Pliocene Age Research Articles

Vertebrate paleontology, biostratigraphy, geochronology, and paleoenvironment of Qaidam Basin in northern Tibetan Plateau

Qaidam Basin is the largest terrestrial basin of the Tibetan Plateau and has the most continuous sedimentary record in the Cenozoic. Although constituting the first known fossil vertebrates of the Tibetan Plateau and discovered in early scientific expeditions in the 1930s, mammalian fossils from Qaidam Basin have not played a significant role in studying the basin stratigraphy. Our explorations in the Qaidam Basin during the past 8 years have resulted in the first well documented collection of fossil vertebrates from there. In addition to being the best organisms for terrestrial biostratigraphy in the Cenozoic, the new fossil vertebrates offer a unique window into the ancient biotas that chronicle the late Cenozoic uplift of the plateau and associated environmental changes. Here we establish for the first time a faunal sequence of early Oligocene to early Pliocene age. Four mammalian faunas are recognized: Olongbuluk Mammal Fauna (middle Miocene), Tuosu Mammal Fauna (early late Miocene), Shengou Mammal Fauna (early late Miocene), and Huaitoutala Mammal Fauna (early Pliocene). All four mammal faunas can be directly or indirectly tied to a paleomagnetic section in the Olongbuluk–Huaitoutala area, permitting robust calibration of the chronology of these faunas. At least four fish faunas are also found: Lulehe Fish Fauna (late early to early late Oligocene), Shengou Fish Fauna (early late Miocene), Eboliang Fish Fauna (late late Miocene to early Pliocene), and Yahu Fish Fauna (early Pliocene). The fish faunas represent the only records of their respective times in the Tibetan Plateau and thus by themselves cannot be used for age determination. However, these fish faunas are either integrated into paleomagnetic sections or directly tied to mammal faunas of known ages, permitting independent assessment of their chronology. Zoogeographically, Qaidam mammal faunas show increasing endemism through time, presumably related to topographic barriers formed by the growth and uplift of the Tibetan Plateau and to climatic changes triggered by the same tectonic process. Fishes that were trapped in internally drained basins developed pachyostotic morphologies caused by hypersaline environments, which are associated with the increasing aridity of the Tibetan Plateau since early Pliocene.

Alseodaphne (Lauraceae) from the Pliocene of China and its paleoclimatic significance

A leaf of Alseodaphne cf. hainanensis Merrill was discovered in diatomitic sediments of middle Pliocene age at Shengzhou, Zhejiang Province, China. The fossil and modern leaves have the same elliptic shape and brochidodromous venation. The cuticle of the fossil leaf was intact. There are some anatomical differences such as the amount of wax, the position of subsidiary cells and the density of trichomes/trichome bases between the fossil and modern leaves. However, these characters could not be used as taxonomic criteria to distinguish the fossil leaf from the modern species. The restricted distribution of A. hainanensis suggests that this tree is stenoecious. The presence of A. cf. hainanensis indicates that the mid-Pliocene climate was much warmer than today and had a higher level of precipitation than eastern China at the present day. Based on the fossil records and the modern distribution it is suggested that the trees of A. hainanensis have retreated southwards since the middle Pliocene.

The first Pliocene mammals from the northeast (Mesopotamia) of Argentina: Biostratigraphic and paleoenvironmental significance

ABSTRACT The record of Neogene faunas from the northeast of Argentina (Mesopotamia) is sporadic, whereas the late Miocene vertebrate-bearing horizons in this area contain a very abundant and diverse fauna, the Pliocene deposits are poorly known and have been unfossiliferous until now. This situation makes the understanding of the biogeographic and evolutionary history of the Mesopotamian taxa difficult. In this contribution, the first mammals are described that were recovered from the most basal levels of the Punta Gorda Group (= Alvear Formation) at Entre Ríos Province, assigned to the late Pliocene (Lower Matuyama) by previous paleomagnetic studies. These beds are paleomagnetically bracketed between 1.95 and 2.6 Ma (late Pliocene) in the Alvear section and help to refine the biostratigraphy of these species elsewhere in northeastern Argentina. The echimyids Paramyocastor diligens (Ameghino, 1888) and Eumysops sp., and the hegetotheriid Paedotherium cf. typicum herein reported support a Pliocene age for the sediments from which they were recovered. These mammals suggest a paleoenvironment characterized by semiarid and open lowlands, markedly different than that inferred for the Late Miocene in this area.

Fluid Inclusion, Rare‐Earth Element and Stable Isotope Study of Carbonate Minerals from the Pongkor Epithermal Gold–Silver Deposit, West Java, Indonesia

AbstractThe Pongkor gold–silver deposit is the largest low‐sulfidation epithermal precious metal deposit in Indonesia, and is of Pliocene age. The deposit consists of nine major subparallel quartz–adularia–carbonate veins with very low sulfide content. Vein infill records five paragenetic sequences, dominated by calcite in the early stage and quartz in the later stage of the hydrothermal evolution. Fluid inclusions in hydrothermal calcite and quartz of all stages indicate a temperature ranging from 180 to 220°C and a meteoric water origin (very low salinity close to 0 wt% NaCl equivalent). Carbon isotope data on calcite display a narrow range from −6.5 to −3.0‰δ13C. The oxygen isotope values have a wider range of +4.6 to +10.1‰δ18O. The broadly positive correlation of the δ13C versus δ18O plot suggests that the carbon species, which equilibrated during the formation of calcite, is dominated by H2CO3 not far from equilibrium with HCO3−. The abundance of rare earth and yttrium (REY) in carbonate samples is very low (>REY mostly <2 ppm). However, there is always a positive Eu anomaly, which indicates a deeper fluid reservoir at >250°C.

