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Between [approximately equal to] 5,800 and 3,600 cal B.P. the biggest architectural monuments and largest settlements in the Western Hemisphere flourished in the Supe Valley and adjacent desert drainages of the arid Peruvian coast. Intensive net fishing, irrigated orchards, and fields of cotton with scant comestibles successfully sustained centuries of increasingly complex societies that did not use ceramics or loombased weaving. This unique socioeconomic adaptation was abruptly abandoned and gradually replaced by societies more reliant on food crops, pottery, and weaving. Here, we review evidence and arguments for a severe cycle of natural disasters-earthquakes, El Nino flooding, beach ridge formation, and sand dune incursion--at [approximately equal to] 3,800 B.P. and hypothesize that ensuing physical changes to marine and terrestrial environments contributed to the demise of early Supe settlements. El Nino | geoarchaeology | Preceramic collapse | Mid-Holocene

Previous research indicates that the Nanchoc Valley in northern Peru was an important locus of early and middle Holocene human settlement, and that between 9200 and 5500 [sup.14]C yr B.P. the valley inhabitants adopted major crop plants such as squash (Cucurbita moschata), peanuts (Arachis sp.), and cotton (Gossypium barbadense). We report here an examination of starch grains preserved in the calculus of human teeth from these sites that provides direct evidence for the early consumption of cultivated squash and peanuts along with two other major food plants not previously detected. Starch from the seeds of Phaseolus and Inga feuillei, the flesh of Cucurbita rnoschata fruits, and the nuts of Arachis was routinely present on numerous teeth that date to between 8210 and 6970 [sup.14]C yr B.P. Early plant diets appear to have been diverse and stable through time and were rich in cultivated foods typical of later Andean agriculture. Our data provide early archaeological evidence for Phaseolus beans and L feuillei, an important tree crop, and indicate that effective food production systems that contributed significant dietary inputs were present in the Nanchoc region by 8000 [sup.14]C yr B.P. Starch grain studies of dental remains document plants and edible parts of them not normally preserved in archaeological records and can assume primary roles as direct indicators of ancient human diets and agriculture. early diets | South America | food production

Recharge by mafic magma is established as a trigger of major explosive volcanic eruptions. However, recharge by silicic magma can also induce perched resident magma to erupt. The evidence of such recharge may be more cryptic than for mafic recharge and requires detailed petrologic and geochemical study to identify. We present a study of plagioclase petrology supported by other data that implicates silicic-silicic magma interaction during the eruption and evolution of the A.D. 1600 eruption of Huaynaputina, one of the largest historical eruptions. Recharge by silicic magma is probably more common than recognized and should be considered an important eruption trigger. Keywords: silicic recharge, crystal mush, magma mingling, eruption trigger, Huaynaputina.

New rhynchonelliformean brachiopods are documented from Upper Cambrian and Tremadoc beds of the Cordillera Oriental and Puna regions, which are representative of the initial radiation of Plectorthoidea on the Andean (South American) shelves of Gondwana. Protorthisina n. gen., so far the oldest known representative of the family Euorthisinidae, and Lesserorthis n. gen. (Euorthisinidae?) are described, as well as the new species Euorthisina? nazarenensis, Kvania mergli, Kvania lariensis, Kvania azulpampensis (with two subspecies), Kvania? primigenia, and Nanorthis calderensis (with two subspecies). Protorthisina, Kvania, and Nanorthis form a stratigraphically continuous series of species displaying well-defined evolutionary trends involving size, shell ornament, and internal features. In the cardinalia, a transition from a V-shaped septalium (typical of Protorthisina) through almost parallel brachiophore plates (typical of Kvania) to the orthoid notothyrial platform of Nanorthis is documented. The species Nanorthis purmamarcaensis Benedetto and 'Nanorthis' grandis (Harrington) are considered as the end members of the lineage. The heterochronic (peramorphic) origin of this trend is supported by ontogenetic evidence from species of Kvania and Nanorthis calderensis. The origin of the 'plectorthoid' cardinalia of Kvania from a euorthisinid configuration present in the stem group, followed by the appearance of a orthoid-like configuration in Nanorthis, pose an intricate systematic problem. The preliminary phylogenetic analysis of the northwestern basin taxa shows that the Upper Cambrian Protorthisina simplex n. gen. and sp. is the stem group of both the nanorthid and euorthisinid clades. On the basis of the new evidence, the genus Nanorthis is removed from the Orthoidea to the Plectorthoidea, and the diagnosis of the families Euorthisinidae and Nanorthidae are revised.

