken to treat of were deposited. We find them mostly formed of thin strata with parallel surfaces, regularly deposited one over the other, and consisting alternately of strata of limestone, clay, and sandstone, thus proving the habitual tranquillity of the water beneath which they were deposited. On the other hand, the large rolled granite rocks testify that occasionally these same waters were violently agitated. Lastly, the great number of strata, the ends of which are visible in some places, assure us that the formation of the fucoidal rocks must have occupied a long period. Gypsum is not so frequent or abundant in rocks of this series as in the other. Sometimes it is arranged in strata, or crystals of considerable size are scattered through the clay; again, it forms large deposits which do not exhibit any signs of stratification: in this case its structure is eminently crystalline. An example of its extraordinary arrangement may be observed a little more than two miles to the west of Melfi, at a place called Masseria del Gesso, and a very large deposit occurs in the territory of Marcerinaro, in the province of Catanzaro, extending more than a mile. Observing the conditions of these deposits, and reflecting that gypsum is not so generally diffused as the other rocks of the same formation, we are of opinion that its origin must have depended on particular causes, probably of the same nature as those which in our days, on a smaller scale, are generating gypsum in the valley of Ansanto, in the province of Avellino. The largest crystals of gypsum formed in argil, are found close to the village of S. Potito, south-east of Piedimonte di Alife. It is not scarce in Terra di Lavoro, being found distinctly stratified near Mola di Gaeta, Casanova, Torrecuso, and in some other places. In the province of Cosenza, strata may be seen in the clay on the right bank of the torrent Pantusa, between Cerisano and Marano, and near the salt pits of Altamonte. In the last region gypsum forms a part of the immense deposits of Rock salt, of which (as it is foreign to the aim of this work to treat of them more particularly) we shall only say, that in our opinion they belong to the fucoidal rocks, and their origin is analogous to that of gypsum. The fossil characteristics of the Macigno formation belong almost exclusively to the vegetable kingdom; different species of fucus are the most remarkable, so that in some places immense numbers of impressions have been found. We met with examples of this kind in the grey marl and limestone in the vicinity of Alberona, in Capitanata, or in the red schistose marl on the banks of the little river which runs at the foot of the hill of Melfi, on the north-west side; and in the same red marl heaped together, impressions of the fucus, Colle delle macine, are found near Lama in Abruzzo Citra. We frequently find, both in the marl and limestone, branched cylindrical concretions, more or less broken, sometimes more than six decimeters in length and easily separated from the rock which contains them. We cannot doubt that they are formed from plants, and they ought probably to be considered fucoids. Small deposits of lignite are also frequent, among which it suffices to mention that of the Vallone della Salla, near Pagliari, to the south of Benevento, in which we have found the stems, leaves, and seeds of carbonized plants in good preservation.[6] It would certainly be of great benefit to science if the species of these plants were precisely defined; we are not aware whether any one has as yet directed attention to this matter, or has published the results of his inquiries. We have not time for it, nor could difficult inquiries of this nature find a place here. As to fossil animals, to repeat our former statement, if there are any, they are very rare. In some limestone strata in the vicinity of Gaeta, which probably belong to this series of rocks, we saw some very distinct impressions of Pecten, which did not appear to us to belong to any of the living species of our seas. And in the limestone near Madonna di Macera, north of Melfi, we found a few fragments of marine shells, but we could not determine with certainty to what genera they belonged. From what has been now said, the difficulty of referring our fucoidal rocks to any formation of a determined epoch must be very evident. However, as they are subsequent to the Apennine limestone, and more ancient than the supercretaceous deposits called sub-Apennine, the question to be decided is, whether they belong to the last of the cretaceous groups, or to the first of the supercretaceous. We do not know whether the question can be further settled, nor do we consider it of sufficient importance to repay the trouble of a closer definition.
Some of these rocks have been confused with the supercretaceous deposits, others have been referred to the cretaceous or (giurassico) Jurassic period. In our opinion they all belong to the same formation, having a similar mineralogical composition, the same paleontological characteristics, and a not discordant arrangement of strata. We consider them, then, as distinct from the real supercretaceous deposits (which they rather resemble in mineralogical character), not only on account of the want of fossil animals, but, what is more important, on account of the disagreement of their strata with that of the marls, and sub-Apennine shelly sands. We have already seen that the difference between them and the cretaceous deposits, or at least those of the Apennine limestone, is still more striking, and therefore we are of opinion that the fucoidal rocks form a distinct system.
Third Series.—Sub-Apennine Rocks.
