REPUBLIGA DE CUBA

SECRETARIA DE AGRICULTURA

FIELD GUIDE TO GEOLOGICAL EXCURSION IN CUBA

BY R: H. PALMER

•

CARASA Y CA., S. EN C. IMPRESORES TENIENTE HEY 12 -14 HABANA FIELD GUIDE TO GEOLOGICAL EXCURSION IN CUBA

BY

R. H . PALMER

This pamphlet has been prepared for -the use of the members of the American Association of Petroleum Geologists who take part in the Cuban Excursion that follows the annual convention held at New Orleans in March, 1938. It is descriptive of the geology along the route of se veral trips that have been planned. These trips have been selected to provide a general idea of one of the major geological units of Cuba. This unit occupies the Province of Habana and the eastern half of the Province of Matanzas. · The area covered has been extended to the east beyond the unit in question to include a part of an area that is believed to have petroleum possibilities.

First excursion: Habana-Matanzas-Col6n (2 days) The route is from Habana to Matanzas by the Hershey Railroad with stops along the way at points of geological interest. This trip and the local geology in and around Matanzas will consume the first day. The following day the excursion will continue to Colon and return to Habana by the Central Highway. The main geological features along the route will be explained.

Second excursion: Habana-Bataban6 (1 day) This excursion is to the south coast. It crosses the principal structures of this part of Cuba and affords a general idea of the cross-section of the island. Localities in and around Habana will be visited to show local details of the column and structures. Third excursion: Bacuranao Oil Field ( Yz day) The Bacuranao Field is the only field in Cuba that has produced petroleum in commercial quantities. It is located 16 kilometers · east of Habana. The preparations for the excursions have had the active support of the Secretary of Agriculture, the Secretary of Public Works and the Tourist Commission. The Department of Engineering of the General Staff of the Cuban Army has done the manual work in the preparation of the geological maps. The co-operation of these various agencies of the Cuban Government has made possible these preparations. HABANA- MATANZAS EXCURSION HERSHEY RAILROAD Habana Harbor. The harbor was excavated when the land was at a. somewhat higher level in respect to the sea than at the present. This may possibly have been during the Pleistocene when the water in the tropics stood at a lower level due to the withdrawal of water incident to the accumulation of glacial ice in the north. The channel leads to the ocean through a deep narrow gorge partially filled with sand to a depth of at least 30 meters. This accumulation ocurred either when the water was restored by the melting of the ice or by a subsequent sinking of the land. The flooded nature of the harbor and the drowned valleys of the rivers along the north coast to Matanzas indicates that this sinking was general. Casa Blanca. The ferry crosses the bay to Casa Blanca which is the terminal of the Hershey Railroad. At the station there is a low exposure of Pliocene (?) which is but a remnant of a much larger deposit that formerly lined the harbor. This lies unconformably on or against the Cojimar (upper Oligocene) which forms the steep slope to the north. The Habana-Matanzas Anticline. On the east edge. of Casa Blanca the railroad enters the upper Cretaceous, Habana formation, terrane, and continues on rocks of this age to Matanzas except for a low saddle at Hershey, where the large sugar mill is located. To the south lies a long low hill of intrusive serpentine. This is the first of numerous serpentine intrusions occurring along the core of the Habana-Matanzas Anticline. The Habana-Matanzas Anticline is a long, well developed structure extending at least as far west as Habana and ending in Matanzas to the east, a distance of 90 kilometers. It forms the hills known as the Cordillera. The railroad follows the north flank to Ma tanzas. The first record of folding of this structure is post-upper Cretaceous and pre-upper Eocene. This synchronizes the formation of this structure with the Larimide Revolution of western United States. Elsewere in Cuba there are definite data that major movements occurred post-middle Eocene and pre-upper Eocenet This was a period of intense folding along the Cordillera. Close folding, shearing and minor overthrusting were regular phenomena. · Erosion removed a large part of the topographic evidence of this first folding. Later subsidence was followed by the deposition of the lower Eocene (Universidad), upper Eocene (upper Principe), upper Oligocene (Cojimar), Oligo-Miocene and Miocene and latter Tertiary. The record does not indicate continuous deposition as no deposits of the disputed Cretaceous-lower Eocene, middle Eocene nor lower Oligocene ages are known within this structure. Late in the Oligocene the forces of compression again became active with the resultant folding and elevation of the structure. It appears that this folding continued intermittently through the Miocene and even into the later Tertiary; In late Ivliocene or possibly later, this structure rose above the surface of the sea and was exposed to erosion. During the subsequent lapse of time the entire Tertiary has been removed from the crest of the anticline and the upper Cretaceous exposed in a belt that is in places 12 kilometers wide. At Barreras is another large intrusion of serpentine. On the north side of this intrusion the Union Oil Company has drilled a number of wells. These wells range from a few hundred to 2.000 feet. This field has been in exploitation since 191 6 and produced to 1937 over 147,000 bbls. Oil seeps have frequently been reported around serpentine intrusions. A few kilometers south of Guanabo an oil well was drilled in 1929 to a depth of approximately 3,300 feet with no results. East of Guanabo a number of serpentine intrusions may be observed on the south side of the railroad. To the south, on the skyline, is a jagged cliff. This is Escaleras de Jaruco (Jaruco Stairs). It is the eroded remnant of the Guines Ls. (Oligo-Miocene) that forms the south flank of the anticline. At Hershey there is a low saddle in the Habana-Matanzas anticline which divides the structure into two nearly equal parts. Here the Tertiary is preserved across the crest from the north ·to the south flank. The resistant limestone of the Oligo-Miocene preserves the elevated topography of the saddle. · Just east of Hershey the railroad drops back into the low, dissected upper Cretaceous terrane and continues to Matanzas. This part of the excursion is practically a duplication of the part from Habana to Hershey. The serpentine intrusions (not mapped) are somewhat less numerous but are larger. One large intrusion running in a north­ west-southeast direction passes directly under Pan de Mantanzas and from the air appears to have elevated this prominent hill. A few cobalt claims have been located on these intrusions and a small amount of ore has been extracted. The eastern part of the core of the structure is called the Yumuri Valley, from the river which occupies its floor. Near the end of the railroad, the Yumuri river is drowned, producing a more or less open swamp -evidence of late sinking.