Cenozoic marine deposits of forearc basins in southern Peru contain a molluscan fauna that includes 15 species of turritelline gastropods. Twelve species were previously known; ten from northern Peru or Chile and two species solely from southern Peru. Three new fossil species are described: Turritella riverae, Turritella cruzadoi, and Turritella salasi. Six species of turritellines with crenulated primary spirals, a distinctive spiral ontogeny, and which are mostly endemic to Peru and Chile, are assigned to Incatella n. gen., including L cingulata (Sowerby, 1825), I. cingulatiformis (Moricke, 1896), I. chilensis (Sowerby, 1846), I. leptogramma (Philippi, 1887), I. hupei Nielsen, new name (=Turritella affinis Hupe, 1854), and I. trilirata (Philippi, 1887). Most Paleogene taxa range from northern to southern Peru, while most Neogene taxa, including all species of Incatella, range from Peru to Chile. This biogeographic asymmetry is attributed to a series of biotic events (e.g., extinctions, immigrations) impelled by global oceanographic changes acting locally in a regime of coastal upwelling.

One of the most important developments in the existence of human society was the successful shift from a subsistence economy based on foraging to one primarily based on food production derived from cultivated plants and domesticated animals. The shift to plant food production occurred in only a few independent centers around the world and involved a commitment to increased sedentism and social interaction and to permanent agricultural fields and canals. One center was Peru, where early civilization and food production were beginning to develop by at least 4,500 years ago. New archeological evidence points to 5,400- and possible 6,700-year-old small-scale gravity canals in a circumscribed valley of the western Andean foothills in northern Peru that are associated with farming on low terrace benches at the foot of alluvial fans in areas where the canals are drawn from hydraulically manageable small lateral streams. This evidence reveals early environmental manipulation and incipient food production in an artificially created wet agroecosystem rather than simply the intensive harvesting or gardening of plants in moist natural areas. This finding is different from previously conceived notions, which expected early canals in lower-elevated, broad coastal valleys. The evidence also points to communal organization of labor to construct and maintain the canals and to the scheduling of daily activities beyond individual households. The development of early organized irrigation farming was combined with a hunting and gathering economy to support an increase in the local population size. agriculture | Peru

Over the last 15 years there have been dramatic shifts in the consensus over how best to cope with natural hazards in economically developing regions such as South America. One very positive outcome of the United Nations sponsored International Decade for Natural Disaster Reduction (IDNDR 1990-2000) has been that there is now greater interchange between the work of earth scientists examining the processes and mechanics of hazard occurrence and impact, and social scientists exploring the causes of human vulnerability to hazard--and thereby disaster. This paper traces the development of this new understanding with reference to earthquakes and volcanic eruptions in Peru, one of the most hazardous countries in South America. Particular focus is placed on the excellent progress currently being made by scientists in better understanding the physical dimensions of natural hazard exposure, and the ground-breaking work by social scientists in promoting new approaches to understanding and mitigating human vulnerability to disaster. The paper concludes by emphasizing the need to build on this research to produce more inclusive, incultured and unified strategies of disaster mitigation at the local, national and international levels. KEY WORDS: Peru, Latin America, earthquake, volcano, tsunami, vulnerability, response

The article describes harvesting guano produced by endangered Humboldt penguins of Peru's Punta San Juan. Harvesting the guano, which is used as organic fertilizer, was timed so it did not conflict with the penguin's breeding cycle, since the birds use guano as material in building nesting burrows.

We analyzed patterns of egg laying and breeding frequency of Humboldt Penguins (Spheniscus humboldti) between 1993 and 1997 at Punta San Juan, Peru. Egg-laying extended from mid-March to the first week of December, showing two well-defined peaks in April and August-September. The extended breeding period of these birds was the result of individuals having a second clutch. About half of the females (n = 189) had two clutches per year, most of which were double broods (73%). The date of completion and outcome of reproduction, or whether a change of mates occurred from the previous year, did not affect timing of egg laying. The majority of first clutches (62%) were laid in April each year. Two-clutch breeders that started laying eggs early in April had a higher breeding success than those starting in late April, and double brooders had greater success than single brooders. Two-clutch breeders started to lay eggs earlier than single-clutch breeders. Taking into account that a penguin breeding cycle (from egg laying to fledging) lasts [similar to] 4 months, laying eggs early in April increases the chance of rearing two successful broods per year. During three consecutive years, females tended to have two clutches instead of only one clutch and an average breeding success of 4.54 fledglings over 3 years. Having as many clutches as possible when conditions are favorable appears to be a strategy used by Humboldt Penguins to maximize their lifetime reproductive success within a productive but unpredictable environment.

