Lithology and stratigraphy of upper Cretaceous ...

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Geological Society of America Special Paper 262 1991

Lithology and stratigraphy of upper Cretaceous volcanic and volcaniclastic rocks of the Tireo Group, Dominican Republic and correlations with the Massif du Nord in Haiti John F. Lewis Geology Department, George Washington University, Washington, D.C. 20052 A. Amarante and G. Bloise* Department of Exploration, Rosario Dominicana, S.A., Santo Domingo, Dominican Republic J. G. Jiménez G.* and H. D. Domínguez* Departamento Recursos Minerales, Universidad Católica Madre y Maestra, Santiago de los Caballeros, Dominican Republic ABSTRACT Tireo Group roeks of late Cretaceous age occupy a 290-km-long belt along the Cordillera Central in the Dominican Republic and the Massif du Nord in Haiti. Lithologies and stratigraphy have been studied in three main areas in the Dominican Republic: Restauración, Juan de Herrera-Constanza-Las Canitas and El Recodo. This chapter attempts a correlation among the recognized units in these areas with studied areas in the Massif du Nord. Two main units are recognized in the Cordilleran Central: 1. Lower Tireo Group (Basic Rocks). The oldest and most extensive rocks (here termed Tireo Formation) are a sequence (>4,000 m) of massive, green, vitric-lithic tuffs with intercalated mudstones, siltstones, and limestones found in the Dominican Republic and in the Massif du Nord. These vitroclastic tuffs probably originated as pyroclastic flows produced from phreatomagmatic and phreatic eruptions and then were deposited as submarine debris flows at abyssal depths. Other units mapped in the Restauración area are interbedded red and green tuffs, well-stratified crystal-lithic tuffs and agglomerate; and a unit of fine silicified tuffs, andesite flows, and pyroclastic basaltic rocks on the border with Haiti. In the Las Canitas-Constanza and adjacent areas important lithologies include high-Ti02 metabasalt (Pico Duarte and Juan de Herrera areas); intercalated limestones (Constanza and Valle Nuevo Members); and cherts (El Convento Member) and graywackes, shales, and mudstones (Rio Blanco and El Recodo areas). Microfossil age determinations indicate a Turonian (possibly late Cenomanian) to early Senonian age for the main volcanism, but sedimentation may have continued until the early Maastrichtian in the northeast. These rocks pass without apparent discordance into the Upper Tireo Group. 2. Upper Tireo Group (Acid Rocks). This group consists of lavas, pyroclastic rocks, and reworked tuffs of mainly dacite and rhyolite (keratophyre) composition. The *Present addresses: Bloise and Jimenez, Departamento de Exploración, Falconbridge Dominicana, S.A., P.O. Box 1343, Santo Domingo, Dominican Republic. Domínguez, Recursos Canyon, Santo Domingo, Dominican Republic. Lewis, J. F., Amarante, A., Bloise, G., Jiménez G., J. G., and Domínguez, H. D., 1991, Lithology and stratigraphy of upper Cretaceous volcanic and volcaniclastic rocks of the Tireo Group, Dominican Republic, and correlations with the Massif du Nord in Haiti in Mann, P., Draper, G., and Lewis, J. F., eds., Geologic and tectonic development of the North America-Caribbean plate boundary in Hispaniola: Boulder, Colorado, Geological Society of America Special Paper 262.

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J. F. Lewis and Others

acid volcanism is concentrated in centers along the southern margin of the belt. The acid volcanism probably did not begin before the late Santonian and ended in the early-middle Campanian. Lower Tireo Group rocks correlate with the Terrier Rouge Series in the Massif du Nord, Haiti, consisting of andesites, andesitic tuffs, tuffites, agglomerates, mudstones, and basalts. Upper Tireo Group correlate with the La Mine Series in Haiti, consisting of dacite flows and stocks, crystal-lithic tuffs, unsorted pyroclastic rocks, and volcaniclastic rocks. The Tireo Group is overlain conformably in the south-central part of the belt by sediments of middle Campanian-Maastrichtian age and younger of the Trois RivieresPeralta Belt. INTRODUCTION Tireo Formation was first used by Bo win (1966, p. 45) to describe the unmetamorphosed volcanic rocks of Late Cretaceous age exposed in the "high rugged mountains of the eastern end of the Cordillera Central." The formation was named after the small town of Tireo in the valley 7 km north of Constanza (Fig. 1). Bowin (1966) described the volcanic rocks of the Tireo Formation as consisting of coarse to fine tuff, lapilli-tuff, and quartz keratophyre. Bedded and fissile limestones (Constanza Member) were reported from the Constanza valley and a limestone from southwest of Monsenor Nouel (now Bonao). Microfossil determinations reported by Bowin (1966) suggested that the age of the Tireo Formation ranges from Cenomanian to Maastrichtian, and therefore spans a large part of the Late Cretaceous. Mapping over the past 12 yr by various groups and in the 1960s by the Mitsubishi Mining Company has shown that the same or similar volcanogenic rocks seen in the Constanza area extend westward as a belt along the Cordillera Central and into the Massif du Nord in Haiti (Fig. 1). The belt extends for 290 km and is as much as 40 km wide. The recent work has shown that there are many more rock types within the Upper Cretaceous volcanic belt than originally described by Bowin (1966) for the Tireo Formation in the type area around Constanza. Because the term Tireo Formation has been used rather loosely in reports to describe the rocks right along the belt, it is suggested that this original term be extended and all the lithologies be included under the name Tireo Group. It is now proposed to give the larger mappable units new formation names; smaller discontinuous units will be given member names. This chapter examines the existing data, suggests a stratigraphy and correlation among the mapped units in the Cordillera Central, and attempts correlation with the rocks in Haiti. A knowledge of the lithologies present is significant in determining the nature and the extent of the volcanism and magma types during the main arc building stage of the Greater Antilles through the Late Cretaceous (Lewis and others, 1990). A sound knowledge of the volcanic rocks of the Tireo Group is of economic importance because certain units contain polymetallic, epithermal Au-Ag, and copper deposits (Rosario Dominicana S.A., 1986; Amarante and others, 1989). This chapter is mainly concerned with a preliminary documentation of the main features of the lithology and stratigraphy of

the Tireo Group, and is a first attempt to determine a stratigraphy and correlation for these rocks right along the belt. Because of the difficulties of access and exposure, the discontinuities in lithologies and the lack of good stratigraphic markers and fossils, many problems remain to be resolved. The rocks are dominantly volcaniclastic in origin and were largely deposited in a submarine environment. There are many difficulties in determining the nature and origin of these types of deposit (Suthren, 1985). REGIONAL DISTRIBUTION AND STRUCTURE OF THE TIREO GROUP In the Dominican Republic, rocks of the Tireo Gorup extend as a continuous belt, from the Haitian border at Restauración in the Cordillera Central to the southeastern part of the Cordillera at El Recodo near Bani (Fig. 1; Lewis and Draper, 1989). To the north Tireo rocks are faulted against the metabasic rocks of the Duarte Complex. To the south Tireo rocks are bounded by the Late Cretaceous-Early Tertiary shale-siltstone turbidite sequences of the Trois Rivieres-Peralta Belt. In places the contact is a disconformity as discussed below; elsewhere the contact is faulted. In several places along the belt, Tireo rocks are intruded by granitoid rocks, mainly tonalite. Two of the granitoid plutons are of batholithic dimensions (Fig. 1). The main information on which this study is based comes from three areas in the Dominican Republic and the Camp Coq area in Haiti (Fig. 1). The main area is that of Restauración in the western Cordillera Central, which has been the subject of a relatively detailed study over the past 5 yr (Lewis and others, 1982; Jimenez and Lewis, 1989; Rosario Dominicana, S.A., reports, 1985, 1986). Considerable information on the stratigraphy and structural features in the central part west of Constanza is contained in the report on the mineral prospects of the Las Canitas area by Mesnier (1980). The adjoining area of Constanza and Valle Nuevo has been studied by Lewis (1980), Vespucci (1982, 1987), Electroconsult (1983), and J. Espaillat (unpublished data, 1986). Vila and others (1982) have contributed useful stratigraphic information on the Las Cañitas and Constanza areas. Some stratigraphic and lithologic data in the southeastern area is included in the master's thesis of Domínguez (1987). Useful petrographic information on Tireo rocks from the Juan de Herrera area was recorded through the German-Dominican mapping program (Harms, 1989; Garcia and Harms, 1988) but the Tireo