MATANZAS AND. VICINITY Y umuri Gorge. The gorge funishes the best known section of the Tertiary succession from the Oligocene into the Pliocene. It was first described by Spencer in 18 9 5. The beds nearest the station on the north side of the river, were named the Matanzas formation by Spencer and are probably Pliocene in age. They are loosely consolidated coralline limestone about 50 feet in thickness. Directly under the Matanzas formation and geographically up the gorge to the northwest, is a series of gravels, limestone ledges and sandstone, 850 feet in thickness. These beds contain a middle Miocene fauna. The upper Miocene is probably also present but the fa una has not been recognized. The next succeeding formation lying below is a hard, resistant limestone which has been called by various names in different parts of Cuba: Giiines Limestone, Porous Limestone, Cavernous Lime­ stone and Y umiri Limestone. It forms the steep walls of the gorge in which occur the numerous caverns with stalactitic curtain-like deposits seen from the road. At the northwest end of the gorge and stratigraphically at the base of the Yumuri series is the Cojimar formation. This is a light gray to white marl carrying an upper Oligocene fauna composed chiefly of foraminifera. Nearly everywhere this formation contains fossil salt. The marl phase of the Cojimar is confined to proximity to the coast. Its inland equivalent is either a hard limestone or a soft white calcareous mud.

La Cumbre (Yumuri Heights). A road leads to the heights forming the rim of the Yumuri Valley on the northeast side of the gorge. On the ascent several Pleistocene terraces are crossed which indicate former exposure to wave action. This part of the valley rim forms the eastern end of the Habana­ Matanzas Anticline. The broad valley opens to the west -a vista of striking beauty. The floor of the valley is upper Cretaceous interrupted by long, narrow tongues of serpentine intrusions. On each side are the flanking cliffs of Tertiary limestone. In the other direction, to the east, is Matanzas Bay. This body of water is intimately connected with the Habana-Matanzas Anticline, as it is the submerged eastern end of the complementary syncline formed south of the anticline. This has been named the Almendares-San Juan Syncline from the rivers that occupy the west-east ends of the axis.

