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Geology of the Amber-Bearing Deposits of the Greater Antilles

MANUEL A. ITURRALDE-VINENT

Museo Nacional de Historia Natural, Obispo no. 61, Plaza de Armas,La Habana Vieja 10100, Cuba.

[email protected]

ABSTRACT.—Amber and associated lignitic rocks are known from Cuba (Miocene lignite), Haiti(Miocene lignite and traces of amber), the Dominican Republic (Miocene lignite and amber in exploitablequantities), Puerto Rico (Oligocene and Miocene lignite and traces of amber), and Jamaica (Maastrichtian-Paleocene amber). However, there is no modern review of the geology of the amber-bearing deposits and thedata available is dispersed in many contributions. This paper fills this gap and presents the results of fiveyears of original research on the subject. Greater Antillean amber probably derived from the resin ofHymenaea protera, an extinct leguminous tree which probably grew in evergreen forests. Amber is theconsequence of diagenetic changes that operate in the resin after burial in the sedimentary pile, sometimesover 1000 m deep, where it is subjected to higher temperature and pressure over millions of years. The originof unusually large Miocene deposits of amber in the Dominican Republic can be explained by the fortunatecombination of adequate conditions of relief and soil for the development of a large populations of resin-producing trees during a constrained warm and humid climate optimum that occurred about 16 m.y. ago.

INTRODUCTION

Dominican amber was known by the na-tives of Hispaniola and was taken to Spainby Cristopher Columbus as one of the trea-sures of the West Indies. During the 20th

century, Dominican amber became famousfor the quality of its fossils, which includeextremely well-preserved fungi, algae,plant remains, land invertebrates (arthro-pods, nematodes, gastropods) and landvertebrates (amphibians, reptiles, remainsof mammals and birds) (Pérez-Gelabert,1999).

Amber has also been reported from Haiti(Maurrasse, 1982), Puerto Rico (Iturralde-Vinent and Hartstein, 1998) and Jamaica(G. Draper, pers. comm.), but none of theseoccurrences has economic value. Despitewidespread interest in amber, there is nomodern review of the geology of the am-ber-bearing deposits of the Greater An-tilles. This paper fill this gap by (1) review-ing the occurrences, age, stratigraphicposition, and environment of deposition ofthe amberiferous beds; (2) presenting newinformation about the age and origin of theamber as a fossil resin; (3) discussing thepaleogeographic scenario when amber-

bearing deposits were formed; and (4) de-scribing the fossil assemblage found not inthe amber itself but in the associated depos-its (Iturralde-Vinent and MacPhee, 1996;Iturralde-Vinent and Harstein, 1998).

WHAT IS RESINITE, RESIN, COPALAND AMBER?

Resin-producing trees are widely distrib-uted in the tropics, but amber in tropicalAmerica most probably derived from theresin of the extinct leguminous tree Hymen-aea protera. Although several extant speciesof this genus occur from the Amazon Basinto Mexico, only two species occur in theGreater Antilles: the widespread H. cour-baril L. (commonly known as courbaril inCuba and as algarrobo in the DominicanRepublic and Puerto Rico), and the north-eastern Cuban endemic H. torrei León. Theextinct amber-producing tree of the Do-minican Republic was named Hymenaeaprotera by Poinar (1991). This taxon is re-lated to H. verrucosa of western Africa andprobably to H. torrei of eastern Cuba (Leeand Langenheim, 1975).

Resinite.—This is an all-encompassing

Caribbean Journal of Science, Vol. 00, No. 0, 141–167, 2001Copyright 2001 College of Arts and SciencesUniversity of Puerto Rico, Mayagüez

141

term for all types of plant-derived resins,regardless of age and physical or chemicalcharacteristics.

Resin.—This term applies to material re-cently exuded from the tree and which hasnot been buried. Its physical and chemicalcharacteristics depend on the species oftree. Resin can be sticky or dry and fragile.It can have a whitish or darker coating, butinternally is transparent, yellowish, red-dish, or brown. Resin is non-volatile, rela-tively inert, hydrophobic, amorphous, andstrongly resistant to decay. Its decay (aswell as that of copal and amber) is due toatmospheric exposure, and the material isbest preserved when deposited in subaque-ous or water-logged environments. Atmo-spheric weathering often produces opaquesurface crusts and oxidation rims, and maycause an overall darkening of the resingrains (Tyson, 1995). Naturally exudedresin seems to be a physical surface barrieragainst infection by plant pathogens (Leeand Langenheim, 1975; Grimaldi, 1996).

Copal.—This is an older resin that can befound in the leaf litter layer or buried in thesoil below the tree. It is usually solid, frag-ile, transparent with a dark surface coating,and internally yellowish, reddish, orbrown. Copal of H. courbaril usually sinksin fresh water and floats in salt water (per-sonal observation). Resin in the form of co-pal accumulates in forest soils and ombrog-enous peat deposits, whose high (domed)water tables aid preservation.

Amber.—This is the fossil equivalent ofcopal. It is usually indurate, massive, andresistent to organic solvents. Amber can betransparent, but more frequently it is trans-lucent with yellow, reddish, brown or blue-brown color. These characteristic are theconsequence of diagenetic changes that op-erate in copal after burial in the sedimen-tary pile, sometimes at depths over 1000 m,where it is subjected to elevated tempera-ture and pressure. Under these conditionsand several millions of years, copal is natu-rally cooked and transformed into amber.Dominican amber usually sinks in freshwater and floats in salt water (personal ob-servation).

After erosional exposure, copal and am-ber are frequently reworked and redistrib-

uted by flash floods and the normal fluvialand runoff processes. Amber can also bereworked by coastal erosion, as in the Balticregion (Schlee, 1990; Grimaldi, 1996). Am-ber clearly has significant potential forredeposition if protected from prolongedexposure to atmospheric oxygen. Langen-heim (1990) indicates that near-flotation al-lows some amber particles to be readilymoved by weak currents and tends to pro-tect them from abrasion and fracture, evenduring prolonged transport. Amber is typi-cally deposited in low energy bays, deltas,river mouths, estuaries, and other coastalareas. Large amounts may be carried fur-ther offshore as inconspicuous microscopicparticles (Grimaldi, 1996).

THE AMBERIFEROUS DEPOSITS OF THEGREATER ANTILLES

Amber and associated lignitic rocks areknown from the Greater Antilles (Fig. 1) inCuba (Miocene lignite), Hispaniola(Miocene lignite and amber), Puerto Rico(Oligocene and Miocene lignite and tracesof amber), and Jamaica (Maastrichtian-Paleocene traces of amber). The followingparagraphs describe the basins and sedi-ments known to contain amber, regardlessof their commercial importance.

HISPANIOLA

The Late Tertiary rocks of the DominicanRepublic occur in a variety of geologicalcontexts, predominantly of sedimentaryorigin, formed in subaerial to deep-marinedepositional environments (see referencesin Mann et al., 1991). Amber in commercialquantities is well known from areas northof Santiago de los Caballeros and northeastof Santo Domingo (Fig. 1; Vaughan et al.,1922). These mining districts are known re-spectively as the Northern Area and theEastern Area. Minor occurrences of amberhave been reported from the Plateau Cen-tral-San Juán Area (Lemoine in Sandersonand Farr, 1960; Garcı́a and Harms, 1988;Harms, 1990). All amber occurrences are oflate Early to early Middle Miocene age andare associated with lignitic material, but

AMBER DEPOSITS IN GREATER ANTILLES142

each represents different depositional envi-ronments, from terrestrial-marine transi-tion to deep marine (Iturralde-Vinent andMacPhee, 1996).

Eastern Mining District

The Eastern Mining District is on thenorthern margin of the Cordillera Oriental,between Sabana la Mar, Hato Mayor, Bay-aguana, and Cotuı́ (Fig. 2). The sedimen-tary rocks that form the substrate aremostly Neogene; along the west, south andeast margins of the basins they directlyoverlay Cretaceous sedimentary, volcanic,and igneous rocks. On the northern side

of the area, a W-NW trending fault is pre-sent along the edge of the Neogene lime-stone. The limestone on the northern blockof the fault is overlain by Pliocene to Recentdeposits. In general, Miocene rocks dipgently toward the north-northeast, so thethickness of the Neogene section variesfrom less than 100 m in the south to severalhundreds of meters in the north (Brouwerand Brouwer, 1982; Toloczyki and Ramı́rez,1991; Lebron and Mann in Mann et al.,1991).

Brouwer and Brouwer (1982) recognizedfour stratigraphic units in the Eastern Min-ing District: the basal conglomerates, theamber-bearing Yanigua Formation, the

FIG. 1. Amber and lignite occurrences in the Greater Antilles. Lignite is not always associated with amber, butthe opposite is true.

FIG. 2. Generalized geological map of Hispaniola showing the amber-bearing areas. Adapted from Iturralde-Vinent and MacPhee, 1996.

