Geology topics
Research about Puerto Rico
Source-linked reports with geographic coverage including Puerto Rico.
The partitioning of copper among selected phases of geologic media of two porphyry copper districts, Puerto Rico
In experiments designed to determine the manner in which copper is partitioned among selected phases that constitute geologic media, we have applied the five-step sequential extraction procedure of Chao and Theobald to the analysis of drill core, soils, and stream sediments of the Rio Vivi and Rio Tanama porphyry copper districts of Puerto Rico. The extraction procedure affords a convenient means of determining the trace-metal content of the following fractions: (1) Mn oxides and “reactive” Fe oxides; (2) “amorphous” Fe oxides; (3) “crystalline” Fe oxides; (4) sulfides and magnetite; and (5) silicates. An additional extraction between steps (1) and (2) was performed to determine organic-related copper in stream sediments. The experimental results indicate that apportionment of copper among phases constituting geologic media is a function of geochemical environment. Distinctive partitioning patterns were derived from the analysis of drill core from each of three geochemical zones: (a) the supergene zone of oxidation; (b) the supergene zone of enrichment; and (c) the hypogene zone; and similarly, from the analysis of; (d) soils on a weakly leached capping; (e) soils on a strongly leached capping; and (f) active stream sediment. The experimental results also show that geochemical contrasts (anomaly-to-background ratios) vary widely among the five fractions of each sampling medium investigated, and that at least one fraction of each medium provides substantially stronger contrast than does the bulk medium. Fraction (1) provides optimal contrast for stream sediments of the district; fraction (2) provides optimal contrast for soils on a weakly leached capping; fraction (3) provides optimal contrast for soils on a strongly leached capping. Selective extraction procedures appear to have important applications to the orientation and interpretive stages of geochemical exploration. Further investigation and testing of a similar nature are recommended.
Floods of September 16, 1975 in the Tallaboa Valley, Puerto Rico
This report provides a record of the flood of September 16, 1975, and associated hydrologic data. These data can be used in making rational decisions in formulating effective flood-plain regulations that would minimize flood problems in the Tallaboa Valley. The Tallaboa Valley (fig. 1) lies on the southwestern coast of Puerto Rico about 12 km (7.5 mi) west of the city of Ponce. The climate is semiarid with a mean annual precipitation of about 1,020 mm (40 in). It is a relatively small valley which until the late fifties was dedicated mainly to the product ion of sugarcane. Since then, the economy started changing from agriculture to industry. At present the lower part of the valley is completely industrialized. The upper part of the valley is used for agriculture--mostly as pastureland. The reach from Highway 132 downstream to the new Highway 2 is mainly agricultural with a few scattered communities. The lower part of the valley that includes the area from the Highway 2 bridge to the mouth is covered with heavy industry concerned with the refinement of oil, and associated industries. The continuous growth of industry and consequently of the urban area of Peñuelas has encouraged growth onto the flood plain. The study area is subject to flooding by the Rio Tallaboa and the Rio Guayanes, its main tributary. The Rio Guayanes is the- cause of flooding in the urban area of Penuelas, encompassing the reach from the northern edge of town downstream to Highway 132 where it joins the Rio Tallaboa. Data are generally referred to in SI (International System) units followed by corresponding inch-pound units in parentheses. The SI units.may be converted to inch-pound units by multiplying the units given by the factors shown.
Flood of September 16, 1975 at Utuado, Puerto Rico
This report provides information on the floods of September 16, 1975 in the Utuado, Puerto Rico area. The report was prepared by the U.S. Geological Survey in cooperation with the Puerto Rico Department of Natural Resources. The study provides data and flood-plain information for planners and designers involved in the use of flood-plain land in the Utuado area. The study included the area flooded by the Rio Grande de Arecibo and Rio Vivi in urban Utuado.
A study of earthquake prediction and the tectonics of the northeastern Caribbean: A continuing experiment in two major seismic gaps
No abstract available.