CIDRA (South from Matanzas)

MADRUGA ANTICLINE

South of the Almendares-San Juan Syncline is a second large anticline of considerably greater length. It has been traced for a distance of 150 kilometers. It may be referred to as the Madruga Anticline, from the town situated near the middle point of its east­ west extent. The Cidra trip was planned to cross the axis of this structure at a point where the upper Cretaceous is exposed. The road south from Matanzas ascends the low hill of the south flank of the Almendares-San Juan Syncline or the north flank of the Madruga Anticline. During the ascent the road passes through a large plantation of henequen, the fiber of which is used for rope. This plant thrives on the shallow, dry Giiines Limestone soil if within reach of the ocean spray brought in by the trade winds. Occasionally a view back to the north, towards Matanzas Bay, discloses the several terraces on the plunging east end of the Habana-Matanzas Anticline. After ascending the hill the road continues to the south on a terrace corresponding to one in the series just mentioned. The belt of Giiines Limestone is about 10 kilometers wide. The landscape is typically a Giiines one. The red soil is characteristic of the formation. Red soil is a product of the weathering of this limestone and is known as laterite. This residual soil is in marked contrast to the residual soil in the temperate zones. The end products in the north are such compounds as carbonates, silicates, hydrous silicates and oxides. These are gray or dark in color. In the tropics, on the other hand, the process of weathering continues to a more advanced stage. The decomposition is more complete and other products are formed. These are for the most part hydroxides of iron and aluminum and are red in color. Other elements are also present but the iron hydroxide imparts the distinctive red color. Another product of tropical weathering occurring in the red soil of the Giiines as well as in other formations is the small black or purple black spheres known as perdigones (shot) . So abundant are these that at times they will give a distinct color to a field. Their origin is not known. At kilometer 13.5 on the highway a serpentine intrusion crosses the road. This is a locality of considerable importance as the contact relationships between the serpentine and Giiines Limestone: are in evidence. It may be noted that the Giiines Limestone is fractured in the vicinity of the contact, that limestone fragments are imbedded in the serpentine and that near the serpentine the limestone is crystalline in cpntrast to its amorphous condition 1 00 yards distant from the intrusion. This locality is taken as evidence that there are post-lower Miocene serpentine intrusions. The dating of the serpentine intrusions in Cuba is a debated subject. As will be indicated later, the intrusion have been placed from pre-upper Cretaceous to post-lower Miocene. At Kilometer Post 15 south of Matanzas is a small outcrop of diorite on the south side of the serpentine. Elsewhere diorite has been observed on the south side of serpentine intrusions. Coincidence is the only explanation offered. Beyond the diorite, at Kilometer 15 the upper Cretaceous is exposed in a belt about 2 kilometers wide across the crest of the Madruga Anticline. The upper Cretaceous narrows rapidly to the east and disappears under the Eocene. It reappears approximately 20 kilometers to the east in the vicinity of Coliseo. A broad belt of Principe (upper Eocene) approximately 10 kilometers wide borders the upper Cretaceous on the south. Beyond this is the Giiines Limestone. A noteworthy feature of the Eocene bordering the Madruga Anticline on the south is its great thickness as compared to its relative thinness in exposures in the Habana-Matanzas Anticline. In Habana, at the type locality, it is 70 feet thick; south of Madruga a thickness of 2.300 feet was measured. In generaL the Principe of the Madruga Anticline is somewhat coarser grained than in the Habana-Matanzas Anticline, indicating shallawer water in the south and deeper water in the north with accompanying paucity of deposition. MATANZAS-COLON