M. A. ITURRALDE-VINENT 143

“caliza Cévicos”, and the “caliza de losHaitises.” According to some authors, thereis only one limestone or caliza unit (Bowin,1966; Toloczyki and Ramı́rez, 1991; Lebronand Mann in Mann et al., 1991). My fieldobservations suggest that the limestonesthat Vaughan et al. (1922) named Cévicosare those found as intercalations in the up-per part of the Yanigua Formation, and arenot worthy of being differentiated as an in-dependent unit. The basal conglomerates,as they occur intercalated with the otherlithologies of the Yanigua Formation, arealso incorporated to this unit. Therefore,only two formations are recognized in theMiocene basin: Yanigua formation (withthe basal conglomerates) and Los Haitisesformation (Figs. 2 and 3).

YANIGUA FORMATION

The Yanigua Formation (Brouwer andBrouwer, 1982) is the amber-bearing unit ofthe eastern Area. Outcrops are locatedmostly around the present-day margins ofthe Neogene basin, at the localities ofAntón Sánchez, Bayaguana, Comatillo, Co-lonia San Rafael, Yanigua, El Pontón,Sabana la Mar, and in several falls along theYanigua and Comatillo rivers (Fig. 4). Itsthickness is calculated from the map asaround 100 m.

The basal conglomerates have limitedoutcrops (Champetier et al., 1980) but mayhave an extensive distribution, as theywere found in several bore holes drilled inthe basin (Brouwer and Brouwer, 1982).The conglomerates are composed of poorlysorted subangular to subrounded elementscontained in a fine grained matrix. Sincefossils have not been reported, their age as-signment remains problematic, but accord-ing to stratigraphic position it can be basalMiocene-Oligocene. Champetier et al.(1982) suggest that these conglomerates arefrequent intercalations in the base of theYanigua Formation in the Samaná area.They do not report fossils from these locali-ties, but the association of conglomeratesand lignite suggest that the basal conglom-erates are a lateral, lowermost facies of theYanigua Formation. Champetier et al. (op.

cit.) reported no amber from this conglom-erates. The sedimentary characteristics ofthe conglomerates (oblique lamination, for-mation of channels, erosional surfaces be-low the coarse grained beds) suggest a flu-vial environment of deposition.

In general, the rest of the Yanigua sectionshows minor lateral differences (Fig. 4).Dark clays and laminated sandy clays con-taining fresh-water mollusks are the mostcommon lithologies, along with lignite andcarbonaceous clays and sandstones. Sandyclays may contain authigenic pyrite and arecomposed of 80-90 % mud and 10-20 %grains of calcite, calcareous earthy parti-cules, detrital quartz, and igneous rockfragments. Laminae in the sandy clays arenormally parallel, but can be slightly dis-turbed by micro-ripples and by isolatedgravel inclusions that indicate local turbu-lent currents. These beds contain flattenedand irregular inclusions of amber, usuallyas pockets or lenses ranging from a fewmillimeters to several centimeters in size,and may also contain fresh- to brackish-water ostracods and mollusks (see below).

The clays are typically dark gray-black,carbonaceous, with rare authigenic pyrite,almost without detritus, and with onlysome grains of calcite and quartz. They areusually fossiliferous and contain fresh- tobrackish-water mollusks, ostracods, fora-minifera, bryozoa, fish teeth, etc. (Tables 1and 2). Mollusk shells have been usuallyfractured and flattened during diagenesis.Fossils of crocodiles, turtles and dugongshave been found in this context (Iturralde-Vinent and MacPhee, 1996). These amber-bearing beds contain abundant fragmentsof carbonaceous material that still showstextures of a vegetal nature. AlthoughBrouwer and Brouwer (1982) report that allthe amber from this source shows erosionalfeatures, all the specimens found by thepresent author have sub-rounded, oval orstalactite-like shapes representing the origi-nal form and not one caused by secondaryerosion.

The lignite is found intercalated with thecarbonaceous clays and sandy-clays. Lig-nite sometimes includes needles and crys-talline aggregates of gypsum, probablyoriginated during diagenesis. The lignite


FIG. 3. Selected columnar sections of the Oligocene and Miocene Greater Antilles amber and lignitic-bearingrocks. Updated from Iturralde-Vinent and Hartstein, 1998.


occurs usually as layers a few millimetersthick, but also occur as beds over 1 m thick.The lignite is hard, compact, and deepblack with a metallic shine. No fossil inclu-sions, other than plant impressions on thesurface of the beds, have been found. Bio-turbation due to animal burrowing andplant root penetration is common in the lig-nite and related sediments. The burrowsare vertical, sometimes with horizontal bi-furcations, and they are filled with materialfrom the layer above.

Locally in the area of Sierra del Agua is awell-developed 1 to 2 m thick, reddish pa-leosol clay layer, located near the top of thelignite. Coarse gravel and sand on top ofthe paleosol is also found in this region(Fig. 4). Dugong and crocodile bones havebeen recovered from the clays that underliethe lignite at this locality.

Environment.—According to Champetieret al. (1982) the section at Yanigua wasformed in a low energy environment,which is the common type of section in the

basin. Van den Bold (1988) studied the os-tracods of two samples of the Yanigua For-mation obtained from amber mines nearLaguana and Bayaguana, and suggestedthat the association indicated a low salinityenvironment. Lithology, sedimentologicalfeatures, and fossil composition clearly cor-roborate the opinion of Brouwer and Brou-wer (1982) concerning the lagoonal tocoastal marine depositional environmentfor most of the Yanigua Formation. Thisopinion was followed by Toloczyki andRamı́rez (1991) when they described theserocks as “marls of littoral facies”.

Toward the top of the Yanigua Forma-tion are beds of biocalcarenites, first inter-calated with the clays (Cévicos limestone),but then dominating the section until theoverlaying Los Haitises Formation. Thesebiocalcarenites are very fossiliferous, withlarge foraminifera, algae, fragmentary ma-rine mollusk shells, echinoids, bryozoa,corals, etc. They also show evidence of bio-turbation due to animal burrowing and oxi-

FIG. 4. Selected lithologic sections of the Yanigua Formation.


TABLE 1. Microfossils from the amber-bearing Yanigua Formation. Samples investigated by Consuelo Dı́az (96RD-10A, -10D), Gena Fernández (96RD-5A, -6A, 10E, 11A,11B, 11C) and ostracods by W.A. van del Bold (96RD-6A, 10E, Bayaguana and Laguana). Blank space = not found.

Microfossils/Samples:

96RD-5AColonia

San Rafael

96RD-6AColonia

San Rafael

96RD-10A

Yanigua

96RD-10D

Yanigua

96RD-10E

Yanigua

96RD-11ASalto delYanigua

96RD-11BSalto delYanigua

96RD-11CSalto delYanigua

Bayaguana, Van den

Bold 1988

LaguanaVan den

Bold 1988

Ammonia beccarii x xAmmonia beccarii ornata xAmmonia beccarii parkinsoniana xAmphistegina sp.Archaias angulatus x xArchaias sp. xElphidium advenum cf.Elphidium cercadensis xElphidium lens aff. xElphidium poeyanum xElphidium puertoricensis x xElphidium sagra xElphidium sp. xMiogypsina antillea x xQuinqueloculina polygona xQuinqueloculina sp x x xTriloculina sp. xCoraline algae x x xCorals xFish teeth x xGastropods x x x x x x x xPelecypods x x x x x x xEquinoid spines x x xOstracods x x x x x x x xAurila amygdala x xAurila galerita x x xBairdia spp. x x xBaidoppilata willisensis xCativela sp. aff. C. moriahensis xCushmanidea howei x xCytherella sp. aff. C. pulchra xCytherella sp. xEucytherella sp. xHemicyprideis agoiadiomensis x x xHemicyprideis cubensis s.s. xHemicyprideis stephensoni x

dized plant roots, which suggests a marineshallow to coastal marsh environment.These succesions of strata record the tran-sition from lagoonal deposition into car-bonate shelf sedimentation (Yaniguathrough Los Haitises Formations).

Age.—The Yanigua Formation was datedas Miocene by Brouwer and Brouwer(1982), who report the fossils Ammonia bec-carii, Elphidium advenum, and Parocnus sp.from Sierra del Agua. [Note: Since Parocnusis a Quaternary sloth, a photograph of thefossil, kindly provided by S. Brouwer, wasexamined along with additional materialrecovered from the same site. The studysuggests that the fossil bones correspond toa Tertiary sirenian, probably Methaxy-ther ium? sp. ( I turralde-Vinent andMacPhee, 1996)].