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Formation is not subdivided on the l:100,000-scale geologic grained tuffs consist of small broken fragments of the same lithic material forming the larger fragments. Crystal fragments of pymap. roxene and feldspar form less than 1 percent of these tuffs. In LITHOLOGIC DESCRIPTION AND STRATIGRAPHY places the rocks are fractured and veined by calcite. Secondary silica is found as a replacement in the matrix in some areas. OF TIREO ROCKS Clastic sedimentary rocks. A 400-m-thick horizon of well-stratified calcareous shales crop out in the western part of the Restauración Area vitric-lithic tuff sequence on the border with Haiti. Two disconAlthough some reconnaissance mapping was done in the tinuous horizons of marine sedimentary rocks, consisting of interRestauración area by the Mitsubishi Mining Company in the late bedded gray and often pinkish mudstones, shales, siltstones, and 1960s, no clear lithologic divisions were determined. Lewis and recrystallized limestones, occur intercalated within the lower cenothers (1982) prepared a preliminary map at 1:50,000, and a tral part of the green vitric tuff sequence north of the intrusives of brief report was submitted on the petrology of the rocks (Jimenez the Rio Limpio valley. Interbeds of calcareous shales also crop and Lewis, 1989). The results of detailed mapping and sampling out in the northwest (Fig. 2), and much of the northern outcrop carried out for mineral exploration studies over the area by the near the contact with the batholith consists of well-lithified dark Dirección General de Mineria and Rosario Dominicana are in- shales with lesser amounts of tuff. Bedding in the tuffs varies from indistinct in thicker units to cluded in the reports of Rosario Dominicana S.A. (1985, 1986). These reports and a map at a scale of 1:25,000 are on file at the well bedded and laminated in thinner units. The tuffs and sediDirección General de Minería, Santo Domingo. A summary is mentary rocks dip to southwest over most of the area. Graded bedding in the clastic sedimentary rocks indicates the direction of included in Amarante and others (1989). The results of the mapping and petrographic studies (Fig. 2) younging is to the southwest. The thickness of the green tuff unit have shown that the volcanogenic rocks of Late Cretaceous age in in the Restauración area must be at least 4,000 m and could be the Restauración area can be divided into two units: a Lower 6,000 m from the map data. Limestone. Recrystallized massive and bedded shelf(?) limeTireo unit of principally layered volcaniclastic rocks of basic to intermediate composition deposited mainly in a marine environ- stone forms the upper part of Loma de Pina Blanca and Loma ment and an Upper Tireo unit of flows and associated volcani- Nalgo del Maco, the highest mountains in the area east of the map (Fig. 2). The limestone appears to form a cap to the underlyclastic rocks of acid (mainly dacite and rhyolite) composition. ing volcanic rocks and could form a remnant of more extensive Lower Tireo (Basic Rocks). Green vitric-lithic tuff unit. Greenish colored vitric tuffs, Upper Cretaceous or Paleogene limestone that supplied carbonlapilli tuffs, and tuff breccias, together with thin horizons of ma- ate detritus to the south. These limestones have not yielded rine sedimentary rocks and minor basalt, make up most of the identifiable diagnostic fossils for dating. Basalts. Small flows of vesicular and amygdaloidal basalts northwestern part of the Restauración area and form the largest and minor basaltic tuff occur within the vitric-lithic tuff unit in exposure of Tireo rocks (Fig. 2). The sequence is intruded along the Restauración area. Two of the occurrences are found along the northern boundary by the Loma de Cabrera tonalite batholith and by small tonalite plutons near Rio Limpio, giving rise to the contact area, with the red and green tuff unit suggesting a narrow contact metamorphic zones and obscuring the original time/space relationship. Dark green, fine-grained, massive basalt clastic textures. Small shallow intrusives of diorite, dacite por- flows accompanied by minor tuff occur along the Rio Libon phyry, and dolerite occur within the volcaniclastics along the south of Paso Viejo, and it is probable that the main part of the northern contact area. None of these latter rocks is considered to Loma de Los Guandules in the south is composed of basalt and be part of the Tireo sequence. A second area of green vitric-lithic basaltic tuff. The basalts are mainly clinopyroxene-phyric, but include tuff crops out about 4 km to the southwest of the town of Restauración near the southwestern border with Haiti and is also in- feldspar-phyric and fine-grained aphanitic types. Plagioclase is invariably albitized. Amygdales are filled by mainly calcite and truded by tonalite. The tuffs, in thick beds, are poorly sorted, and lithic frag- chlorite, and less commonly by a colorless zeolite. The reddish ments (lapilli) range from less than 2 mm to more than 1 cm color of many of the basalts results from fine-grained hematite, across (Fig. 3). The fragments make up more than 70 percent of often forming opaque masses and opaque rims to mafic minerals. Stratigraphic position, nature of volcanism, and depositional the rocks and are angular to subrounded. They are composed mainly of grayish green to pale gray nonvesicular fragments (less environment. None of the sedimentary rocks in the green vitriccommonly, of opaque black vesicular fragments), and secondar- lithic tuff sequence has yielded diagnostic fossils for age determiily, of yellow-brown to green angular, devitrified glass (pala- nation, and there is no clear structural evidence to show the age gonite) shards with some vesicles. The shards are most commonly relations with other adjacent units. However, the absence of 1 to 3 mm in their largest dimension. Lithic fragments rarely quartz-bearing clasts in this lithology indicates these rocks must contain phenocrysts or even microphenocrysts. The matrix of predate the acidic volcanic rocks to the south. Although a detailed study of the lithologic variations and these lapilli tuffs and the ash-sized material comprising the fine-

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169 J. F. Lewis and Others

Figure 3. A, Tuff breccia, large boulder in Jimenoa River. Grain size of fragments decreases to lapilli size to the right of photograph. B, Crude layering (bedding) due to variation in grain size in lapilli tuff, large boulder in Jimenoa River; hammer head gives scale. C, Polished surface of large hand specimen of poorly sorted vitric lapilli-tuff from the El Rio-Bonao road section. Note the vitric-lithic fragments, light gray in color (L), and the angular devitrified glass shards, dark gray in color (S). D, Photomicrograph of vitroclastic tuff. Glass shards (S) with brown centers, and cryptocrystalline lithic fragments (L) in a fine-grained (devitrified) glassy matrix. Field of view, 6 mm. Specimen is from El R i o Bonao road section. E, Photomicrograph of vitric-lapilli-tuff showing angular glass shards (S), minor broken fragments of accretionary lapilli (A), and lithic fragments (L) in fine devitrified glassy matrix. Field of view, 3.3 mm. Specimen is from El Rio-Bonao road section. F, Wellbedded units of crystal lithic tuff overlying thick massive unit of same basic lithology. Exposure is in the Arroyo Yobasilio, north of Restauración.

Tireo Group, Dominican Republic, and Massif du Nord, Haiti


sedimentary structures within the Tireo green vitric-lithic tuff unit has yet to be done, present available data allow a preliminary interpretation of the probable nature of the origin and deposition of the material. However, there are many difficulties in interpreting submarine volcanogenic deposits (Wright and Mutti, 1981), and unless good exposure is available, it is difficult to distinguish subaqueous pyroclastic flow deposits generated directly from eruptions from other types of mass flow (Suthren, 1985). It is clear from the thickness and extensive nature of the Tireo deposits that the material was supplied repeatedly and in abundance from a string of nearby active volcanoes. The basaltic lavas intercalated within the tuffs presumably originated from these volcanoes, but no remnant features of a volcano have been identified. Unfortunately, even the few good outcrops of the Tireo do

149

not show features of the textures and structures necessary to study the sedimentation processes. However, observations of very large "clean" boulders in the rivers draining the Tireo terrane show that deposits include units of chaotic matrix-supported breccias, with a thickness of at least 4 m with clasts measuring as much as 0.75 m across, which grade into the more common massive vitriclithic tuff (Fig. 3). Other large boulders show a gradation from the massive unsorted vitric-lithic tuffs into finer grained, poorly bedded, and poorly sorted tuffs (Fig. 3). Although no statistical studies have been made, it is considered unlikely that the particulate matter in either the breccias or the tuffs was in hydraulic equilibrium. It is therefore suggested that these deposits were probably formed by resedimentation processes (submarine gravity flow processes), such as debris flows and turbidity currents. An important feature is that Tireo vitric-lithic tuffs are composed of two contrasting types of fragmental material produced by two contrasting types of volcanic activity (Fig. 3). The most abundant material is composed of angular, mainly lapilli-sized fragments of nonvesicular devitrified glass. As suggested by Fiske (1963), this type of material might originate through the fracturing and fragmentation of flows and domes by steam-blast explosions, that is, phreatic eruptions. The other type of fragmental material is of dark, vesicular pumice or scoria and angular glass (palagonite) shards commonly showing large vesicles. These fragments are considered to have originated by explosive magma/ water interaction (phreatomagmatic activity). The Tireo deposits are very similar to subaqueous pyroclastic flows of the Ohanapecosh Formation, Washington State, U.S., described by Fiske (1963), but the Tireo deposits are much more extensive. The overall nature of the Tireo vitric-lithic tuff deposits suggests they also were mainly submarine pyroclastic flow deposits produced by phreatic and phreatomagmatic explosion eruptions. Although this material might have originated as pyroclastic flows, it probably traveled as extremely mobile slurries and was redeposited as thick tabular deposits with nearly planar tops and bottoms. Red and green tuff unit. Thick interbedded green and reddish purple-colored coarse- to fine-grained tuffs are the dominant rocks in the area southwest of the town of Restauración. Contacts between the red and green facies are sharp. Also present in the sequences are intermediate to basic lavas, breccias, and rare cherts. Small discontinuous bodies of gray limestone occur within the red and green tuff unit along the contact with the gray crystallithic tuffs to the north. The direction of dip is variable but is most commonly to the northeast at a high angle. Graded bedding indicates the beds young to the south. The red tuff facies are in places well bedded and laterally continuous, but at least two reddish purple tuff layers are discontinuous and lens-shaped and have a length of about 1.5 km. The green colored tuffs are generally similar in composition to the green vitric-lithic tuffs in the main unit to the northeast. The composition of the lapilli and ash-sized particles in both the red and green tuffs is the same except that the fragments in the red beds are oxidized. A high concentration of yellow-brown shards