From Matanzas the route follows the Carretera Central (Central Highway). The road crosses San Juan river and follows around the south end of the bay which marks the axis of the Almendares- San Juan Syncline. ' On leaving the city the road rises on a. low terrace or bench formed in the flat-lying Giiines Limestone. With the exception of a few kilometers, this formation continues to Colon. The Giiines Limestone terrane is characterized by red soil, a rough, jagged surface with "Dientes de perro" (dog's teeth), sink holes and an almost complete absence of surface drainage pa~terns and channels. The drainage is almost entirely by sub­ terranean channels. Caves and underground water courses are common. Many of these ;underground channels have a distinctive fauna of blind fishes, shrimps, etc. A kilometer south of Guanabana low hills on either side of the road mark the north edge of the Madruga Anticline. Here the structure turns to the southeast and the corner is crossed by the road. In the road cuts beds of upper Cretaceous age are exposed. Before reaching the bridge over Canimar River, the road again enters the Giiines Limestone. Here the topography is almost entirely controlled by the collapsing and sinking of the Giiines Limestone due to subterranean stoping by underground drainage. From Limonar a line of hills is seen to run southeast. These hills continue in the same direction to the vicinity of the large serpentine peak, San Miguel de los Baiios. Here they turn abruptly north and the west face proceeds some 1 0 kilometers northward. At Coliseo the road passes through the west face and emerges into a flat plain. This hill of limestone with the steep sides has the aspect of a fault block that has been elevated. Closer inspection, however, reveals that it is, rather, a tongue extending from the Giiines Lime­ stone I ying along the north flank of the anticline. It is a remnant of the limestone that formerly covered - the axis of the structure and joined the Giiines limestone on the south.

COLISEO -CARDENAS

North of Coliseo the road passes over the Giiines limestone to C1rdenas. At Marney it ascends a long oval swell more than 200 feet high and 9 miles long, known as Lorna Triana. West of this hill is the large . serpentine intrusion which makes a notable topo­ graphic feature in the otherwise flat terrane. The serpentine intrudes the west end of the hill just mentioned. Along the contact are many large oil seeps. The long hill is under denouncement for oil. North of Lorna Triana is Cirdenas and beyond is C1rdenas Bay, cut off from the sea by the Peninsula de Jicacos. In passing it is of interest to note that formerly asphalt was dredged from Cardenas Bay and sold commercially.

COLISEO - JOVELLANOS - PERICO - COLON

Between Coliseo and Perico there is a low, flat plain. This is one of the · two localities where the Giiines limes tone crosses the entire island. The other is in the Province of Camagiiey. About 2 kilometers east of Coliseo the red soil suddenly changes to a dark color. This marks the Giiines limestone-lower Tertiary contact which is immediately followed by a wide exposure of upper Cretaceous. The Cretaceous is bordered on the south and east by upper Eocene. Both these formations disappear under the Giiines some 5 kilometers to the east. These outcrops appear to mark tlie eastern limit of the Madruga anticline. At the eastern edge of Perico, a change in the color of the soil again appears. The red soil and limestone ledges are replaced by a uniformly brown clay of lower Oligocene age. This may be referred to as the Tinguaro marl, from the sugar mill east of Perico. This change marks the western end of the Colon Anticline to be discussed later. The Carretera Central continues in the Tinguaro marls to about kilometer post 18 5 where a re-entrant- from the Giiines Limestone from the south crosses the highway bringing with it the red soil. The Giiines now ocuppies the terrane for a distance of riearly I 5 kilometers, or 9 kilometers east of Colon, where the highway makes a long bend to the northeast and again enters the Tinguaro marls. Here a road cut gives a good exposure of the Giiines­ Tinguaro contact. COLON ANTICLINE

This structure is some 30 kilometers long. Data on its width are not at hand. The exposure of Tinguaro marl reaches a width of 20 kilometers about 25 kilometers to the east. · This structure is entirely under denouncement for petroleum by the Shell and the Atlantic Oil Companies. It has· been carefully investigated by both geological and geophysical studies.

MOTEMBO FIELD

The Motembo Field is located 25 kilometers northeast of Colon, in a serpentine terrane. The deepest well thus far drilled reached 2.400 feet and like a.ll others in this field encountered nothing but serpentine. .. Production appears to occur in fractured areas in the serpentine. These zones have no particular depth but vary from 400 to 1.200 feet. The product is a pure, white, gasoline about 60 o Baume. It. is retailed without refining on a par with other gasoline. In the 18 months preceding July, 1935, 2,300,00 gallons were produced.

MERCEDES STRUCTURE

Ten kilometers south of Colon is the Mercedes structure, located on the lands of the Mercedes sugar mill. The surface evidence of the structure is an exposure of Tinguaro marls (lower Oligocene) surrounded by Giiines Limestone. The marl area is roughly triangular in shape, about 2 kilometers long and 1 kilometer wide at the base. This structure is also under denouncement.