Approximately 750 000 people live at risk in the city of Arequipa, whose center lies 17 km from the summit (5820 masl [meters above sea level]) of the active El Misti volcano. The composite edifice comprises a stratovolcano designated Misti 1 (ca. 833-112 ka), partially overlapped by two stratocones designated Misti 2 and Misti 3 (112 ka and younger), and a summit cone Misti 4 (11 ka and younger). Eight groups of lava flows and pyroclastic deposits indicate the following volcanic history. (1) Three cones have been built up since ca. 112 ka at an average eruptive rate of 0.63 [km.sup.3]/k.y. (2) Several episodes of growth and destruction of andesitic and dacitic domes triggered dome-collapse avalanches and block-and-ash-flows. Deposition of these flows alternated with explosive events, which produced pyroclastic-flow deposits and tephra-fall and surge deposits. (3) Nonwelded, dacitic ignimbrites may reflect the formation of a 6 X 5 km incremental caldera collapse on Misti 2 (ca. 50 000 and 40 000 yr B.P.) and a 2 X 1.5 km summit caldera on Misti 3 (ca. 13 700 to 11 300 yr B.P.). (4) Tens of pyroclastic flows and at least 20 tephra falls were produced by Vulcanian and sub-Plinian eruptions since ca. 50 ka. On average, ash falls have occurred every 500 to 1500 yr, and pumice falls, every 2000 to 4000 yr. (5) Misti erupted relatively homogeneous andesites and dacites with a few rhyolites, but Misti 4 reveals a distinct mineral suite. Less evolved andesites prevail in scoriaceous products of group 4-1 including historical ash falls. Scoriae of Misti 4 and the ca. 2300-2050 yr B.P. banded pumice commonly show heterogeneous textures of andesite and rhyolite composition. This heterogeneity may reflect changes in physical conditions and magma mixing in the reservoir. (6) Deposits emplaced during the Vulcanian A.D. 1440-1470 event and the sub-Plinian eruption(s) at ca. 2050 yr B.P. are portrayed on one map. The extent and volume of these deposits indicate that future eruptions of El Misti, even if moderate in magnitude, will entail considerable hazards to the densely populated area of Arequipa. Keywords: Arequipa, caldera, eruption, Misti, Peru, tephra, volcano.

Morton L. Isler (1,4) Jose Alvarez Alonso (2) Phyllis R. Isler (1) Bret M. Whitney (3) ABSTRACT.--Ornithological studies undertaken in certain sandy soil habitats of lowland northeastern Peru uncovered a [...]

A new species of antwren (Myrmotherula fjeldsaai) closely related to Myrmotherula haematonota is described from the lower tropical zone of eastern Ecuador and immediately adjacent Peru. It primarily differs from M. h. haematonota by its brown instead of red back in both sexes. New distributional data for nominate M. h. haematonota shows that it meets the new species north of the Rio Maranon, between the Rios Napo and Pastaza, with no apparently significant physical barrier between them., Two species of 'stipple-throated' antwrens, Ornate Antwren (Myrmotherula ornata) and White-eyed Antwren (Myrmotherula leucophthalma) show distinct geographical variation in back color. In some populations of each species the back is [...]

Fish and mammal bones from the coastal site of Cerro Azul, Peru shed light on economic specialization just before the Inca conquest of A.D. 1470. The site devoted itself to procuring anchovies and sardines in quantity for shipment to agricultural communities. These small fish were dried, stored, and eventually transported inland via caravans of pack llamas. Cerro Azul itself did not raise llamas but obtained charqui (or dried meat) as well as occasional whole adult animals from the caravans. Guinea pigs were locally raised. Some 20 species of larger fish were caught by using nets; the more prestigious varieties of these show up mainly in residential compounds occupied by elite families.

The largest explosive eruption (volcanic explosivity index of 6) in historical times in the Andes took place in A.D. 1600 at Huaynaputina volcano in southern Peru. According to chronicles, the eruption began on February 19 with a Plinian phase and lasted until March 6. Repeated tephra falls, pyroclastic flows, and surges devastated an area 70 x 40 [km.sup.2] west of the vent and affected all of southern Peru, and earthquakes shook the city of Arequipa 75 km away. Eight deposits, totaling 10.2-13.1 [km.sup.3] in bulk volume, are attributed to this eruption: (1) a widespread, [approximately]8.1 [km.sup.3] pumice-fall deposit; (2) channeled ignimbrites (1.6-2 [km.sup.3]) with (3) ground-surge and ash-cloud-surge deposits; (4) widespread co-ignimbrite ash layers; (5) base-surge deposits; (6) unconfined ash-flow deposits; (7) crystal-rich deposits; and (8) late ash-fall and surge deposits. Disruption of a hydrothermal system and hydromagmatic interactions are thought to have fueled the large-volume explosive eruption. Although the event triggered no caldera collapse, ring fractures that cut the vent area point to the onset of a funnel-type caldera collapse.