150



occurs in reddish beds adjacent to basalt flows, suggesting these are at least in places a hyaloclastite facies. Stratified beds commonly contain layers from 3 mm to 3 cm thick, consisting of abundant pisolites (accretionary lapilli). The individual lapilli usually measure from 3 to 7 mm but can reach as much as 1.1 cm across. The matrix to the pisolite-bearing beds is commonly partly or completely filled by carbonate (calcite). Accretionary lapilli occur in green beds, but are apparently much less common because they were observed only as boulders. Examples found as boulders show alternating green and red beds of accretionary lapilli of variable grain size and porosity, suggesting the oxidation is a diagenetic factor produced by ground water. Areas of oxidation cross-cutting bedding and structure near modern rivers support this idea. Depositional environment and relation to other units. The red and green tuff is considered to be stratigraphically above, and gradational into, the main exposure of green vitric-lithic tuffs to the northwest and those to the southwest, but clear proof of this has not been established. Because the basic lithologies of the red and green tuff unit and the green vitric-lithic tuff unit are the same, and because of the stratigraphic relations pointed out above, it is concluded that the two units are essentially related facies that were deposited in the same basin. In order to account for the oxidation and pisolite beds in the red tuffs, it is assumed the red tuffs were deposited in relatively shallow water transitional into a subaerial environment, whereas the green vitric-lithic tuffs were deposited in a relatively deep-water environment. Another possibility suggested by A. Smith (1989, personal communication) is that the red tuffs were produced by eruptions that gave rise to substantial subaerial eruptive columns, whereas the green tuffs were erupted subaqueously. This could also explain the inch-scale red and green layering of the accretionary lapilli described above. It is to be expected that abundant accretionary lapilli will be preserved only in the shallow-water facies, since they would be largely destroyed because of their fragile nature in their passage into deeper water, particularly in slurries of rock particles. Fragmented particles of accretionary lapilli are common. Crystal-lithic tuff and agglomerate. Thinly bedded dark gray to greenish crystal-lithic tuffs separated by massive coarser grained tuffs, along with thick units of agglomerates and rare gray limestones, from a distinct unit in the northwest part of the Restauración area (Figs. 2, 3f). The relative percentages of crystals and lithic fragments in the tuffs vary considerably. The main crystal fragments are altered plagioclase feldspar and fresh augite with minor amounts of magnetite. Minor quartz is present but appears to be mainly secondary (hydrothermal) in origin. Clastic quartz does not form more than 1 percent of the rocks examined. Lithic fragments vary from dark, almost opaque, angular vesicular scoria fragments to pale gray subangular fine-grained crystalline fragments. About 1 percent of the fragments are small, greenish brown, and shardlike, and have been altered to chlorite. The lithic fragments appear to be slightly more crystalline and felsic compared with

those in the green vitric-lithic tuffs. The crystal and lithic fragments are from a source rock of intermediate (andesite) composition, apparently different from the source of the green vitric-lithic tuffs and the upper acid unit. Age and depositional environment. The occurrence of fragments of the red and green tuff unit within the crystal tuffs indicates a younger age for the crystal tuffs. The paleontologic determinations on the interbedded limestones (Table 1) discussed below also suggest a younger age for this crystal tuff unit compared with the other sedimentary rocks in the Lower Tireo. The sedimentary and petrographic features suggest that the crystal-lithic tuffs are reworked tuffs produced by subaqueous gravity flows. It is suggested that the laminated granular tuffs were deposited from laminar grain flows probably riding in front of, or beneath, debris flows carrying large angular blocks forming the beds of breccia (Fisher, 1984). Tuff-basalt unit. Andesitic tuffs, andesitic and basaltic flows, and fine-grained silicified tuffs form a separate volcanicsedimentary packet in the extreme western part of the area along the border with Haiti. Similar rocks have been mapped for at least 15 km to the west from the border into Haiti (unpublished map at 1:200,000 of the United Nations Development Programme). Upper Tireo (Acid Rocks). The rocks of the Upper Tireo are mainly of dacite, less commonly of rhyolite (keratophyre) composition, and cover an area of about 16 km in the southcentral part of the Restauración map area. The rocks are flows and pyroclastic rocks, mainly tuffs, and breccias. Rocks of this Upper Tireo unit are in fault contact and also sedimentary contact with the sedimentary rocks of the Trois Rivieres or Ocoa Formation to the south. Dacite. Rocks of dacite composition form centers composed of volcanic domes and flows surrounded by breccias, tuff breccias, hydrothermal breccias, and probably explosion breccias. The main centers form the domal hills of El Montazo, Cerro El Guano, and Candelones (Amarante and others, 1989). Dacites are porphyritic and composed dominantly of plagioclase feldspar and embayed quartz phenocrysts with clinopyroxene and/or hornblende as the mafic minerals. Rhyolites and Quartz Keratophyres. Fine-grained clear gray to pinkish gray volcanic rocks with phenocrysts of quartz and white plagioclase feldspar form small domes as at Jiña de Mocha and Cerro Pan de Azúcar and dike-like intrusive bodies. The rocks are characterized by their fine-grained quartzo-feldspathic composition of the matrix and lack of mafic minerals, and are clearly distinguishable from the dacites. Keratophyres are distinguished by the occurrence of albite and epidote and contain more than 73 percent SÍO2 and more than 4 percent Na2Ü. These rocks are commonly hydrothermally altered with abundant hydrothermal quartz and feldspar. It is probable that some of the more acidic hydrothermally altered rocks are altered dacites, but this does not appear to be the case for all the rocks we have termed rhyolites or quartz keratophyres. Dacite Porphyry. Small bodies of subintrusive rocks (por2



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TABLE 1. MICROPALEONTOLOGY, AGE, AND LITHOLOGIES OF TIREO GROUP SAMPLES Age

Reference*

Lithology

Fauna

X-24 South Constanza Town

Gray limestone (biomicrite) Constanza member

Ticinella roberti Praeglobotruncana delrioensis Globigerìna washitensis Guembollina sp. Mevenolla meyerì

Late Cretaceous Probably Cenomanian

1

South of Constanza Town

Clear biomicrite in Constanza member

Globotruncana helvetica Globotruncana sigali Globotruncana renzi

Turonian

2

South of Constanza

Clear biomicrite

Globotruncana coronata Globotruncana angustlcarinata Globotruncana sigali Globotruncana schneegansi Globotruncana lapparent

Middle Coniacian Lower Santonian

2

Near Las Canitas

Red shaly biomicrites, reddish gray or green

Hedbergelles, Gumbelines Globotruncana Globotruncana Globotruncana Globotruncana

Lower Senonian

2

Locality

cf. gr. gr. ci.

tricarinata arca convexa 1apparenti concavata

B 136 Rio Yuma

Globotruncana fornicata Globotruncana 1apparenti bulloides Globotruncana stuarti stuartiformis Guembellina sp. Rugoglobigerina

Middle Campanian Maastrichtian

1

84 ML 87 Rio Yuma

Globotruncana marginata Globotruncana gr. arca convexa Globotruncana arca Globotruncana tricarinata Globotruncana gr. stuartiformia Globotruncana gr. arca Globotruncana gr stephonsi Globotruncana cf. calciformis Globotruncana? cf. calcarata

Upper Campanian Maastrichtian

3

Upper Campanian Maastrichtian

3

Rio Yuma

RM160 North of Restauración Arroyo Yobasilio (21845E; 213975N)

Dark gray limestone

Hedbergella1? Mandrini Hedbergella spp. Whiteinella baltica/paradubia gr. Heterohelix reussi Heterohelix sp.

Cretaceous Turonian(?) to Coniacian

4 5

RB513 West of Restauración (2124E; 21413N)

Dark gray limestone

Globotruncana ?helvetica Heterohelix spp. Hedbergella spp.

Cretaceous ?Turonian

4 5

*1, Bowin (1966); 2, Vila and others (1982); 3, Boisseau (1987); 4, this chapter; 5, E. Robinson, 1983, unpublished data.

152



phyries) of dacite composition intrude the green vitric-lithic tuff unit and form domal hills, as for example, at Cerro Jimenez and Var de Vaca. The dacite porphyries are composed of phenocrysts of subhedral plagioclase feldspar, anhedral quartz, and altered hornblende phenocrysts in an equigranular matrix of the same crystal composition. This lithology is considered to be part of the Upper Tireo Group because of the field distribution and because of the similarity in petrographic and chemical composition with the abundant dacites. However, these subintrusives could possibly represent a shallow-level manifestation of the tonalite magmatism. Volcaniclastic Rocks. Thickly bedded volcaniclastic rocks consisting mainly of breccias and lesser amounts of tuff are exposed along the road east of the rhyodacite dome of Loma de Jiña de Mocha and in the Rio Neita (Jimenez and Lewis, 1989, Figs. 6,7). These bedded volcaniclastic rocks appear to grade into the Trois Rivieres sequence (discussed below) to the south, but the relations have not been clearly established.