OTHER CONCESSIONS

In the broad, flat plain between Coliseo and Colon there have been many denouncements for oil. Most of the structures on which the concessions were based do not appear at the surface but were determined by geophysical means. East of Colon, in Santa Clara Province, the Atlantic Refining Company has concessiqns that cover large portions of the Province, from the north almost to the south coast of the island.

MATANZAS-HABANA

Leaving Matanzas for Habana the highway ascends the low hill that is the south flank of the Habana-Matanzas Anticline. At the hospital on the west edge of town there is a good exposure of middle Miocene carrying a distinctive fauna. A common form is Gypsina globulus var. pilaris Brady, a foraminifer about the size of a BB shot. These beds are the time equivalent of the Bowden form'ation of Jamaica. They line the valley for several kilometers . to the west and are last seen in the cut just west of the railroad bridge, 2 kilometers west of Ceiba Mocha. This marks the western . end of the middle Miocene incursion of the sea up the Bay of Ma­ tanzas. From Matanzas the highway follows the Almendares-San Juan Syncline nearly to Madruga. About 2 kilometers west of Ceiba Mocha it enters a series of low, Giiines Limestone hills that lie in the south flank of the syncline or the north flank of the Madruga Anticline as far as Madruga. These hills have no particular structure as they are the result of cavings over underground drainage. The hills in the eastern portion of this area are curiously aligned, roughly in lines convex to the east, that is, they curve to the east as they cross from the north side of the road to the area on the south. No explanation of this alignment is known. The rainfall in this area has an average of 60 inches per year, yet as will be noted, there are no drainage lines developed on the surface. The entire precipitation enters the ground and is carried off by underground courses. About 3 kilometers east of Madruga, the road makes a sharp turn to the south and crosses Lorna del Grillo in a deep cut. Within the cut is the contact between the Giiines Limestone and the serpentine. Observers are not in accord as to the nature of this contact. On one side it is said that it is an intrusive contact. It is pointed out that the limestone shows incipient crystallization next to the serpentine and that small pyrite crystals occur in this narrow zone, both of which are taken as evidence of contact meta- morphism, and further, there is no trace of serpentine pebbles in the contiguous limestone as would be expected if the limestone were deposited on a serpentine base. The opponents to this theory deny there is any trace of contact metamorphism and that the limestone was deposited upon the serpentine mass. This same controversy exists nearly everywhere in Cuba where there is serpentine. Likewise the dating of the serpentine is every­ where a controversial subject. The intrusions have been variously placed in the column from pre-upper Cretaceous to Miocene. The town of Madruga is located on the south edge of a medium sized serpentine mass. The road leaves the serpentine on the west edge of town at the railroad bridge and enters the upper Cretaceous Habana formation exposed along the axis of the Madruga Anticline. The Cretaceous outcrops along the southern anticline are con­ siderably more limiteq than those in the neighboring anticline to the north. Evidently the folding and elevation was somewhat less on the south side of the island. The Cretaceous sediments exposed by the two anticlines are entirely similar except that those of the Habana-Matanzas Anticline appear on the whole to be somewhat finer grained. There is more chalk and the conglomerates of the upper beds are somewhat more fine grained. This suggests that the land mass supplying the clastic deposits now exposed in Cuba lay to the south. · The highway passes the San Antonio sugar mill and crosses the Cretaceous outcrop diagonally. About I kilometer west of the mill it enters the upper Eocene chalk. The upper Cretaceous is steeply folded in marked contrast to the low gentle folds of the Eocene. Eight kilometers west of Ma­ druga the road passes through a deep cut and out of the Eocene and back into the Gtiines Limestone to Cotorro, 15 kilometers south­ east of Habana. Structurally the highway is in the Almendares-San Juan Syncline. From La Catalina westward the north flank of the Madruga Anticline follows the road on the south. From Zaragoza, a low, broad, flat raise may be seen in the distance, directly to the west. This has been called the Bejucal Uplift. It is an enlarge­ ment of the Madruga Anticline. Asphalt has been mined in this area for several years. At Ganuza the highway turns to the north­ west towards Habana and follows along the east side of the Bejucal Uplift. At Jamaica two large limestone hills on either side of the road form a gateway. These are erosional remnants of Gtiines Limestone. The axis of the syncline is at Cuatro Caminos: It is marked by the Almendares river which in this region is a sluggish, meandering stream filled with cat-tails and water hyacinths. A kilometer or so northwest of Cotorro a narrow intrusion marks the northern edge of the Guines Limestone. Beyond this the road is in the Upper Cretaceous of the Hq_bana-Matanzas Anticline. Half a kilometer southeast pf San Francisco de Paula in a deep road cut there is a good exposure of several members of the Habana formation. The upper beds (first encountered) are termed the Big Boulder Bed; the gray and white rocks are the Cone Sandstone, Lime Gravels and Chalk. The remaining 12 kilometers of the route to Habana is over the highly folded beds in the Cretaceous of the Habana-Matanzas Anticline. End of Excursion. HABANA-BATABANO

