Article

Oligocene deposition and Cenozoic sequence boundaries in the Pisco Basin (Peru)

May 1998
Journal of South American Earth Sciences 11(3):217-231

May 1998
11(3):217-231

Authors:

A newly identified early Oligocene marine transgression across the Pisco Basin of southern Peru resulted in the deposition of at least 150m of fossiliferous sandstones and siltstones, informally designated the Otuma formation. Basal sandstones can usually be recognized in the field by the presence of the gastropod, Turritella woodsiLisson 1925. New stratigraphic data demonstrate that Cenozoic marine sediments were deposited in the Pisco Basin between about 41-34 Ma, 31-28 Ma, 25-16 Ma, 15-11 Ma, 10-5 Ma, and 4-2 Ma. Most sequence boundaries in the Pisco Basin coincide with compressional tectonic events and/or eustatic low stands of sea level.

Laterally-continuous dolomite layers of the Miocene Pisco Formation (East Pisco Basin, Peru): A window into past cyclical changes of the diagenetic environment

Article

Oct 2022
MAR PETROL GEOL

Along the Peruvian coast, the sedimentary succession of the East Pisco Basin is exposed in the Ica Desert. At Cerro Los Quesos, laterally continuous dolomite layers characterise the diatomaceous sediments of the P2 sequence of the Miocene Pisco Formation, where a large number of marine vertebrates are exceptionally preserved, many enclosed in dolomite nodules. In this work, cemented layers from this sequence were described and sampled for petrographic, chemical, microscopic and isotopic analyses. Dolomite occurs in continuous 10–50 cm thick well cemented layers, formed by sediment of different nature: biogenic, terrigenous, volcanoclastic, and phosphatic. The underlying sediments exhibit a yellow layer with sparse dolomite crystals, a black layer with abundant Mn-oxides, and a reddish layer rich in Fe-oxides, indicating redox-related fronts. Two generations of dolomite can be recognised: an early diagenetic microcrystalline one, and a sparry one, filling the large cavities. As observed in both thin sections and on broken surfaces, microcrystalline dolomite also fills the inner spaces of the diatom areolae replicating their finest ultrastructure, such as foramina and cribra and replace calcite shells of foraminifera. δ¹⁸O and δ¹³C values from the microcrystalline dolomite of two layers, selected based on the absence of other carbonate phases (e.g. calcite) and the lack of sparry cement, are in agreement with those reported for the Peru margin and fall in the fields of either sulphate-reduction or methanogenesis. All the data point to dolomite precipitation associated with low-temperature early diagenesis that typically occurs in upwelling settings, where high surface water productivity is responsible for high rates of organic carbon flux to the sea bottom and for the cyclical oxygen depletion at the bottom. Such conditions also promote high abundances of marine vertebrates and the exceptional preservation of their skeletons in the sediments.

An overview of the fossil record of cetaceans from the East Pisco Basin (Peru)

Article

Full-text available

Jun 2022

The East Pisco Basin is one of the forearc basins that formed during the Cenozoic along the coast of Peru due to the subduction of the Farrallon-Nazca plate beneath the South American plate. The sedimentary fi ll of this basin is extensively exposed along the coastal Ica Desert, and includes a succession of Eocene to Pliocene marine sediments that account for a ~50-myr-long history of semi-continuous deposition. These rocks are characterized by an outstanding fossil content that remarkably contributed to our understanding of the evolutionary history of the main groups of Cenozoic marine vertebrates. In the Ica desert, the most common and signifi cant vertebrate remains belong to cetaceans. Knowledge on the fossil cetaceans of the East Pisco Basin has grown dramatically in the last fi fteen years thanks to several international research projects involving, among many others, the authors of the present article. These research eff orts have led to the discovery of several hundred fossil skeletons, the most signifi cant of which have been collected, prepared and partly published. Furthermore, interdisciplinary studies were also conducted in order to provide a high resolution chronostratigraphic framework for this fossil record. Remarkable cetacean specimens (42.6 Ma) Yumaque strata are home to the quadrupedal protocetid archaeocete Peregocetus pacifi cus, which documents the fi rst arrival of cetaceans in the Pacifi c Ocean. Geologically younger (36.4 Ma) Yumaque deposits have yielded the holotype skeleton of Mystacodon selenesis, the oldest mysticete ever found. This ancestor of the modern baleen whales had a skull provided with a complete dentition and retained hindlimbs, albeit reduced in size. In the Otuma Formation, a nine-m-long basilosaurid (Cynthiacetus peruvianus) has been discovered. The Chilcatay Formation records the fi rst great radiation of the odontocetes, represented by Inticetidae (Inticetus vertizi), basal Platanidelphidi (Ensidelphis riveroi), Squalodelphinidae (Furcacetus fl exirostrum, Huaridelphis raimondii, Macrosqualodelphis ukupachai and Notocetus vanbenedeni), Platanistidae (aff. Araeodelphis), Physeteroidea (Rhaphicetus valenciae and cf. Diaphorocetus), Chilcacetus cavirhinus, indeterminate Eurinodelphinidae, and Kentriodontidae (Kentriodon). Overall, this roughly coeval assemblage displays a considerable disparity in terms of skull shape and body size that is possibly related to the development of diff erent trophic strategies, ranging e.g., from suction to raptorial feeding. In the Pisco Formation, starting from P0, the baleen-bearing whales (Chaeomysticeti) represent the most frequent cetacean fossils (only a few mysticetes are known from the Chilcatay strata). Two chaeomysticete lineages are found in the Pisco Formation: Cetotheriidae (from Tiucetus rosae in P0 to Piscobalaena nana in P2) and Balaenopteroidea (from Pelocetus in P0 to several undescribed species of Balaenopteridae in P2, testifying to a progressive trend toward gigantism). Odontocetes are rare in P0, the "kentriodontid" Incacetus broggii being the only species described from these strata, but they become more abundant and diverse in P1 and P2. In P1, the commonest toothed whale is Messapicetus gregarius, a member of Ziphiidae featuring an extremely elongated rostrum and a complete set of functional teeth. Another ziphiid from P1 is Chimuziphius coloradensis, known only from the fragmentary holotype cranium. The P1 strata also record the appearance of the crown Delphinida, with the superfamily Inioidea being represented by two small pontoporiids (Brachydelphis mazeasi and Samaydelphis chacaltanae) and one iniid (Brujadelphis ankylorostris). Moreover, P1 is also home to the stem physeteroid Livyitan melvillei; featuring a three-m-long skull and teeth reaching 36 cm in length, L. melvillei was one of the largest raptorial predators and, possibly, the biggest tetrapod bite ever found. Acrophyseter is another macroraptorial sperm whale, distinctly smaller than L. melvillei, known from both P1 and P2. Even smaller in size are the kogiids Platyscaphokogia landinii and Scaphokogia cochlearis, both of which are known from the upper strata of P2. The same allomember is also home to the ziphiids Chavinziphius maxillocristatus and Nazcacetus urbinai, the "kentriodontids" Atocetus iquensis and Belenodelphis peruanus, and undescribed members of Phocoenidae.

Age and provenance of the Mio-Pleistocene sediments from the Sacaco area, Peruvian continental margin

Article

Full-text available

Apr 2022
J S AM EARTH SCI

Over the last decades, rocks from the East Pisco Basin (EPB), on the Central Peruvian coast (13°-16°S), have yielded an abundant and diverse collection of coastal-marine fossils, which are key for characterizing the onset and evolution of the modern Humboldt Current. Despite its paleontological richness, and after almost 40 years of study, the spatio-temporal context of the deposits of the southern part of the EPB (Sacaco area) remains only broadly constrained, being mostly tailored to particular vertebrate-rich levels occurring throughout the area. Here we build a composite stratigraphic section for the Sacaco area including three lithostratigraphic units (Pisco, Caracoles, and Pongo formations), which documents several discontinuities and intraformational unconformities. We infer depositional ages based on new radiometric (U–Pb), isotopic (Sr) and biostratigraphic data, synthesize previous litho-, chemo-, and bio-stratigraphic studies, and present a comprehensive chronostratigraphic review of the Mio-Pleistocene record for the Sacaco sub-basin that allows us to identify various local and basinal events. Our results indicate that, in the Sacaco area, the Pisco Formation ranges from ∼9.6 to 4.5 Ma, the overlying Caracoles Formation from 2.7 to ∼1.9 Ma, and the Pongo Formation accumulated from ∼1.9 up to at least 1.4 Ma. These sedimentary successions accumulated in a continually subsiding setting and show a shallowing-upwards trend. Zircon U–Pb provenance analysis mainly record Neoproterozoic, Cretaceous, and Mio-Pleistocene populations, revealing discrete up-section changes in source areas. Mio-Pleistocene and Cretaceous sources are continuously present, while older recycled-orogen sources vary through time in presence and abundance, indicating either paleogeographic changes or source exhaustion.

(Bio)stratigraphic overview and paleoclimatic-paleoceanographic implications of the middle-upper Eocene deposits from the Ica River Valley (East Pisco Basin, Peru)

Article

Jul 2021
PALAEOGEOGR PALAEOCL

The Eocene sediment successions of the East Pisco Basin (southern Peru) host an exceptionally rich and well-preserved assemblage of vertebrate fossils. However, due to the dearth of geochronological and biostratigraphic controls as well as of stratigraphic correlations, our understanding of these rocks and their fossil content remains elusive. This paper provides a comprehensive calcareous nannofossil, diatom, and silicoflagellate biostratigraphic framework for the Eocene strata exposed at four localities along the Ica River Valley, permitting a robust chronological calibration of the marine vertebrate fauna entombed therein and a better definition of important appearance/ extinction events. The Paracas Formation, deposited directly on top of the Proterozoic and Paleozoic rocks of the crystalline basement, is formed by a siliciclastic-bioclastic gravel-sized deposit (Los Choros member) and calcareous-terrigenous siltstone (Yumaque member) that was deposited from the Lutetian (47.8–41.2 Ma) through the Bartonian (41.2–37.7 Ma) to the early Priabonian (37.7–33.9 Ma). The unconformably overlying Otuma Formation consists of a basal sand, followed by calcareous siltstone intercalated by diatomite layers towards the top. In the study area, the Otuma Formation is Priabonian in age and is truncated at the top by an unconformity at the base of the overlying Miocene Chilcatay Formation. Due to the angular nature of the unconformity, the upper Otuma strata reach the Oligocene elsewhere. Average sedimentation rates range from 17 to 24 m/My in the Yumaque member of the Paracas Formation and increase to 147–170 m/My in the Otuma Formation. The microfossil assemblages witness a coastal setting with warm-temperate conditions for the Paracas Formation that become slightly cooler (though still temperate) in the upper Otuma Formation. Diatomaceous layers in the upper Otuma Formation indicate an overall increase in nutrient availability, which could reflect the global reorganization of ocean currents at the Eocene-Oligocene transition. However, the taxonomic composition of the diatom assemblage suggests seasonal rather than persistent upwelling conditions.

The Miocene stratigraphy of the Laberinto area (Río Ica Valley) and its bearing on the geological history of the East Pisco Basin (south-central Peru)

Article

Aug 2021
J S AM EARTH SCI

Global sea-level changes and substantial vertical displacement along the Monte Grande Fault (MGF) in the lower Río Ica Valley of south-central Peru influenced the accumulation of bioclast-bearing and diatom-bearing Miocene siliciclastic sediments in an area of the East Pisco forearc basin (EPB) colloquially known as Laberinto. Two depositional hiatuses in the Laberinto area (~17–14 Ma, ~12.5–10 Ma) manifest as sediment-filled erosional depressions a few kilometers in breadth. Erosion of the older depression was preceded by an ~18-Ma massive debris flow, possibly triggered by motion on the MGF causing lower Miocene lithoclastic olistoliths of up to two hundred meters length to spill off the footwall block. Sediment shed from the same footwall block may have formed previously recognized early Miocene deltas. From 14–13 Ma, the older depression filled with sediments herein assigned to the provisionally named Laberinto, Pampa, and Naranja members of the Pisco Formation, the latter member being characterized by marine delta foreset beds. The three members are at least partly correlative with the Pisco-0 sequence of the Pisco Formation. The younger depression was overrun at 10 Ma by debris flows of lithoclastic and granitic cobbles and boulders, then filled with diatomaceous silty sand with five-meter-sized lithoclastic olistoliths. The two lithologies constitute the provisionally named Mature Formation. Radiometric and newly revised biochronological data from throughout the EPB coupled with new diatom data from the Laberinto area have provided new insights into the correlation of sequences within the Chilcatay and Pisco formations and the interaction of local and basin-wide tectonism and global eustatic sea-level events across the basin.

ESTRATIGRAFÍA, SEDIMENTOLOGÍA Y EVOLUCIÓN TECTÓNICA DE LA CUENCA PISCO ORIENTAL, 2008

Technical Report

Full-text available

Apr 2021

La presente publicación es el resultado de los trabajos de investigación (Proyecto: Estratigrafía, Sedimentología y Evolución Tectónica de las Cuencas de Antearco de la Costa Central del Perú) realizados en la cuenca de antearco denominada Pisco Oriental, y han permitido aumentar el conocimiento de la geología de esta cuenca de extensión ubicada en la margen central peruana. El presente estudio de la Cuenca Pisco Oriental contiene abundante información del Cenozoico marino (estratigráfía, sedimentología y evolución tectónica); obtenida de los estudios de campo, medición de secciones estratigráficas y sedimentológicas, cartografiado geológico, construcción de secciones estructurales y estudios de micropaleontología. La estratigrafía del Pre - Cenozoico se describe en forma sintetizada porque no ha sido objetivo el estudiarla en detalle. Así mismo, solo se presenta una síntesis del marco tectónico del margen peruana.