The rocks of this series most frequently consist of marly clays, sandstone, limestones, and a particular conglomerate of large pebbles. The arrangement of these rocks is not so regular as those of the preceding series, the strata are not so distinct, and they are always found horizontal, or but slightly inclined to the horizon, so that they do not appear to have been disturbed from the primitive position in which they were deposited. The topographical configuration of these rocks, which are often of such little thickness that we might even call them superficial, has no distinctive character. For example, lying over the cretaceous limestone of the Murge, they merely render the plain more uniform or level, which but for them would have had greater inequalities. In the midst of the Apennines, or at the foot of these mountains, they form hills with a gentle descent somewhat level on the top. And if in any rare instance, as in that of the eminence upon which the city of Ariano is built, they have a more elevated and developed form, it appears to have been occasioned by the ancient topographical conditions of the place having been changed, a great part of the rocks having been carried elsewhere, while they continued with those that remained. The sub-Apennine limestone is usually tufaceous in appearance, very friable, and almost entirely formed of minute fragments of zoophytes and marine shells, many specimens of which are found enclosed in a complete state of preservation in the rock. This rock, which is most abundant in the province of Bari, we have never found in the heart of the Apennines. Sometimes it is not so tenacious, and not so rich in fossils. The sandstones (arenarie), are generally friable, and one might rather say were deposits of sand; thus they are easily distinguished from the compact sandstone of the preceding formation, called Macigno. They often enclose small pebbles of different kinds, which, gradually increasing in size and number, at last form a conglomerate of large pebbles, of which there are amazing deposits. The greater number of these pebbles are formed of limestone, often marly, of Piromaco which sometimes changes into Diaspore, and of very compact sandstone. There are some pebbles of granite and other crystalline rocks, which we can easily understand came from the Macigno of the preceding formation, which, as we have seen, sometimes contains them in great abundance. From the other rocks of the same formation, or from the Apennine limestone, they have undoubtedly obtained other kinds of pebbles. We may mention those of quartz and Piromaco, which often still preserve between two opposite surfaces the limestone in which the Piromaco had been imbedded in the form of little strata, precisely as we find it in rocks of the first series. Deposits of pure sand with small pebbles are met with everywhere; but the large pebbly conglomerate is only found in mountainous regions, or near them, whilst the Calcareous Tufa exclusively covers the plains. The argil then, which is always more or less marly, is habitually of a sky-coloured grey, and, owing to its plastic qualities, is much better adapted for pottery than the fucoidal argil. In Calabria, where there are extensive mountains of rock crystal, the sub-Apennine deposits occasionally manifest particular characteristics, owing to the mineralogical elements of the neighbouring mountains which enter into their composition. One of the most beautiful examples is furnished by certain conchiliferous breccia, in the vicinity of Cosenza, with fragments of granite, and a great quantity of mica, which at first sight one might say was formed of granite, and which might lead the unskilful to think that they had found granite filled with marine shells like sedimentary rocks. The limestone of this series, whether tufaceous or compact, is more abundant beneath, or in the more ancient deposit; whilst the argils and sands usually occupy the upper position whenever they are found with the limestone. As to the conglomerate of large pebbles, it may be considered the most recent sub-Apennine deposit, as it is never found beneath any other kind of neptunian rock of this series. It is frequently found lying on rocks of the preceding series; the conglomerate on which Ripacandida is built, and that on which the city of Lavello is founded, furnish us with examples in the vicinity of the Vulture; the latter deposit of conglomerate extends level for many miles, from the tavern of Rendina, to the northern district of the territory of Lavello. The southern declivities of the Vulture which are included in the name Monticchio, are formed of deep deposits of the same conglomerate, which will by-and-by claim our attention. The cities of Venosa and Carbonara are also built on extensive deposits of large pebble conglomerate, the arrangement of which differs so much from that of the preceding instances, because it lies on conchiliferous sub-Apennine marl, which is distinctly visible near La Fontana de' trenta Angeli, little more than two miles N.N.E. of Venosa. The immense quantity of pebbles which are frequently found heaped together in the heart of our Apennines is an evident proof of the great diluvial action to which these regions were subjected after the deposition of the supercretaceous rocks. Abandoning the inquiry into the unknown cause of this catastrophe, we may, with better hope of success, seek to discover whether it preceded the emergence of Southern Italy from the sea, or whether it was subsequent to it. Of these opinions, the second is perhaps the more likely to be true, as no marine fossils have ever been found in the conglomerate of which we have spoken; and although we have never been so fortunate as to meet with any land animal remains, yet in the Mineralogical Museum of the Royal University of Naples, there are some elephants' tusks (difesi elefante), found near Chiaromonte in Basilicata, and an upper jaw with the molar teeth, belonging to the same class of quadrupeds, which was found last year near Chieti, to which fossils some pebbles are adhering, which lead us to presume that they had been dug out of the conglomerate.
Sub-Apennine paleontology is distinguished by possessing many species yet existing in the Mediterranean Sea. The subject has been treated by Brocchi and Philippi, and several other notices have been published by Neapolitan writers. Meanwhile the question whether deposits are found with us, which belong to the lower supercretaceous rocks, otherwise called Eocene, in which fossils of species analogous to the existing species are much less frequent, needs further investigation; and as we cannot conclusively determine it, it suffices to remark that the fossils of the supercretaceous rocks of Pizzo, in the province of Catanzaro, mostly belong to lost species, and that the other deposits of Gargano manifest the same condition still more strikingly.
- ↑ Scacchi. 'Geological Memoir of Campania.' Naples: 1849. Pp. 19, 20.
- ↑ Limestone passing into chalk is found abundantly in many other places, especially in the lateral valleys to the westward of Padula.—R. M.
- ↑ Kidney-formed masses.
- ↑ Tenore and Gussone. 'Memoirs of Tours performed in the Years 1834–1838.' Naples: 1842. Pp. 75, 76.
- ↑ Scacchi. 'Lessons in Geology.' Naples: 1842. P. 131.
- ↑ Breislak, notes this deposit in the 'Physical Topography of Campania.' Florence: 1798 Pp. 63, 64.