Juan de Herrera-Pico Duarte-Las Tireo- Valle Nuevo Area

Canitas-Constanza-

This is the central of the three main areas described here along the Tireo belt (Fig. 1). Much of the area lies in higher altitudes of difficult access, but there is reasonable approach to the Tireo and Constanza Valleys. For descriptive purposes, the area is divided into subareas. Juan de Herrera. The following description is taken from the l:100,000-scale map and the report of the DominicanGerman survey of the area (Garcia and Harms, 1988). Some information comes from the Cordillera Central traverses made in 1984 and 1985 in a combined project between the Dirección General de Mineria, the Universidad Católica Maestra, and the George Washington University. Although the Tireo Formation is undivided on the San Juan 1:100,000 map, the petrographic descriptions of samples and the chemical analyses indicate a wide variety of volcanic rock types and also plutonic rocks are present in the area mapped as Tireo Formation. High-titanium basalts (TiC>2 = 2:25-3:51 percent) crop out across the northern part of the Juan de Herrera map sheet south of the Macutico batholith at Loma Atravesada, El Monte Llano, and Loma Alto de La Vida. These basalts can be correlated with the extensive outcrop of apparently similar basalts (metabasalts) in the Pico Duarte-La Pelona area described below. In the southern part of the area, Tireo rocks seem to be mainly tuffs with minor intercalated sedimentary rocks. A biomicritic limestone from the Yaque del Sur has been dated as Turonian to Coniacian by J-M. Vila (Garcia and Harms, 1988). This correlates with the tuffaceous units in the Lower Tireo in the Las Canitas and Restauración areas (cf. Table 1). Dacites, rhyodacites, and quartz porphyries are a significant lithology. Some of the rhyodacites and quartz porphyries are probably equivalent to the rocks termed quartz keratophyres in the Restauración area; others are reported to show granoblastic and porphyroblastic textures (Harms, 1989). In the north, Tireo

rocks are intruded by the Macutico tonalite batholith that has metamorphosed the volcanic country rocks to hornblende hornfels facies (amphibolites). A smaller intrusion occurs to the southeast at El Gajo de Toro. Pico Duarte. Reconnaissance mapping has shown this area to be composed of metabasalt, now mainly amphibolite, which is intruded by tonalite, representing the western extension of the El Rio bvatholith (Domínguez and others, 1982). These metabasalts lie on the western and northwestern flanks of Pico Duarte and La Pelona and pass to the south into the vitroclastic lapilli tuff typical of the Lower Tireo. Several chemical analyses have shown these amphibolites to be metabasalts characterized by a high-TiC>2 content (J. F. Lewis, unpublished data, 1984). The metabasalts are therefore considered to belong to the basal part of the Tireo sequence and appear to have similar relation to the Lower Tireo basic vitroclastic tuff unit as seen at Restauración. Las Canitas Area. Las Canitas area was first mapped in 1975 by N. Russell for Falconbridge Dominicana C por A. The distribution of rock types and stratigraphy was examined in more detail by Mesnier (1980); his mapping is reproduced in Figure 4. Mesnier recognized a lower basal unit, equivalent to the Lower Tireo Group, of volcano-sedimentary rocks of basic composition, consisting of vitroclastic tuffs and breccias (in places, reddish in color) intercalated with siliceous sediments (radiolarian cherts) and limestones. Minor flows of basalt are also formed within the unit. This unit is dated as Turonian in age, based on foraminifera from limestones of the Constanza member of Bo win (1966). The upper unit, here termed the Upper Tireo Group, is also composed of volcano-sedimentary rocks, but of acidic composition, and overlies the basic unit without apparent discordance. The acid rocks consist of crystal tuffs, vitroclastic tuffs, lapilli tuffs and breccias, ignimbrites, and rhyolites. Limestone lenses dated as lower Senonian occur within the upper part of the acid sequence. A further unit of intermediate (dacite?) character but of minor extent lies at the margins of the acidic rocks and appears to cover both the main acidic and basic units and might overlap both units in time. This unit is composed of fine vitroclastic tuffs, reddish, tuffs, silicified sediments, and limestone lenses also dated as lower Senonian. In the southwest area at Los Guayuyos chlorite tuffs of sedimentary(?) origin occur intercalated with limestones, fine silicified tuffs, and with manganese-bearing cherts (jasper). In a later report on the Las Canitas area, in which the geology is largely based on the work of Mesnier, the Japanese group (JICA, 1986) divided the Tireo into three members. The lower member consisted of mainly andesite (actually metabasalt) in the Pico Duarte area, a middle member described as mainly pyroclastic rock intercalated with dacite, and an upper member consisting of mainly neritic sediments including shale. This concurs with the divisions on Mesnier's map and those adopted here, except that the neritic sediments are considered to belong to the Trois Rivieres or Ocoa Formation, as discussed below. Tireo-Constanza- Valle Nuevo Area. The extensive unit of vitroclastic tuffs and breccias of basic composition (the lower

GUAYUYOS

DE

MONTE LAS

CANITAS

Figure 4. A, Geologic map of the Las Canitas area, southern Gajo del Monte topographic sheet, scale 1:50,000. (after Mesnier, 1980). B, Generalized schematic east-west cross section across the Las Canitas are (4A) showing the inferred lithostratigraphy (after Mesnier, 1980). Lithologies as for Figure 4A.

LOS

GAJO

PLEISTOCENE

Rocks

Basalt flows

Vitroclastic tuff and breccia (andesitic)

Turonian

Lower Senonian

Dikes and stocks of quartz microdiorite

Dikes and stocks of porphyritic dacite

Rhyolite

Rocks

Volcanic

Intrusive

Basic

Limestone (Lower Senonian)

Crystal tuff, rhyolite ignimbrite

Stratified crystal tuff and breccia. Sedimentary breccia

Vitroclastic tuff (dacite) Sediment intercalations

Acid Volcanic Rocks

Chlorite tuff

UPPER CRETACEOUS

Reddish limestone siltstone

CRETACEOUS-PALEOCENE

PLIO

3

Ul u>

Ä

&

Sí

a ft.

&

S B"

a

2

o 3

S

y i' Ci

154



unit of Mesnier, 1980) extends east from Las Canitas and covers the area of the Constanza and Tireo Valleys and extends eastward into the hills around Valle Nuevo. In the Valle Nuevo area, Tireo rocks are intruded, and partly covered by, the volcanic products of Late Cenozoic volcanism. The Valle Nuevo area has been mapped in connection with studies of the young volcanic rocks themselves (Lewis, 1980; Vespucci, 1982, 1987) and in connection with a geothermal exploration project (Electroconsult, 1983). The geology of the mapped area around Valle Nuevo is reproduced in Figure 5. The dominant rocks are poorly stratified to massive, green to greenish gray lapilli tuffs as seen to the west. In this area the tuffs are commonly altered to chlorite and frequently to argillite, presumably the result of Cretaceous hydrothermal alteration. Two limestone horizons, each about 200 m thick and separated by about 300 m of tuff, have been mapped in the Valle Nuevo area. The regional dip is to the south. A horizon of some 600 m of well-bedded to laminated varicolored cherts occurs on the Constanza-El Convento road. The dominant colors are yellowish to greenish yellow and reddish. Recrystallization and weathering have destroyed the details of the structure of radiolaria in these rocks. It is convenient to refer to this marker horizon as the El Convento Chert Member. The volcaniclastic-sedimentary sequence is intruded by rhyolite, which is exposed as several dome-like protrusions forming the hills of Loma Cuchille del Montazo and Cerro El Castillo. Associated with the large rhyolite domes are rhyolite breccias and crystal tuffs, products of acidic explosive volcanism. K/Ar determinations on two rock samples from the rhyolite domes yielded ages of 71.5 ± 3.6 and 85.1 ± 4.3 Ma (Electroconsult, 1983). Tireo rocks are unconformably overlain by a thick conglomerate unit of apparent mid-Tertiary age at Loma de Bandera and are intruded and overlain by the late Cenozoic volcanic rocks of the Valle Nuevo volcanic field (Fig. 5). This is the northeastern most and youngest of three adjacent volcanic fields. The young volcanic rocks of the Valle Nuevo area are dated at 1.2 Ma (Electroconsult, 1983). North of the towns of Constanza and Tireo, a good part of the Tireo sequence has been intruded by the El Rio tonalite batholith. However, exposures of the vitroclastic-lapilli tuffs similar to those to the south occur along the El Rio-Bonao road section on the north side of the batholith. Unfortunately, most of the exposures are now covered. This section shows the repeated massive continuous layers of unsorted lapilli tuff. The color of the tuffs varies from grayish green to dark green to almost black. Reddish colored horizons are present, but uncommon. A horizon of thinly bedded gray siltstone and calcareous graywacke is exposed within the tuffs along the El Rio-Bonao Road. Tireo rocks east of Constanza. Tireo rocks east of Constanza to the Bonao fault are known only in a general way because of difficulty of access and poor exposure. The information given below is drawn from the unpublished Mitsubishi re-