In one common type of industrial continuous casting, partially molten metal is extruded from a vessel through a shaped orifice called a mold in which the metal assumes the cross-sectional form of the mold as it cools and solidifies. Continuous casting can be sustained as long as molten metal is supplied and thermal conditions are maintained. I propose that a similar process produced parallel sets of grooves in three geologic settings, as follows: (1) corrugated metamorphic core complexes where mylonitized mid-crustal rocks were exhumed by movement along low-angle normal faults known as detachment faults; (2) corrugated submarine surfaces where ultramafic and mafic rocks were exhumed by normal faulting within oceanic spreading centers; and (3) striated magma extrusions exemplified by the famous grooved outcrops at the Inca fortress of Sacsayhuaman in Peru. In each case, rocks inferred to have overlain the corrugated surface during corrugation genesis molded and shaped a plastic to partially molten rock mass as it was extruded from a moderate- to high-temperature reservoir.

Strict coevolution requires that interactions among organisms be species-specific. We assessed the relative roles of host- and habitat-specificity in determining the match between a genus of myrmecophytic trees and a guild of obligate plant-ants in the moist tropical forests of Madre de Dios, Peru. Four locally coexisting but habitat-restricted Cecropia species were cultivated in screen tents until all plants had developed myrmecophytic traits. Saplings were then placed within replicate blocks of each of two habitat types: riversides and small forest light gaps. Colonization events were recorded every 3 d between June and August of 1992, and queens were later removed from stem internodes for identification and brood censuses. A similar experiment, conducted in September through November of 1993, included just two species of Cecropia hosts. Effects of host species and habitat on queen colonization rates were evaluated by log-likelihood goodness-of-fit tests and contingency table tests. For three ant species, we also conducted queen preference experiments to compare queen behaviors across a range of host plants. Differences among ants in the extent of habitat-specificity vs. host-specificity provide evidence for multiple evolutionary routes to obligate association with Cecropia. Habitat-specificity exceeded host-specificity in Azteca ovaticeps (Dolichoderinae), for which queen preference experiments revealed no significant discrimination among hosts. This extreme riverside specialist is thought to have descended from generalist live-stem nesters in second-growth habitats. In Azteca australis; host-specificity was strong, and in this species only, directed toward hosts where brood production was most successful. Conflicting habitat associations in the two experiments indicated the weakness or absence of a consistent habitat affiliation in Azteca australis and suggested that colonization frequencies were influenced instead by proximity to foundress sources. Close relatives of A. australis live in exposed carton nests, which may have been positioned ancestrally on key resource plants, e.g., those producing lipid- and amino-acid-rich pearl bodies. Pachycondyla luteola (Ponerinae) exhibited both strong habitat and host associations and may have undergone pair-wise coevolution with its forest-gap-dwelling primary host. Queens of Camponotus balzani (Formicinae), possibly a recent and secondary associate of Cecropia, were overrepresented in forest gap habitat but were host generalists, underrepresented only on a host with extremely small internodes. Apparently greater host-specificity in C. balzani at later stages of colony establishment may be due to differential post colonization mortality on the various hosts. Attack of ant queens by parasitoid wasps was strongly concentrated in the linear riverside habitat and weak to absent in the patchily distributed forest gap habitat. Due to lower rates of either parasitoid attack or other forms of queen mortality, Camponotus balzani experienced greater success in the forest gap habitat, where it was overrepresented in colonization experiments. Historical coincidences and preadaptations appear to have strongly influenced pairings between Cecropia species and their obligate plant-ants and account for much of the 'apparent' niche partitioning observed in the system. Species-specificity seems to be determined mainly by coincident habitat affiliations of ants and plants ('coordinated dispersal') and by preadapted capacities of ants to distinguish among host-plant species. Multiple mechanisms for species-specificity may be characteristic of relationships in which associates disperse separately from one another (i.e., show horizontal transmission). Our results are consistent with the view that coadaptation and co-cladogenesis are more likely in systems where dispersal of associates is tightly coupled. Key words: ant-plant; ants; Cecropia; coevolution; colonization; coordinated dispersal; ecological fitting; habitat-specificity; host-specificity; mutualism; parasitoid wasps; preadaptation., INTRODUCTION A key challenge of coevolutionary studies is to understand the ecological and evolutionary factors driving interacting species to undergo progressive bouts of reciprocal evolutionary change (Ehrlich and Raven 1964, [...]