An investigation of vermetid reefs from the Miocene of Peru, with the description of a new species

Article

Feb 2021
J S AM EARTH SCI

Exquisitely preserved fossils of a new reef-building vermetid species from shallow-marine lower Miocene (Burdigalian) deposits of the Chilcatay Formation and upper Miocene (Tortonian) sediments of the Pisco Formation of Peru are here reported and described in detail for the first time. These finds are assigned to the living genus Thylacodes and recognized as representatives of a new species, Thylacodes devriesi sp. nov. This new taxon is known by long, almost straight tube-like shells that display peculiar ornamentations in form of striated lamellae and are arranged in an organ-pipe fashion. This discovery represents an important addition to the knowledge of the systematics and distribution of Thylacodes in South America in the geological past. Paleoenvironmental and taphonomic inferences drawn by the fossil remains of this reef-forming species are herein discussed for both the Chilcatay and Pisco formations in the broader framework of the South American fossil record of Vermetidae.

First report on the cirratulid (Annelida, Polychaeta) reefs from the Miocene Chilcatay and Pisco Formations (East Pisco Basin, Peru)

Article

Apr 2021
J S AM EARTH SCI

Tube-dwelling cirratulids from the Miocene Chilcatay and Pisco Formations of southern Peru are described herein for the first time. These worms constitute tube aggregates cropping out in Burdigalian and Tortonian strata of the East Pisco Basin. These specimens are here referred to the extinct species Diplochaetetes mexicanus Wilson, 1986, which was so far known from the Oligocene and lower Miocene of the Pacific Mexico. The new finds represent the first described fossil record of cirratulids from South America. Different morphologies of the tube aggregates are described, as well as their internal framework and the tube wall features. The palaeoecological and palaeobiogeographical implications of these Miocene cirratulid reefs are then discussed.

Diverse types of bone preservation from the Pisco-Sacaco Fossil-Lagerstätte (Miocene, Peru)

Conference Paper

Nov 2020

Fossil bone can persist over geological times passing through significant textural, mineralogical, and chemical changes starting from the early stages of burial and continuing for long time. In the case of marine vertebrates, various processes and factors affect the bones during the early post-mortem history. The investigation of bone characteristics can provide significant information about the fossilization processes and allow for palaeontological and palaeoecological reconstructions. In Southern Peru, the marine vertebrate Pisco-Sacaco Fossil-Lagerstätte exhibits a high diversity of bone preservation styles, revealed by different macroscopic, mineralogical and compositional characteristics. Six types of bones have been recognized based on color and hardness, but the complete spectrum exists between these categories. The six groups differ for bone microstructure, mineralization degree, cavity fillings, microcracks permeation, Fe-oxides distribution, and major and trace element composition. During the early diagenetic stages, two main mineral formation mechanisms appear to have controlled the preservation of the bone tissue: the apatite dissolution-recrystallization, and the dolomite precipitation (formation of carbonate concretions). More generally, bone characteristics allow for recognizing the processes variably contributing to the fossilization path, from burial at the seafloor to exposure i n the present-day desert environment.

Ghosts of the Holobiont: Borings on a Miocene Turtle Carapace from the Pisco Formation (Peru) as Witnesses of Ancient Symbiosis

Article

Full-text available

Dec 2022

In spite of the widespread occurrence of epibiotic turtle barnacles (Coronuloidea: Chelonibiidae and Platylepadidae) on extant marine turtles (Chelonioidea: Cheloniidae and Dermochelyidae), and although the association between these cirripedes and their chelonian hosts has existed for more than 30 million years, only a few studies have investigated the deep past of this iconic symbiotic relationship on palaeontological grounds. We describe probable platylepadid attachment scars in the form of hemispherical/hemiellipsoidal borings on an Upper Miocene (Tortonian) fragmentary turtle carapace, identified herein as belonging to Cheloniidae, from the Pisco Lagerstätte (East Pisco Basin, southern Peru). When coupled with the available molecular data, this and other similar ichnofossils allow for hypothesising that platylepadid symbionts were hosted by sea turtles as early as in early Oligocene times and became relatively widespread during the subsequent Miocene epoch. Chelonian fossils that preserve evidence of colonisation by platylepadid epibionts in the form of pits on the turtle shell should be regarded as fossil holobionts, i.e., palaeontological witnesses of discrete communal ecological units formed by a basibiont and the associated symbionts (including the epibiota). A greater attention to the bone modifications that may be detected on fossil turtle bones is expected to contribute significantly to the emerging field of palaeosymbiology.

Towards deciphering the Cenozoic evolution of the East Pisco Basin (southern Peru)

Article

Full-text available

May 2022
J MAPS

The Cenozoic succession of the East Pisco Basin preserves the sedimentary record of several episodes of deformation of the forearc crust along the Peruvian margin. The 1:50,000 scale geological map presented here encompasses an area of about 1,000 km2 lying astride the Ica River, and contributes to our understanding of the timing and mode of basin filling and deformation. Our novel two-fold megasequence framework provides a sound basis for establishing a first-order tectono-stratigraphic setting of the mid-Eocene–upper Miocene succession exposed in the study area. We interpret that the mid-Eocene to lower Oligocene succession studied in this work (megasequence P) was deposited in a single forearc basin, which was dissected into the present-day West and East Pisco basins by a fault-bounded basement high during the late Oligocene, and subsequently overlain by the Miocene fill of the East Pisco basin (megasequence N).

TecTONIC EvoLUTION oF THE ANDES OF ECUADOR, PERU, BOLIVIA AND NoRTHERNMOST CHILE

Preprint

Full-text available

Mar 2021

Mineralogical and geochemical characterization of fossil bones from a Miocene marine Konservat-Lagerstätte

Article

Jan 2021
J S AM EARTH SCI

Fossil bones, together with teeth, are the most common remains of vertebrates that could manage to get preserved over geological times, providing information on the diagenetic and fossilization processes that occurred in the depositional paleoenvironment. Fossil bones from the marine vertebrate Konservat-Lagerstätte in the East Pisco Basin and Sacaco area (Peru) show a high variety of different textural and chemical features, suggestive of different processes variably contributing to the fossilization path. At the macroscopic scale, bone samples can be grouped into six different categories on the basis of the color (red to gray to white) and hardness (which relates to the mineralization degree); a variety of case studies can be found between these categories. Microscopically, the original microstructure of the bone tissue, both compact and cancellous, is well preserved in all the studied samples, with differences in cavity fillings, distribution of microcracks, and presence of Fe oxides in the diverse bone types. The bone composition and mineralogy correspond to fluorapatite. Differences in color, mineralization degree and geochemistry can be interpreted in terms of different fossilization paths, from burial at the seafloor to exposure in the present-day desert environment. The fossilization paths are strongly conditioned by the factors controlling the interplay of the mechanisms of apatite dissolution-recrystallization and dolomite precipitation (formation of carbonate concretions) as well as the fixation of iron in finely disseminated sulfides in the very early stages of fossilization.

Strontium dating and the termophilic fauna of the lower Pisco Formation (Peru) suggest a Late Miocene strengthening of the Humboldt Current

Conference Paper

May 2020

We seek to elucidate the Cenozoic history of the upwelling system off Peru-Chile, which currently forms the basis for one of the most productive fisheries in the world. To pursue this aim, we investigate the outstanding record of Eocene–Pliocene sedimentation and associated marine fossils in the East Pisco Basin of southern Peru, where the lower Miocene Chilcatay Formation is overlain by the Pisco Formation, the latter containing three allomembers, each reflecting a transgressive cycle: P0, P1 and P2, in ascending stratigraphic order. The Chilcatay Formation and the overlying middle Miocene P0 allomember (based on our recent strontium isotope stratigraphy) are comprised of lithologies (sandstones and siltstones) that suggest a limited upwelling. Furthermore, a warm-water palaeoenvironment is indicated by the thermophilic fossil assemblage in these units, including mollusks (architectonicids, cypraeids, and the genus Ficus), the only coral colony known from the basin (a rhizangiid scleractinian from P0), and the extinct snaggletooth shark Hemipristis serra. The overlying P1 and P2 allomembers are late Miocene in age and are characterized by abundant diatomites that suggest high primary productivity conditions. The present-day Peruvian coastal upwelling system results from a combination of the Peru Coastal Current and the offshore Humboldt Current. A precursor of this upwelling system emerged after the K/Pg boundary, and a proto-Humboldt Current originated only in the late Eocene. The Miocene transition in the East Pisco Basin from warm-water conditions to high-productivity and cooler conditions shows that there was a strengthening of the Humboldt Current during the late Miocene.

The potential of chemical fingerprinting of tephra for stratigraphic correlations in the fossil Lagerstätte of the Pisco Formation (Peru)

Conference Paper

Apr 2017

The upper Miocene Pisco Formation (Peru) represents a world-known fossil Lagerstätte containing abundant and exceptionally well-preserved marine vertebrates. A detailed chronostratigraphic reconstruction is indispensable to study this fossil record and to understand the evolution of marine vertebrates. Recent work (Bianucci et al., 2016; Di Celma et al., 2016; Gariboldi et al., in press) in the area of the western Ica River Valley defined a detailed chronostratigraphic framework for the Pisco Formation, containing all the fossil vertebrates observed in the area. Such chronostratigraphic framework, based on new 40Ar/39Ar ages on biotite from tephra layers integrated with diatom biostratigraphy, implements previous scattered radiometric data (Brand et al., 2011; Esperante et al., 2015). Tephra layers representing primary air-fall deposition of volcanic ash from the Peruvian Andes volcanoes are very frequent in the Pisco Formation. Several of them do not show evidence of reworking or bioturbation. Due to their regional dispersal and to their geologically instantaneous deposition (Lowe, 2011), they provide the opportunity not only to date specific layers, when suitable for radiometric age determination, but also to correlate different localities, through the chemical fingerprinting of tephra. We collected more than 200 tephra layers from different localities in the Ica Desert along six measured stratigraphic sections. Based on the estimated stratigraphic position, we analyzed specific tephra layers through petrographic characterization, glass shard morphology, electron probe microanalyses of glass shards and, where present, biotite crystals. Despite some difficulties encountered, such as similar magma or mineral composition, local weathering, lack of record due to marine current transport and change in depositional environments among different localities, the correspondence of the obtained data allowed to verify correlations that were supposed during field work and to trace tephra layers from distant outcrop localities, allowing to refine the chronostratigraphy of the Pisco Formation in the western Ica River Valley. Bianucci G. et al (2016) Journal of Maps, 12: 1037–1046. Brand L.R. et al (2011) J. South Am. Earth Sci., 31: 414–425. Di Celma C. et al (2016) Journal of Maps, 12: 1020-1028. Esperante R. et al. (2015) Palaeogeography, Palaeoclimatology, Palaeoecology, 417: 337–370. Gariboldi K. et al (in press) Newsletters on Stratigraphy. Lowe D.J. (2011) Quaternary Geochronology, 6: 107-153.

Strontium Isotope Stratigraphy and the thermophilic fossil fauna from the middle Miocene of the East Pisco Basin (Peru)

Article

Jan 2020
J S AM EARTH SCI

New age estimates obtained via Strontium Isotope (87 Sr/ 86 Sr) Stratigraphy and new paleoclimatic data are here presented for the Miocene Chilcatay and Pisco formations exposed in the East Pisco Basin, an Andean forearc basin of southern Peru, which is renowned worldwide for its exceptional content of fossil marine vertebrates. Mol-lusk and barnacle shells, carbonate nodules, and shark teeth were collected along three stratigraphic sections for applying Strontium Isotope Stratigraphy on both carbonates and phosphates. To avoid diagenetic biases, mollusk and barnacle shells were analyzed in detail by means of optical and scanning electron microscopy, cathodolumi-nescence, and inductively coupled plasma-optical emission spectrometry, whereas only the enameloid from the best-preserved shark teeth was sampled. The obtained 87 Sr/ 86 Sr ages confirm a late early Miocene (Burdigalian) age for the Chilcatay strata, and reveal middle Miocene (Langhian to Serravallian) ages for the lower Pisco unit (i.e., the P0 sequence)-a result that matches the relatively archaic aspect of its cetacean fossil assemblage. New and literature data about the fossil assemblage of the lower Pisco beds highlight the presence of several ther-mophilic invertebrates and vertebrates, thus suggesting a warm-water, tropical paleoenvironment for this middle Miocene sequence. Such a paleoenvironmental scenario recalls the warm conditions associated with the Chilcatay Formation, rather than the cooler setting inferred for the remainder of the Pisco Formation (i.e., the P1 and P2 sequences). This pattern likely reflects the late Miocene trend of global cooling, as well as a middle to early late Miocene strengthening of the Humboldt Current.

Biostratigraphic, evolutionary, and paleoenvironmental significance of the southernmost lepidocyclinids of the Pacific coast of South America (East Pisco Basin, southern Peru)

Article

Oct 2019
J S AM EARTH SCI

Lepidocyclinids are one of the most common group of Cenozoic large benthic foraminifera and, thanks to their clear evolutionary patterns, they are extensively used in biostratigraphy. They originated during the Eocene in the American region and then spread eastward, reaching a worldwide distribution in the Oligocene. This paper investigates the southernmost population of lepidocyclinids ever found along the Pacific coast of South America, located in the lower part of the Paracas Formation (Los Choros Member) of the East Pisco Basin of Peru. The examined Los Choros strata are composed of mixed siliciclastic-bioclastic coarse-grained deposits. The skeletal assemblage is dominated by large benthic foraminifera and mollusks with subordinate echinoids and barnacles, suggesting a deposition in a shallow, tropical, shelf environment with a moderate nutrient supply. The large benthic foraminiferal assemblage is largely dominated by Lepidocyclina rdouvillei. This species is extremely primitive, exhibiting ancestral characters such as a straight wall separating the protoconch and deuteroconch, very large principal auxiliary chambers and a poorly organized equatorial plane. The presence of common and primitive L. rdouvillei, supported by the associated occurrence of Polylepidina, suggests an age comprised between 43.6 Ma and 40.5 Ma for the Los Choros Member in the study area. This range is confirmed by nannofossil assemblages that indicate an age between 42.37 Ma and 40.34 Ma for the base of the overlying Yumaque Member of the Paracas Formation. These results highlight the potential of lepidocyclinids for biostratigraphy and paleoenvironmental reconstructions in South America.