This trip is planned to give a general view of a cross-section of Cuba from the north to the south coast. This section is typical of the provinces of Habana and Matanzas. The other provinces are quite distinct. One of the notable features of this section is the complete absence of all igneous rocks. The column is entirely sedimentary. The oldest rocks are upper Cretaceous in age and very probably equivalent to the Senonian of southern Europe. These are exposed from Habana south to Calvaria in the west end of the H abana­ Matanzas Anticline. These rocks comprise the Habana formation in which four lithologic members haye been recognized. At Mantilla one of the members is well exposed. This has been named the Lime Gravels, a name somewhat descriptive of its lithologic characteristics. This member carries a fair foraminiferal fauna but other fossils are rare and badly eroded. A locally com­ mon foraminifer is the Omphalocyclus similar to a form occurring in the Maestrichtian of Europe. A kilometer easts of Mantilla there is a quarry in what has been named the Cone Sandstone from the presence of cone shaped concretions that form in the rocks. The member is stratigraphically directly above the Lime Gravels. It is a gray, salt an pepper, calcareous sandstone much used for construction purposes. No fossils have been found in this member. The quarry in question is a poor representative of the Cone Sandstone as it contains a large percentage of shale. Stratigraphically above the Cone Sandstone is the Big :Boulder Bed, so named from the presence of numerous boulders in fields over this formation. A small remnant of the Big Boulder Bed is exposed at Calvaria. Unfortunately this particular exposure has but few boulders. This member carries a rich fauna of mollusks, corals, echinoids and foraminifera. At Calvaria the highway passes directly from the Cretaceous into the Guines Limestone (Oligo-Miocene). The route now crosses the south flank of the Habana-Matanzas Anticline and into the Almendares-San Juan Syncline. The axis of this structure is occupied by the Almendares river which is crossed at Chorrera. The Gi.iines Limestone continues to a kilometer or more south .of Managua where low hills form a break in the topography. This is the north edge of the Bejucal Uplift. The Bejucal Uplift is simply a widened portion of the Madruga Anticline. It has been given a distinctive name as it is a more or less inde~ndent unit cut off from the main structure by low saddless on the east and west sides. The Madruga Anticline is a long struc­ ture extending east and west for a distance of 15 0 kilometers. It crosses the entire Province of Habana and the western half of Ma­ tanzas Province. In and around the Bejucal Uplift the column above the Cretaceous is well represented. The disputed Cretaceous-lower Eocene beds are well developed. in various places a higher horizon in the lower Eocene, middle Eocene and upper Eocene (Principe formation) have been recognized. Around the margin upper Oligocene is exposed in a wide band. The Cretaceous is not exposed in this structure. The Bejucal Uplift is not a simple structure but is, rather a :series of small dome-like forms included within the Uplift. Several asphalt mines have been opened in this structure and the product marketed. Three oil wells have been drilled in the Bejucal Uplift. None was located favorably. Two were dry and one encountered a small amount of oil that rose in the well and flowed a small trickle for several years. Serpentine was encountered in this well. At about San Antonio de las Vegas the road passes out of the Eocene and into the Oligocene (Cojimar formation). The Coji­ mar is a light gray, granular, clastic marl that is practically indis­ tinguishable from the upper Eocene except by the faunal content. One kilometer south of San Antonio de las Vegas the Giiines Limestone begins and continues to the coast. Pleistocene and recent sands cover the Giiines for the last 2 or 3 kilometers.