ports and maps (late 1960s), an unpublished report on the Jayaco concession (U.S. Geological Survey, 1985); and from a traverse along the Rio Blanco made by J. F. Lewis and I. Ta vares in 1977. The rugged terrane south of the Rio Blanco has not been visited. The dominant rocks in this area seem to be volcaniclastic and sedimentary types. Major flows and/or centers of acidic rocks appear to be absent, although keratophyres are present. The volcaniclastic rocks include coarse breccias, interpreted as debris flow deposits in the U.S. Geological Survey report, and coarse well-bedded sandstones and shales present as turbidites of volcanic origin. Bioturbated fossiliferous mudstone and pyritic laminated black mudstone constitute the dominant lithology in the upper reaches of the Rio Blanco. Thin-bedded limestones, chert—commonly interbedded with limestones, and red pisolite rock with calcite cement are exposed along the trace of the Bonao Fault. The main limestone, exposed at the mouth of the Rio Blanco, apparently overlies the debris flow units, and therefore should give an upper limit to the age of the Tireo in this area. The limestone exposed in the sequence in the Rio Yuma along the Bonao fault, as well as the limestone near the mouth of the Rio Blanco, both yield Maastrichtian ages, the youngest dates recorded in Tireo rocks (Table 1). Nature of volcanism and depositional environment. The mapping is not detailed enough to estimate the thickness of the main massive green vitric-lithic tuff unit in the area. Its thickness must be more than the 1,500 m estimated in the Valle Nuevo area. The general features of this unit are the same as in the Restauración area. The fragmental material is also the same, although the relative percentage of the larger nonvesicular lithic fragments (lapilli) varies with respect to the smaller yellowbrown to green glass (palagonite) shards. Some of the lithic tuffs from this area are composed of a high percentage of glass shards and are possibly welded tuffs. Although a much more detailed study needs to be made in this area the overall origin for the extensive vitroclastic material seems to be similar to that of the Restauración area already discussed.

Southeast area—El Recodo Tireo rocks can be traced to the southeasternmost exposures of the Cordillera Central north of Bani. Although no general study has been made of Tireo rocks in the southeast, a small area at El Recodo has been examined in some detail in connection with mineral prospecting in the region (Domínguez, 1987). Rocks of the Tireo Group are well-tectonized and are the oldest rocks exposed in the El Recodo area. The dominant rocks are flows of fine-grained basaltic andesites, porphyritic andesites, and dacites with minor thin beds of lapilli and/or ash fall tuffs. Major units of pyroclastic rocks interbedded with the flows are andesitic tuffs, lapilli tuffs, red accretionary lapilli tuffs, and lithic tuffs with abundant crystal and glassy fragments. Also present are breccias and agglomerates. One breccia unit is considered to be of laharic origin. Sedimentary rocks interbedded within the pyroclastic units



155 PLIO- PLEISTOCENE phlogopite Basalt

-v.-.. V "v.. »•

Basalt Augite Basaltic Andesite Hornblende/ Biotite Trachy-Andesite NEOGENE Conglomerate UPPER

CRETACEOUS Rhyolite

Limestone

Vltric

Fault

Road

1 km

2500 2000

1500 1000

500 O m

Phiogopi te Basalt

B

A u g i t e Basaltic Andesite

Conglomerate

Rhyolite

Limestone

Vitric T u f f

Figure 5. A , Geologic map and cross section of the Valle Nuevo area. After Lewis (1980), Vespucci (1980, unpublished, 1987), Electroconsult (1983). B, East-west cross section of the Valle Nuevo area (5A), showing the stratigraphie position of the limestone units within the vitric tuffs of the Lower Tireo Group. Lithologies as for Figure 5A.

Tuff

156



are minor beds of partly recrystallized limestones and black available and only age for the extensive vitric-lithic tuff of the cherts. Poorly sorted lithic sandstones and graywackes lie above Lower Tireo Group. The probable Cenomanian age given by these pyroclastic units. Bowin (1966) for the Constanza limestone locality has been revised by Vila and others (1982). They have determined a Turonian age, but the fossil material does not appear to be the same. AGE OF UNITS IN TIREO GROUP An early Senonian age is given by Vila and others (1982) for gray Fossil microfauna data, an A r / A r date and K/Ar dates limestone samples from Las Canitas area. A Turonian-Coniaon intrusives into the Tireo give some constraints on the age of cian? age has been determined by Robinson for the gray limeunits within the Tireo Group. A listing of all the presently avail- stones intercalated within the crystal-lithic tuff sequence at able fossil data is given in Table 1. A generalized interpretation of Restauración (Table 1). the available age data in relation to the lithostratigraphy is given The youngest age given for the Lower Tireo is the early in Figure 6. Maastrichtian date on the Rio Yuma limestone indicating these The oldest date is that for the Constanza Member, a lime- tuffs were still being deposited, at least in the northeastern part of stone exposed in the Constanza Valley. This gives the best the belt, after the acid volcanism had begun in the early Campa40

39

RESTAURACION

MASSIF DU NORD

Middle

^

m •• • • •• ;i

M 81.2 + 0.8 Ma-

\AA AA AAAAAAAAA \AAAAAA/ fA« I l l \ l l

'\ S\ Ss S\ S\ S\ 'S \/ s s

\/ \ \

/\ \ \

Shale, mudstone,

xxxxxx.

yyyy.yy^

/ \ / \ / \/ \/ X / /\

' \ / \ / \/ s \ \ \ \ s

TuronianConiacian

.^ /N/ \ / \ / \/ N/ /\ s s I ¿ ^/ \ Vy \ /s\ /' V/s >, S/ \ / S/ N/ /N /\ , \ V/ \/ \/ \/ \/ \ \ V \ \ \ \ S \ V// \ // \// \// /\/ //\ , \i ^\ \ \ SS \ K// N// N// \// /N/ //\ , \

rock Purple

Upper Cretaceous)

mudstone

kAAA AAAAA"AA A r,\/N|\

V

V~

Perches Series

Jurassic

Morne Cabril Series

¿'¿J

+

fe 4

r ** L "j * J * ;• * r

* V» 1 Andesites, tuffs, V A a- i A > < Í '" A < • / • + + + r tuffite, agglomerate .r ± r* * u > -1 r ,, A < • , A + > si mudstone, basalt ' r + ++ + r — J • Carbonaceous . J+ +* *+ * + shales, silicified - — I * + + ++ — — E Pzr^: tuff ' 'i* J

Lower Cretaceous

-

Vr-« ;

chert Terrier Rouge Series

-

zjT

Pyroclastic rocks, dacite flows and subvolcanic stocks

,> ¿

Mafic and ultramafic rocks

J

+

P f

1

U

+

0 t l g l |

Figure 7. Lithostratigraphy of Upper Cretaceous rocks in the Massif du Nord, Haiti. After Louca (1985).

by Ph. Nicolini (1977), and the upper unit named La Mine Series by Louca (1985). These units were originally mapped by UN geologists at the 1:200,000 scale as the basic volcanic unit and the acid volcanic unit, respectively (Nicolini, 1977; Nicolini, 1981; United Nations, 1978). These units are separated by a 50-m-thick horizon of cherts and chert tuffites, as seen in the Plaisance-Pilate area (Louca, 1987).

Terrier Rouge Series The lower unit, the Terrier Rouge Series, consists of andesites, andesitic tuffs, tuffites, agglomerates, mudstones, and basalt (Louca, 1985). Nicolini (1977) divided the Terrier Rouge Series, as exposed in the Grand Bassin area, into a lower detrital unit (or complex) and an upper volcanic complex. The lower detrital complex consists of interbedded red and green pebble-sized conglomerates and dominantly green "agglomerates," with levels of finer grained reddish detrital rocks (pelite rouges). Limestones are found within the red facies along with calcareous pseudopisolites, indicating a marine origin for at least part of the series. Examination by us in 1987 of cores drilled as part of the UNRFNRE program suggested a strong resemblance in hand specimen between the Terrier Rouge red and green "tuffs" and the interbedded red and green tuff sequence at Restauración. Judging from the available descriptions, it would appear that the green vitric-lithic tuff unit may not be so extensive to the west in the Massif du Nord. Vitric fragments in the "agglomerates" described by Nicolini suggests that this material resembles the vitroclastic deposits in the Lower Tireo. Although Nicolini (1977) called the clastic rocks in the Terrier Rouge "detrital," his descriptions suggested that these may not be reworked clastics,

but might be, at least in part, primary pyroclastic material. Until further work is done, it is clear that the Terrier Rouge Series should be retained as a separate formation, but still can be considered part of the Lower Tireo Group (Fig. 6). The Terrier Rouge Series is well developed in the northeast of the Grand Basin area. Here, the thickness is nearly 1 km. Nicolini (1977) recognized three types of andesite lavas. Finegrained homogenous andesites with a "doleritic" texture seem to represent the base of flows. Amygdaloidal gray or green andesites with amygdales from 2 to 10 mm across containing epidote, chlorite, quartz, and zeolites apparently form the tops of flows. Other hornblende or orthopyroxene-bearing amygdaloidal andesites with a "classical ophitic" texture form flows in the eastern part of the Grand Basin area. Although Nicolini (1977) stated these rocks are "andesite" in composition, the pétrographie descriptions and mineralogy suggest some of the rocks are basalts, basaltic andesites, or quartz dolerites. Such rock fragments form about 1 percent of the lithic fragments in the green vitric-lithic tuffs of the Lower Tireo Group in the Restauración and Constanza areas.