The new genus Herminespina comprises extinct South American species of 'Thais'-like ocenebrine gastropods with prominent colabral folds and a labral spine. Geographic range extensions into Peru are reported for the late Pliocene H. mirabilis and the late Miocene to Pliocene H. philippii, both previously known only from Chile. A new early Pliocene species, H. saskiae, is described from the Sacaco Basin of southern Peru and compared with an early Miocene muricid from Peru and Chile, Acanthina katzi. Herminespina is one of several genera of Neogene muricids in western South America that bear labral spines.

Indigenous cultures throughout the world have substantial, systematic knowledge of soils gained during many generations of land use; however, little of this knowledge has been scientifically documented. Recent literature indicates that knowledge among traditional cultures could add to scientific understanding of soils and be useful in international agricultural development. This study investigated indigenous soil knowledge in the Colca Valley, Peru, where terrace agriculture has been practiced for at least 15 centuries. Previous research suggested enhanced tilth and fertility of ancient agricultural soils, measured by criteria such as thickened A horizons, lower bulk density, and greater levels of organic C, N, and P relative to nearby uncultivated Mollisols. Long-term soil conservation is partly attributed to traditional management practices such as terracing, a form of conservation tillage, fertilization, and irrigation. To test the hypothesis that a body of knowledge underlies traditional soil management practices, interdisciplinary studies were conducted, involving linguistic evaluation of soil terms, anthropological field interviews, soil and geomorphic mapping, and basic morphological and laboratory characterization of soils identified by farmers. Anthropological research revealed a hierarchical soil classification system, with up to four categorical levels and about 50 soil and earth material names, that emphasizes soil texture and other properties important in agricultural management. Soil analyses indicated a fairly close correspondence between indigenous texture classes and those used in U.S. soil classification. Local farmers recognize several soil features and horizons such as duripans, soil variation with depth, distribution of soils on the landscape, and changes in soil behavior under different conditions.

The El Nino/Southern Oscillation (ENSO) decreased and increased gonad production in the Gari solida population of Bahia Independencia, Peru, during 1992 and 1993, respectively. The water temperature was lower in 1993 as compared to 1992 but the period of warm temperature lasted longer. The bivalves spawned several times during 1993, and this was probably the reason for the decreased growth in 1993 as compared to 1990. Sublethal temperatures during ENSO may be lethal due to the decrease in energy assimilation in G. solida.

Patricia Majluf's long-term behavioral research on the South American fur seal, Arctocephalus australis, is a first. Majluf's doctoral dissertation dealt with her discovery that the lactation periods of her subjects, such as Galapagos fur seals, ranged from two to four years and that this variation was connected with El Nino, the Pacific Ocean's periodic warming. Majluf explains that Peru once had the world's richest marine ecosystem and she would like it at least to keep Punta San Juan, one of the few refuges left for seals and seabirds

Snap-traps, live-traps, and baits affect the ability to capture small mammals, but few previous studies have involved sampling communities of small mammals in tropical environments. We tested differences in captures of small marsupials and rodents by Victor snap-traps versus Sherman live-traps and by two types of bait in lowland rainforest at Reserva Cuzco Amazonico, southeastern Peru. Snap-traps took ca. 3.5 times as many individuals as live-traps. Snap-traps also captured more species (and more rare species), but we attribute this to more numerous captures overall because the relative proportions of species captured by the two traps generally were the same. Type of bait had little impact on our trapping results. Key words: bait, community structure, Neotropics, Peru, Sherman traps, small mammals, snap-traps

I observed a population of White-winged Trumpeters (Psophia leucoptera) in undisturbed rain forest in Peru for over 2,400 h between 1983 and 1987. At this site, I was able to habituate and band three groups of trumpeters and make occasional observations on four unhabituated groups. The habituated trumpeters lived in cooperatively polyandrous groups that defended large ([Mathematical Expression Omitted]) permanent territories against conspecifics. The habituated groups always contained a dominant male and female, and usually contained two unrelated subordinate adult males, one unrelated subordinate adult female, and the group's offspring. Only the dominant female contributed eggs to the clutch, and the group's adult males competed to obtain copulations with her. In the habituated groups, the dominant male obtained the majority of the successful copulations with the breeding female during her fertile period, and the beta male obtained a greater number of copulations than the gamma male. Individuals assisted to varying degrees with helping to rear the group's chicks. Subordinate males provided significantly more food to the chicks than the dominant male, and the subordinate female provided significantly less food than the dominant female, while the dominant male and female fed chicks equivalent amounts of food. Offspring usually helped raise one brood of siblings, but both males and females dispersed from their natal group at about two years of age, when they reached sexual maturity. The evolution of cooperative breeding in White-winged Trumpeters appears to be related to the need to defend large permanent territories to provide access to sufficient food during the dry season when resources are scarce. Defense of large territories results in a surplus of adults in the trumpeter population relative to the number of available breeding positions. The low probability of acquiring a breeding position for individuals that remain on their natal territory appears to result in sexually mature offspring dispersing from their natal groups and attempting to join new groups where they have some chance of breeding nonincestuously. The apparent need to have multiple adult males within a group for successful territory defense may explain why unrelated males are accepted into territorial groups, where they are able to copulate surreptitiously with the breeding female.