Tephra fingerprinting and tephrostratigraphy in the Miocene Pisco Formation (Peru)

Conference Paper

Jul 2019

Tephra fingerprinting is a unique tool for reconstructing a high resolution stratigraphy (Lowe, 2011; Smith et al., 2011). In the upper Miocene succession of the Pisco Formation (East Pisco Basin, Peru) the presence of distal volcanic ashes from the Central Andes represents a great opportunity for dating and correlating stratigraphic sections at distant localities. The importance of a detailed chronostratigraphic reconstruction is given by to the paleontological significance of this formation, which hosts a globally renowned marine vertebrate Fossil-Lagerstätte (Lambert et al., 2010; Bianucci et al., 2016). For reaching this goal, 39Ar–40Ar dating and tephra fingerprinting were applied on ash layers. Regarding to 39Ar–40Ar dating, an essential part of our work were electron microprobe tests of stoichiometry and monomodality, so as to only date unaltered, homogeneous tephra. Despite the similar glass composition and mineral assemblage, together with the shallow marine depositional environment limiting tephra preservation, correlations between distant localities can be realized by fingerprinting tephra layers on the basis of petrographic and compositional investigations, grain-size analyses, and glass shard morphology. Major element composition of biotite proved to be a valuable tool for discriminating ash layers and correlating different stratigraphic sections located several kilometers apart from each other. This study, in part published this year on the Journal of the Geological Society (Bosio et al., 2019), highlights the applicability of tephra fingerprinting in tephra archives as old as the Miocene as well as in unfavorable shallow marine environments, and allows a great increase of the chronostratigraphic detail.

Strontium Isotope Stratigraphy of Miocene sedimentary successions in the Peruvian East Pisco Basin

Conference Paper

Jul 2019

The 87Sr/86Sr ratio of oceanic seawater has varied through geological time and can be used to date marine minerals and correlate stratigraphic sections of marine deposits (McArthur et al., 2012). The Miocene Chilcatay and Pisco formations exposed in the East Pisco Basin (southern Peru) are well-known for their exceptional content of fossil marine vertebrates, but also contain a rich fossil invertebrate fauna. A chronostratigraphic reconstruction based on 39Ar ̶ 40Ar dating and biostratigraphy was recently pursued (Di Celma et al., 2017), but the age of the lowest allomember of the Pisco Formation, P0, remains unresolved. For dating P0, mollusks (i.e. ostreids and pectinids), barnacle shells, and shark teeth were collected for applying the Sr-isotope stratigraphy on carbonates and phosphates. Their preservation was studied with petrographic, morphological, chemical and cathodoluminescence analyses since diagenetic processes and weathering can alter the original 87Sr/86Sr of the shell (Ullmann & Korte, 2015). The samples thus selected include oysters and pectinids showing a well-preserved microstructure of the shell together with a homogeneous and low luminescence, the least porous and best-preserved part of barnacles, i.e. the sheat, and the least permeable tissue of shark teeth, i.e. the enameloid layer. Sr-isotopic results, made at the Ruhr-Universität of Bochum and elaborated with the LOWESS Table 5 made for the GTS2012 timescale (McArthur et al., 2012), gave Burdigalian ages for the Chilcatay Formation and Langhian to Serravallian ages for the P0 allomember. The obtained ages for the Chilcatay Formation perfectly agree with previous 39Ar–40Ar and biostratigraphic results, confirming the feasibility of the method in this succession. New middle Miocene ages for the P0 allomember agree with the age estimated by DeVries & Jud (2018) for the lowest Pisco Formation and with the archaic aspect of the cetacean assemblage (Di Celma et al. 2017; Marx et al., 2017).

A new Late Miocene beaked whale (Cetacea, Odontoceti) from the Pisco Formation, and a revised age for the fossil Ziphiidae of Peru

Article

Full-text available

May 2024

The previously scarce fossil record of Ziphiidae (beaked whales) has greatly increased recently thanks to the serendipitous discovery of high specimen concentrations along deep seafloors as well as to abundant inland finds from the Upper Miocene of the Pisco Formation (East Pisco Basin, Peru). In the latter unit, ziphiid remains are indeed among the most prevalent of the whole cetacean assemblage, being represented by four distinct genera and species plus at least two as-yet unnamed taxa. Here, we describe a fifth ziphiid genus and species from the Pisco strata, Mamaziphius reyesi n. gen. n. sp., based on a partial cranium from mid-Tortonian (lower Upper Miocene, 9.1-9.0 Ma) strata exposed at the locality of Cerros la Mama y la Hija. Though reminiscent of the extant genus Berardius, the holotype skull lacks two diagnostic characters of Berardiinae, namely, an isolated rounded protuberance formed by the interparietal or frontals on the posterior part of the vertex, and a posterior transverse narrowing of the nasals and frontals at the vertex. Our phylogenetic analysis reveals that Mamaziphius n. gen. is nested within the crown ziphiids, as sister group of the berardiines. In addition, we introduce two new clade names within Ziphiidae, namely, Messapicetiformes (for the so-called "Messapicetus clade") and Vomeroziphii (for Ziphiinae + Hyperoodontinae and closely related forms). Another fragmentary specimen from the Pisco Formation is also briefly described herein. Furthermore, a comprehensive reappraisal of the geological age of the fossil beaked whales of Peru is provided based on new age calibrations, thus restricting the whole rich Peruvian record of this family (including the earliest-branching ziphiid, Ninoziphius platyrostris, which comes from Pisco-equivalent strata of the Sacaco area) to a Tortonian-Messinian interval younger than 9.10 Ma. No other inland unit worldwide preserves a record of fossil ziphiids as abundant, diverse and chronostratigraphically well-constrained as the Pisco Formation. In view of this, the absence of Vomeroziphii from the fossil content of the Pisco strata remains quite enigmatic.

Evaluación de las condiciones paleoceanográficas desde el Mioceno tardío hasta el Pleistoceno temprano en la Cuenca Pisco, Perú

Thesis

Full-text available

Sep 2023

Renzo Gonzales

The Humboldt Current System (HCS) presents particular oceanographic conditions that make it the most productive ecosystem in the world. The origins of these conditions, however, are still unknown. Marine sediments indicate much warmer conditions in the eastern tropical Pacific during the Miocene and Pliocene, which lead to the Hypothesis of permanent El-Niño-like conditions. The modern East-West temperature gradient of the Pacific may have progressively grown with glacial conditions during the Early Pleistocene. How environmental conditions have evolved on the coast of Peru remain unclear. In the Miocene, the Andes were not as high as today, and a shallow epicontinental sea, protected from the open ocean by a mountain ridge, was present along the southern coast. This sedimentary basin, known today as the Pisco formation, has yielded one of the most extraordinary fossil record of marine vertebrate evolution. In this study, we collected fossil shells and shark teeth from the East Pisco Basin (EPB) from different sedimentary deposits from Late Miocene to Pleistocene, the ages of these deposits were determined by radiogenic dating and strontium isotopic stratigraphy. We compared the strontium isotopic signature between fossil shark teeth, which are indicators of open ocean oceanographic conditions, and mollusks as indicators of coastal conditions. Results shows for different ages an important connectivity between EPB and the oceanic waters, despite the barrier that the Coastal Cordillera could represent. However, for the Sacaco Chacra locality (Late Miocene) a considerable restriction did not allow complete mixing between the EPB and oceanic waters. Results shows for this locality a continental waters contribution would reach up to (~45%), affecting considerably the salinity of EPB. We analyzed the sclerochronology and the monthly variation δ18O and δ13C at high resolution in 19 shells for three ages. Mean δ18O indicate a cooling of the oceanic waters from Late Miocene to Pleistocene. High-resolution evaluation of δ18O and δ13C for Late Miocene (Sacaco Chacra locality) in 15 Anadara chilensis fossil shells would indicate El Niño events, with 2.9 years of frequency. Additionally, these El Niño events would cause flooding events in the EPB, showing that Peruvian south coast was not hyperarid for this time as it is currently known. My results represent the oldest direct record of El Niño activity.

Double-phased controlled and influenced biomineralization in marine invertebrates: The example of Miocene to recent reef-building polychaete cirratulids from southern Peru

Article

Apr 2024
PALAEOGEOGR PALAEOCL

Cretaceous nannostratigraphy of the Kopet Dagh Mountain Range (northeast Iran)

Conference Paper

Full-text available

Mar 2015

The Kopet-Dagh Mountain Range, which stretches nearly 650 km in a WNW-ESE direction east of the Caspian Sea from the former Soviet Union through Iran and into Afghanistan, is composed of a succession of gently folded rock. The base of this succession is only exposed in the eastern part of this mountain range in Iranian territory. The most complete Cretaceous sedimentary succession in eastern Iran is found in the Kopet Dagh Mountain Range and is comprised of marine shales, marls, and limestones and a subordinate amount of sandstone. This sequence appears to represent all major stages of the Cretaceous (Stocklin, 1968). These deposits are exposed throughout most of the Kopet Dagh Range with few exceptions. For the first time, calcareous nannofossils were used to determine the age of these sedimentary beds. The distri- bution and relative abundances of Cretaceous calcareous nannofossil taxa were recorded from the lower and upper boundaries of all formations (e.g., Mozduran, Shurijeh, Sarcheshmeh, Sanganeh, Aitamir, Abderaz, Abtalkh, Nizar, and Kalat) in both the eastern and western part of the Kopet Dagh. For this study, samples were collected about 5 m above and below the lithological boundaries of the forma- tions in 4-6 sections (Lower-Upper Cretaceous). These samples were prepared with a smear slide technique and photographed with a light microscope. Based on nanno- plankton biostratigraphic results, a correlation chart for the Cretaceous sediments of Kopet Dagh range was made. Results show that the ages of the studied formations were almost the same from east to west, except for the Aitamir- Abderaz, Abderaz-Abtalkh, Abtalkh-Nizar, and Nizar- Kalat formational boundaries in the west. The Abtalkh and Nizar Formations are absent in the west, as evidenced by the absence of Zones CC21-CC25. A discontinuous sedimentary pattern between the Abderaz and Kalat Formations is suggested. The vari- ability of species abundances in the studied section is likely related to paleoenvironmental conditions. Quan- titative studies of species suggest that the Cretaceous formations were deposited in a shallow-marine basin that increased in depth from east to west. The results match studies from adjacent areas.

Burial in the western Central Andes through Oligocene to Miocene ignimbrite flare‐ups recorded by low‐temperature thermochronology in the Cañete Canyon, Peru

Article

Full-text available

Jun 2023

Thermochronological data are essential to constrain thermal and exhumation histories in active mountain ranges. In the Central Andes, bedrock outcrops are rare, being blanketed by widespread late Palaeogene–Neogene and younger volcanic formations. For this reason, the exhumation history of the Western Cordillera (WC) in the Peruvian Andes has only been investigated locally along the mountain range. Dense thermochronological data are only available in canyons of the Arequipa (16° S) and Cordillera Negra regions (10° S). We present new apatite (U-Th)/He and fission-track data from the 1 km deep Cañete Canyon (13° S), where the Oligo-Miocene deposits are preserved lying conformably on an Eocene palaeo-topographic surface. Thermal modelling of thermochronological data indicate that the 30–20 Ma ignimbrite deposits overlying the bedrock were thick enough to cause burial reheating. We demonstrate that burial associated with thick volcanic formations should be taken into account when interpreting thermochronological data from the WC or in similar volcanic-arc settings.

A puzzling occurrence of the bite mark ichnogenus Linichnus from the Lower Miocene Chilcatay Formation of Peru

Article

May 2023
Neues Jahrbuch Geol Palaontol Abhand

An upper anterior tooth of Cosmopolitodus hastalis (Elasmobranchii: Lamnidae) from Burdigalian strata of the shallow-marine Chilcatay Formation exposed at Zamaca (East Pisco Basin, Peru) exhibits the remarkable occurrence of a serrated bite mark consistent with Linichnus serratus (Praedichnia: Machichnidae). In marine successions of Cenozoic age, traces belonging to the ich-nogenus Linichnus are typically found occurring on the bones of marine mammals and interpreted as due to predation or scavenging by sharks provided with smooth-edged (Linichnus bromleyi) or denticulated (L. serratus) teeth. Only a few fossil shark teeth exist preserving serrated bite marks, all of which have been interpreted as due to self-biting, which may occur when a shark loses a tooth while feeding and accidentally bites into it. Since C. hastalis is a smooth-toothed species, self-biting cannot explain our unusual find of L. serratus, which in turn may either reflect some kind of trophic interaction between large carnivorous sharks (with a late juvenile or young adult C. hastalis being fed upon by another elasmobranch, possibly a large-sized carcharhinid) or testify to accidental biting during multispecies shark scavenging on the carcass of a third organism that did not get preserved alongside the bitten tooth.