Toloczyki and Ramı́rez (1991) ascribedan Upper Miocene to Lower Pliocene age tothe Yanigua Formation, while Lebron andMann (in Mann et al., 1991) ascribed to it anUpper Miocene age (however, neither pre-sented supporting paleontological data).Several samples collected by the author indifferent parts of the basin were examinedfor foraminiferans, ostracods, and nanno-fossils. The samples 96RD-10A, 96RD-10Dand 96RD-11A were collected at theYanigua river and in mines, from limestonebeds intercalated near the top of theYanigua Formation. The foraminiferal as-semblages suggest a late Early Miocene age(Table 1, Fig. 4). The microfossils insamples collected 2-3 m below these lime-stones (96RD-10E, 11B, 11C; Table 1) and inColonia San Rafael mines (96RD-5A, 6A;Table 1) are not as distinctive and suggest alate Early to Middle Miocene age. Van denBold (1988) reported late Early to early

Middle Miocene ostracods for two samplesfrom Laguana and Bayaguana amber minesand corroborated this date with samplessupplied by the author (Table 1). Therefore,the Yanigua Formation can be dated as lateEarly to early Middle Miocene (Miogyp-sina-Soritiidae zone of Iturralde-Vinent(1969)), or slightly younger, about 15 to 20million years old according to the scale ofBerggren et al. (1995).

LOS HAITISES FORMATION

The Haitises Formation (Brouwer andBrouwer, 1982) represents a shallow watershelf limestone overlying the Yanigua For-mation. These limestones have been namedLos Haitises or Cévicos in previous litera-ture but Los Haitises is used herein. Theyare fossiliferous, containing mollusks(Strombus sp., Kuphus sp. and many others),corals (Porites sp., Acropora spp.), echino-derms, and algae. The age has been as-signed without paleontological justificationas Pliocene-Quaternary (Toloczyki andRamı́rez, 1991), but Middle to Late Mioceneis more likely because it rests conformablyabove the Yanigua Formation (Figs. 3 and4). The thickness of the Los Haitises lime-stone can be estimated as 300 m minimumconsidering that it rests nearly horizontaland gives rise to steep karstic hills, some ofthem over 250 m high.

Northern Mining District

The Northern Mining District is locatedin the Cordillera Septentrional, north ofSantiago de los Caballeros (Figs. 1, 2). Thisfault-bounded unit was designated as theLa Toca Block (Dolan et al., 1991; de Zoeten

TABLE 2. Macrofossils identified by Paula M. Mikkelsen (AMNH) from Dominican Republic samples.

Sample Mining area Formation Macrofossils Habitat

96/RD-2A Sierra del Agua Yanigua Large oyster Lagoonal

96/RD-10E Yanigua YaniguaPectinidae, small Arcidae,small ?Veneridae Marine

96/RD-21El Pontón delCuatro Yanigua Bivalves Aquatic

96/RD-21BEl Pontón delCuatro Yanigua Large Cardiidae or Arcidae Marine

96/RD-18 El Cacao La Toca Pisania? or Turridae Marine


and Mann, 1991), and part of the El MameyBelt, represented by deformed Mesozoicand Cenozoic rocks. The La Toca block islimited today by the Camu, Septentrional,and Rı́o Grande fault zones (de Zoeten andMann, 1991) (Fig. 5).

Originally, the La Toca Block was a partof a larger basin filled with Oligocene toPliocene sedimentary rocks that uncon-formably overlies deformed and partiallymetamorphosed Lower Eocene and olderigneous and sedimentary rocks (Toloczykiand Ramı́rez, 1991, Dolan et al., 1991; deZoeten and Mann, 1991). The Late Tertiarydeposits have been recently described as LaToca and Villa Trina Formations (Fig. 3;Dolan et al., 1991; de Zoeten and Mann,1991). The amber-bearing deposits in thearea are probably in the upper part of theLa Toca Formation.

LA TOCA FORMATION

The La Toca Formation (de Zoeten, 1988)was originally described as a clastic Oli-

gocene to lower Middle Miocene unit (deZoeten, 1988; de Zoeten and Mann, 1991). Itis equivalent to the Altamira facies of the ElMamey Formation of Eberle et al. (1980)(Fig. 5). The La Toca Formation has manysimilarities in composition, sedimentology,and age to the Oligocene to Early MioceneMaquey Formation of the Guantánamo Ba-sin of eastern Cuba (Nagy et al., 1983; Cal-ais et al., 1992; Iturralde-Vinent, 1994) andto the Thomonde Formation of the westernpart of the Plateau Central-San Juán area,but neither of these formations is amberif-erous (Nagy et al., 1983; Butterlin, 1960;Maurrasse, 1982). The La Toca Formationwas subdivided into three units that arecharacterized below according to de Zoeten(1988), with additional observations by thepresent author.

The lower conglomerate unit is about 300 mthick and corresponds with amalgamatedconglomeratic facies and minor interbed-ded sandstones. Disorganized, matrix-supported facies and thinner, clast sup-

FIG. 5. Simplified geologic map of the northern mining district of the Dominican Republic. Adapted fromseveral sources.


ported facies, comprise the lower 200 m ofthe unit measured by de Zoeten (1988)along the Rı́o Grande section. Most bedsare tabular, medium-bedded to massive,with planar basal contacts which rarelydrape over clasts protruding from the un-derlying bed. The internal organization ofthe unit seems to increase upward in thesection. In the later part, inversely gradedfacies are interbedded with clast -supported, parallel, stratified conglomer-ates. Clasts in the base range from granuleto boulder in size. They are equidimen-sional to oblate in shape, and are subangu-lar to rounded. The composition of theclasts near the outcrops of the underlyingPedro Garcı́a Formation are about 70 % vol-canic rocks (tuffs, andesites, and lavas), 20% intrusives (tonalites) and 10 % sand-stones, argillites, recrystalized limestone,quartz veins, serpentinite, and coral rud-stones. This suggests that the major sourcefor the clastics were uplifted lands withrocks like those of the Pedro Garcı́a Forma-tion. Such rock types are found not only inCordillera Septentrional but also in Cordil-lera Central and Cordillera Oriental (Toloc-zyki and Ramı́rez, 1991).

The flysch unit consists of alternating,thin- to medium-bedded, thinning-upwardsandstones and shale couplets. A sectionmeasured by de Zoeten (1988) consists of500 m of thick very thin- to medium-bedded sandstones and shales. The bedsare tabular, laterally continuous, and ex-hibit sharp basal contacts. Basal sands arerelatively coarse-grained, graded or struc-tureless, and have mud-rich, massive, bio-turbated upper divisions. A few thin- tomedium-bedded, lens-shaped calcareoussandstone beds are interbedded with thesandstone and shale couplets. Higher in thesection, lithic-rich calciturbidites and lithicconglomerates are interspersed betweenthin-bedded siliciclastic couplets. Togetherwith the 1-2 m-thick conglomerate beds,calciturbidites form small (1-5 m thick)coarsening- and thickening-up cycles. Theunit is laterally interbedded with the lowerconglomerates. These deposits carry abun-dant planktonic foraminifera and nanno-fossils, as well as small benthic foraminif-

era typical of marine bathyal depth (500-1500 m) (Dolan et al., 1991).

The upper unit, 300 m thick according tode Zoeten (1988), is composed of thick-bedded sandstones with lesser amounts ofconglomerate beds. Sandstone beds havehigh sand to silt ratios (2:1 to 10:1) and arecommonly tabular, laterally continuous,and thick- to very thick-bedded (0.5 to 3.5m). Basal sands range from gravel to me-dium sand in size. The lower divisions ofthe beds are coarse-tail graded, or massive,and grade up into parallel laminated sandsrarely containing ripplemarks. Load castsare the dominant type of solemarks. Theupper division in many beds contains con-centrations of lignite and amber fragmentsthat define parallel laminae in the silt-stones. The finer fraction of the beds ismud-poor and parallel-laminated or mas-sive. Considerable amounts of small car-bonized plant fragments, including seeds,have been observed in these beds. Theflysch and upper unit grade laterally intoeach other and become almost indistin-guishable in the field.

Occurrence of amber:—Eberle et al. (1982)indicate that amber is always contained inlignite-rich sandstone beds or in ligniteseams, and that considerable amounts havebeen mined from a few tens of metersabove prominent conglomeratic horizons.However, according to Redmond (1982)amber is very rarely associated with theconglomerates and occurs in laminated,blue-gray, biotite-bearing siltstone with arich organic content, sometimes concen-trated in lignite stringers within the silt-stone. Lignite beds are several inches thickat least in one location. Redmond alsopointed out that amber-bearing siltstone isoverlain almost always by thick, or moreusually massive sandstones. This suggeststhat the amber was deposited in a mid-fanbelow the end of the channels, and that themassive sand from the channel was laiddown later, prograding over the amberifer-ous bed. For Redmond, the amber seemedto occur in three to five horizons, suggest-ing that the it was deposited during a shortperiod of time and not during all the timelapse of deposition of La Toca.