I studied the breeding biology of a population of White-winged Trumpeters (Psophia leucoptera) in undisturbed lowland rain forest in Manu National Park, southeastern Peru. At this study site, it was possible to habituate trumpeters to humans, allowing groups to be followed and observed at distances of a few meters for entire days. I found that White-winged Trumpeters lived in cooperatively polyandrous groups of 4 to 13 individuals that defended permanent year-round territories. Clutches that averaged three eggs were laid by the dominant female on the floor of elevated cavities in trees. Eggs were incubated for about four weeks, primarily by the group's dominant male and female. Chicks hatched around the end of October at the beginning of the rainy season. If at least one of the brood survived, a subsequent clutch was not laid until the following breeding season. Predation on eggs and chick mortality resulted in an average of 1.6 young per group-year surviving to adulthood. White-winged Trumpeter chicks were precocial and left the nesting cavity the day after they hatched, able to walk and climb. Chicks were dependent on older birds to provide them with all of their food for over three weeks and were still receiving more than one-half of their food from adults at two months. Trumpeters reached sexual maturity at about two years of age, at which time both male and female offspring dispersed from their natal groups.

Late Quaternary sediments from the Peru upwelling zone have been investigated using backscattered electron imagery. The dysaerobic to anaerobic conditions which persist within the strong oxygen minimum zone intersecting the shelf and upper slope sediments, have resulted in the preservation of a wide range of microscopic fine structure relating to biological activity. Two forms of pelletal structures are present: pellets and aggregate structures. (1) Pellets are oval in cross section with a mean diameter of 610 [[micro]meter] and sharp boundaries; three common pellet types have been identified: (a) crushed diatom and clay pellets; (b) intact diatom pellets; and (c) silt pellets. (2) Aggregate structures are smaller than pellets with a mean diameter of 360 [[micro]meter]. They have indistinct boundaries and may be composed either of pure diatom ooze or a mix of clay, silt and diatoms. The size, shape and mode of occurrence of aggregate structures suggest that they are the product of a meiofauna, redistributing the topmost sediment during periods of very slight increases in oxygen. Most of the crushed diatom/clay pellets and intact diatom pellets are probably also the product of a surficial deposit-feeding fauna tolerant of low dissolved oxygen levels such as polychaete worms. Silt pellets may record the chamber building activities of agglutinating foraminifera. Keywords: pellets, upwelling, dysaerobic, anaerobic, fabric.

Analyses of protein electrophoretic and mitochondrial cytochrome b sequence data support association of Tomopeas ravus with the chiropteran family Molossidae. Although analyses of protein electrophoretic data present no clear placement of Tomopeas within the Molossidae, analyses of the sequence data support the recognition of Tomopeas as a basal and phylogenetically distant member of Molossidae. As a result of these analyses, we present a new taxonomic placement of this distinctive and taxonomically problematic bat.

Abstract: Apatite and zircon fission-track ages of three samples of the Huachon granite and one sample of the Quiparacra granite, from ts, Eastern Cordillera of the Andes of central Peru, have been determioed. Zircons from ts, Huachon granite yielded two groups of ages. An older group, made up of zircons with tse lowest uranium content,kgave an age of c. 270 Ma. Ts, zircons with high uranium content from tsis granite gave ages of c. 160 Ma. Ts, zircon ages from tse Huachon granite showkno correlation with elevation. The age of 270 Ma is interpreted as tse age of probabl, emplacement; tse 160 Ma age is evidence of a mild cooliol ([greater than or equal]200[degrees]C) event tsatkended in late Mid-Jurassic time. Tsis cooliol correlates, in central Peru, with tsick conglomerates in the Sub-Andes and strool exhumation in the Eastern Cordillera duriol Bathonian to Malm tim,s. Zircons from ts, Quiparaca granite, which is a component of a composite batholith of possibl, Precambrian to Tertiary age, showkages of c. 30 Ma which are interpreted as tse emplacement age. Ts,se zircons w,re totally annealed prior to the cooliol in the Oligocene. Tsis required temperatures >200[degrees]C. Apatite fission-track datiol of the Huachon granite yielded only Neogene ages which reflect tse total annealiol of the tracks present in the apatite before exhumation began c. 22 Ma. Apatite ages showka correlation with elevation and indicate two periods of cooliol duriol the Neogene at c. 21 Ma and between 12 Ma and the Present. Ts,se youol ages suggest approximately 4 to 6 km of erosionkin ts, Eastern Cordillera of central Peru in the past 30 Ma. Ts,se amounts are consistent with known geological data and fission-track ages obtained from other parts of tse eastern Andes.