Ultrastructure, composition, and 87Sr/86Sr dating of shark teeth from early Miocene sediments of southwestern Peru

Conference Paper

Jun 2021

As other marine minerals, phosphates - and in particular bioapatite - incorporate Sr from seawater during formation (Staudigel et al., 1985). Due to long-term variations in the relative abundance of Sr isotopes in the global ocean, 87Sr/86Sr values can be measured in minerals and compared to calibration curves for obtaining age estimates via Strontium Isotope Stratigraphy (SIS) (McArthur et al., 2020). Although hydroxyapatite is susceptible to alteration and Sr concentration in fish teeth can change during burial and diagenesis (Martin & Scher, 2004), fossil shark teeth have been successfully used for Sr-dating, especially when enameloid is analyzed (Schmitz et al., 1997; Harrell et al., 2016). In order to test the feasibility of this method in the fish tooth-rich marine sediments of the East Pisco Basin (Peru), and aiming to date some poorly-constrained strata of this region, we analyzed the ultrastructure and composition of fossil shark teeth from the Chilcatay Formation. This Miocene formation consists of massive sandstones and basement boulders overlain by bioclastic sandstones and diatomaceous and tuffaceous siltstones (Di Celma et al., 2019). It is characterized by an abundant marine vertebrate assemblage, among which elasmobranchs are present (Landini et al., 2019). Teeth of Isurus sp., Cosmopolitodus hastalis, Isurus oxyrinchus, Megalolamna paradoxodon and Physogaleus contortus were collected from Chilcatay beds at the localities of Zamaca, Media Luna and near Cerro Colorado. Teeth were investigated through an optical microscopy and SEM. After taphonomic observations, 11 teeth underwent ICP-OES and 87Sr/86Sr analyses. Shark teeth show a compact and non-porous outer enameloid layer that is distinctly separated from the more porous and heterogeneous inner core of dentine. Ultrastructure analysis shows that the enameloid is formed by highly-ordered bundles of fluoroapatite crystallites, which are often well-preserved, whereas the dentine displays a bone-like structure showing tubuli and crystalline artefacts from diagenesis (Lübke et al., 2015). SEM-EDS mapping shows differences in distribution of Ca, P, F, and S in the enameloid and dentine, and the shiny layer is compositionally recognizable (Enax et al., 2014). ICP-OES data show Sr contents that are comparable to those of recent lamniform teeth. 87Sr/86Sr results compared to the LOESS 6 calibrated on GTS2020 (McArthur et al., 2020) give ages between 19 and 18 Ma for the Chilcatay strata at the Ica Valley localities, in agreement with radioisotopic and biostratigraphic ages (Bosio et al., 2020). At Media Luna, a locality 25 km to the west of the Rio Ica, the Chilcatay strata have here been dated for the first time, resulting in a slightly older age ranging between 22 and 20 Ma. Not least, these results strengthen the notion that the Sr-ratio of shark teeth can be successfully used for obtaining reliable age estimates through SIS.

4 MA UPLIFT CYCLES OF THE SOUTHERN PERUVIAN FOREARC SINCE THE LATE MIOCENE

Conference Paper

Full-text available

Jan 2022

We explore coastal morphology along a 500 km long uplifted coastal segment in the central Andes, between the cities of Chala (Peru) and Arica (Chile). We use accurate DEM and field studies to extract uplifted shoreline sequences along the study area. In addition, we consider continental pediment surfaces that constrain both the geographic and vertical extent of marine landforms. We establish a chronology based on published dates for marine landforms and pediment surfaces. We extend this corpus with new 10Be data on uplifted shoreline platforms. We find that the last 12 Ma is marked by three periods of coastal stability or subsidence dated at ~12-11 Ma, ~8-7 Ma, and ~5-2.5 Ma. Uplift that accumulated between these periods of stability has been ~1000 m since 11 Ma; its rate is up to 0.25 mm/a (m/ka). For the last period of uplift only, during the last 800 ka, the forearc uplift has been accurately recorded by the cutting of numerous coastal sequences. Within these sequences, we correlated marine terraces with high sea levels (interglacial stages and substages) up to MIS 19 (790 ka), i.e., with a resolution of ~100 ka. The uplift rate for this latter uplift period increases westward from 0.18 mm/a at the Peru-Chile border to ~0.25 mm/a in the center of the study area. It further increases northwestward to 0.45 mm/a due to the influence of the Nazca Ridge. In this study, we document unusual cyclic forearc uplift with cycles of ~4 Ma in duration. This periodicity is consistent with predictions made by Menant et al. (2020) based on numerical models, and may be related to episodic tectonic uplift (subduction slab detachment) beneath the coastal forearc zone.

Ultrastructure, composition, and 87Sr/86Sr dating of shark teeth from lower Miocene sediments of southwestern Peru

Article

Jul 2022
J S AM EARTH SCI

Bioapatite of fossil bone and teeth is susceptible to alteration and ion exchange during burial and diagenesis, varying its Sr content through the geological time. Nevertheless, fossil shark teeth are a powerful proxy for both chronostratigraphic and paleoecological reconstructions, thanks to the presence of the enameloid, a hard outer layer consisting of resistant fluorapatite crystallites. Here, we analyze fossil shark teeth from the Miocene sediments of the Chilcatay Formation of the Pisco Basin (southwestern Peru) with the aim of dating poorly constrained strata in this region. (Ultra)structural and compositional analyses of fossil lamniform and carcharhiniform teeth are performed through macroscopical observations, optical microscopy and SEM-EDS for evaluating the preservation state of the collected teeth. Shark teeth display a compact and well preserved outer enameloid layer formed by highly ordered bundles of crystallites that is distinctly separated by a more porous and heterogeneous inner core of dentine featuring diagenetic artefacts and microborings. Compositional mapping highlights differences in the distribution of Ca, P, F, and S in the enameloid and dentine, and chemical results show a Sr content that is consistent with the range reported for extant shark teeth. The best preserved teeth were selected for Strontium Isotope Stratigraphy (SIS), measuring the 87Sr/86Sr values in the enameloid and obtaining numerical (absolute) age estimates. In the Ica River Valley, SIS dates the Chilcatay strata to the Burdigalian (between 19.1 and 18.1 Ma), in agreement with previous radiometric, isotopic and biostratigraphic ages obtained in the same region. At Media Luna, the Chilcatay strata are dated herein for the first time, resulting in a slightly older age of 21.8–20.1 Ma (late Aquitanian–early Burdigalian). These results strengthen the notion that the Sr-ratio of shark teeth can be successfully applied for obtaining reliable age estimates via SIS.

Late Miocene -Quaternary forearc uplift in southern Peru: new insights from 10Be dates and rocky coastal sequences

Article

Full-text available

Feb 2021
J S AM EARTH SCI

We explore the coastal morphology along an uplifting 500 km-long coastal segment of the Central Andes, between the cities of Chala (Peru) and Arica (Chile). We use accurate DEM and field surveys to extract 20 sequences of uplifted shorelines along the study area. In addition, we consider continental pediment surfaces that limit both the geographical and vertical extent of the marine landforms. We establish a chronology based on published dates for marine landforms and pediment surfaces. We expand this corpus with new 10 Be data on uplifted shore platforms. The last 12 Ma are marked by three periods of coastal stability or subsidence dated ~12-11 Ma, ~8-7 Ma and ~5-2.5 Ma ago. The uplift that accumulated between 25 these stability periods has been ~1000 m since 11 Ma; its rate can reach 0.25 mm/a (m/ka). For the last period of uplift only, during the last 800 ka, the forearc uplift has been accurately recorded by the carving of numerous coastal sequences. Within these sequences, we correlated the marine terraces with the sea level highstands (interglacial stages and sub-stages) up to MIS 19 (790 ka), i.e., with a resolution of ~100 ka. The uplift rate for this last period of uplift increases westward from 0.18 mm/a at the Peru-Chile border to 30 ~0.25 mm/a in the center of the study area. It further increases northwestward, up to 0.45 mm/a, due to the influence of the Nazca Ridge. In this study, we document an unusual forearc cyclic uplift with ~4 Ma-long cycles. This periodicity corresponds to the predictions made by Menant et al. (2020) based on numerical models, and could be related to episodic tectonic underplating (subducting slab stripping) beneath the coastal forearc area.

Distribution and paleoenvironmental framework of middle Miocene marine vertebrates along the western side of the lower Ica Valley (East Pisco Basin, Peru)

Article

Full-text available

Jan 2021
J MAPS

We report 130 vertebrate fossils preserved as bony elements and the co-occurring assemblage of fish teeth and spines from the lower strata of the Pisco Formation exposed along the western side of the lower Ica Valley (East Pisco Basin, Peru). Geological mapping at 1:10,000 scale reveals that all these fossils originate from the Langhian–Serravallian P0 allomember. In the study area, P0 is up to ∼40 m thick and features a sandy lower portion, reflecting shoreface deposition, that fines upwards into a package of offshore silts. Marine vertebrates only occur in the lower sandy layers and include whales, dolphins, reptiles, birds, and bony and cartilaginous fishes. The reconstructed paleoenvironment is consistent with a warm-water, marginalmarine setting with a strong connection to the open ocean. This work helps to elucidate the rich yet still poorly understood middle Miocene portions of the Pisco Formation, and highlights the need to conserve this outstanding Fossil-Lagerstätte.

First Toothless Platanistoid from the Early Miocene of Patagonia: the Golden Age of Diversification of the Odontoceti

Article

Full-text available

Jun 2021
J Mamm Evol

Lower Miocene outcrops from Patagonia (Gaiman Formation, Burdigalian) may reveal more clues for the yet unknown aspects for this period in the evolution of odontocetes. Here, we present the first toothless platanistoid dolphin from the lower Miocene of Patagonia, Dolgopolis kinchikafiforo, gen. et sp. nov. The specimen includes an incomplete skull, with no mandibles or earbones, but sufficiently different from other named odontocetes to propose a new genus and species. Phylogenetic analyses indicate it is a platanistoid of uncertain position within the group, and that it shares some homoplastic characters with physeteroids and ziphioids. Given the absence of defined alveoli and teeth and an inferred moderately short and wide rostrum, we interpreted this new species as most likely a capture suction feeder. Based on our phylogenetic hypothesis, the optimization of feeding strategies recovered raptorial feeding as the plesiomorphic method, and convergent evolution of capture suction feeders in at least four lineages. Platanistoids recorded all feeding strategies during the late Oligocene-early Miocene, although raptorial is the predominant method. This suggests a partitioning of the ecological niches in the early phases of platanistoid evolution, as well as a high diversification of feeding methods previously underestimated for this period. Thus, ecological adaptations have a strong evolutionary pressure in odontocete communities and should be further explored.

Earliest Miocene calcareous nannofossil biostratigraphy from the low-latitude Pisco Basin (Peru)

Article

Jun 2019

Arquitectura estratigráfica, paleogeografía y proveniencia sedimentaria de las rocas cenozoicas del sur de Perú (Tacna, 18° S)

Article

Full-text available

May 2020

The Cenozoic rocks lying in the Province of Tacna (18° S), southern Perú, represent approximately 600 m of stratigraphic thickness. This stacking groups the Sotillo (Paleocene), Moquegua Inferior (Eocene), Moquegua Superior (Oligocene), Huaylillas (Miocene) and Millo formations (Pliocene), and these are the sedimentary fill of the Moquegua Basin. The sediments of the three latter formations are organized into nine sedimentary facies and five architectural elements. Their facies associations suggest the existence of an ancient highly channelized multi-lateral fluvial braided system, with upward increase of pyroclastic and conglomeratic depositions. The heavy mineral spectra make each lithostratigraphic unit unique and distinguishable, being the sediments of the Moquegua Superior Formation rich in garnets, titanites and zircons; while the sediments of the Huaylillas and Millo formations in clinopyroxenes. This mineral arrangement becomes an excellent tool for stratigraphic correlations between outcrops and subsurface stratigraphy (by means of well cores studies) and allow to sketch out a new stratigraphic framework and a complex of rocky blocks bounded by normal faults, often tilted. The sediment mineralogy also suggests that the rocks conforming the Western Cordillera were the main source of sediments for the Moquegua Basin in Tacna. In this context, the detritus of the Moquegua Superior Formation derives mainly from the erosion of the rocks forming the Coastal Basal Complex (Proterozoic), the Ambo Group (Carboniferous) and the Junerata/Chocolate Formation (Early Jurassic). The Huaylillas Formation is a pyroclastic and sedimentary unit which components derived mainly from the Huaylillas volcanism (Miocene) and partly from the denudation of the Toquepala Group (Late Cretaceous). The Huaylillas Formation widely contrasts to the underlying Moquegua Superior Formation due its mineralogy and facies. Finally, the detritus of the Millo Formation derived mostly from the rocks forming the Barroso Formation (Pliocene), and their facies represent a higher contrast in relation to the underlying units due its notorious conglomerate facies.

Scaphokogia totajpe, sp. nov., a new bulky-faced pygmy sperm whale (Kogiidae) from the late Miocene of Peru

Article

Apr 2020

The modern pygmy and dwarf sperm whales (Physeteroidea, Kogiidae) are remnants of a highly diverse group, which flourished in the Miocene oceans. Unlike their modern suction-feeding, deep-diving relatives, the past diversity of this family includes animals with disparate ecological habits. Here, we describe Scaphokogia totajpe, sp. nov., a new species of kogiid based on a well-preserved skull from the upper Miocene strata of the Pisco Formation, Peru. A phylogenetic analysis places S. totajpe as sister taxon of S. cochlearis and divides Kogiidae into two clades: the first including both species of Scaphokogia and the second including Kogia, Koristocetus, Praekogia, and Nanokogia. Similar to S. cochlearis, S. totajpe has a tubular rostrum with a hypertrophied mesorostral canal, a large supracranial basin, and a leftward deviated facial sagittal crest, but it differs by possessing a proportionately shorter rostrum, a reduced projection of the lacrimojugal between the frontal and the maxilla, and a flat occipital shield. The cranial morphology of Scaphokogia indicates that the extent of the nasal complex was greater than in modern kogiids. Furthermore, the overall rostrum shape and the reconstructed muscle insertion sites indicate that Scaphokogia retained some plesiomorphic features related to a more generalist ecology. Inclusion of S. totajpe into the context of the Pisco Formation indicates that during the late Miocene, the Peruvian coastal system was a hot spot for the diversification of physeteroids, with at least four species coexisting. Finally, Scaphokogia totajpe highlights a late Miocene diversity peak for sperm whales in the global oceans, before the Pliocene odontocete turnover.