Several mining areas were visited by the


present author to verify the position of am-ber in the La Toca Formation. In the PaloAlto Mine (Fig. 5), a section about 30 mthick was deposited under moderate en-ergy and is composed of a set of completeor incomplete cycles of fine sand, carbon-aceous silt, supracarbonaceous shale withamber, and infracarbonaceous shale andlignite (Champetier et al., 1982). Large frag-ments of amber, some weighing up to 13.6kg, have been recovered from this mine. InLa Toca Mine (Fig. 6), the beds overlyingthe amberiferous horizons are a set of 3-5cm thick fine to coarse grained sands with-out gradation or coarsening upward. Twoor three beds of conglomerates, up to 60cm-thick, are intercalated in the section;they have a peculiar gradation from finegrains at the base to coarse grain in themiddle and fine grains on the top. The am-beriferous section is about 30 m thick and iscomposed of interbedded black, laminar,medium-to-fine grained sands and lignifer-ous silt. There are some thin beds of actuallignite measuring up to 5 cm thick. The sec-tion contains many carbonaceous plant re-mains and very small mollusks, both typi-cal of a brackish water environment. The

clastic materials in the rocks are composedof grains of igneous rocks and detrital min-erals, including some quartz and calcite.The amber appears as flattened lenses, sta-lactites, and also as irregularly shaped,typically detrital fragments.

El Cacao Mine is located very close to LaToca, on the southern side of the samemountain range (Fig. 6). This site is particu-larly known for its unique blue amber. Theamber-bearing section is about 20 m thickand is represented by fine grained, well-bedded (20-40 cm thick), black sandstonewith some thinning upward gradation. Thesandstone contain abundant small gastro-pods. Palo Quemado Mine (Fig. 6) is a fewkilometers south of the previous mine. Thesection oberved is about 30-40 m thick andis represented by a well bedded, 10-20 cmthick stratum of fine grained, laminated,black sandstone. Coarse grained sandstonewith carbonate cement is interspersed inthe section. This sandstone became locallyconglomeratic, as it contains isolated largepebbles within the matrix.

The section at Los Higos Mine is about 30m thick and is represented by well-bedded,laminated, black, fine-grained sandstone

FIG. 6. Detailed geologic map of the La Toca, Palo Quemado, and Los Cacaos mining areas. Location in figure5. Modified from de Zoeten (1988).


and silt, interspersed with coarse grained,40-50 cm thick layers of sandstone and con-glomerate. These beds are similar to thoseseen in La Toca, with a peculiar gradationfrom fine grains at the base to coarse grainsin the middle and finer grains on the top,sometimes laminated, with intercalated lig-nite layers up to 2 cm thick. As in Palo Que-mado, isolated pebbles are found on thevery top of these beds. Amber occurs asirregular fragments, 20 to 40 cm long, em-bedded in the fine-grained rocks. Scatteredfragments of lignite, approximately 6 cmlong and 3 cm wide, are also present.

In all the mining areas visited, the amberis always associated with ligniferous mate-rial, and occurs in laminated sands and siltsof deep marine environments. The amber-iferous horizons occur within rock sectionsup to 40 m thick. Samples collected fromthese mines did not produced a precisedate (up to the nanostratigraphic zone), soit was impossible to accurately correlate thesections from mine to mine. However, allthe samples lie within the late LowerMiocene-early Middle Miocene interval,about 15 to 20 m.y. (Iturralde-Vinent andMacPhee, 1996). Therefore, it is possible toaccept the conclusion of Redmond (1982),that all the amber mines are within thesame stratigraphic level in the upper part ofLa Toca Formation.

Environment.—Composition and sedi-mentary features of the lower conglomerateunit suggest that they were derived from alocal source, and probably laid down asrapid, cohesive debris flows in terrestrial tonear shore environments; probably relatedto the active uplift of a highland area. How-ever, the deposition of the flysch and upperamberiferous units took place in marine en-vironments close to a fluvial plain with del-taic development.

According to Eberle et al. (1982), the li-thological association of the flysch and up-per unit of La Toca Formation point to a fandelta depositional environment, the amber-iferous beds being deposited in interchan-nel flats, while marly units would representthe distal fan base environment. Accordingto de Zoeten (1988), because vertical orga-nization is lacking in the thick, tubularsandstone beds, it is unclear if the beds

were deposited as lobes, channel-lobe tran-sitional facies, or as delta front sands.Moreover, the microfossil assemblage andsedimentary features of the flysch unit sug-gested to Redmond and to de Zoeten andMann that the beds were deposited as tur-bidity flows in a deep water basin. North-west paleocurrent directions in La Toca andthe isochronous Las Lavas Formations sug-gest that the sediment source was locatedtoward the southeast (de Zoeten and Mann,1991).

Lithological observations and paleonto-logical evidence indicate that the flysch andupper units were deposited in a deep basi-nal environment located close to a forestedmountain range. All the samples recoveredfrom the previously mentioned mining ar-eas contain planktonic and small benthicforams in associations suggesting a deposi-tion depth over 500 m, probably 1000-1500m (de Zoeten, 1988). The common presenceof nannofossils agrees with this interpreta-tion, although some of these fossils are re-deposited from older beds.

Age.—No fossils have been found in thelower conglomerate, but its age is probablyOligocene-Early Miocene because the unitis typically at the base of the sections orpartially interfingers with the flysch. Theconglomerate probably represents a lateralequivalent of the basal conglomerate of theYanigua Formation (Fig. 4).

Samples with microfossils reported by deZoeten (1988) and Dolan et al. (1991), col-lected from different levels in the flysch,yielded ages of latest Oligocene and EarlyMiocene (7787, 10487, 13887; Table 3) andEarly to Middle Miocene (P-14, D-229,11587, 13187, 13487, 14087; Table 3). In theMiocene samples there is some reworkingfrom late Oligocene, which may suggestautocannibalism of the basin sediments.From the same localities (La Toca, PaloAlto, and Rı́o Grande mines), Cepek (inSchlee, 1990) dated the rocks as MiddleEocene through Middle Miocene based onunlisted nannofossils (see also Grimaldi,1995). The microfossils older than latestOligocene found by Cepek are probably re-deposited, since this process is common inthe basin and samples taken from the samemines were dated as Miocene (see below).


Although microfossils are rare in the ac-tual amber-bearing beds, several samplescollected by the present author containidentifiable fossils. Sample 96RD-15, col-lected in the flysch several hundred metersstratigraphically below the La Toca minearea, yielded a poorly constrained Oli-gocene or Early Miocene assemblage (Table4). The La Toca mine amber-bearing sand-stone sample 96RD-12B carries a poorlypreserved Oligocene or Early Miocene as-semblage (Table 4). From just over the sec-tion at La Toca, sample 96RD-12C from theVilla Trina limestone yielded a very lateMiocene or Pliocene assemblage (Table 5).Additional samples of different Mioceneages were identified using foraminiferafrom the Palo Quemado, El Cacao, and Los

Higos mines (Figs. 5, 6; Table 4). This agerange was corroborated by nannofossils(Table 4) from LaToca (96RD-12), Los Ca-caos (96RD-18), and Los Higos (96RD-19and 20). Only the results from Palo Que-mado (96RD-17) samples are contradictory,since according to its nannofossils thesample is probably Late Oligocene and ac-cording to the foraminifera it is Miocene.However, both samples are poorly fossilif-erous and the age assignments are not wellconstrained, being mostly based on absenceof some index taxa.

Therefore, the entire range of the age ofthe La Toca Formation can be identified asLate Oligocene through Middle Miocene,as pointed out by de Zoeten (1988) and deZoeten and Mann (1991); but the amberif-

TABLE 3. Microfossils from the La Toca Formation. Samples investigated by J.B. Saunders (16946–19648) inBaroni-Urbani and Saunders (1982); and P. MacLaughlin, E. Robinson and G. Monetti (P14 to RD3-229) in DeZoeten, 1988 and Dollan et al, 1991. Blank space = absent.

Microfossils/Samples: 16946 16947 16948 P14 7787 10487 11587 13187 13487 13887 14087RD3-229

Amphistegina sp. x xCassidulina subglobosa x x x xCassigerinella chipolensis x x xCatapsydrax dissimilis x x x x x xCatapsydrax unicavus xGlobigerina ciperoensis x x xGlobigerina selli ? x x ?Globigerina venezuelana x x x x xGlobigerinoides primordius x xGlobigerinoides trilobus gr x x ?Globigerinoides tril. inmaturus xGloborotalia obesa xGloborotalia mayeri x x x x x x xGloborotalia opima continuosa ?Globorotalia opima nana x xGloborotalia opima opima x xGloborotalia peripheroronda ?Hanzawaia sp. xPullenia bulloides xSiphonina pulchra xSiphonina tenuicarinata xSpiroloculina depressa cf. cf.Uvigerina sp. xDiscoaster druggi xDiscoaster exilis xDiscoaster variabilis xHeliscosphaera sellii xSphaenolithus ciperoensis xSphaenolithus conicus xSphaenolithus heteromorphus x


erous beds are more probably restricted tothe upper half of the formation, which islate Early to early Middle Miocene in age(Iturralde-Vinent and MacPhee, 1996).

VILLA TRINA FORMATION

The Villa Trina Formation (Vaughan etal., 1922) is composed of shallow marinemarls and calcarenites resting unconform-ably above La Toca Formation (Figs. 3, 5).The base of the unit is coincident with abasal conglomerate (Eberle et al., 1982). Theage of the limestone has been assigned asMiddle Miocene to Pliocene (de Zoeten andMann, 1991), but samples of the Villa Trinalimestone collected by the author (Table 5)yield assemblages of Late Miocene andPliocene age. The thickness of the limestoneunit can reach several hundred meters as canbe inferred from present day topography.