La Mine Series

In contrast, the upper unit is of felsic composition and composed of dacite flows and stocks, crystal-lithic tuffs, and unsorted pyroclastic and volcaniclastic rocks. Laharic breccias and welded tuffs (ignimbrites), as at Camp Coq, have also been reported, indicating subaerial volcanism and reworking. The felsic rocks of the La Mine Series are concentrated along the southern part of the belt in Haiti and carry the associated barite-polymetallic sulfide Au-Ag mineralization (Louca, 1985, 1987). It is apparent that La Mine Series correlates directly



with the upper unit of the Tireo Group in the Dominican Republic (Fig. 6). A good example of the rocks comprising the La Mine Series has been described by Louca (1987) from the Camp Coq exploration area between Plaisance and Limbe (Fig. 1). Louca (1987) recognized a sequence of five principal lithologic units: massive dacite, quartz-eye crystal tuff, quartz-feldspar crystal-lithic tuff, and rhyodacite tuffs and breccias. The massive dacite of Massabiel is overlain by a coarsegrained polymictic tuff breccia with angular fragments as much as 20 cm in diameter. The stratigraphic relationship between the quartz-eye crystal tuff and other units is not clear. The extensive crystal-lithic tuff unit consists of alternating volcaniclastic and pyroclastic deposits in which a white spotted crystal tuff predominates. The crystal tuffs grade locally into lithic-crystal tuffs, vitric-lithic tuffs, and tuff breccias. Interbedded agglomerates, tuffites, and lava flows also occur. The uppermost unit is composed of welded rhyodacite tuffs, and, locally, a heterogeneous pyroclastic horizon. The rhyodacitic tuffs include tuff breccias at the base with laminated tuffs and welded tuffs above the crystal-lithic tuffs. The volcanic rocks of the La Mine Series are overlain conformably by the Trois Rivieres Series that includes, in the Camp Coq area, graywackes, mudstones, thin bedded microconglomerates, and tuffites. The occurrence of tuffite interbeds at the base of the Trois Rivieres Series in this area suggests a gradational relationship with the La Mine Series. In the Massif du Nord the mapping has shown that the acid rocks of the La Mine Series are much more extensive than in the Dominican Republic, and the distinction of this series from the more basic rocks of the Terrier Rouge Series is very clear. No ages have been determined for either the Terrier Rouge Series or the La Mine Series in Haiti. Some workers (Nicolini, 1977; Nicolini, 1981) considered the Terrier Rouges Series to be of pre-Albian age, but this was revised by Louca (1985, 1987), who considered both the Terrier Rouge and the La Mine Series to be Late Cretaceous in age, which is in agreement with the Dominican field data. Louca (1987) mapped a 50-m-thick horizon of cherts and cherty tuffites exposed in the Plaisance-Pilate area that marks the contact between the Terrier Rouge and La Mine Series. It is very possible that this unit can be correlated with the small area of chert exposed on the main highway 5 km south of Restauración. These cherts south of Restauración are apparently intruded by quartz keratophyre to the north and are in contact with the acidic volcanic rocks to the south, and thus could well form the base to the acidic volcanic rocks in the Restauración area. STRATIGRAPHIC RELATION OF TIREO ROCKS TO THE OVERLYING TROIS RIVIERES AND OCOA FORMATIONS Reddish purple calcareous mudstone (limestone), shales, and siltstone are found in the southern area of the Tireo terrane, which our data show belong to the sequence of shales, siltstones-

159

sandstones, and limestones to the south known as the Trois Rivieres Formation (Butterlin, 1954, 1960) in Haiti and the Peralta and Ocoa sequences in the Dominican Republic (Garcia and Harms, 1988; Lewis and others, 1990; Dolan and others, this volume). Relations with the Tireo rocks are not always clear, and previous workers, for example, the Japanese International Cooperation Agency (JICA, 1986) considered these reddish calcareous sedimentary rocks in the south Las Cañitas area (Fig. 3) to be within the upper part of the Tireo Formation. The contact between the Tireo Group rocks and the siltstones and shales of the Trois Rivieres-Peralta Belt are mainly faulted, although in several places the contact is stratigraphically conformable. The structural and stratigraphic relations are best seen in the southern part of Restauración area. Here the reddish calcareous mudstones, shales, and siltstones are seen to be an early facies of the gray calcareous shale-siltstone sequence to the south (Trois Rivieres or Ocoa Sequence). In the area northwest of Rosso, thick calcareous sandstones of the Trois Rivieres Formation grade northward into interbedded grayish and reddish shale and siltstones with occasional thin calcarenite beds. In the Rio Artibonito (grid reference 2262E; 2130IN) the siltstone-shale sequences grade upstream into thick purple-red calcareous mudstones. Minor volcanic rocks occur intercalated with the interbedded siltstone and shales in the area of Cruz de Cabrera. In the area immediately north of Cruz de Cabrera, a thin slice, or block, of reddish interbedded calcareous mudstones, shales, siltstones, and sandstones is in-faulted within the Tireo volcanic rocks. In the Rio Neito (grid reference 2197E; 21316N), the Tireo volcaniclastic rocks appear to conformably overlie the calcareous shales. However, graded bedding indicates that the section is overturned. Boisson (1987) showed the contact between the Tireo and Trois Rivieres Formations in Massif du Nord to be, for the most part, an unconformity except near the Haitian-Dominican border. Here a sequence of sedimentary and volcanic rocks, termed the Bois de Laurence unit and forming the lower part of the Trois Rivieres Formation, is shown to conformably overlie the Tireo Group. The Bois de Laurence unit consists of purplecolored micrites, varicolored beds of chert, and coarse- and finegrained volcaniclastics, and seems to be the western continuation of the lithologies described above from south of Restauración in the Rosso and Cruz de Cabrera areas. Figure 6 shows generalized stratigraphic columns showing the gradation from the Tireo volcanic and volcaniclastic rocks into sedimentary rocks of the Trois Rivieres Formation, as seen in the south Cordillera Central and eastern Massif du Nord. Sample numbers show the stratigraphic position of samples dated by paleontology. Samples examined for both foraminifera and nannoplankton (Table 2) show that the age of the purple and reddish calcareous shales, mudstones, and micrites from both areas is late Campanian early Mastrichtian, and the age of the gray siltstoneshale sequence and the limestones at the base of the Trois Rivieres Formation is Campanian-Maastrichtian. The Campanian- early Maastrichtian dates for these rocks are younger than the pre-

160



TABLE 2. MICROPALEONTOLOGY, AGE, AND LITHOLOGIES OF TROIS RIVIERES FORMATION Locality

Lithology

Age

Fauna

Middle to late Campanian

1 2

82-14 Cerro de la Colonia (22435E; 21283N)

Foraminiferal-peloidal sparite

Sulcoperculina Aktinorbitoides

85-A-54 near Rosso (22605E; 21307N)

Planktonic foraminiferal micrite

Striate Guembelina sp. Double-keeled Gtobotruncana spp. Globotruncana spp. G. ?calcarata Pseudotextularia elegans Rugoglobigerina spp.

Middle Campanian to Maastrichtian G. calcarata(?) indicates late(?) Campanian

82-58 near Rosso

Reddish mudstone

?double-keeled Globotruncana sp. ?Heterohelix sp. ?Hedbergella sp.

Late Cretaceous

DR-82-142 International Gray shale Highway (2231 E;212575N)

Micula descussata Watznaneria barnesae Arkhangelskiella sp. (small) Cretarhabdus conicus Micula mina

Zone 26 Late Maastrichtian

1 3

DR-82-97 Rio Artibonito (22322E; 212775N)

Gray shale

Micula decussata Watznaneria barnesae Arkhangelskiella sp. Cretarhabdus conicus Micula conicus Cribosphaerella ehrenbergii Tetralithus trifudus

Zones 22 and 23 of early Maastrichtian//late Campanian transition

1 3

DR-82-89b Northeast Rosso (2266E; 21290N)

Reddish gray shale

Watznaneria barnesae Broinsonia parca Eiffelith us turriseiffeli Micula decussata Eiffelithus eximius Cretarhabdus conicus Cretarhabdus ehrenbergii Ceratolithoides aculens Lithastrinus grillii Tetralithus gothicus

Zone 21-22 of late Campanian

1 3

Watznaneria barnesae

Age indeterminate, but probably same as DR82-89b

1 3

DR-82-84 Cruz de Cabrera Reddish gray shale (2208E; 213125N)

globosa browni

Reference*

*1, This chapter; 2, E. Robinson, 1983, unpublished data; 3. Ming-Jung Jiang, 1983, unpublished data.

