Geology of the Amber-Bearing Deposits of the Greater Antilles

Caribbean Journal of Science, Vol. 00, No. 0, 141–167, 2001 Copyright 2001 College of Arts and Sciences University of Puerto Rico, Mayaguëz 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 exploitable quantities), 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 the data available is dispersed in many contributions. This paper fills this gap and presents the results of five years of original research on the subject. Greater Antillean amber probably derived from the resin of Hymenaea protera, an extinct leguminous tree which probably grew in evergreen forests. Amber is the consequence of diagenetic changes that operate in the resin after burial in the sedimentary pile, sometimes over 1000 m deep, where it is subjected to higher temperature and pressure over millions of years. The origin of unusually large Miocene deposits of amber in the Dominican Republic can be explained by the fortunate combination 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 bearing deposits were formed; and (4) de- scribing the fossil assemblage found not in Dominican amber was known by the na- the amber itself but in the associated depos- tives of Hispaniola and was taken to Spain its (Iturralde-Vinent and MacPhee, 1996; by Cristopher Columbus as one of the trea- Iturralde-Vinent and Harstein, 1998). sures of the West Indies. During the 20th century, Dominican amber became famous for the quality of its fossils, which include WHAT IS RESINITE,RESIN,COPAL extremely well-preserved fungi, algae, AND AMBER? plant remains, land invertebrates (arthro- pods, nematodes, gastropods) and land Resin-producing trees are widely distrib- vertebrates (amphibians, reptiles, remains uted in the tropics, but amber in tropical of mammals and birds) (Pe´rez-Gelabert, America most probably derived from the 1999). resin of the extinct leguminous tree Hymen- Amber has also been reported from Haiti aea protera. Although several extant species (Maurrasse, 1982), Puerto Rico (Iturralde- of this genus occur from the Amazon Basin Vinent and Hartstein, 1998) and Jamaica to Mexico, only two species occur in the (G. Draper, pers. comm.), but none of these Greater Antilles: the widespread H. cour- occurrences has economic value. Despite baril L. (commonly known as courbaril in widespread interest in amber, there is no Cuba and as algarrobo in the Dominican modern review of the geology of the am- Republic and Puerto Rico), and the north- ber-bearing deposits of the Greater An- eastern Cuban endemic H. torrei Leoń. The tilles. This paper fill this gap by (1) review- extinct amber-producing tree of the Do- ing the occurrences, age, stratigraphic minican Republic was named Hymenaea position, and environment of deposition of protera by Poinar (1991). This taxon is re- the amberiferous beds; (2) presenting new lated to H. verrucosa of western Africa and information about the age and origin of the probably to H. torrei of eastern Cuba (Lee amber as a fossil resin; (3) discussing the and Langenheim, 1975). paleogeographic scenario when amber- Resinite.—This is an all-encompassing 141 142 AMBER DEPOSITS IN GREATER ANTILLES term for all types of plant-derived resins, uted by flash floods and the normal fluvial regardless of age and physical or chemical and runoff processes. Amber can also be characteristics. reworked by coastal erosion, as in the Baltic Resin.—This term applies to material re- region (Schlee, 1990; Grimaldi, 1996). Am- cently exuded from the tree and which has ber clearly has significant potential for not been buried. Its physical and chemical redeposition if protected from prolonged characteristics depend on the species of exposure to atmospheric oxygen. Langen- tree. Resin can be sticky or dry and fragile. heim (1990) indicates that near-flotation al- It can have a whitish or darker coating, but lows some amber particles to be readily internally is transparent, yellowish, red- moved by weak currents and tends to pro- dish, or brown. Resin is non-volatile, rela- tect them from abrasion and fracture, even tively inert, hydrophobic, amorphous, and during prolonged transport. Amber is typi- strongly resistant to decay. Its decay (as cally deposited in low energy bays, deltas, well as that of copal and amber) is due to river mouths, estuaries, and other coastal atmospheric exposure, and the material is areas. Large amounts may be carried fur- best preserved when deposited in subaque- ther offshore as inconspicuous microscopic ous or water-logged environments. Atmo- particles (Grimaldi, 1996). spheric weathering often produces opaque surface crusts and oxidation rims, and may cause an overall darkening of the resin THE AMBERIFEROUS DEPOSITS OF THE grains (Tyson, 1995). Naturally exuded GREATER ANTILLES resin seems to be a physical surface barrier Amber and associated lignitic rocks are against infection by plant pathogens (Lee known from the Greater Antilles (Fig. 1) in and Langenheim, 1975; Grimaldi, 1996). Cuba (Miocene lignite), Hispaniola Copal.