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.