Plateau Central-San Juán area

This basin, unlike those previously de-scribed, is located south of the CordilleraCentral in southwestern Hispaniola (Fig. 2).The depression was filled with Late Ter-tiary clastic and carbonate sediments, manyhundred meters thick, which show impor-tant differences in environment of deposi-tion (Fig. 3). Only the Sombrerito and Mais-sade Formations, which contain amber andlignite, are described here. Garcı́a andHarms (1988) and Maurrasse (1982) pro-vide more information about this area.

SOMBRERITO FORMATION

The Sombrerito Formation is mostly de-veloped in the eastern part of the PlateauCentral-San Juán Basin (Fig. 2). It is repre-sented by about 500 m of pelagic limestone,

TABLE 4. Microfossils from the La Toca Formation. Samples investigated by Timothy L. Bralower (nannos),Gena Fernández (forams) and Rafaela Perez (forams) for this paper. Blank spaces = absent.

Microfossils/Samples:96RD-

12B96RD-12W

96RD-13A

96RD-15

96RD-17W

RD96-17X

96RD-17Z

96RD-18A

RD96-18B

RD96-19A

96RD-19B

Amphistegina sp. x x fragm xAmphistegina angulata xAmphistegina gibba ? xGlobigerina angustiumbilicata aff.Globigerina tripartita s.l. xGlobigerinoides altiaperturus xGlobigerinoides primordius xGlobigerinoides sp. x x xGlobigerinoides ruber xGlobigerinoides trilobus grGlobigerinoides tril. inmaturusGloborotalia archeomenardii xGloborotalia obesa xGloborotalia sp. xGloboquadrina altispira altispira xGloboquadrina altispira conica xGyroidina soldanii xNodosaria spp xPraeorbulina transitoriaQuinqueloculina sp. xRectobulimina sp. xUvigerina sp.Dictyococcites bisectus x xSphaenolithus belemnus xSphaenolithus ciperoensis x xSphaenolithus heteromorphus x xGastropods x


marls, and calcarenite. The marls are rich inpelagic and small benthic microfossils. Cal-carenites are coarse to fine grained, graded,with sedimentary features indicating tur-bidity current origin. Sedimentary featuresand microfossils suggest that the formationwas deposited in a lower slope, middlebathyal setting open to the sea. The forma-tion has been paleontologically dated aslate Early to early Middle Miocene (N8 -N12) (Garcı́a and Harms, 1988).

It should be emphasized that this unitgenerally lacks detritus from older rocks,suggesting that little erosion of the catch-ment area was taking place at the time ofthe Sombrerito Formation deposition (Gar-cı́a and Harms, 1988). The detritus materialin the calcarenites is dominated by isochro-nous shallow water organic fragments de-rived from a carbonate shelf and coral reefenvironment. Nevertheless, the calcarenitesthat crop out east of Presa Sabaneta containisolated fragments of amber (1-3 cm) asso-ciated with small remains of carbonizedplants and detrital grains of quartz, plagio-clase, and probably glauconite (Garcı́a andHarms, 1988; Harms, 1990). This clearly in-dicates that local erosion was taking placein the catchment area of the basin, but thesize and type of the detritus suggests thatthe source area was a low land mass. Thissedimentary environment contrasts withthat of the amber-bearing La Toca Forma-tion, which corresponds to a clastic-dominated section representing extensiveerosion of a highland source.

MAISSADE FORMATION1

The Maissade Formation (Jones, 1918) oc-curs near the town of Maissade in centralHaiti, and over the southwestern part of thePlateau Central-San Juán Basin. Lemoine(in Sanderson and Farr, 1960) reportedtraces of amber in a sample recovered froma well drilled in the Maissade area (Figs. 2,3). The formation consists of 200 m-thickclay, shale, marl, gypsum, some sandstone,and characteristically lignite beds. Thelower part of the unit is blue clay contain-ing shallow water marine mollusks (Turri-

tella sp., Arca sp., and Ostrea sp.), overlainby black carbonaceous shale, hard shalysandstone, lignite, lignitic gray clays, graysandy shales, gray argillaceous marls, blueclays, and some gypsiferous horizons.These beds usually contain the brackish-water mollusks Potamides sp., Hemisinussp., Hydrobia sp., Nerita sp., Scapharca sp.,and Mytylopsis sp. (Woodring et al., 1924;Butterlin, 1960; Maurrasse, 1982).

The Maissade Formation overlies with alocal unconformity the latest Oligocene-lowermost Miocene Madame Joi Forma-tion, and is overlain in turn by the PlioceneHinche Formation (Butterlin, 1960; Maur-rasse, 1982). The Maissade is generally con-sidered a lateral facies of the Thomondeand Las Cahobas Formations (Bermúdez,1949). The age of the Maissade is thereforelate Early Miocene to Middle Miocene (But-terlin, 1960), but some beds similar to Mais-sade can probably reach the Pliocene(Maurrasse, 1982).

The Maissade represents an initial shal-low marine landward invasion followed bya coastal-swamp environment (Woodring,1922; Woodring et al., 1924; Maurrasse,1982). In many respects, the Maissade For-mation resembles the amberiferousYanigua Formation of the Dominican Re-public, the Cibao Formation of Puerto Rico,and the Los Arabos, Lagunitas, and Magan-tilla Formations of Cuba, although amberhas not been reported from these last units.

PUERTO RICO

Amber has been discovered in two locali-ties in Puerto Rico, one of Oligocene andthe other of Miocene age. The Oligoceneamber is a tiny droplet recovered by theauthor in 1999 from ligniferous clays of theSan Sebastián Formation near Lares (Figs.1, 7). Miocene amber was collected from awell south of the Cementerio Nacional inSan Juán (Fig. 7). At the latter locality theamber occured in gray-blue marl and sand-stone of the upper part of the late Early toearly Middle Miocene Cibao Formation(Iturralde-Vinent and Hartstein, 1998).

Two small pieces of Miocene amber havebeen collected from the same horizon. Onepiece (originally 20x30x15 mm) is a some-1See note added in proof on page 167.


what flattened, deep red, transparent frag-ment, with subangular edges suggestingthat it experienced some transportation.The piece is brittle, has several fractures,and resembles low quality amber from theeastern mines (Yanigua and Colonia SanRafael) of the Dominican Republic. The fra-gility and low density of the Puerto Ricanamber suggest that it suffered slight diage-netic transformation. This is confirmed bythe presence of non-crystalline lignitic bedsin the same stratigraphic position as theamber. The Miocene lignitic and amberifer-ous beds are within the transitional Early toMiddle Miocene upper part of the CibaoFormation. Features common to all theselignitic occurrences are the deep black colorof the sediment, the presence of fresh watermollusks, and the position within the up-permost part of the Cibao Formation nearthe contact with Aguada limestones (Itur-ralde-Vinent and Hartstein, 1998). In thesebeds there are shark, ray, and barracudateeth, other unidentified fish elements,crocodilian teeth and vertebrae, sirenianribs and vertebrae, and many turtle scuts.

CUBA

Amber has not been discovered in Cuba,but Miocene ligniferous rocks occur in the

Los Arabos and equivalent Formations(Iturralde-Vinent, 1969). The best occur-rence has been reported in the Las Tunasbasin of eastern Cuba (Figs. 1, 3), where theNeogene strata unconformably overlieEocene and Cretaceous rocks within a lowrelief plain. In this basin, the Early toMiddle Miocene Los Arabos Formation isrepresented by more than 130 m of marls,calcareous clays, and marly limestones,with thin lenses of gypsum. Some isolatedbeds of lignite and plant-bearing clays arefound. Clays are more common toward thebottom of the unit, while carbonate mate-rial is more abundant in the upper region.Pyrite and microfossils with pyrite-filledchambers are common like in the YaniguaFormation. The biocenosis includes fresh andbrackish water forams, ostracods, mollusks,and echinoids. The Los Arabos Formation isconformably overlaid by more than 80 m ofthe Guines/Vásquez Formations, repre-sented by Middle Miocene shallow-watermarine limestone (Iturralde-Vinent, 1969).

The resin-producing tree Hymenaea torrei, theclosest relative of H. protera and H. courbaril,occurs today in eastern Cuba (Bisse, 1988).

JAMAICA

The oldest occurrence of amber in theGreater Antilles, from the Maastrichtian-

FIG. 7. Generalized geologic map of Puerto Rico showing lignitic and amber occurrences. Updated fromIturralde-Vinent and Hartstein, 1998.


Paleocene Cross Pass Formation of Jamaica,was reported recently to the author byGrenville Draper (pers. comm.). Accordingto Draper, during a field trip led by Geof-frey Wedge in 1971, they found somepieces of dark brown amber with manydark inclusions, within a bedding plane ofthe well-bedded shales of the Cross PassFormation. The amber was found at a smallwaterfall, close to the Indian Cony Rivernear Bath in the Blue Mountains. Accord-ing to Wadge and Draper (1978), the CrossPass Formation is a deep marine well bed-ded with arenaceous to argilaceous cyclicturbidites, with many intercalated beds ofcoarse volcaniclastic sandstones. The unitwas dated as Maastrichtian-Paleocene ac-cording to its stratigraphic position and theoccurrence of reworked latest Cretaceousmicrofossils (Pseudorbitoides? rutteni rutteniand Globotruncana sp.) (Krijnen and LeeChin, 1978).