SOUTH COAST

The configuration of the coast of Cuba gives quite en erroneous concept of the real Cuba. A lowering of the sea only 25 feet would give a much truer picture of the island. At present the narrowest part of Cuba is a few kilometers west of the Habana-Pinar del Rio boundary line. Here it is less than 40 kilometers in. width. The suggested lowering of· the sea 25 feet would make the Isle of Pines a part of the mainland and increase the width to 170 kilo­ meters. It would also add large areas to the west along the south coast as well as wide strips along the north coast. With this lowering of the sea Cuba would be surrounded by deep water on all sides and its outline would give a truer picture of this large unit. A curious feature of the coast between Bataban6 and the Tri­ nidad Mountains is the deep indentation or bay that brings the deep water into the shallow shoals and even into the present island. Soundings of 1.000 fathoms have been made in this bay. The embayment splits at the northwest end. The west fork, Golfo de Cazones, is confin.ed to the shoals. The east fork, Cochinos Bay, form a tongue 20 kilometers long in the present mainland. A depth of 300 fathoms has been recorded in this bay. The Isle of Pines is a broad, low island composed in the main of crystalline limestone and schists. These appear to be genetically conrrected with similar types of rocks that make up the Trinidad Mountains 270 kilometers to the east. End of Bataban6 Excursion.

RETURN FROM BATABANO

The return trip is by the same route until the south edge of Habana is reached. At Arroyo Apolo the Bejucal road to the southwest is taken. Nothing of importance is passed until Arroyo Naranjo is reached. This town is located just south of the Cretaceous-Gaines Limestone contact. The red lateritic soil is the residual product of the weathering of this formation. At Calabazar the highway crosses the axis of the Almendares-San Juan Syncline. As at Cuatro Caminos on the Carretera Central and at Chorrera the Almendares River follows the synclinal axis. The aviation field is located at Rancho Boyeros. Here the route turns north and continues to Habana by the new paved road. At Vento the road passes from the Giiines Limestone into the disputed Cretaceous-lower Eocene. The water supply for Habana comes from Vento. The disputed Cretaceous-lower Eocene has been named the Capdevila formation from a locality on this highway. The Capdevila is a thick series of sandstones, shales and conglome­ rates that compose the terrane for half the distance between Vento and Habana. Judging from ripple marks and the coarse material scattered through the series, it must have been deposited near shore in essentially shallow water conditions. Thus far no mollusks nor corals have been found in this formation. Only two badly eroded echinoid spines are known. It carries a meager foraminiferal fauna that has a species in common with the Midway and also a Cretaceous orbitoid. The Capdevila is intensely folded, overturned and overthrust, as the exposures in the cuts along this road indicate. This folding is entirely similar to that occurring in the upper Cretaceous, which suggests Cretaceous relationships. On the other hand, in Santa Clara Province, the Cretaceous has been overthrust over the middle Eocene. This opens possibility that the Capdevila may be lower Eocene. The Capdevila problem in Cuba is the same as in Texas, Europe and elsewhere in the world where the upper Cretaceous and lower Eocene transitional zone is involved. North of Cienaga and near the church on the west side of the road the Capdevila is left behind and beds ·Of definitely Cretaceous age agam appear. On entering Habana near the University, Avenida de las Pre­ sidentes makes a deep cut between Castillo de Principe and the University. In this cut there is a very fine exposure of the upper Eocene Principe formation. This is the type locality of the forma­ tion. The Principe is a fine grained, white marl or chalk with an abundance of fossil salt. A few species of echinoids, mollusks and crinoids occur in this formation. with a wealth of foraminiferal material in an excellent state of preservation. This fauna is of a type that lived at about the I 00 fathom 'line or on the edge of the continental shelf. Below the Principe and separated by an unconformity is the Universidad formation. so named because the University is located on it. The Universidad has a distinctive foraminiferal fauna that has been correlated with the Aragon (lower Eocene) of Mexico. It also carries a very beautiful radiolarian fauna. So abundant are these forms in another locality near Habana that they make up more than half the rock content. These rocks are easily distinguished by their very light weight. The upper beds of the Universidad are a white chalk indistinguishable from the Principe. The lower beds in this exposure are sandy and in other places a brown marl. At the south entrance to the cut the lower beds of the Universidad are stained with asfalt. They are faulted at about the base of the hill and the asfalt probably rose along the fault plane. Near the north end of the cut, where the statue of Maximo Go­ mez is located, the Giiines limestone lies directly on the Principe. The Cojimar (upper Oligocene) is missing though it is well represented in a cut near the Almendares River bridge only a kilometer or so to the southwest. The Principe in the exposure just described has a low dip to the west. This marks the western end of the Habana-Matanzas Anticline. Along this north-south line the Anticline, carrying with it the Cretaceous, plunges to the west beneath the Tertiary. Farther to the west small patches of Cretaceous again appear at the surface indicating that the structure may continue below the surface.