—This is an older resin that can be (Miocene lignite and amber), Puerto Rico found in the leaf litter layer or buried in the (Oligocene and Miocene lignite and traces soil below the tree. It is usually solid, frag- of amber), and Jamaica (Maastrichtian- ile, transparent with a dark surface coating, Paleocene traces of amber). The following and internally yellowish, reddish, or paragraphs describe the basins and sedi- brown. Copal of H. courbaril usually sinks ments known to contain amber, regardless in fresh water and floats in salt water (per- of their commercial importance. sonal observation). Resin in the form of copal accumulates in forest soils and ombrog- enous peat deposits, whose high (domed) HISPANIOLA water tables aid preservation. Amber.—This is the fossil equivalent of The Late Tertiary rocks of the Dominican copal. It is usually indurate, massive, and Republic occur in a variety of geological resistent to organic solvents. Amber can be contexts, predominantly of sedimentary transparent, but more frequently it is trans- origin, formed in subaerial to deep-marine lucent with yellow, reddish, brown or blue- depositional environments (see references brown color. These characteristic are the in Mann et al., 1991). Amber in commercial consequence of diagenetic changes that op- quantities is well known from areas north erate in copal after burial in the sedimen- of Santiago de los Caballeros and northeast tary pile, sometimes at depths over 1000 m, of Santo Domingo (Fig. 1; Vaughan et al., where it is subjected to elevated tempera- 1922). These mining districts are known re- ture and pressure. Under these conditions spectively as the Northern Area and the and several millions of years, copal is natu- Eastern Area. Minor occurrences of amber rally cooked and transformed into amber. have been reported from the Plateau Cen- Dominican amber usually sinks in fresh tral-San Juań Area (Lemoine in Sanderson water and floats in salt water (personal ob- and Farr, 1960; Garcıá and Harms, 1988; servation). Harms, 1990). All amber occurrences are of After erosional exposure, copal and am- late Early to early Middle Miocene age and ber are frequently reworked and redistrib- are associated with lignitic material, but M. A. ITURRALDE-VINENT 143 FIG. 1. Amber and lignite occurrences in the Greater Antilles. Lignite is not always associated with amber, but the opposite is true. each represents different depositional envi- of the area, a W-NW trending fault is pre- ronments, from terrestrial-marine transi- sent along the edge of the Neogene lime- tion to deep marine (Iturralde-Vinent and stone. The limestone on the northern block MacPhee, 1996). of the fault is overlain by Pliocene to Recent deposits. In general, Miocene rocks dip Eastern Mining District gently toward the north-northeast, so the thickness of the Neogene section varies The Eastern Mining District is on the from less than 100 m in the south to several northern margin of the Cordillera Oriental, hundreds of meters in the north (Brouwer between Sabana la Mar, Hato Mayor, Bay- and Brouwer, 1982; Toloczyki and Ramı´rez, aguana, and Cotuı´ (Fig. 2). The sedimen- 1991; Lebron and Mann in Mann et al., tary rocks that form the substrate are 1991). mostly Neogene; along the west, south and Brouwer and Brouwer (1982) recognized east margins of the basins they directly four stratigraphic units in the Eastern Min- overlay Cretaceous sedimentary, volcanic, ing District: the basal conglomerates, the and igneous rocks. On the northern side amber-bearing Yanigua Formation, the FIG. 2. Generalized geological map of Hispaniola showing the amber-bearing areas. Adapted from Iturralde- Vinent and MacPhee, 1996. 144 AMBER DEPOSITS IN GREATER ANTILLES “caliza Ce´vicos”, and the “caliza de los cit.) reported no amber from this conglom- Haitises.” According to some authors, there erates. The sedimentary characteristics of is only one limestone or caliza unit (Bowin, the conglomerates (oblique lamination, for- 1966; Toloczyki and Ramı´rez, 1991; Lebron mation of channels, erosional surfaces be- and Mann in Mann et al., 1991). My field low the coarse grained beds) suggest a flu- observations suggest that the limestones vial environment of deposition. that Vaughan et al. (1922) named Ce´vicos In general, the rest of the Yanigua section are those found as intercalations in the up- shows minor lateral differences (Fig.

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