This isolated occurrence of amber in theBlue Mountains is important because it isthe oldest from the Caribbean realm. How-ever, the specimens are not available forstudy and their origin from a leguminousor other tree cannot be determined. Addi-tional search should be conducted withinthe outcrops of the Cross Pass Formation tocollect more amber.

AGE OF THE GREATER ANTILLEAN AMBER

The precise determination of the age ofthe amber deposits is very important be-cause current data suggests that Dominicanamber has the same age as the sedimentswhere it is found, and because the age gen-erally coincides with a climate maximadated elsewhere as 16 m.y. (Tsuchi, 1990)which may have enhanced resin produc-tion.

Several authors have proposed that Do-minican amber may be older than the stratain which it occurs, from Cretaceous (Brou-wer and Brouwer, 1982) to pre-LowerMiocene (Baroni-Urbani and Saunders,1982). This has been discussed in papers byGrimaldi (1995) and Iturralde-Vinent andMacPhee (1966), who concluded that thereis no solid data to indicate that amber hasbeen redeposited from older deposits.

However, lack of redeposition from olderrocks does not rule out that contemporane-ous relocation may have taken place duringthe transportation of copal from the forestlitter to the final repository.

Arguing against redeposition from olderdeposits is the fact that Dominican amberhas not been reported, in large amounts,from rocks of indisputable Cretaceous, Pa-leocene or Eocene age. The only Oligocenereport is a tiny droplet found by the authorin ligniferous clays of the San SebastianFormation in Puerto Rico, and this is noproof that there were amberiferous Oli-gocene sediments in the Greater Antilles.Furthermore, since Eocene and Oligocenerocks are not exposed in the catchment ar-eas of the eastern mining district (Brouwerand Brouwer, 1982; Toloczyki and Ramı́rez,1991) they cannot be the source of olderamber, if such amber deposits ever existed.Paleogene rocks occur in the CordilleraCentral and Cordillera Septentrional ofHispaniola, west and south of the northerndistrict, but they do not contain amber (Fig.3). Also, the mean paleocurrent directionsmeasured in the La Toca Formation (Dolanet al., 1991) suggest that those Paleogenerocks were not the source of the clastic ma-terial in the amberiferous deposits. Thesemeasurements suggest that sediments inthe northern district were derived from asource located southeast, which points tothe same catchment basin that producedthe eastern district sediments (see also Itur-ralde-Vinent and MacPhee, 1996).

In connection with the age of Dominicanamber, it is important that organisms pre-served in amber can almost always be allo-cated to extant groups at low hierarchicallevels and many seem to differ little fromrelatives living in Hispaniola today (cf.Baroni-Urbani and Saunders, 1982;Grimaldi, 1995, 1996; Poinar and Poinar,1999). If Dominican amber is of late Meso-zoic or Paleogene age, more primitive fau-nal elements should be well represented(Grimaldi, 1996). For all these reasons, it islogical to conclude that Dominican amberis of the same age as the sediments thatcontain it; that is, that redeposition of am-ber of different ages did not occur (Itur-ralde-Vinent and MacPhee, 1996).


This conclusion does not, however, agreewith efforts to date amber using exometh-ylene resonance signatures visualized bynuclear magnetic resonance spectroscopy(NMRS) (Lambert et al., 1985). To derive anage assessment by this method, resonanceintensity must first be calibrated againstNMRS results for specimens of known age.The only calibration curve (Lambert et al.,op. cit.) relevant to the dating of Dominicanamber is based on two data points: amberfrom Palo Alto mine (northern district), ac-cepted as Early Miocene because sedimentsyield microfossils of that age (Baroni-Urbani and Saunders, 1982); and a resinsample from Hymenaea coubaril. Age esti-mates based on this curve (Lambert et al.,1985) indicate a Late Eocene age for amberrecovered from mines at La Toca and Tam-boril in the northern district, and a MiddleMiocene age for specimens from Bay-aguana and Cotuı́ in the eastern area. Mi-crofossil evidence supports a Miocene agefor amber-bearing sediments in the minesat Bayaguana (Van den Bold, 1988), but mi-crofossils also establish that the La Tocamines are Miocene, which contradicts theNMRS results. If amberiferous sediments atLa Toca, Palo Alto, and Bayaguana are pa-leontologically equivalent in age, then theexomethylene decay curve does not pro-duce meaningful results (Grimaldi, 1996;Iturralde-Vinent and MacPhee, (1996).

The most interesting aspect of theMiocene amber found in Puerto Rico is thatit was found in the uppermost part of theCibao Formation, dated as Early to MiddleMiocene (with large Sorites marginalis andthe absence of Miogypsina sp. and Lepidocy-clina sp., which occur stratigraphically be-low). The Cibao Formation underlies theMiddle Miocene Aguada Formation (withArchaias angulatus, S. marginalis, and Penero-plis sp.) (Monroe, 1980; Iturralde-Vinentand Hartstein, 1998). These data place theMiocene amber-bearing bed of Puerto Ricowithin the same time frame as those of His-paniola (Fig. 3).

PALEOGEOGRAPHY

Having established the age of the amberin Hispaniola and Puerto Rico (Cibao For-

mation) as late Early to early MiddleMiocene (20-15 m.y., probably close to 16m.y.), the next step is to produce a paleo-geographic map to determine the origin ofthe amber. Several attempts have beenmade to produce a paleogeographic recon-struction and historical geologic interpreta-tion of the Greater Antilles during the LateTertiary, but although authors were wellaware of plate tectonics, they produced es-sentially fixist reconstructions (Maurrasse,1982). Plate tectonic reconstructions such asthose of Calais et al. (1992) or Pindell (1994)are directed to solving geometric problemsof terrane location and not of physical ge-ography (relieve). Only recently has therebeen an attemp to presented maps combin-ing tectonic reconstruction and physical pa-leogeography (Iturralde-Vinent andMacPhee, 1996, 1999). Developing thistheme, three maps are presented to illus-trate the paleogeographic scenario of theGreater Antilles before, during, and afterformation of the Dominican amber (Fig. 8).The data to construct these maps were com-piled by Iturralde-Vinent and MacPhee(1996, 1999) and Iturralde-Vinent (1969).

Paleogeography during the amber epoch

The paleogeographic reconstruction pre-sented here displays the Greater AntillesRidge as subdivided into several groups ofislands separated due to the presence of ashallow water shelf surrounded by moder-ate to deep water channels or basins. Thefirst scenario for the Late Oligocene (27-25m.y.) displays three main archipelagos asWestern Cuba, Central Cuba and easternCuba-Cordillera Central-Puerto Rico-Virgin Islands (Fig. 8). These insular groupschanged little until the Early-MiddleMiocene (Fig. 8: 16-14 m.y.), when separa-tion between eastern Cuba and Hispaniola-P.R.-Virgin Islands became apparent due toactivity along the Oriente fault (MacPheeand Iturralde-Vinent, 1995). It is at this timewhen resin was produced in large quanti-ties in northern Hispaniola and in smallamounts in southern Hispaniola and north-ern Puerto Rico. During the MiddleMiocene (Fig. 8: 12-10 m.y.) the subdivisionof eastern Cuba and Hispaniola was com-


FIG. 8. Paleogeographic maps of the Greater Antilles for the Late Oligocene (27-25 m.y.), Lower Miocene(16-14 m.y.) and Middle Miocene (12-10 m.y.). Updapted from Iturralde-Vinent and MacPhee (1999) includinga new map.


pleted and resin production had declinedand stopped within the interval; a probablecause being a climate change induced bythe new oceanographic scenario that arosefrom the opening of a marine channel be-tween eastern Cuba and the CordilleraCentral of Hispaniola.

In the early Neogene, the terranes ofnorthern Hispaniola were located west oftheir current positions, closer to present-day southeastern Cuba. Then, the easternand northern mining districts were part ofthe same structural depression, locatednorth of the ancestral Cordillera Central.Their present (Holocene) position is due topost-Oligocene left-lateral displacementalong the northern Caribbean plate bound-ary. It is proposed here that the paleogeo-graphic basin represented by both thenorthern district and the eastern districtduring the Neogene be called the ComatilloBasin (Fig. 8) because there is no such fea-ture today in the geography of the island.