Earliest Miocene calcareous nannofossil biostratigraphy from the low-latitude Pisco Basin (Peru)

Article

Jun 2019

Stratigraphic studies, based on lithology, diatoms, and mollusks, have suggested different chronostratigraphic placements for formations in the Pisco Basin. This study focusses on a stratigraphically important, calcareous nannofossil-bearing unit between the Chilcatay and Pisco formations. The Eocene-Pliocene Pisco Basin is located at low latitude (-14 degrees S) in a forearc basin in central coastal Peru. The objective of this study is to use nannofossil biostratigraphy to constrain the age of an interval for ongoing stratigraphic work in the region. We analyzed nannofossils from two sections located on the northern end of the Cerros Yesera de Amara trend and in Cerro Las Tres Piramides. A tuff bed above the top of the section is dated to 17.70 +/-0.24Ma based on a single Ar-Ar age from biotite. Analysis of productive samples from the two locations show rare to common calcareous nannofossil occurrence with poor to moderate preservation. Nannofossils show strong dissolution and/or overgrowth in almost all samples. Based on the first occurrence (FO) of Helicosphaera carteri in association with Cyclicargolithus abisectus, Reticulofenestra bisecta, and Triquetrorhabdulus carinatus, we suggest that the assemblage recovered represents an age of earliest Miocene, Zone NN1 (CN1b). Studies from the equatorial Pacific region indicate rare and discontinuous occurrence of Reticulofenestra bisecta (<10 micrometers) in late Oligocene and earliest Miocene (NN1), making it difficult to determine if its occurrence in the assemblage is caused either by low productivity or by reworking. The absence of Discoaster druggii might suggest that the assemblage is not younger than NN1, although Discoaster druggii tends to be rare and difficult to find even in well preserved sediments.

Tephrochronology and chronostratigraphy of the Miocene Chilcatay and Pisco formations (East Pisco Basin, Peru)

Article

Mar 2020
NEWSL STRATIGR

Strata of Chilcatay and Pisco formations exposed in the Ica Desert (East Pisco Basin, southern Peru) preserve one of the most complete and rich records of Miocene marine vertebrates of the world. Despite its exceptional importance, the chronostratigraphy of these fossil-bearing deposits has been only sporadically studied in the literature until recently. This work presents a detailed reconstruction of the chronostratigraphic framework, achieved by mapping and logging of seven sections of the Miocene Chilcatay and Pisco formations along the western side of the Ica River. The Chilcatay Formation consists of two allomembers, namely Ct1 and Ct2, bounded at the base by unconformities CE0.1 and CE0.2, respectively. Similarly, the immediately overlying Pisco Formation is divided into allomembers P0, P1, and P2, bounded at the base by unconformities PE0.0, PE0.1 and PE0.2, respectively. The new 39Ar–40Ar results presented here, combined with ages of previous work, provide precise constraints on the age of several stratigraphically referenced volcanic ash layers intercalated in the studied fossil-bearing succession, placing its vertebrate fossil fauna within a refined temporal framework and laying the solid ground for its detailed regional and global comparison. The ages of the allomembers, and thus their associated faunas, can be reliably estimated by the combination of 39Ar–40Ar dating on tephra layers with diatom biostratigraphy. In the study area, the two methods are mutually consistent and constrain the deposition of the Chilcatay Formation between 19.2 and 18.0 Ma, that of P1 between 9.5 and 8.6 Ma, and that of P2 between 8.4 and 6.7 Ma. In the absence of direct dating of the P0 allomember, which lacks both preserved tephra suitable for 39Ar–40Ar dating and microfossils, its age can be constrained to the temporal gap between the youngest age available from the underlying Chilcatay strata (18.0 Ma) and the oldest age available from the overlying P1 strata (9.5 Ma).

A new barnacle (Cirripedia: Neobalanoformes) from the early Miocene of Peru: Palaeoecological and palaeobiogeographical implications

Article

Jun 2019
Neues Jahrbuch Geol Palaontol Abhand

A new megabalanine barnacle, Austromegabalanus carrioli sp. nov., is described from lower Miocene strata of the Chilcatay Formation (East Pisco Basin, southern Peru). An assessment of the value of interlaminate figures in distinguishing species within the tribe Austromegabalanini from thin sections is provided-a useful identification tool with fossil taxa such as the austromegabalanines, which are commonly found only as fragmented shells. The paper concludes with a reassessment of the palaeobiogeography and distribution patterns of the austromegabalanines, proposing a circum-equatorial origin for this tribe.

An Amphibious Whale from the Middle Eocene of Peru Reveals Early South Pacific Dispersal of Quadrupedal Cetaceans

Article

Apr 2019
CURR BIOL

Cetaceans originated in south Asia more than 50 million years ago (mya), from a small quadrupedal artiodactyl ancestor [1-3]. Amphibious whales gradually dispersed westward along North Africa and arrived in North America before 41.2 mya [4]. However, fossil evidence on when, through which pathway, and under which locomotion abilities these early whales reached the New World is fragmentary and contentious [5-7]. Peregocetus pacificus gen. et sp. nov. is a new protocetid cetacean discovered in middle Eocene (42.6 mya) marine deposits of coastal Peru, which constitutes the first indisputable quadrupedal whale record from the Pacific Ocean and the Southern Hemisphere. Preserving the mandibles and most of the postcranial skeleton, this unique four-limbed whale bore caudal vertebrae with bifurcated and anteroposteriorly expanded transverse processes, like those of beavers and otters, suggesting a significant contribution of the tail during swimming. The fore- and hind-limb proportions roughly similar to geologically older quadrupedal whales from India and Pakistan, the pelvis being firmly attached to the sacrum, an insertion fossa for the round ligament on the femur, and the retention of small hooves with a flat anteroventral tip at fingers and toes indicate that Peregocetus was still capable of standing and even walking on land. This new record from the southeastern Pacific demonstrates that early quadrupedal whales crossed the South Atlantic and nearly attained a circum-equatorial distribution with a combination of terrestrial and aquatic locomotion abilities less than 10 million years after their origin and probably before a northward dispersal toward higher North American latitudes. VIDEO ABSTRACT.

Palaeoenvironmental analysis of the Miocene barnacle facies: Case studies from Europe and South America

Article

Full-text available

Dec 2018
GEOL CARPATH

Acorn barnacles are sessile crustaceans common in shallow-water settings, both in modern oceans and in the Miocene geological record. Barnacle-rich facies occur from polar to equatorial latitudes, generally associated with shallow-water, high-energy, hard substrates. The aim of this work is to investigate this type of facies by analysing, from the palaeontological, sedimentological and petrographical points of view, early Miocene examples from Northern Italy, Southern France and Southwestern Peru. Our results are then compared with the existing information on both modern and fossil barnacle-rich deposits. The studied facies can be divided into two groups. The first one consists of very shallow, nearshore assemblages where barnacles are associated with an abundant hard-substrate biota (e.g., barnamol). The second one includes a barnacle-coralline algae association, here named "barnalgal" (= barnacle / red algal dominated), related to a deeper setting. The same pattern occurs in the distribution of both fossil and recent barnacle facies. The majority of them are related to very shallow, high-energy, hard-substrate, a setting that represents the environmental optimum for the development of barnacle facies, but exceptions do occur. These atypical facies can be identified through a complete analysis of both the skeletal assemblage and the barnacle association, showing that barnacle palaeontology can be a powerful tool for palaeoenvironmental reconstruction.

The extinct nautiloid Aturia in the Middle Miocene of Pacific South America: new data from the Pisco Lagerstätte of Peru

Article

Apr 2023
Neues Jahrbuch Geol Palaontol Abhand

We report on an aturiid (Cephalopoda: Nautiloidea) shell from the Pisco Formation, a Neogene marine sedimentary unit of the East Pisco Basin (southern Peru) that is widely known for its rich and exquisitely preserved marine vertebrate fossil content, including an outstanding cetacean assemblage. The studied specimen was collected from Middle Miocene strata exposed in the vicinity of Cerro Submarino. It consists of an internal mould of a phragmocone and is tentatively identified herein as belonging to the widespread, long-ranging species Aturia cubaensis. This fossil represents the first occurrence of Aturia in the Middle Miocene of the Pacific margin of South America; as such, it fills a gap in the chronostratigraphic distribution of the Southeastern Pacific finds of this genus, helping to bridge the Lower and Upper Miocene segments of its regional fossil record. The rarity of Aturia in the shelfal Cenozoic deposits of the East Pisco Basin may reflect the palaeoenvironmental habits of this extinct cephalopod genus, which may have lived in the upper bathyal zone, at about 250-350 m water depth. Despite recent suggestions that some extinct and extant marine mammal eco-morphotypes (including some odontocetes) were likely predators of nautiloids, there is no indication that any member of the diverse and abundant toothed whale faunas of the Pisco Formation exploited these shelled cephalopods as a relevant food source.

Laterally-Continuous Dolomite Layers of the Miocene Pisco Formation (East Pisco Basin, Peru): A Window into Past Cyclical Changes of the Diagenetic Environment

Article

Jan 2022

Vertebrate Palaeoecology of the Pisco Formation (Miocene, Peru): Glimpses into the Ancient Humboldt Current Ecosystem

Article

Full-text available

Oct 2021

The northward-flowing Humboldt Current hosts perpetually high levels of productivity along the western coast of South America. Here, we aim to elucidate the deep-time history of this globally important ecosystem based on a detailed palaeoecological analysis of the exceptionally preserved middle–upper Miocene vertebrate assemblages of the Pisco Formation of the East Pisco Basin, southern Peru. We summarise observations on hundreds of fossil whales, dolphins, seals, seabirds, turtles, crocodiles, sharks, rays, and bony fishes to reconstruct ecological relationships in the wake of the Middle Miocene Climatic Optimum, and the marked cooling that followed it. The lowermost, middle Miocene Pisco sequence (P0) and its vertebrate assemblage testify to a warm, semi-enclosed, near-shore palaeoenvironment. During the first part of the Tortonian (P1), high productivity within a prominent upwelling system supported a diverse assemblage of mesopredators, at least some of which permanently resided in the Pisco embayment and used it as a nursery or breeding/calving area. Younger portions of the Pisco Formation (P2) reveal a more open setting, with wide-ranging species like rorquals increasingly dominating the vertebrate assemblage, but also local differences reflecting distance from the coast. Like today, these ancient precursors of the modern Humboldt Current Ecosystem were based on sardines, but notably differed from their present-day equivalent in being dominated by extremely large-bodied apex predators like Livyatan melvillei and Carcharocles megalodon.

Nasal compartmentalization in Kogiidae (Cetacea, Physeteroidea): Insights from a new late Miocene dwarf sperm whale from the Pisco Formation

Article

Feb 2021

Facial compartmentalization in the skull of extant pygmy whales (Kogiidae) is a unique feature among cetaceans that allows for the housing of a wide array of organs responsible for echolocation. Recent fossil findings indicate a remarkable disparity of the facial bone organization in Miocene kogiids, but the significance of such a rearrangement for the evolution of the clade has been barely explored. Here we describe Kogia danomurai sp. nov., a late Miocene (c. 5.8 Ma) taxon from the Pisco Formation (Peru), based on a partially preserved skull with a new facial bone pattern. Phylogenetic analysis recovers K. danomurai as the most basal representative of the extant genus Kogia, displaying a combination of derived (incipiently developed and excavated sagittal facial crest) and plesiomorphic features (high position of the temporal fossa, and antorbital notch not transformed into a narrow slit). Furthermore, when compared with the extant Kogia, the facial patterning found in K. danomurai indicates differential development among the facial organs, implying different capabilities of sound production relative to extant Kogia spp. Different facial bone patterns are particularly notable within the multi-species kogiid assemblage of the Pisco Formation, which suggests causal connections between different patterns and feeding ecologies (e.g. nekton piscivory and benthic foraging). At c. 5.8 Ma, K. danomurai was part of a cetacean community composed of clades typical of the late Miocene, and of other early representatives of extant taxa, a mixture probably representing an initial shift of the coastal faunas toward the ecosystem dynamics of the present-day southeastern Pacific.

A new small, mesorostrine inioid (Cetacea, Odontoceti, Delphinida) from four upper Miocene localities in the Pisco Basin, Peru

Article

Full-text available

Jul 2020

The moderately rich past diversity of the superfamily Inioidea (Cetacea, Odontoceti) in both the Atlantic and Pacific oceans contrasts with the present survival of a single genus (Inia, Amazon river dolphin, family Iniidae) in freshwater deposits of South America and of a single species (Pontoporia blainvillei, franciscana, family Pontoporiidae) along the eastern coast of that continent. However, part of the late Miocene – Pliocene inioid fossil record consists of relatively fragmentarily known species, for which systematic affinities remain poorly understood. Based on a sample of six cranial specimens from lower upper Miocene (Tortonian, 9.5–8.6 Ma) marine deposits of the Pisco Formation exposed at four localities of the East Pisco Basin (southern coast of Peru), we describe a new genus and species of inioid, Samaydelphis chacaltanae. This mesorostrine, small‐sized species is characterized by an upper tooth count of c. 30 teeth per row, a moderately elevated vertex of the cranium displaying a long anteromedial projection of the frontals and interparietal, and the plesiomorphic retention of a premaxilla–nasal contact. Recovered as a member of the family Pontoporiidae in our phylogenetic analysis, S. chacaltanae falls as sister group to Meherrinia isoni, from the upper Miocene of North Carolina (USA), which has previously been tentatively referred to the Iniidae or regarded as a stem Inioidea. Originating from the P1 allomember of the Pisco Formation, the mesorostrine S. chacaltanae was contemporaneous and sympatric with two other inioids, the brevirostrine pontoporiid Brachydelphis mazeasi and the longirostrine iniid Brujadelphis ankylorostris.