Campanian dates recorded from the sediments within the Tireo Group in the Restauración area. Thus, although there is some conformable intercalation between the uppermost part of Tireo volcanics and the reddish calcareous mudstones, shales, and siltstones, it is apparent from the field evidence and biostratigraphy that the purple and reddish calcareous mudstones and siltstones are a facies of the Trois Rivieres Formation.

The contact between the Tireo volcanics and the siltstoneshale sequence to the south has also been examined to some extent north of Padre las Casas in the rugged terrane between Padre las Casas and Las Canitas. The northern part of the Padre las Casas 1:50,000 sheet mapped by Vespucci (Lewis and others, 1989; Vespucci, 1987) is mainly composed of sequences of interbedded gray siltstones, sandstones, and shales (turbidites) with



intercalated horizons of limestones. This is part of the belt of rocks termed the Trois Rivieres-Peralta belt that can be followed westward along the southern flank of the Cordillera Central and that can be correlated with similar rocks of the Trois Rivieres Formation discussed above in the south Massif du Nord and south of Restauración. Micropaleontologic studies have shown that siltstone-shalelimestone sequences on the northern Padre las Casas sheet are Eocene in age and contain reworked Upper Cretaceous microfossils (Lewis and others, 1989). In the northern part of the Padre las Casas 1:50,000 sheet in the Arroyo Guarico area (grid reference 3018E; 208IN), basalts are intercalated with the reddish colored siltstone-shale sequence for which a Maastrichtian age was obtained. This sequence is gradational upward into the cliffs of white limestone of proven Eocene age. It therefore seems likely that in the Padre Las Casas area there is a gradation between a reddish facies of Maastrichtian age of the Ocoa Formation into a gray colored facies of Eocene age. Similar stratigraphic relations as seen in the Restauración and Padre las Casas-Las Canitas areas appear to be present on the Juan de Herrera map sheet, which lies west of Las Cahitas and northeast of San Juan de la Maguana (Fig. 1). Garcia and Harms (1988) pointed out that the upper part of the Tireo Group as presented on the 1:100,000-scale geologic map consists of thin beds of dark gray argillaceous shales, partly calcareous and partly siliceous, and fine granular sandstones that occur within a pyroclastic sequence. The reddish biomicritic limestones that crop out along the contact with the Ocoa Formation are presumably equivalent to the same reddish purple calcareous mudstones south of Restauración. Garcia and Harms (1988) reported that the quantity of sediment increases in the upper part of the Tireo, and as much as 100 m of alternating argillaceous shales, sandstones, and dark micritic limestone, as well as pyroclastic rocks, occurs along the El Palmer-La Cucarita Road (grid reference 2910E; 2086.8N). This section, which occurs at the contact with the Ocoa Formation, appears to be very similar to that of the Bois de Laurence unit in the Massif du Nord and that at Cruz de Cabrera, south of Restauración as described above. INTERPRETATION AND SUMMARY OF TIREO VOLCANISM The Tireo Group sequence of volcaniclastic and volcanic rocks represents a 290-km-long belt of continuous volcanism that took place over late Cenomanian to early Campanian time, i.e., it lasted for a period of about 10 to 12 m.y. There is only limited information available from which to deduce the depositional and tectonic environment of the accumulation of the Tireo deposits. The composition of the volcanic rocks (Jimenez and Lewis, 1989) and the distribution of the sedimentary facies indicate that the deposits of the green vitric tuff sequence accumulated in one or more long, narrow basins situated in an island-arc setting. The occurrence of radiolarian cherts and other fossil indicators shows that at least part of the basin was

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at abyssal depths in an open ocean. A more shallow environment is indicated by the accretionary lapilli beds and possibly by the redbed facies. The northern boundary to the Tireo is presently faulted for its entire length, but there is no definite proof that the basin boundary was faulted at the time of deposition of the Tireo. However, the occurrence of relatively thin deposits of volcaniclastic rocks apparently of the same type and age outside the main basin as near Hatillo (Bowin, 1966; Boisseau, 1987) suggests the possibility of a rapid change in depth of the basin and fault control. A caldera collapse related graben structure has been suggested for the Kuroko deposits in Japan, and a similar volcano-tectonic depression structure might be suggested for the Tireo basin. It is likely that extensional tectonics was an important factor in the area, at least in the later stages, since prominent fractures were important in providing fluid conduits for the hydrothermal activity. Amarante and others (1989) considered that hydrothermal activity occurred in the late stages of the acid volcanism, and hence the main fractures would have been developed in the Campanian at the latest. The nature of the basement onto which the Tireo volcanic and volcaniclastic rocks were deposited is also not clear. The absence of any association or rocks of any type other than the metabasic rocks of the Duarte Complex in the Dominican Republic and the metabasic and ultrabasic rocks of the Morne Cabrit Series in Haiti suggests that these rocks lie below the Tireo. A discussion of the magmatic affinities of the volcanic rocks is beyond the scope of this chapter, requiring more detailed investigation; it should be stated that it is likely the acid volcanism of the Upper Tireo unit is the volcanic equivalent of the tonalite plutonism. The source of the initial basic volcanism that gave rise to the extensive vitroclastic tuffs is not known, but was probably from a string of basaltic volcanoes along a ridge structure to the north. One suggestion for a possible source for the volcanism, at least in the eastern end of the belt, is the Siete Cabezas Formation (Bowin, 1966), a suite of vitric basaltic lavas and breccias of Cenomanian, possibly Santonian, age and of probable submarine origin, now exposed along the southwest margin of the peridotite belt. Vitroclastic tuff breccias and tuffs with the same petrographic features as found in the Tireo vitroclastic tuffs and breccias occur intercalated with basalts of the Siete Cabezas Formation in drill cores from the La Lomita area east of the town of Villa Altagracia (J. F. Lewis, 1989, unpublished observations). This likely correlation between the Siete Cabezas and Tireo Formations can be tested with further petrographic and chemical data. The nature of the vitroclastic fragmental material indicates a submarine pyroclastic origin from both phreatomagmatic eruptions and phreatic eruptions. The material was transported as massive debris flows(?) and was deposited at abyssal depths. The acid volcanism, which began and apparently followed the basic volcanism without a hiatus, evolved from centers along the southern margin of the belt. The acid centers are mainly concen-

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trated in the northwestern, that is, Haitian, part of the belt; only two distinct centers of dacite volcanism are known on the Dominican side, age dating indicates that the acid volcanism did not begin before the Senonian and peaked at or before 81 Ma, then ceased before middle Campanian time, that is, by about 79 m.y. B.P. This was not before late stage hydrothermal activity had taken place within the acidic rock centers, producing significant epithermal polymetallic Au-Ag sulfide-barite deposits. It is not known whether the Cordillera Central was covered by sedimentary rocks through the Tertiary. The main uplift of the Cordillera Central to its present position is considered to have taken place in the Plio-Pleistocene (Lewis and others, 1990). It is important to note that the extensive Late Cretaceous volcanic and volcaniclastic rocks in central Cuba, in the Zaza Zone of arc rocks south of the ophiolite belt (Diaz de Villavilla, 1985; Lewis, 1990) appear to be the lithologic and time equivalent of the Tireo Group in Hispaniola. The sedimentary basins might have been separate, but the general nature of the magmatism and tectonism was the same. ACKNOWLEDGMENTS Our work on the Tireo rocks really began in 1975, when M. Feigenson mapped around the Rio Limpio area north of Restauración. The work has been supported under several projects since that time. We thank the Dirección General de Mineria, Universidad Católica Madre y Maestra, and Rosario Dominicana for much logistic support. Lewis has been supported by the U.S. National Science Foundation Latin American Cooperative Program Grant INT-85-11432. Lewis thanks G. Draper and H. Domínguez, who spent several weeks of arduous field work in 1982 in Restauración and I. Tavares, P. Vespucci, and J. Espaillat, who assisted with reconnaissance surveys in the Constanza, Valle Nuevo, and Rio Blanco areas. We are grateful to K. Louca of the United Nations Revolving Fund for Natural Resources Exploration, and to M. P. Marthurin, formerly Director of the Bureau des Mines, Haiti, for arranging a field trip in early 1987 enabling us to examine the deposits in the Massif du Nord. We also thank E. Force and colleagues of the U.S. Geological Survey for sharing with us their observations of the eastern Tireo terrane, and FranzJiirgen Harms for discussion of the results of the mapping of the German-Dominican group in the Juan de Herrera area. The manuscript was improved markedly through constructive reviews by K. Louca, P. Mann, and A. Smith. REFERENCES CITED Amarante, J. A., Jimenez, J., and Lewis, J. F., 1989, Geology, hydrothermal alteration, and geochemistry of epithermal Au-Ag mineralisation in the Restauración area, Dominican Republic, in Barker, L., ed., Transactions of the 11th Caribbean Geological Conference, Barbados, 1986: St. Michael, Barbados, Energy and Natural Resources Division, p. 1-15, 26. Boisseau, M., 1987, Le flanc nord-est de la Cordillere Centrale Dominicaine, Hispaniola, Grandes Antilles; Un edifice de nappes Cretace polyphase [Doctoral thesis]: Paris, France, University of Paris, 200 p.