The relief and configuration of paleo-Hispaniola was very peculiar in the Earlyto Middle Miocene (16-14 m.y.). A large up-lifted ridge that includes present-day Mon-tagnes Noires, Cordillera Central, Cordil-lera Oriental, and continued into PuertoRico and the Virgin Islands was at that timethe largest land mass in the Greater An-tilles. Several small islands formed an ar-chipelago south of the Plateau Central-SanJuán Basin, and westward another large is-land was present which is represented to-day by southeastern Cuba (Fig. 8). The re-lief of these islands was differentiated withlow and high topography. Some mountainswere present west of the Comatillo Basinembayment and were the source for thehuge amounts of clastics deposited in thestructural depresion known today as LaToca block and the Cibao basin (La Tocaand Baitoa Formations). Highlands werealso present in southeastern Cuba and pro-vided the clastic deposits of the Maqueyand Imı́as Formations (Nagy et al., 1983;Fig. 3).

The mountains in both source areas weredissected by small rivers that dischargedinto the littoral plains, giving rise to silici-clastic ramps were alluvial fans and deltastypically developed. Massive coarse-

grained debris flows that deposited thickconglomeratic beds in the littoral and basinareas occured locally. The rest of the up-lifted territory was probably lowland, asthe seashore was characterized by lagoonsand mangrove swamps. These fresh tobrackish-water lagoons were filled withvery fine-grained sediments, resulting fromslope-wash drainage of the surroundingsareas. There were locally small rivers thatdeposited some gravel and coarser clastics.

The plant-derived organic debris in theamber and in the clastic rocks north of theHispaniolan paleo-island suggest that thehighlands were covered by humid tropicalforest, like that which exists today on thewindward side of higher elevationsthroughout the Greater Antilles. Humidforests also occurred in the lowlands facingthe lagoonal-mangrove swamp coastal ar-eas, as suggested by the common occur-rence of lignite and the high organic con-tent of the sediments.

The ecological interpretation of the am-ber biota (Grimaldi, 1996; Poinar and Poi-nar, 1999) and the presence of amber in thesediments, indicate that Hymenaea treeswere abundant in the humid forest sur-rounding the Comatillo Basin (Fig. 9) onthe northern slope of the Hispaniolan pa-leo-island. The presence of some amber inthe Sombrerito, Maissade, and Cibao For-mations suggest that some Hymenaea treeswere also present in the southwestern slopeof the Hispaniolan area and in the north-eastern slope of the Puerto Rican area.

ORIGIN OF THE MIOCENE AMBER

Miocene Hispaniolan and Puerto Ricanlignitic and amber deposits occur withinthe same time interval as Miocene ligniticdeposits of Cuba (Fig. 1). This suggeststhat the unusual accumulation of Earlyto Middle Miocene amber and ligniticdeposits was correlated with a non-sedimentological event, probably a warmclimatic optimum (Tsuchi, 1990). However,a single factor is not sufficient to explainthe production and accumulation of largedeposits of amber, as demonstrated by theuniqueness of the commercially exploitable


amber deposits of the Dominican Republic(Schlee, 1990; Grimaldi, 1996).

There are important differences betweenthe Miocene lignitic lagoonal deposits ofthe Dominican Republic and those of Cuba,Haiti, and Puerto Rico. These differencesare the state of diagenesis and the thicknessof the lignitic beds. Lignite in the YaniguaFormation of the Dominican Republic ismore crystalline and thicker than in theother deposits (Los Arabos, Magantilla,and Cibao Formations). This suggests alarger primary accumulation of plant re-mains in the original basin and deeperpost-depositional burial. The lignite foundin Cuba, Haiti, and Puerto Rico is not crys-talline and occurs in thin beds generallyrepresented by ligniferous clays.

The author believes that the occurrenceof important concentrations of amber in the

mining districts of the Dominican Republicis due to the combination of several factorsthat are considered in the following para-graphs (see also Figs. 9 and 10).

The botanical factor is the unusual abun-dance of a peculiar species of Hymenaea,presumably H. protera, in the Early Neo-gene of the Greater Antilles. This speciesproduced large amounts of resin resistantto weathering and biological degradation.After segregation, the resin was polymer-ized, transformed into copal (Langenheim,1990), and accumulated in the ground withother plant debris as part of the organic-rich litter (Fig. 10A; Grimaldi, 1996). Theoccurrence of abundant plant and solid in-clusions in the amber, as well as presentday accumulation of copal in the soilaround H. courbaril trees, demonstrate theimportance of this factor.

FIG. 9. Paleogeographic map of eastern -Hispaniola during the deposition of copal in the Comatillo basin(marine embayment embracing the northen and eastern mining districts restored to their Miocene -16-14 m.y.-paleogeographic position). SF Septentrional fault, RGF Rı́o Grande fault. Modified from Iturralde-Vinent andMacPhee, 1996.


It is generally accepted that the produc-tion of resin by H. courbaril is the result ofmechanical and/or biotic wounds becauseresin protects against infection (Langen-heim, 1990; Grimaldi, 1996). However, dur-ing 1996 and 1997 the author observed inthe Dominican Republic several H. courbariltrees that naturally exude very smallamounts of resin (also noted by Wu, 1997).Resin was not produced when brancheswere artificially broken or when the cortexwas damaged. The author observed noresin production by H. courbaril during No-vember 1998, several weeks after HurricaneGeorges severely damaged many trees inthe Dominican Republic The only placewhere H. courbaril contained resin was un-

der the bark, in places where termites, ants,and other insects built their nests. Unex-pectedly, the resin was clear and containedno trapped animals. Botanists workingwith species of Hymenaea in Peru and Bo-livia have not noticed massive exudates ofresin (Robin Foster, pers. comm.).

According to Sergio Leiva, an old amberminer and nature observer from El Valle,Dominican Republic, H. courbaril producessmall amounts of resin about two weeksafter its cortex is damaged. He indicatesthat large amounts of resin are producedonly if the tree is struck by lighting. Sergioshowed the author that digging deeplyaround the trunk of an old H. courbaril co-pal may be found, sometimes in large

FIG. 10. Formation of the amber/lignitic deposits in the Comatillo basin, Dominican Republic.


amounts and with biotic inclusions. It iswell known in the Dominican Republic thatcopal is sometimes collected and sold asamber.

Brouwer and Brouwer (1982) consideredthat forest fires can force trees to producelarger amounts of resin. High temperatureproduced by fire could work as efficientlyas lighting, but significant amounts of ashor burned animals and plants have notbeen reported in Dominican amber.

The climate-geography factor is related tothe position of the Hymenaea-rich forest onthe northern slope of the Hispaniolan high-lands, south of the Comatillo lagoonal-marine basin (Fig. 9). Today, a humid rainforest (more than 2000 mm/year rainfall)exists on the northern slopes of the GreaterAntilles because winds bring moisture thatproduces rainfall. The northern slope of theMiocene mountains probably receivedmuch rainfall and the forest was frequentlyexposed to rainstorms and thunderstorms.The high relative humidity would have en-hanced bacterial, fungal and insect attackson the trees (Langenheim, 1990), while theaction of the wind produced mechanicaldamage.

The hydrodynamic factor is related to therapid burial of the copal. This was very im-portant because weather destroys exposedcopal. Frequent rains washed the organic-rich soil of the forest and transported copaldown-slope. In the Comatillo basin, organiclitter was efficiently transported and de-posited in the lower reaches of the slope, atthe lagoonal and coastal areas, creating agrowing bed of turf (peat) intercalated withorganic-rich clays containing largeamounts of copal. This process was favoredby the fact that the Hymenaea-rich forestfaced a well-protected marine enbayment(Figs. 8, 9). At least three main depositionenvironments were present in this basin: la-goonal, deltaic, and deep marine.

In river and lagoons, resin and copal willfloat in fast moving water but sink as soonas the current is negligible (Fig. 10: B). Inthe sea, some copal will float and dispersein high energy environments and some willsink. Sinking may be enhanced by high-density material adhered to the copal, suchas soil and decayed wood, and by the oc-

currence of density flows which carry thecopal mixed with mud (Fig. 10: C). The oc-currence of isolated fragments of amber inwell-documented turbidites has been re-ported (Garcı́a and Harms, 1988; Harms,1990), so it is likely that copal can sink intodeep-water deposits. Theoretically, a high-energy, heavy mudflow can carry largeamounts of copal down-slope if they arewell-incorporated in the high density mud.When the mud flow reached the seafloorand spread laterally in layers a few centi-meters thick, the copal probably concen-trated along with the sand. The occurrenceof thin beds of lignite within this deep-water section is probably due to secondaryaccumulation of the lighter vegetal debrisembedded in water and carried into the seaby the density flow.

The Yanigua Formation represents thedepositional scenario in the low-energy la-goon and coastal swamp environments.The reduced amount of rock detritus inYanigua clearly indicates that erosion in theforest facing the lagoon was not very exten-sive, and that the soil and organic litterwere mostly removed during rainstorms.Some isolated turbulent flows that depos-ited lenticular beds of gravel within theclay are so limited in area and scale, thatthey probably represent the action of localhigh energy water conducts, such as localcreeks.