End of Excursion.

w.,;&. HABANA - BACURANAO OIL FIELD

The Bacuranao field is located 16 kilometers east of Habana. Structurally it is within the Habana-Matanzas Anticline. At Lu­ yan6, a suburb on the south side of Habana, the road to Bacuranao turns north from the Central Highway. Near this turn is a small serpentine intrusion with a lesser intrusion of diorite on the south side. This is the easternmost intrusion in the Habana-Matanzas Anticline. The road them continues over the upper Cretaceous to Guana­ bacoa. Here one of the large serpentine intrusions forms a long, oval hill oriented in and east-west direction paralleling the main structur:e. The flora of this intrusion is typical of serpentin~ and is of a desert type. The road follows the south edge of the intrusion several kilo­ meters and finally leaves it by a narrow tongue a short distance west of Bacuranao. At La Gallega the road turns north and con­ tinues across the Cretaceous sediments to the small town of Barreras. Beyond Barreras a few tongues of serpentine intruding the Cre­ taceous cross the road. · The long, low ridge lying to the north and paralleling the coast is the Tertiary north flank of the Habana­ Matanzas Anticline. Near this ridge the road enters another large serpentine intrusion. The Bacuranao oil field is located on the north edge of this latter intrusion along the contact with the upper Cretaceous sediments. It appears that the intrusion fractured the underlying rocks on its way upward and turned the Cretaceous sediments up along the contact. The upper Cretaceous shales effectually closed the avenues of escape and made possible the accumulations of oil that the various wells have encountered. The Bacuranao field has been worked since 1916 and to date has produced 14 7,000 bbls. of crude oil. Fifty-nine wells have been drilled. The producing wells vary in depth from 223 to 1.223 feet. The deepest well drilled reacher 2.300 feet. The gravity is about 2 7 Baume. The origin of the petroleum in this field as well as in the numerous seeps eastward on the island as far as Oriente Province is taken to be the Aptychus Beds. These have been determined to be lower Cretaceous in age. The folding in the Habana-Matanzas Anticline has not been of sufficient magnitude to bring the Aptychus Beds to the surface except in one locality near the city of Matanzas. The formation is well exposed in Pinar del Rio. Matanzas, Santa Clara and Camagiiey Provinces. Occasionally on the surface, as in Pinar del Rio Province, and at depth, the Aptychus Beds are highly bituminous. The Aptychus Formation is extremely important in Cuba. It is known to extend a distance of 3 7 5 miles in an east-west direction from Pinar del Rio Province to eastern Camagiiey Province. It is very uniform throughout this distance. The thickness varies from 1. 700 feet to at leasts 5.000 feet. At present this formation appears to be the most likely source of petroleum in quantity in Cuba. It is, however, possible that source beds may occur in the Tertiary in Habana and Pinar del Rio Provinces in the Madruga Anticline. In this southern structure the Tertiary is several fold thicker than on the north side of the island. Asfalt and small oil showings are known to occur within rocks of this age that are separated from the underlying lower Cretaceous by a thousand or more feet of sediments. Within the intervening strata there are thick, impervious beds that would probably prevent the upward passage of oil from the Aptychus beds into the overlying Tertiary.

(;l~G) ~•.E...