Comparaciones faunísticas de los tiburones y rayas del Neógeno del norte y sur del Perú

Conference Paper

Full-text available

Sep 2010

Los fósiles de elasmobranquios han sido reportados en la región sur del Perú, en especial desde la década de los ochenta en la en los departamentos de Ica y Arequipa, de donde se han colectado algunos especímenes individuales articulados, dientes y partes duras desarticuladas (vértebras, espinas, dentículos dérmicos) que son los materiales más comunes. A pesar de ello, los listados faunísticos son escasos y limitados. En la costa sur del Perú, se tienen registros de la Formación Chilcatay del Oligoceno superior al Mioceno inferior, y de la Formación Pisco del Mioceno medio al Plioceno inferior. Del Departamento de Piura en el Noroeste del Perú, se han registrado en esta década varias asociaciones faunísticas de tiburones y rayas que permiten realizar correlaciones bioestratigráficas. Cinco de estas localidades, ubicadas entre las provincias de Piura y Sechura, han sido atribuidas a la Formación Miramar de edad Mioceno superior a Plioceno inferior. Otras localidades serían de edad Plio-Pleistoceno y correlacionables con parte de la Formación Taime definida en el Distrito de El Alto (Provincia de Talara) al norte del Departamento de Piura. La presencia-ausencia de algunas especies de tiburones, totalmente fósiles o actualmente existentes, puede ser referida para diferenciar Mioceno, Plioceno y Pleistoceno.

La hiperdiversificación de Physeteroidea (Cetacea: Mammalia) del Mioceno tardío en el Pacifico Sur, nuevos fósiles del área de Sacaco, Arequipa, Perú

Article

Full-text available

May 2020

Los cachalotes (Physeteroidea) son un grupo de cetáceos con una ecología restringida en la actualidad. Las tres especies actuales son el remanente de un grupo que alcanzó su máxima diversificacion durante el Mioceno, incluyendo cinco especies simpátricas descritas en la Formación Pisco, Ica-Arequipa, Perú. Entre estas se incluyen formas piscívoras, bénticas, así como carnívoros de tamaño medio e hipercarnívoros. Se reportan dos dientes aislados provenientes del Mioceno superior de las localidades de Sacaco y Sacaco sur, que corresponden con la morfología típica de Physeteridae. Esta morfología dentaria es similar a la de taxones presentes en el hemisferio norte como Orycterocetus o Aulophyseter del Mioceno medio. Debido a esto se presume que los restos corresponderían a physetéridos con hábitos piscívoros, que quizás poseyeron un desarrollo incipiente de la capacidad de succión. La presencia de este linaje indicaría que a fines del Mioceno los parientes de los modernos Physeter y Kogia compartieron el mar peruano con formas extintas, sin solapamiento de nichos debido a la morfología altamente derivada de cada grupo. Este nuevo registro expande la comunidad de cetáceos fósiles de Sacaco, que se vio favorecida por la gran diversidad de ambientes poco profundos que dominaron el litoral peruano hasta el establecimiento final del Sistema Humboldt.

Extensive Diversity and Disparity of the Early Miocene Platanistoids (Cetacea, Odontoceti) in the Southeastern Pacific (Chilcatay Formation, Peru)

Article

Full-text available

Mar 2020

Several aspects of the fascinating evolutionary history of toothed and baleen whales (Cetacea) are still to be clarified due to the fragmentation and discontinuity (in space and time) of the fossil record. Here we open a window on the past, describing a part of the extraordinary cetacean fossil assemblage deposited in a restricted interval of time (19–18 Ma) in the Chilcatay Formation (Peru). All the fossils here examined belong to the Platanistoidea clade as here redefined, a toothed whale group nowadays represented only by the Asian river dolphin Platanista gangetica. Two new genera and species, the hyper-longirostrine Ensidelphis riveroi and the squalodelphinid Furcacetus flexirostrum, are described together with new material referred to the squalodelphinid Notocetus vanbenedeni and fragmentary remains showing affinities with the platanistid Araeodelphis. Our cladistic analysis defines the new clade Platanidelphidi, sister-group to Allodelphinidae and including E. riveroi and the clade Squalodelphinidae + Platanistidae. The fossils here examined further confirm the high diversity and disparity of platanistoids during the early Miocene. Finally, morphofunctional considerations on the entire platanistoid assemblage of the Chilcatay Formation suggest a high trophic partitioning of this peculiar cetacean paleocommunity.

Integrated chronostratigraphy and taphonomic studies in Miocene sedimentary successions of the East Pisco Basin (Peru)

Article

Full-text available

Nov 2019

Giulia Bosio

Published extended abstract of the PhD thesis by Giulia Bosio

Mystacodon selenensis, the earliest known toothed mysticete (Cetacea, Mammalia) from the late Eocene of Peru: anatomy, phylogeny, and feeding adaptations

Article

Full-text available

May 2019

Mystacodon selenensis Lambert, Martínez-Cáceres, Bianucci, Di Celma, Salas-Gismondi, Steurbaut, Urbina & Muizon, 2017 is a toothed mysticete that represents the earliest member of the suborder in the current state of knowledge. Its holotype is a relatively complete skeleton from the upper Eocene (early Priabonian, c. 36.4 Ma) Yumaque Member of the Paracas Formation from the southern coast of Peru. The thorough description of this specimen is presented here and reveals numerous similarities with the contemporaneous basilosaurids including the retention of an innominate that originally articulated to the unpreserved hind limb. However, several characters of M. selenensis clearly relate this taxon to the mysticetes, such as the large palate with a dorsoventrally flattened rostrum, the posterior extension of the palate with an infraorbital plate of the maxilla, the shortening of the premaxillary part of the rostrum, the zygomatic process of the squamosal being closely apposed to the postorbital process of the frontal, and the humeral head being oriented more proximally than posteriorly. A parsimony analysis retrieves Mystacodon as the earliest diverging branch of the Mysticeti with no close phylogenetic relationship with Llanocetus the second oldest known mysticete (c. 34.2 Ma). The dental formula of M. selenensis is that of basilosaurids (I 3/3, C 1/1, P 4/4, M 2/3). The anterior teeth (incisors and canine) are distinctly proportionally smaller than in basilosaurids, whereas the cheek teeth are very close in relative length, but are relatively larger than in most other toothed mysticetes (except Coronodon). The large cheek teeth of Mystacodon suggest a raptorial feeding strategy, probably assisted with some degree of suction, as indicated by the large size of the palate. The anterior teeth of the holotype display a subhorizontal apical wear facet and the cheek teeth a moderately sloping wear surface, differing from the subvertical attrition facets of basilosaurids. This pattern suggests an efficient dental abrasion resulting from feeding upon abrasive food items or/and from the ingestion of sediment during prey capture, which could indicate some degree of bottom feeding. On the forelimb, the size and orientation of the acromion, the great length of the deltopectoral crest, the massiveness of the olecranon of the ulna, and the strong radial anterior process indicate powerful shoulder movements, which suggest an active use of the forelimb when foraging for food on the sea floor. The robustness of digits and the pachyosteosclerosis of ribs with pestle-like distal end corroborate such a scenario. Mystacodon selenensis represents a first step in the evolutionary history of feeding adaptations of early mysticetes; the latter are likely to have experimented an abundant set of feeding strategies and were probably very eclectic in prey choice and capture before hyperspecialized filter feeding became widespread in the suborder.

Allostratigraphy and paleontology of the lower Miocene Chilcatay Formation in the Zamaca area, East Pisco basin, southern Peru

Article

Full-text available

May 2019
J MAPS

Based on mapping of laterally traceable stratigraphic discontinuities, we propose a high-resolution allostratigraphic scheme for one of the world's foremost fossil marine vertebrate Lagerstätten: the lower Miocene strata of the Chilcatay Formation exposed along the Ica River near Zamaca, southern Peru. Measured sections combined with 1:10,000 scale mapping of a 24 km 2 area provide an overview of the stratal architecture, as well as a general facies framework and interpretation of the various depositional settings. As a whole, the Chilcatay alloformation is bounded by the CE0.1 unconformity at the base and the PE0.0 unconformity at the top. An internal Chilcatay surface, termed CE0.2, splits the alloformation into two distinct allomembers (Ct1 and Ct2). The Ct1 allomember comprises three facies associations recording deposition in shoreface, offshore, and subaqueous delta settings. The Ct2 allomember comprises two facies associations, recording deposition in shoreface and offshore settings. Using these data, we place the rich marine vertebrate assemblage in a precise spatial and stratigraphic framework. The well-diversified vertebrate assemblage is dominated by cetaceans (mostly odontocetes) and sharks (mostly lamniforms and carcharhiniforms); rays, bony fish, and turtles are also present. Taxonomic novelties include the first records of baleen whales, platanistids, and eurhinodelphinids from the Chilcatay Formation.

(New data on the age of Pisco Formation, Peru).

Article

Full-text available

Jan 1986

New radioisotopic datations of volcanic ruffs extend the age of the Pisco Formation in the Sacaco area (Peru) to the base of the Late Miocene (approx. 10 Ma).-English summary

L’âge mio-pliocène de la Formation Pisco (Pérou).

Article

Full-text available

Jan 1980

Nouvelles données sur l’âge de la Formation Pisco (Pérou).

Article

Full-text available

Jan 1986

( Diatom biostratigraphy dating of Tertiary formations from the Pisco basin, Peru).

Article

Full-text available

Jan 1987

Characteristic diatom assemblages from the three sedimentary units of the Pisco basin allow the following age assignments: late Eocene to earliest Oligocene, latest Oligocene to late early Miocene, and middle or late Miocene to Pliocene. -English summary

Geology and paleontology of late Cenozoic marine deposits in the Sacaco area (Peru)

Article

Full-text available

Oct 1985

Paleontologic, stratigraphic and geochronologic (K-Ar) evidence demonstrate the presence of both late Miocene and Pliocene marine deposits in the Pisco Formation in the area of Sacaco, Peru. Tuffaceous sandstone, siltstone, and shelly sandstone comprise the greater part of the ca. 350 meters sequence. The fine grained sediments have accumulated in large coastal lagoons, while coarser sediments were deposited in semiprotected littoral and nearshore environments. A rich marine vertebrate fauna from the Sacaco basin includes fossil selachians, teleost fishes, marine birds, cetaceans, marine carnivores, and a single edentate species. A diverse invertebrate fauna consists principally of venerid and muricid molluscs. Five vertebrate levels have been correlated with five provisionally defined molluscan zones. The vertebrate fauna has some affinity with faunas of the Miocene Yorktown Formation at the Lee Creek Mine of North Carolina (USA). Distinctive Miocene and Pliocene molluscan assemblages of the Pisco Formation and Pleistocene molluscan assemblages from overlying terrace deposits become progressively more similar to Chilean assemblages of equivalent age and less similar to Tethyan faunas of the Panamic and Caribbean regions.

A multiple microfossil biochronology for the Miocene

Chapter

Full-text available

Jan 1985

A multiple microfossil biochronology is presented for the Miocene which allowsresolution of time approaching 100,000 years. Carbonate stratigraphy is integrated togreatly enhance this resolution. Graphical correlation techniques were applied to over20 DSDP (Deep Sea Drilling Project) sections to identify 175 planktonic foraminiferal,calcareous nannofossil, radiolarian, and diatom datum levels between 24.0 and 4.3 Mawhich show the most consistent (isochronous) correlations. Ages are estimated for thesedatum levels through 72 direct correlations to paleomagnetic stratigraphy and extrapolationbetween the correlation points. The resulting Miocene time scale resembles previouslypublished time scales except for the early Miocene, where recent paleomagneticcorrelations result in changes.The three CENOP (Cenozoic Paleoceanography Project) time slices (-21,16, and8 Ma) are characterized biostratigraphically (planktonic foraminifers, calcareous nannofossils, radiolarians, and diatoms) and in terms of carbonate stratigraphy. The ages ofthe time slices are estimated as follows: the early Miocene time slice (21.2-20.1 Ma;given as 22 Ma in this volume), the late early Miocene time slice (16.4-15.2 Ma), and thelate Miocene time slice (8.9-8.2 Ma).An alternate time scale utilizing a paleomagnetic Anomaly 5-paleomagnetic Chron11 correlation is also presented. Estimated ages for microfossil zones and datum levels inthe late middle and early late Miocene (14-7 Ma) utilizing the alternate time scale aregenerally younger than those for the more traditional time scale. The late Miocene timeslice has an estimated age of 8.0-7.0 Ma.