Boisson, D., 1987, Etude géologique du Massif du Nord d'Haiti, HispaniolaGrandes Antilles [Doctoral thesis]: Paris, France, University of Paris, 232 p. Bourdon, L.. 1985, La Cordillere Orientale Dominicaine, Hispaniola, Grandes Antilles; Un arc insulaire Cretace polystructure [Doctoral thesis, 3rd cycle]: Paris, France, Universite Marie et Pierre Curie, 203 p. Bourdon, L., Mercier de Lepinay, B„ and Vila, J-M., 1985, Etude géologique de la Cordillere Orientale, Dominicaine, Hispaniola, Grandes Antilles, in Geodynamique des Caribes Symposium, Paris, France: Mitions Technip, p. 317-328. Bowin, C. O., 1966, Geology of the central Dominican Republic; A case history of part of an island arc, in Hess, H. H., ed., Caribbean geological investigations: Geological Society of America Memoir 98, p. 11-84. Butterlin, J., 1954, La geologie de la Republique d'Haiti et ses rapports avec celle de regions voisines: Publication Comité 150 anniversaire Independence, Port-au-Prince, no. 1, 446 p. , 1960, Geologie generale et regionale de la Republique d'Haiti; Travaux et Mémoires de l'Institut des Hautes Etudies de l'Amerique Latine: Paris, France, Universite de Paris, v. 7, 194 p. Cheilletz, A., 1976, Etude géologique et metallogenique des indices a cuivre et molybdene de type porphyre cuprifere de la zone de Vert de Gris-Jean Rabel, Presqu'île de Nord-Ouest, Haiti [Doctoral thesis]: Nancy, France, University of Nancy, 177 p. Diaz de Villavilla, L., 1985, Proposicion para una division de la llamada formadon Tobas, Provincias Cienfuegos, Villa Clara y Sancti Spiritus: La Habana, Ministerio de Industria Basica, Central Investigaciones Geológicas, Serie Geologica, v. 1, p. 133-154. Domínguez, H„ and 5 others, 1981. Geologia del area de Manabao [Thesis]: Santiago de los Caballeros, Dominican Republic, Universidad Católica Madre y Maestra, 126 p. Domínguez, H. S., 1987, Geology, hydrothermal alteration, and mineralization of the El Recodo porphyry copper prospect, southeastern Cordillera Central, Dominican Republic [M.S. thesis]: Washington, D.C., George Washington University, 203 p. Electroconsult, 1983, Estudio de pre-facibilidad del area geotermica YayasConstanza, Dominican Republic: Santo Domingo, Dirección General de Mineria, unpublished report, 23 p. Fisher, R. V., 1984, A review of submarine volcanism, transport processes, and deposits, in Kokelaar, B. P., and Howells, M. F., eds., Marginal basin geology; Volcanic and associated sedimentary and tectonic processes in modern and ancient marginal basins: Geological Society of London Special Publication 16, p. 5-28. Fiske, E. A., 1963, Subaqueous pyroclastic flows in the Ohanepecosh Formation, Washington: Geological Society of America Bulletin, v. 74, p. 391-406. Garcia, E., and Harms, F-J., 1988, Informe del Mapa Geologico de la República Dominicana, San Juan: Santo Domingo, Dirección General de Mineria, Secretaria de Estado de Industria y Comercio, 97 p., scale 1:100,000. Harms, F-J., 1989, Tabellen zu geochemischen, mineralogische, petrographischen, und biostratigraphischen Untersuchungen auf dem Blatt 5972 San Juan der Geologischen Karte der Dominikanischen Republik: scale 1:100,000.

JICA, 1986, Report on geological survey of Las Canitas area, Dominican Republic; Consolidated report, Japan International Cooperation Agency and the Metal Mining Agency of Japan: Santo Domingo, Dirección General de Mineria, 93 p. Jimenez, G. J., and Lewis, J. F., 1987, Petrologia del area de Restauración, República Dominicana, in Duque-Caro, H., ed.. Transactions of the 10th Caribbean Geological Conference, Cartagena, Colombia, 1983: Bogota, Colombia, Ingeominas, p. 445-453. Kesler, S. E., 1971, Petrology of the Terre-Nueve igneous province, northern Haiti, in Donnelly, T. W., ed., Caribbean geophysical, tectonic, and petrologie studies: Geological Society of America Memoir 130, p. 119-137. Lewis, J. F., 1980, Field trip F, first day; The south slope of the Cordillera Central, in Field Guide for the 9th Caribbean Geological Conference, Santo Domingo, Dominican Republic, Amigo del Hogar Publishers, p. 169-188.



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, 1990, Cuba, in Lewis, J. F„ and Draper, G., Geology and tectonic evolu- Rosario Dominicana S.A., 1985, Projecto de Exploración de Restauración, Estion of the northern Caribbean margin, in Dengo, G., and Case, J. E., The tado Actual: Rosario Dominicana, S.A., unpublished report. Caribbean region: Boulder, Colorado, Geological Society of America, The , 1986, Projecto de Exploración de Restauración, Estado Actual: Santo Geology of North America, v. H, p. 78-93. Domingo, Rosario Dominicana, S.A., unpublished report. Lewis, J. F„ Draper, G„ and Domínguez, H., 1982, Preliminary report on the Suthren, R. J., 1985, Faciès analyses of volcaniclastic sediments; A review, in geology of the Restauración area: Santo Domingo, Dirección General de Brenchley, P. J., and Williams, B.P.J., eds., Sedimentology; Recent develMineria, unpublished report and map, 8 p. opments and applied aspects: Geological Society of London Special PublicaLewis, J. F., Vespucci, P., Robinson, E., Jiang, M., and Bryant, A., 1987, Paleotion 17, p. 123-146. gene stratigraphy of the Padre las Casas and adjacent areas of the southeast United Nations, 1978, Geologic map of the Republic of Haiti: Port-au-Prince, Cordillera Central, Dominican, in Duque-Caro, H., ed., Transactions of the Haiti, United Nations Development Programme, scale 1:200,000. 10th Caribbean Geological Conference, Cartagena, Colombia, 1983: Bo- Vespucci, P., 1982, Preliminary account of the petrology of the late Cenozoic gota, Colombia, Ingeominas, p. 229-237. volcanic province of Hispaniola, in Transactions of the 9th Caribbean GeoLewis, J. F., and 5 others, 1990, Hispaniola, in Lewis, J. F., and Draper, G., logical Conference, Santo Domingo, Dominican Republic: Santo Domingo, Geology and tectonic evolution of the northern Caribbean margin, in Dengo, Amigo del Hogar Publishers, p. 379-389. G., and Case, J. E., The Caribbean region: Boulder, Colorado, Geological , 1987, Petrology and geochemistry of the Late Cenozoic volcanic rocks of Society of America, The Geology of North America, v. H, p. 94 -112. the Dominican Republic [Ph.D. thesis]: Washington, D.C., George WashLouca, K., 1985, Metallogenesis of base metals and gold in northern Haiti: United ington University, 223 p. Nations Revolving Fund for Natural Resources Exploration Report 23, 17 p. Vila, J-M., and Feinberg, H., 1982, Les discordances successives a la terminaison , 1987, Precious and base metals exploration in northern Haiti; Geology, sud-est de la Cordillère centrale dominicaine; Un enregistrement du calenexploration, and mineral resources of Camp Coq Exploration Zone E: drier tectonique d'Hispaniola, Grandes Antilles: Bulletin Société géologique United Nations Revolving Fund for Natural Resources Exploration Report France, v. 24, no. 1, p. 153-156. 26,31 p. Vila, J-M., Bourgois, J., and Sigal, J., 1982, Nouveaux elements de datation des Mesnier, H. P., 1980, Report on the mineral prospects of the Las Canitas area, formations volcanogenes de type Tireo dans la Cordillère Central DominiDominican Republic: Santo Domingo, Dirección General de Mineria, uncaine, Hispaniola, Grandes Antilles, in 9th Reunion annuelle des Sciences de published report, 55 p. la Terre, Paris, 1982: Société Géologique de France, p. 624. Nicolini, P., 1981, Geologie Haitienne, in Maurrasse, F.J-M., ed., ler Colloque Wright, J. V., and Mutti, E., 1981, The Dali Ash, Island of Rhodes, Greece; A sur geologie d'Haiti, Port-au-Prince, Haiti: Port-au-Prince, Imprimerie Le problem of interpreting submarine volcanogenic sediments: Bulletin VolcanNatal S.A., p. 105-115. ologique, v. 44, p. 153-167. Nicolini, Ph., 1977, Les porphyres cupriferes et les complexes ultra-basiques du Nord-Est Haiti; Essai de gitologie provisionnelle [Doctoral thesis]: Paris, France, Universite Marie et Pierre Curie, 203 p. MANUSCRIPT ACCEPTED BY THE SOCIETY OCTOBER 16, 1 9 9 0


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Geological Society of America Special Papers Lithology and stratigraphy of upper Cretaceous volcanic and volcaniclastic rocks of the Tireo Group, Dominican Republic and correlations with the Massif du Nord in Haiti John F. Lewis, A. Amarante, G. Bloise, et al. Geological Society of America Special Papers 1991;262; 143-164 doi:10.1130/SPE262-p143

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