The amber deposited in the scenario ofdeltaic and open marine environments (LaToca Formation) followed a different pro-cess (Fig. 10: C). The rivers that cut acrossthe Cordillera Central carried largeamounts of silt, sand, and gravel that be-came intermingled with the slope-wash or-ganic-rich input. As is common for sedi-ment-rich rivers, large deltaic-fan depositsprobably developed in the siliciclastic rampfacing the marine basin (Fig. 9). The copal-bearing alluvium was deposited in theriver delta, mostly along the low-energyenvironments of the interchannel flat. Fre-quent sinking of plant debris probably con-centrated as turf layers which diagenesistransformed into lignite. As is normal indeltas, contemporaneous erosion of alreadydeposited beds will carry fragments of turf(future lignite) and copal (future amber)


into deeper areas of deposition in the basinsea floor (Fig. 10: C). Therefore, in the sedi-mentary basin the hydrodynamic factorwas responsible for rapid burial and resedi-mentation (recycling) of the copal in thedifferent depositional environments. Thisguarantees that the copal was additionallyprotected from the action of erosion andsurface biodegradation, which is the firstand most important requisite for fossiliza-tion.

Amber is usually found as local concen-trations in particular horizons (Brouwerand Brouwer, 1982; Redmond, 1982; Eberleet al., 1982). This implies that the factor con-trolling the concentration of copal frag-ments operates during sedimentation-acombination of paleo-relief and transport.In the lagoonal and coastal swamp environ-ments, where slope-wash caused by rain isthe main way of transporting copal to thebasin, it can be suggested that the paleo-relief of the basin floor and source areasdetermined the areas of accumulation anddispersion. Where a mountain ridge facedthe basin, little copal accumulated in frontof the ridge, whereas increased accumula-tion took place in places where a local am-phitheater faced the basin. The irregulari-ties of the water table in the lagoon andcoastal swamps created additional localbarriers where more copal accumulated;this was probably most important in thedeltaic flat, where slow-moving waters orlocal sandy bars and vegetal barriers prob-ably enhanced the accumulation of organic-rich material, including copal. The way co-pal was concentrated in deep-watersediments in the La Toca Formation canalso result from secondary concentrationdue to density segregation within the mud,and the shape and extension of the tur-biditic lobes.

Diagenesis was another key factor in theformation of amber (Fig. 10:D). Diagenesisincludes the chemical and physical modifi-cations that occurred in the sediments afterdeposition. Autigenic pyrite is found in thelagoonal deposits of the Yanigua Forma-tion, suggesting that diagenesis took placein an anoxic, sulfur-rich environment(Brouwer and Brouwer, 1982). In theYanigua Formation, the lignitic beds are

thick, very hard, brittle, and the interca-lated clays and silts have gone throughcompaction strong enough to break andflatten mollusk shells. This phenomenonwas produced by confined pressure due todeep burial of the copal-bearing sediments,probably up to one kilometer below theearth’s surface, since the Yanigua Forma-tion is covered by a few hundred meters oflimestone (Los Haitises Formation). Thisevent, which lasted several million years,placed the sedimentary pile under condi-tions of increased temperature and pres-sure, ultimately producing sediment com-paction, diagenesis, and lithification. In theLa Toca Formation, diagenesis also tookplace in anoxic conditions, as demonstratedby the dark color of the organic-rich amber-iferous beds. As in the previous example,the sediments were deeply buried, morethan one kilometer below earth’s surface,during several millions of years. Copal ma-tured under this condition until it becameamber.

Still, it is a puzzle why the Maissade andCibao Formations do not contain large ac-cumulations of amber, since they have thesame lithology and age as the Yanigua For-mation (Fig. 2). Another puzzle is why am-ber is unknown from Cuba and SouthAmerica, where Hymenaea trees are com-mon today. No less problematic is the rareoccurrence of small amounts of amber inthe Sombrerito Formation of south centralHispaniola (Garcı́a and Harms, 1988). Theexplanation is probably related to somemissing factor among those previouslylisted for the amber-bearing region ofnorthern Hispaniola. For example, it is evi-dent in the paleogeographic map (Fig. 8)that the Comatillo basin was surroundedby a large slope forest, providing more areafor the development of the Hymenaea prot-era forest. Land areas near the Plateau Cen-tral-San Juán basin of Hispaniola and theLas Tunas basin of Cuba were probablysmaller. Perhaps H. protera was not widelydistributed in the Greater Antilles, ormaybe the tree was more abundant in thenorthern slope of paleo-Hispaniola due toparticularly favorable conditions of altitudeand humidity.

A secondary factor that may be involved


is modern topography (Fig. 10: E). For ex-ample, the dissected mountain ranges effi-ciently expose the amber-bearing deposits,in such a way that many years ago amberwas even mined along rivers. The Maissadeand Los Arabos Formations outcrop in ar-eas of less dissected relief, and natural ex-posures are sparse and heavily weathered.Geological exploration is required before afinal conclusion can be reached about theamber prospect of these formations. Never-theless, the Sombrerito (south central His-paniola), San Sebastián, and Cibao Forma-tions (Puerto Rico) are well exposed indeeply dissected areas, but only small iso-lated fragments of amber have been re-ported (Garcı́a and Harms, 1988; Iturralde-Vinent and Hartstein, 1998).

In conclusion, the origin of the unusuallylarge Miocene deposits of amber in Do-minican Republic remain a puzzle, but canprobably be explained as the fortunatecombination of:

i) Adequate conditions of relief and soilfor the development of a large localpopulation of resin-producing trees;

ii) Abundant occurrence of Hymenaea pro-tera, with peculiar characteristics for theproduction of resin;

iii) A timely constrained warm and humidclimatic optimum nearly 16 m.y. ago,which enhanced the production ofresin, maybe as a consequence of largerpopulations of tree-dwelling bacteria,insects and fungi, but especially due tofrequent thunderstorms;

iv) Special conditions for the rapid deposi-tion of copal in marine basins locatednear the source;

v) Adequate environment of diagenesisdue to deep burial of copal and turfbearing sediments.

Acknowledgements .—I thank RossMacPhee and David Grimaldi (AmericanMuseum of Natural History, N.Y.), Salva-dor Brouwer (Sociedad Dominicana deGeólogos, D.R.), Iván Tabares (DirecciónGeneral de Minerı́a, D.R.), Victor González(San Juán, Puerto Rico), Jake Brodzinski(Santo Domingo, D.R.), Jorge Caridad (Mu-seo Mundo de Ambar, D.R.), Dyoris Perez

(Museo Nacional de Historia Natural,D.R.), and José A. Ottenwalder (OficinaPNUD, D.R.) for assistance during fieldwork. Consuelo Dı́az and Rafaela Perez (In-stituto de Geologı́a y Paleontologı́a, La Ha-bana), Gena Fernández (New York Botani-cal Garden, N.Y.), W.A. van den Bold(Holland), Paula M. Mikkelsen (AmericanMuseum of Natural History, N.Y.), andTimothy Bralower (University of NorthCarolina at Chapel Hill) identified the fos-sils from the samples collected by the au-thor. Grenville Draper (Florida Interna-tional University) kindly providedunpublished data about the occurrence ofamber in Jamaica. Grenville Draper, R. A.Davis, Jr. (University of Southern Florida),and Robin Foster (Field Museum of NaturalHistory, Chicago) reviewed the manuscriptand made many useful suggestions. Thiswork was supported by grants from the Of-fice of Grant and Fellowships of the Ameri-can Museum of Natural History, the formerRARE Center for Tropical Conservation,and the National Geographic Society (6009-97).

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NOTE ADDED IN PROOF

During a recent trip to Haiti (September15-30, 2001) supported by an NGS researchgrant to the author, a crew of the MuseoNacional de Historia Natural (Reinaldo Ro-jas, Stephen Diaz, and the author) discov-ered amber in two localities of the PlateauCentral, near Hinche. Preliminary field ob-servations indicate that both sites are in

Miocene sediments strongly resembling theCibao Formation of Puerto Rico and the La-gunitas Formation of Cuba. The main dif-ference with the amberiferous Yanigua For-mation in Dominican Republic is that thesections in Haiti contain non-crystalline lig-niferous horizons. One of the amberiferoushorizons, located north of Thomonde, isrepresented by indurate gray calcareousclaystones, with isolated corals, mollusks,and teeth of bony fish, shark and rays, aswell as turtle fragments. Also present arelarge specimens of Sorites sp. like thosefrom the Lagunitas, Cibao, and YaniguaFormations. The amber was found withinstrongly oxidized subrounded inclusions ofvegetal origin (seeds, fragments of roots,and other plant parts), some of which aredark reddish pieces of indurate resinite,with diameters less than 10 cm. The secondlocality, northwest of Hinche, is an aluvio-deltaic section of gray to light brown sandyclays with intercalations of ligniferousbeds, conglomerates, gravels, and isolatednodular limestone lenses. The ligniferousbeds are poorly indurate, few centimetersthick clays and sandy clays with lamellarlevels of black plant fragments. These hori-zons contained tiny pieces of light coloredyellowish indurate resinite. No macrofos-sils other than vegetal fragments were ob-served. These new amberiferous sites dis-covered in Haiti are particularly interestingbecause they are of the same general age asother miocene amber deposits in Hispani-ola and Puerto Rico.


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