Stratigraphic significance of siliceous microfossils collected during Nautiperc dives (off Peru, 5 °–6°S)

Article

Full-text available

Feb 1995
Mar Micropaleontol

The geological evolution of the northern Peru convergent margin can be traced using samples collected during deep-sea dives of the submersible Nautile. In the Paita area (5°–6°S), the sedimentary sequence was intensively sampled along the main scarp of the middle slope area. It consists of Upper Miocene (7–9 Ma) to Pleistocene siltstone, sandstone and rare dolostone. The age distribution of these samples is the basis for a new geologic interpretation of the multichannel seismic line CDP3.Siliceous microfossils (both diatoms and radiolarians) show influence of both cold and temperature waters (local species mixed with upwelling ones). Diatom assemblages studied from the NP1-13 and NP1-15 dives bear a strong resemblance to assemblages from the Pisco Formation of southern Peru.Micropaleontological data from siliceous microfossils, provide evidence for two main unconformities, one is at the base of the Quaternary sequence and the other corresponds to a hiatus of 1 Myr, separating the Upper Miocene (7–8 Ma) sediments from uppermost Miocene (5–6 Ma) sediments.During the past 400 kyr, a wide rollover fold developed in the middle slope area associated with a major seaward dipping detachment fault. A catastrophic debris a valanche occurred as the results of an oversteepening of the landward flank of the rollover fold. The gravity failure of the slope, recognized by SeaBEAM and hydrosweep mapping, displaced enough material to produce a destructive tsunami which occurred 13.8 ± 2.7 kyr ago.

Tectonics and uplift in Central Andes (Peru, Bolivia and Northern Chile) from Eocene to present

Article

Full-text available

Jan 1988

L'analyse des séries sédimentaires et volcaniques affleurant dans le sud du Pérou, la Bolivie et le nord du Chili permet d'établir l'évolution chronologique des Andes centrales de l'Eocène à l'actuel. Cette analyse est basée sur des observations de terrain et une réévaluation des données géologiques disponibles. Elle met en évidence six phases tectoniques compressives datées de l'Eocène supérieur au Quaternaire ancien

Oligo-Miocene transgression along the Pacific margin of South America: new paleontological and geological evidence from the Pisco Basin, (Peru)

Article

Full-text available

Jan 1988

Diagnostic species of fossil diatoms (genus Bogorovia, Triceratium, Thalassiosira), and molluscans (genus Pitar, Cucullaea, Peruchilus) demonstrate the presence of a late Oligocene-early Miocene sedimentary unit in the Pisco Basin, south-central Peru. The transgressive basal facies of this unit unconformably overlap older rocks, upward the unit shows subsident shelf conditions. This transgression took place after a compressional tectonic event which had affected the region by late Oligocene. These data, and data from other places in western South America, indicate that the late Oligocene-early Miocene was a transgressive period along this continental margin. These phenomena appear associated to 1) a global change in plate kinematics reflected by an increase of the convergence rate between the Nazca and South American plates; and 2) a global rise of oceanic temperatures; factors which could have favoured a sea-level rise. The amplitude of this transgression is variable along the margin which shows segments with different rates of subsidence; the northern and southern Andean segments display a mainly subsident character, whereas the central Andean margin exhibits a dominant tendency to uplift. Our data confirm that the central Peru segment is characterized by subsidence and constitutes an exception within the central Andean forearc. This characteristic is thought to be related to the presence of dense mantle material within the central-Peru forearc crust. -Authors

Late Oligocene–Early Miocene major tectonic crisis and related basins in Bolivia

Article

Full-text available

Jan 1990
GEOLOGY

Recent advances in biochrology, geochrology, magnetostratigraphy, structural geology, and basin analysis make untenable the traditional correlation of the first major Andean-age deformational episode in Bolivia with the middle Eocene "Incaic tectonic phase" defined in central Peru and intead demostrate that the episode took place in late Oligocene and early Miocene time. This major tectonic crisis resulted in contemporary development of the Subandean external foreland basin and Altiplano intermontana basin, which were separeted by the initiation of thrusting in the present Cordillera Oriental area. The deformation suggests that the Bolivian orocline began to develop at that time. It is likely that this tectonic upheaval is genetically linked to the maked increase in rate of plate convergence produced by the contemporaneus creakup of the Farallon plate. (Résumé d'auteur).

Chronology of Fluctuating Sea Levels Since the Triassic

Article

Full-text available

Apr 1987

Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new generation of Mesozoic and Cenozoic global cycle charts that chronicle the history of sea level fluctuations during the past 250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop a realistic and accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented in public domain outcrop sections from various basins with this chronostratigraphic framework. A description of this approach and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals, are presented.

Mid-Oligocene Transgression in Southern Peru: GEOLOGICAL NOTES

Article

Jan 1953
AAPG BULL

W. Ruegg R. M. Stainforth

The presence of a foraminiferal assemblage indicative of late middle or early upper Oligocene age in basal sandy and conglomeratic beds of a predominantly continental series which has generally been regarded as Pliocene, near Camana, southern Peru, indicates that the regional mid-Oligocene transgression extended farther south than was formerly recognized.

Descriptions of Tertiary fossil shells from South America

Article

G. Sowerby

Taxonomic remarks on cenozoic pseudolivid gastropods from South America

Article

Jan 1997
VELIGER

The neogastropod family Pseudolividae was represented in the Neogene of Peru and Chile by a single genus, which we name Testallium to replace Gastridium Sowerby, 1846, non Gastridium Sowerby, 1842, or Gastridium Modeer, 1793. Besides the type species, Testallium cepa (Sowerby, 1846), from the Miocene of Peru and Chile, we recognize T. voluta (Olsson, 1932) from the early Miocene of northern Peru, and T. escalonia, sp. nov. from the Pliocene of Chile. Gastridium retusum Philippi, 1887, is assigned to Buccinorbis Conrad, 1865.

Fundamental data on Cenozoic biostratigraphy of the Pacific coast of Ecuador

Article

Jan 1988

The Camana Formation and its bearing on the Andean post-orogenic uplift

Article

Jan 1952

W. Ruegg

Fundamental data on Cenozoic biostratigraphy of Chile

Article

Jan 1988

Demonstration of two pulses of Paleogene deformation in the Andes of Peru

Article

May 1985
EARTH PLANET SC LETT

New radiometric ages of about 25 m.y. on volcanic materials in a marine intercalation within clastic continental strata of the Upper Moquegua Formation near Caraveli, southern Peru, together with an age of 25.3 +/- 0.4 m.y obtained by Tosdal et al. from a locality about 300 km to the ESE, show that the formation contains strata of late Oligocene as well as Miocene age, and demonstrate that the coastal region was at a low elevation during latest Oligocene time. Because the unconformities between the Upper Moquegua Formation and the underlying Lower Moquegua Formation, and between the Lower Moquegua Formation and underlying Paleocene rocks cannot both represent the same tectonic event, two discrete Paleogene events must be present in the Andes of Peru. Although the exact timing of these events is uncertain, the unconformities are likely to be of Paleocene and middle Eocene age or possibly of middle Eocene and Oligocene age.

Cenozoic marine sedimentation in the Sechura and Pisco basins, Peru

Article

Apr 1990
PALAEOGEOGR PALAEOCL

The central and northern Peruvian margin consists of a series of 8 paired forearc basins which may be separated into an inner set of shelf basins and a seaward set of slope basins. We have examined the Cenozoic stratigraphy of the onshore portions of the Sechura Basin (5–7°S) and Pisco Basin (13–16°S), two shelf basins which have accumulated marine sediment discontinuously since the mid to late Eocene. Cenozoic sediments in the Pisco Basin were deposited during at least three major transgressive cycles. Each sequence is preserved as a similar vertical progression of facies including coarse nearshore bioclastic conglomerates and sandstones grading upwards into sandy siltstones and mudstones, and capped by biogenic deposits including diatomites, diatomaceous mudstones, dolomitic horizons, and phosphate deposits. Stratigraphic nomenclature for the Pisco Basin has recently evolved; a stratigraphy presented here includes the Eocene Caballas Fm., upper Eocene Los Choros fm., upper Eocene to lowermost Oligocene Yumaque fm., uppermost Oligocene to middle Miocene Chilcatay fm., and upper Miocene to Pliocene Pisco Fm. Major hiatuses in the Pisco Basin span the Late Cretaceous to middle Eocene, early to late Oligocene, middle Miocene, and late Pliocene/Pleistocene to Recent. Cenozoic sediments of the Sechura Basin were deposited within at least 4 major transgressive cycles with hiatuses during the Paleocene to middle Eocene, Oligocene, early to middle Miocene, and late Miocene. Based on recent biostratigraphic studies, sediments enriched in biogenic components accumulated between about 40-36 Ma, 24-16 Ma, and 11-3 Ma in the Pisco Basin and between 40-37 Ma and 8.5-4.5 Ma in the Sechura Basin. In both basins, the most diatomaceous sediments are restricted to the Late Eocene and Late Miocene through Pliocene. The temporal distribution of biogenic sediments suggests that high productivity conditions linked to coastal upwelling have occurred episodically since at least the Late Eocene. The occurrence of diatomites and phosphorites is diachronous between the Pisco and Sechura Basins and between the Peruvian forearc and other circum-Pacific Monterey Formation analogs, a reflection of the strong influence of local tectonism on sedimentation patterns. The volume of Neogene sediments along the Peruvian forearc is nearly twice that of the Monterey Fm.; despite basin-to-basin facies diachroneity, these deposits very likely contributed to fluctuations of the late Miocene carbon/CO2 system by acting as large carbon sinks.

A New Geomagnetic Polarity Time Scale for the Late Cretaceous and Cenozoic

Article

Sep 1992

We have constructed a magnetic polarity time scale for the Late Cretaceous and Cenozoic based on an analysis of marine magnetic profiles from the world's ocean basins. The new time scale has several significant differences from previous time scales. For example, chron C5n is ~0.5 m.y. older and chrons C9 through C24 are 2-3 m.y. younger than in the chronologies of Berggren et al. (1985b) and Harland et al. (1990). Additional small-scale anomalies (tiny wiggles) that represent either very short polarity intervals or intensity fluctuations of the dipole field have been identified from several intervals in the Cenozoic. Spreading rates on several ridges were analyzed in order to evaluate the accuracy of the new time scale. Globally synchronous variations in spreading rate that were previously observed around anomalies 20, 6C, and in the late Neogene have been eliminated. The new time scale helps to resolve events at the times of major plate reorganizations. -from Authors

Major Neogene events of the Southeastern Pacific: the Chilean and Peruvian record

Article

Apr 1990
PALAEOGEOGR PALAEOCL

Rubèn Martinez-Pardo

According to the biochronostratigraphic model proposed, the Neogene marine deposits in Chile and Peru represent two independent transgressive sequences (Alloformations), separated by a major regional hiatus. The earlier sequence, NSEPS-I, would stretch from the top of the Early Miocene up to the base of the Late Miocene (ca. 19-10 m.y. B.P. The upper sequence, NSEPS-II would correspond, in turn, to the Late Pliocene (ca. 3.5-1.6 m.y. B.P.). The regional hiatus separating both sequences would encompass the Late Miocene and the Early Pliocene (ca. 10-3.5 m.y. B.P.). The planktonic foraminiferal events described suggest an age of terminal Early Miocene-Middle Miocene and Late Pliocene, respectively. The paleoclimatic events recorded are three: a "Warming" Event lasting from the terminal Early Miocene to the end of the Middle Miocene (MMWE), 18-11.5 m.y. B.P.; a "Cooling" Event of the middle Late Pliocene (LPCE), 2.5±0.2 m.y. B.P.; and "Warming" Event spanning most of the Late Pliocene (LPWE), 3.5-2.2 m.y. B.P., restricted to the surface and intermediate sea waters of the middle and low latitudes. The last paleoclimatic event, not recorded as such so far, is both synchronous and mutually exclusive in latitudinal terms with the second one. Three tectonic regional events are analyzed: the Quechuan-1 Phase (19±1.5 m.y. B.P.); the Quechuan-2 Phase (10±1 m.y. B.P.); and the Geographic (=Rhodanian) Phase (3.5±0.5 m.y. B.P.). In the studied area there is no Late Miocene marine sedimentary record to confirm the terminal Tortonian or Quechuan-3 tectonic phase (ca. 7 m.y. B.P.), admitted to occur in the volcanoclastic continental sequences of northern Chile and southern Peru.

Systême des animaux sans vertèbres ou tableau général des classes, des ordres et des genres de ces animaux...

Article

Jan 1801

Jean-Baptiste LAMARCK

Eocene Diatom Assemblages from the Kellogg and "Sidney" Shales, Mt. Diablo Area, California

Article

Jan 1957

Taro Kanaya

This paper describes diatom species of two Eocene shales (Kellogg and "Sidney") in the Mt. Diablo area, California, and establishes a local diatom sequence of the "Kreyenhagen shale" and its equivalents in California. The shales crop out north and east of Mt. Diablo. The "Sidney" shale is a the middle member of the Markley formation, and the Kellogg shale is below the Markley. Nine samples from the Kellogg and nine from the "Sidney", all collected rom the same sections from which Clark and Campbell (1942) described radiolarian faunas, are selected to represent 90 feet of the Kellogg shale, and 85 feet of the diatomaceous part of the "Sidney" shale. Thirty-nine species, including a new one, are described from the samples. Frequencies of occurrences, and relative abundances of the species, taken by single counts of 200 specimens at each horizon, are shown in the distribution chart (Chart II). The assemblages of the Kellogg and "Sidney" shales are a common floral type.

Initial Reports Proceedings of the Ocean Drilling Project College Station, Texas. Muizon de, C. and Bellon, H. (1980) L'aÃ ge mio-plioceÁ ne de la for-mation Pisco Nouvelles donneÂ es sur l'aÃ ge de la formation Pisco, PeÂ rou

Jan 1985
547-563

J Mascle
G P Lohman
P D Clift

Mascle, J., Lohman, G.P., Clift, P.D. et al. (1996) Initial Reports. Proceedings of the Ocean Drilling Project. Ocean Drilling Program, College Station, Texas. Muizon de, C. and Bellon, H. (1980) L'aÃ ge mio-plioceÁ ne de la for-mation Pisco, Perou. C. R. Acad. Sci. (Paris) Series D 290, 1063±1066. Muizon de, C. and Bellon, H. (1986) Nouvelles donneÂ es sur l'aÃ ge de la formation Pisco, PeÂ rou. C. R. Acad. Sci. (Paris) Series D 303, 1401±1404. Muizon de, C. and DeVries, T.J. (1985) Geology and paleontology of the Pisco Formation in the area of Sacaco, Peru. Geol. Rundschau 74, 547±563.