The world's driest coastal desert is in South America along the coasts of Peru and Chile. The desert's maintenance is investigated by studying the local dynamics of the low-level southerly flow along the coast. A linear boundarylayer model is used in which a Boussinesq atmosphere is driven by a surface thermal contrast on a [beta] plane. The resting basic state is stably stratified. Constant mechanical and thermal diffusivities are assumed in the momentum and heat equations, respectively. The dynamics of the buoyancy field is governed by a three-dimensional eighth-order differential equation in which the meridional dependence enters parametrically. Results are shown for different values of the constants involved as well as for solutions on an f plane and a semigeostrophic [beta] plane. The results indicate that the effect of nonuniform rotation is responsible for the presence of subsidence along the coast and inland. This coastal subsidence helps maintain the desert by increasing the static stability and suppressing deep convection. The predicted vertical wind profiles agree well with the observations for Lima, Peru. Sensitivity tests indicate that the flow depends on the interplay between stratification, friction, and the Coriolis parameter and its variation ([beta]). The mechanical frictional effects are mainly constrained to a shallow Ekman layer, whereas the thermal effects are manifested in deeper layers controlled by the [beta] effect.

The degree of soil development on moraines and radiocarbon ages indicate that the Cordillera Oriental, a part of the eastern Andes in northern Peru (7 degrees 30'-7 degrees 55'S; 77 degrees 20'-77 degrees 35'W), was last glaciated during the last glacial maximum (marine isotope stage 2). This glaciation was the most extensive late Quaternary glaciation in the area. Radiocarbon-dated sedimentological changes in six sediment cores from three lakes and one bog reveal that the last deglaciation is marked by a two-stepped transition from rhythmically laminated inorganic sediment to massive, organic-rich sediment. The first step of this transition commenced before 12.1 + or - 0.2 ka (+ or - 1 Sigma) and probably by ca. 13.5 ka. Glaciers covered less than 50% of their last glacial maximum area by 12.1 + or - 0.6 ka, and cirques west of the main divide were probably ice-free by this time. A return to rhythmically laminated inorganic sediment in the lakes and the bog occurred between 12.1 + or - 0.6 and 10.3 + or - 0.4 ka. This may reflect an episode of increased stream discharge and glacier expansion during which glaciers reoccupied cirques above approximately 3,800 m. This glacier expansion adds to widespread evidence of a late-glacial readvance in the tropical Andes. All cirques have been ice-free since between 10.3 + or - 0.4 and 9.7 + or - 0.5 ka.