Floods of September 16, 1975 in the Tallaboa Valley, Puerto Rico
This report provides a record of the flood of September 16, 1975, and associated hydrologic data. These data can be used in making rational decisions in formulating effective flood-plain regulations that would minimize flood problems in the Tallaboa Valley. The Tallaboa Valley (fig. 1) lies on the southwestern coast of Puerto Rico about 12 km (7.5 mi) west of the city of Ponce. The climate is semiarid with a mean annual precipitation of about 1,020 mm (40 in). It is a relatively small valley which until the late fifties was dedicated mainly to the product ion of sugarcane. Since then, the economy started changing from agriculture to industry. At present the lower part of the valley is completely industrialized. The upper part of the valley is used for agriculture--mostly as pastureland. The reach from Highway 132 downstream to the new Highway 2 is mainly agricultural with a few scattered communities. The lower part of the valley that includes the area from the Highway 2 bridge to the mouth is covered with heavy industry concerned with the refinement of oil, and associated industries. The continuous growth of industry and consequently of the urban area of Peñuelas has encouraged growth onto the flood plain. The study area is subject to flooding by the Rio Tallaboa and the Rio Guayanes, its main tributary. The Rio Guayanes is the- cause of flooding in the urban area of Penuelas, encompassing the reach from the northern edge of town downstream to Highway 132 where it joins the Rio Tallaboa. Data are generally referred to in SI (International System) units followed by corresponding inch-pound units in parentheses. The SI units.may be converted to inch-pound units by multiplying the units given by the factors shown.
Geologic map of the Fajardo and Cayo Icacos quadrangles, Puerto Rico
No abstract available.
Maps showing composition of surficial sediments on the insular shelf of southwestern Puerto Rico
The limited availability of onshore sand deposits for use in construction appears to be a future major problem in Puerto Rico (U.S. Bureau of Mines, 1972; Committee on Puerto Rico and the Sea, 1974). Consequently, the mining of offshore sand deposits as supplemental sources of construction aggregate may becom e necessary. For this reason, the U.S. Geological Survey and the Department of Natural Resources of the Commonwealth of Puerto Rico have conducted investigations of potential offshore sand deposits on the Puerto Rico insular shelf. This report provides information on the composition of surficial sediments on the southwestern Puerto Rico shelf (fig. 1), an area that may be one of the more favorable potential sites for offshore sand resources. Water depths over most of the study area are less than 22 meters (m). The sea floor is composed of live and dead patch and fringing reefs, areas of rock exposures, and sedim ent-covered areas. The adjacent coastline includes prominent embaym ents and a conspicuous rock promontory (Cabo Rojo) connected by a tombolo to the mainland of Puerto Rico. The study area is in the belt of northeast trade winds. Waves approach the coast predominantly from the southeast, resulting in a predominantly westward littoral drift along the south coast (Grove and Trumbull, 1978). Local sand movement on the southern shelf is shown by an active sand wave field south of Bah1a Sucia in which the sand wave crests have migrated toward the southwest (Grove and Trumbull, 1978). The presence of the sand wave field suggests that large volumes of sand having potential for mining are locally present in the study area.
Reconnaissance of six solid-waste disposal sites in Puerto Rico and effects on water quality
Five solid-waste landfills and an open burning dump were studied in Puerto Rico to obtain physical, chemical and biological data on leachates, give an overview of their pollution potential, and determine the adequacy of monitoring at these or similar sites. These sites are operated by the municipal governments of Arecibo, Caguas, Cayey, Humacao, Mayaguez and Guayama. The bulk of waste is of domestic origin but wastes from local industries and institutions are also handled. Data were collected between February and July 1976. Parameters measured included temperature, specific conductance, pH, color, common ions, cyanide, macronutrients (nitrogen and phosphorus species), total organic carbon, dissolved oxygen, BOD5 (biochemical oxygen demand), COD (chemical oxygen demand), total and fecal conform, trace metals, and phenols. The results obtained indicated that leachate from most sites is enriched in common ions, macronutrients, and trace metals. A sample obtained from runoff at the Cayey landfill was the only one with an acidic pH (5.8). It had a common ion concentration of 10,750 mg/L (milligrams per liter), or twice that found in leachate contained within the buried refuse. The leachate from the Caguas site had the highest common ion concentration (12,520 mg/L). Maximum values for other parameters were as follows: Temperature, 33°C (or about 10°C above ambient ground-water temperature); specific conductance, 19,200 micromhos per centimeter; color, 2,200 units; cyanide, 30 ug/L (micrograms per liter); total nitrogen, 600 mg/L; total phosphorus, 4.3 mg/L; total organic carbon, 500 mg/L; 5-day biochemical oxygen demand, 5,540 mg/L; chemical oxygen demand, 3,000 mg/L; total coliform bacteria, 410,000 colonies per 100 milliliters; fecal coliform bacteria, 14,000 colonies per 100 milliliters; total arsenic, 54 ug/L; total cadmium, 15 ug/L; total chromium, 1,600 ug/L; total lead, 1,10C ug/L; total mercury, 2.6 ug/L; total nickel, 1,300 ug/L; and total phenols, 1,100 ug/L. Pollution of water resources is limited to the periphery of the sites. A major problem throughout seems to be related to operating methods. Under the conditions found, large quantities of rainwater and runoff could be available for leachate production. Generation of leachate may not be significant at present probably because of the recent establishment of the landfills (less than 5 years). Monitoring at these or similar sites in Puerto Rico can be limited to defining present baseline water-quality conditions and implementation of a sampling program. Baseline data could be limited to specific conductance, pH, color, common ions, and dissolved oxygen. A scheduled sampling program could be limited to specific conductance readings and measurement of concentration of bicarbonate, chloride, and dissolved oxygen.