Contributions to the Tertiary paleontology of northern Peru: Part 1, Eocene Mollusca and Brachiopoda. Bulletins of American Paleontology 14

Jan 1928
47-154

A A Olsson

Olsson, A.A. (1928) Contributions to the Tertiary paleontology of northern Peru: Part 1, Eocene Mollusca and Brachiopoda. Bulletins of American Paleontology 14, 47±154.

Molluscs of the Pisco Basin In Cenozoic ge-ology of the Pisco Basin. Guidebook to Regional IGCP 156 Field Workshop, Genesis of Cenozoic phosphorites and associated or-ganic-rich sediments: Peruvian continental margin

Apr 1988

T J Devries

DeVries, T.J. (1988b) Molluscs of the Pisco Basin. In Cenozoic ge-ology of the Pisco Basin. Guidebook to Regional IGCP 156 Field Workshop, Genesis of Cenozoic phosphorites and associated or-ganic-rich sediments: Peruvian continental margin, ed. R.B. Dunbar and P.A. Baker, 127±134. Lima, Peru, May 16-25.

Geological Notes: Mid-Oligocene transgression in southern Peru American Association of Petroleum Geologists Bulletin 37 Tertiary geology of the Quebrada Huaricangana area, East Pisco Basin, southern Peru: Late Paleogene to Neogene transgressive sedimentation within a forearc basin

Jan 1953

R M Stainforth
W Ruegg

Stainforth, R.M. and Ruegg, W. (1953) Geological Notes: Mid-Oligocene transgression in southern Peru. American Association of Petroleum Geologists Bulletin 37, 568±569. Stock, C.E. (1990) Tertiary geology of the Quebrada Huaricangana area, East Pisco Basin, southern Peru: Late Paleogene to Neogene transgressive sedimentation within a forearc basin. Unpublished Masters thesis. Rice University., Houston, Texas.

Eocene to early Miocene planktonic foraminifera from the south of Paracas, central Peru

Jan 1993
77

Ibaraki

Ibaraki, M. (1993) Eocene to early Miocene planktonic foraminifera from the south of Paracas, central Peru. Report Fac. Sciences, Shizuoka University 27, 77±93.

Fundamental data on Cenozoic biostratigraphy of the Paci®c coast of Peru

Jan 1988
45-70

R Tsuchi
T Shuto
A Fujiyoshi
I Koizumi
M Ibaraki
C Aldana-A

Tsuchi, R., Shuto, T., Fujiyoshi, A., Koizumi, I., Ibaraki, M., Rangel-Z, C. and Aldana-A, M. (1988) Fundamental data on Cenozoic biostratigraphy of the Paci®c coast of Peru. Report on Andean Studies, Shizuoka University, Special Volume 2, 45±70.

Tectonics and uplift in Central Andes (Peru, Bolivia, and north-ern Chile) from Eocene to Present Late Oligocene-early Miocene major tectonic crisis and related basins in Bolivia Biostratigraphic summary for Leg 138 Descriptions of Tertiary fossil shells from South America

Jan 1846

M Sebrier
A Lavenu
M Fornari
J P Soulas
±106 Sempere
T Heâ Rail
G Oller
J Bonhomme
M G 946±
N J Shackleton
J Baldauf
J-A Flores
M Wai
T C Moore
Jr
I Ra
E Vincent
G B Sowerby

Sebrier, M., Lavenu, A., Fornari, M. and Soulas, J.P. (1988) Tectonics and uplift in Central Andes (Peru, Bolivia, and north-ern Chile) from Eocene to Present. GeÂodynamique 3, 85±106. Sempere, T., HeÂ rail, G., Oller, J. and Bonhomme, M.G. (1990) Late Oligocene-early Miocene major tectonic crisis and related basins in Bolivia. Geology 18, 946±949. Shackleton, N.J., Baldauf, J., Flores, J-A., Wai, M., Moore, T.C. Jr, Ra, I. and Vincent, E. (1995) Biostratigraphic summary for Leg 138. In Proceedings of the Ocean Drilling Project, Scienti®c Results, ed. N.G. Pisias, L.A. Mayer, T.R. Janecek, Julson A. Palmer and T.H. van Andel, 138, 517±536. Sowerby, G.B. (1846) Descriptions of Tertiary fossil shells from South America. In Geological observations on South America, being the third part of the geology of the voyage of the Beagle, under the Command of Capt. Fitzroy, R. N., during the years 1832 to 1836, ed. Darwin C., 249±264. Smith, Elder, and Co, London.

Fundamental data on Cenozoic biostratigraphy of the Paci®c coast of Peru Taxonomic remarks on Cenozoic pseudolivid gastropods from South America

Jan 1990
23-28

R Tsuchi
T Shuto
T Takayama
I Koizumi
A Fujiyoshi
M Ibaraki
M Aldana-A
E Villavicencio-R
G J Vermeij
T J Devries

Tsuchi, R., Shuto, T., Takayama, T., Koizumi, I., Fujiyoshi, A., Ibaraki, M., Aldana-A, M. and Villavicencio-R, E. (1990) Fundamental data on Cenozoic biostratigraphy of the Paci®c coast of Peru. Supplement. Report on Andean Studies, Shizuoka University, Special Volume. 3. 47±58. Vermeij, G.J. and DeVries, T.J. (1997) Taxonomic remarks on Cenozoic pseudolivid gastropods from South America. Veliger 40, 23±28.

Neogene planktonic foraminiferal biostratigraphy on the coast of Peru and its paleoceanographic implications

M Ibaraki

Ibaraki, M. (1992a) Neogene planktonic foraminiferal biostratigra-phy on the coast of Peru and its paleoceanographic implications. In Paci®c Neogene: environment, evolution, and events, ed. R. Tsuchi and J.C. Ingle Jr, 71±81. University of Tokyo, Tokyo.

Stratigraphy and chemical sedimentology of Cenozoic biogenic sediments from the Pisco and Sechura basins

R C Marty

Marty, R.C. (1989) Stratigraphy and chemical sedimentology of Cenozoic biogenic sediments from the Pisco and Sechura basins, Peru. Unpublished Ph.D. dissertation. Rice University, Houston, Texas. 268 p.

Contributions to the Tertiary paleontology of northern Peru: Part 4, The Peruvian Oligocene. Bulletins of American Paleontology 17 Geolog| a de los cuadrangulos de CamanaÂ y La Yesera

Jan 1931
33-76

A A Olsson
V Pecho
G Morales
G Petersen

Olsson, A.A. (1931) Contributions to the Tertiary paleontology of northern Peru: Part 4, The Peruvian Oligocene. Bulletins of American Paleontology 17, 124 p.. Pecho, V. and Morales, G. (1969) Geolog| a de los cuadrangulos de CamanaÂ y La Yesera. Serv. Geol. Minera 21, 1±72. Petersen, G. (1954) Informe preliminar sobre la geolog| a de la faja costanera del departamento de Ica. Empresa Petroleum Fiscal 1, 33±76.

Reconocimiento geoloÂ gico de la regioÂ n Pisco-Nazca Demonstration of two pulses of Paleogene deformation in the Andes of Peru

Jan 1956
345-349

N D Newell

Newell, N.D. (1956) Reconocimiento geoloÂ gico de la regioÂ n Pisco-Nazca. Bol. Soc. Geol. PeruÂ 30, 261±295. Noble, D., Sebrier, M., Megard, F. and McKee, E. (1985) Demonstration of two pulses of Paleogene deformation in the Andes of Peru. Earth and Planetary Science Letters 73, 345±349.

Concholepas Lamarck 1801 (Neogastro-poda:Muricoidea): A Neogene genus native to South America

Apr 1995
58-68

T J Devries
±
De
P Wever
J Bourgois
J-P Caulet
E Fourtanier
J Barron
P Dumitricaá

DeVries, T.J. (1995) Concholepas Lamarck 1801 (Neogastro-poda:Muricoidea): A Neogene genus native to South America. Veliger 38, 284±297. De Wever, P., Bourgois, J., Caulet, J-P., Fourtanier, E., Barron, J. and DumitricaÁ, P. (1995) Stratigraphic signi®cance of siliceous microfossils collected during NAUTIPERC dives (o Peru, 58-68S). Mar. Micropaleontology 24, 287±305.

Contribution to the Tertiary paleontology of Peru Chronology of ¯uc-tuating sea levels since the Triassic

Jan 1925

J Gryzbowski
G D Hanna
M C Israelsky

Gryzbowski, J. (1899) Die Tertiarablagerung des nordlichen Peru und ihre Molluskenfauna. N. Jahrb. f. Min. Geol. Paleont. 12, 610±664. Table 1. Correlation of depositional hiatuses in the Pisco Basin with eustatic and tectonic events Interval of Unconformity/ Shoaling (Ma) Eustatic Low-stand Hanna, G.D. and Israelsky, M.C. (1925) Contribution to the Tertiary paleontology of Peru. Proceedings of the California Academy of Sciences Fourth Series, 14, 37±75. Haq, B.U., Hardenbol, J. and Vail, P.R. (1987) Chronology of ¯uc-tuating sea levels since the Triassic. Science 235, 1156±1167. HupeÂ, H. (1854) Malacologia y conquiliogia. In Historica ®sica y politica de Chile. Volume 8 and Atlas (Zoologica), ed. Gay C., 499 pp. Maulde et Renou, Paris.

Moluscos fósiles de la Formación Paracas, departamento de Ica

Jan 1957
165

Rivera

Rivera, R. (1957) Moluscos foÂ siles de la FormacioÂ n Paracas, depar-tamento de Ica. Bol. Soc. Geol. PeruÂ 32, 165±220.

Algunos foÂ siles de PeruÂ PeruÂ 1, Oligo-Miocene transgression along the Paci®c margin of South America: new paleontological and geological evidence from the Pisco basin (Peru) GeÂodynamique 3, Datation des formations ter-tiares du bassin de Pisco (PeÂ rou) aÁ partir d'asociations de diato-meÂ es

Jan 1925

C I Lisson
±
J Machareâ
T Devries
J Barron
E Fourtanier
±
J Machareâ
E Fourtanier

Lisson, C.I. (1925) Algunos foÂ siles de PeruÂ. Bol. Soc. Geol. PeruÂ 1, 23±30. MachareÂ, J., DeVries, T., Barron, J. and Fourtanier, E. (1988) Oligo-Miocene transgression along the Paci®c margin of South America: new paleontological and geological evidence from the Pisco basin (Peru). GeÂodynamique 3, 25±37. MachareÂ, J. and Fourtanier, E. (1987) Datation des formations ter-tiares du bassin de Pisco (PeÂ rou) aÁ partir d'asociations de diato-meÂ es. C. R. Acad. Sci. (Paris) Series II 305, 407±412. Martinez-Pardo, R. (1990) Major Neogene events of the southeast-ern Paci®c: the Chilean and Peruvian record. Palaeogeography, Palaeoclimatology, Palaeoecology 77, 263±278.

Evolution and paleoceanography of the Pisco Basin (Peru) Unpublished Master’s thesis

P O Rønning

Rùnning, P.O. (1990) Evolution and paleoceanography of the Pisco Basin (Peru) Unpublished Master's thesis. Cand. Scient. Oppgave Geol. Inst. Avd. B, Univ. I Bergen, Norway. 135 p.

Actinocyclus ehrenbergii, A. ingens, Coscinodiscus marginatus, Thalassionema longissima, Thalassiosira fraga. Late early Miocene. Locality 87DV 591 Cerro Tiza, SE corner, SW face. 14840'140S 75840'540W Lomitas quadrangle

591-1

Diatoms

Diatoms: Actinocyclus ehrenbergii, A. ingens, Coscinodiscus marginatus, Thalassionema longissima, Thalassiosira fraga. Late early Miocene. Locality 87DV 591 Cerro Tiza, SE corner, SW face. 14840'140S 75840'540W Lomitas quadrangle. Sample 87DV 591-1

Eocene diatom assemblages from thèKellog' and Sidney' shales, Mt

Jan 1957

T Kanaya

Kanaya, T. (1957) Eocene diatom assemblages from thèKellog' and Sidney' shales, Mt. Diablo area, California. Sci. Rep. Tohoku Imp. Univ., Series 2 (Geol.) 28, 1±124. Lamarck, J.B. (1801) SysteÁme des animaux sans verteÁbres, ou tableau general des classes, des ordres et des genres des ces animaux, 432 pp. Chez Deterville, Paris.

Concholepas Lamarck 1801 (Neogastropoda:Muricoidea): A Neogene genus native to South America

Jan 1995
284

DeVries

Tertiary geology of the Quebrada Huaricangana area, East Pisco Basin, southern Peru: Late Paleogene to Neogene transgressive sedimentation within a forearc basin

C E Stock

Sur l’existence du Pliocene marin le long de la côte du Sud du Perou

Jan 1976
12

Beaudet

Proceedings of the Ocean Drilling Project

W B Curry
N J Shackleton
C Richter

Genesis of Cenozoic phosphorites and associated organic-rich sediments: Peruvian continental margin

T J Devries

Catalogue systématique et raissonédes curiositées de la nature et de l’art

G Fischer Von Waldheim

1854) Malacologia y conquiliogia

H Hupé

Algunos fósiles de Perú

Jan 1925
23

Lisson

Oligocene deposition and Cenozoic sequence boundaries in the Pisco Basin (Peru)

Abstract

No full-text available

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