In sosuthern Peru, the pre-Oligocene volcanic suite (the late Cretaceous to early Paleocene silicic tuff, agglomerate, and ignimbrite of the Toquepala Group) have positive [epsilon] [Nd.sub.i] (+0.6 to +5.3) and commonly negative [epsilon] [Sr.sub.i] values (-7.0 to +8.0), with [sup.206.Pb]/[sup.204.Pb] ratios comparable to those ascribed to arc magmas. Although the former generally display unfractionated La/Yb (2 to 15) and low Th/U (0.1 to 4.2), the post-Oligocene volcanic suite, comprising early Miocene to Pleistocene calc-alkaline andesite flows and ignimbrite sheets with minor basaltic intercalations, has elevated La/Yb (9 to 34) and Th/U (3 to 8), which are correlated with negative [epsilon] [Nd.sub.i] (-0.9 to -12.0), positive [epsilon] [Sr.sub.i] values (+13 to +64) and low [sup.206.Pb]/[sup.204.Pb]. The principal trace-element and isotopic characteristics that strongly characterize the post-Oligocene volcanic suite are precisely those that confer the unusual signature to the Precambrian basement granulite and gneiss exposed in the area of study (the Arequipa Massif). The latter commonly display high Th/U (20-70) and La/Yb (14 to >57), low [sup.206.Pb]/[sup.204.Pb] (16.11 to 17.10) but present an extreme enrichment in radiogenic Sr ([epsilon] Sr +396 to +999). The contrasting trace-element and isotopic signatures exhibited by both suites can be best explained if the pre- and post-Oligocene vilcanic suites orginated from an isotopically depleted subcontinental mantle wedge, with the ignimbrite (rhyolite) being derived by crystal fractionation from andesitic parents. In this hypothesis, the post-Oligocene magmas must have undergone substantial crustal contimination (mainly by a thick Andean crust having a large Precambrian component) during fractionation, whereas the pre-Oligocene volcanic rocks underwent little contamination, perhaps because they ascended through a thinner latte Mesozoic crust. We suggest, as one possibility, that the increasing degree of crustal contamination experienced by the post-Oligocene volcanic suites is partly related to the tectonic thickening of the Precambrian basement which took place during late Mesozoic-early Cenozoic time, a process which would promote larger degrees of contamination of mantle-derived magmas upon ascent. If this assumption is correct, then the rapid Cenozoic crustal thickening of the southern Peruvian Andean crust could result from a combination of massive introduction of juvenile magmas in the lower crust, underplating of a buoyant subducted oceanic plate, and crustal shortening, the latter mechanism being perhaphs similar to that actually occurring in the sub-Anes where the Brazilian Shield is underthrusting the Eastern Cordillera.

Significant precipitation along the north-central coast of Peru (lat 5[degrees]-10[degrees]S) occurs exclusively during El Nino incursions of warm water into the Peruvian littoral. Flood deposits from this region therefore provide a proxy record of extreme El Nino events. I present a 3500 yr chronology of the extreme events based on radiocarbon dating of overbank flood sediments from the Rio Casma (lat 9.2[degrees]S). The flood-plain stratigraphy suggests that the El Nino phenomenon has occurred throughout the Holocene and that flood events much larger than that which occurred during 1982-1983 occur here at least once every 1000 yr.

Integrated field study and radiometric dating in the Llama-Bambamarca area of the Western Cordillera of nortern Peru have resulted in major revisions in the stratigraphic and structural relations and ages of thick sequences of Tertiary volcanic rocks and constrain the timing of compressive deformation, magmatic activity, and uplift. Rocks of the upper part of the Llama Formation yield K-Ar mineral dates of 54.8 [+ or -] 1.8 and 44.2 [+ or -] 1.2 Ma; altered volcanic rocks composing the lower part of the formation in the western part of the area may be older. Eocene K-Ar dates have been reported for several granitic plutons in the region, and other plutons of probable similar age intrude the Llama Formation and are overlain by upper Eocene strata. The pervasive alteration that affects much of the Llama Formation may be the result of large hydrothermal systems driven by a coeval, and presumbly cogenetic, batholith. The Chota Formation, which is mostly volcaniclastic, has yielded ages of about 50 and 44 Ma. The Chota Formation thus does not predate the Llama Formation but rather is an eastern distal-facies equivalent of rhyolitic ash-flow sheets and dacitic volcanic rocks of the Llama Formation. The major unconformity at the base of the Llama Formation reflects deformation during Late Cretaceous (Peruvian tectonic phase) and/or Paleocene (Incaic I) time. The time of Incaic II deformation is backeted between the 44.2 [+ or -] 1.2 Ma date on the Llama Formation and the age of about 39 Ma of a thick ash-flow sheet that comprises the lower part of the unconformably overlying Huambos Formation. Dates on rocks postdating Incaic II tectonism in central Peru suggest that deformation had ceased by about 41 Ma. Incaic II tectonism in northern and central Peru appears to have been a short but intense compressive event that peaked about 43 m.y. ago. The Incaic II event is coeval with formation of the Hawaiin-Emperor bend and with a period of rapid convergence of the Nazca and South American plates and therefore may reflect a major plate change in lithospheric plate movement patterns. A largely volcaniclastic sequence of early Miocene age shows that the early Neogene pulse of volcanic activity recognized throughout the Central Andes is represented in northern Peru. Beds of conglomerate within this sequence are probably the result of Quechua I tectonism, although the 23.2 [+ or -] 1.5 Ma date obtained on tuff from the unit appears somewhat older than the time of about 19 Ma recognized for Quechua I tectonism in central and southern Peru. Units of partly welded and unaltered ash-flow tuff that fill deeply incised paleovalleys have ages of about 8.2 and 11.4 Ma, showing that the Western Cordillera of northern Peru was uplifted before late Miocene time.