Marine geologic map of the Puerto Rico insular shelf, Isla Caja de Muertos area
This marine geologic map covers the western half of the Isla Caja de Muertos shelf off the south coast of Puerto Rico. Coverage extends from Playa de Ponce on the west to Punta Petrona, near the town of Santa Isabel, on the east, a distance of 26 km. Within the mapped area the shelf ranges in width from a minimum of 4 km to a maximum of 18 km. Clover (1971, p. 89) named the shelf for the prominent Isla Caja de Muertos, a small upfaulted block of lower and middle Tertiary rocks located near the center of the map area. The Isla Caja de Muertos shelf is not known to be bounded by faults, though Glover suggested faults on the west and south boundaries, and the bathymetry of the insular slope reveals a large east-west fault about 6 to 8 km south of the shelf edge.
Geology of the middle Tertiary formations of Puerto Rico
Rocks of Oligocene and Miocene age crop out in both N and S Puerto Rico. They rest with angular unconformity on volcanic and related sedimentary and intrusive rocks that range in age from Early Cretaceous to M. Eocene. The older rocks crop out on the upland that extends E-W through the center of the island. The surface on which the M. Tertiary rocks were deposited is very irregular, having a local relief of at least 200m. Although the rocks of N and S Puerto Rico are approximately the same age, there was no nearby marine connection during Oligocene time; as a result, neither the lithologic characteristics nor the faunas contained in the rocks permit exact correlation from one side of Puerto Rico to the other. During Miocene time, there may have been a connection of the two seas around the W end of present-day Puerto Rico. -from Author
Water resources data for Puerto Rico, water year 1977. Surface and quality-of-water records and ground water records
No abstract available.
Relationship between physical condition of the carbonate fraction and sediment environments: Northern Puerto Rico shelf
Each of three sediment types recognizable on the northern Puerto Rico shelf and beaches is characterized by calcareous material in different physical condition. Dark terrigenous sand is accumulating at a relatively rapid rate and has a carbonate fraction containing fresh-appearing angular particles. The pure-carbonate skeletal-sand sediment type has a much lower rate of deposition, and its old-appearing calcareous particles have a dull surface luster. The third sediment type, a mixture of the first two, is largely from beaches and is characterized by highly polished, very well-rounded grains. Differences in length of sea-floor exposure and intensity of abrasion appear to be responsible for the variable physical condition of the carbonate fractions. We suggest that on other shelves having less distinctive sedimentary regimes, the physical condition of the carbonate grains could be used to interpret present shelf processes.
Map showing landslides and areas of susceptibility to landsliding in Puerto Rico
No abstract available.
Seawater intrusion, south coast of Puerto Rico, 1966-77
A salinity reconnaissance of the south coast alluvial aquifer of Puerto Rico, including the areas of Guenica, Guayanilla-Yauco, Tallaboa, Juana Diaz, and Jobos was made during 1966-68. In this investigation seawater was detected in the Guayanilla-Yauco and Tallaboa areas. Since 1968, water level and quality-of-water data have been collected from selected wells in the south coastal areas between Guanica and Patillas. The 1968-77 study indicated two additional areas of possible seawater intrusion in the Ponce-Santa Isabel area. Another area of possible seawater intrusion was found in the southeastern section of the Salinas fan in the Jobos area.
Puerto Rico seismic program seismological data summary, July 1, 1975-December 31, 1977
The purpose of this data summary is to compile and make available preliminary data acquired from a network of seismic stations (Tarr and King, 1976) in order to facilitate current studies of earthquake occurrence.