La microflore de diatomées au passage mio-pliocène en Corse

The “Aleria formation”, described in northeastern Corsica, consists of siliciclastic deposits referred to a deltaic environment and comprises diatomitic lenses exposed at Casabianda. The Aleria formation fills a depression of the Messinian erosional surface and is overlain by Early Pliocene sediments in several places. This suggests a late Messinian-earliest Pliocene age. Diatom microflora is well-preserved and contains 59 species. Pennates indicate a very large diversity with 54 species, while Centrics are represented only by five species. Diatom assemblages show a relative constant composition along the studied interval. The species Aulacoseira granulata is the dominant taxon with about 90% in all samples. Taxa are of different salinity classes and different modes of life (planktic, tychoplanktic, benthic, epiphytic…), suggesting multiple environmental factor interactions. The environmental model suggested by sedimentological and biological data led as to assume a pond-like coastal receptacle common in deltaic system. This receptacle was slightly influenced by the close marine waters and was supplied by permanent freshwaters from continental run-off and alluvial sheet. This model based on diatom assemblages provides new data for palaeoenvironmental and chronological interpretations of the so-called Messinian Lago-Mare deposits.

Taxonomic review of fossil Proboscidea (Mammalia) from Langebaanweg, South Africa

Comparative morphological and metric study of proboscidean dental fossils from the Quartzose (QSM) and Pelletal Phosphate (PPM) Members of the Varswater Formation at Langebaanweg, South Africa identifies the presence in the fauna of an anancine gomphothere and two species of elephant. The gomphothere, from the QSM and PPM, displays a unique combination of primitive and derived molar features, and consequently is placed in a new species (Anancus capensis sp. nov.) that is regionally distinct from other African species of Anancus. A new species of loxodont elephant (Loxodonta cookei sp. nov.) is identified from the PPM, distinguished from penecontemporaneous L. adaurora by having anterior and posterior accessory central conules that contribute to the formation of strong median sinuses throughout its molar crowns. It is further differentiated from other loxodont elephants by its primitive retention of permanent premolars, lower crown height, fewer molar plates, thicker enamel, and lower lamellar frequency, and extends the L. exoptata-L. africana lineage back into the late Miocene. A second elephant species, from the QSM, is referable to Mammuthus subplanifrons, and represents the most archaic stage of mammoth evolution. The elephants appear to have been more cosmopolitan in distribution than the gomphothere. Together, these taxa support a latest Miocene-early Pliocene age of ca. 5.0 Ma for the Vars-water Formation. Based on isotopic analyses of congeners from other African sites, it may be inferred from the occurrence of these taxa that open conditions were present locally and abundant grazing resources were available in the ecosystems of Langebaanweg during the time of deposition of the QSM and PPM.

First European evidence for transcontinental dispersal ofCrocodylus(late Neogene of southern Italy)

It is generally assumed that the Neogene crocodylian fauna of Europe has been represented only by brevirostrine alligatoroid Diplocynodon and longirostrine false gharials ( Gavialosuchus and/or Tomistoma ), which became extinct prior to 6 Mya. Although several lines of evidence suggest that Crocodylus originated in Africa during the Miocene and then promptly dispersed to other continents, the occurrence of this genus in Europe has never been rigorously proven and the traditional palaeontological approach failed to identify a monophyletic group of fossil Crocodylus (simply leading to a proliferation of extinct taxa). The new remains reported here, from an endemic insular fauna from southern Italy, Late Messinian to earliest Pliocene in age (5‐6 million years old), represent the youngest European crocodylian, and allow, for the first time in a phylogenetic context, an unambiguous demonstration that Crocodylus dispersed into Europe, possibly during the Tortonian. If the peculiar morphology of the medial maxillary edge is interpreted as evidence for a medial dorsal boss, the southern Italian Crocodylus could be related to C. checchiai from the late Neogene of Libya. The presence of this African immigrant in Europe confirms the role of climate change for faunal dispersal and island colonization. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 149 , 293‐307. ADDITIONAL KEYWORDS: Crocodylus bambolii ‐ Diplocynodon ‐ endemic faunas ‐ late Miocene/early Pliocene ‐ Mediterranean area ‐ Messinian ‐ Microtia fauna ‐ Tomistoma ‐ Tortonian ‐ transmarine dispersal.

Geochronology and genesis of subalkaline basaltic lava rivers at the Dzhavakheti highland, lesser Caucasus: K-Ar and Sr-Nd isotopic data

The paper reports newly obtained K-Ar isotopic-geochronological data on the age of three lava flows (Khrami, Mashavera, and Kura), which begin at the Dzhavakheti volcanic highland in southern Georgia. All of the dated rocks, including those from the Kura Flow, which was previously considered as the Pleistocene, are demonstrated to have a Pliocene age. The lavas of the longest Khrami Flow were erupted at 3.25-3.10 Ma, and those of the Kura and Mashavera Flows at 2.20-2.05 Ma, a fact testifying to two pulses of volcanic activity at the Dzhavakheti Highland. The petrogeochemical and isotopic characteristics of the rocks ( 87 Sr/ 86 Sr = 0.7039-0.7042; = 3.4-5.1) indicate that they are subalkaline within-plate basalts formed by the fractional crystallization of a basic mantle melt with the usually discontinuous selective or rarely continuous contamina- tion with material that was not in geochemical equilibrium with the melt. The volcanics of the Khrami Flow are characterized by the less radiogenic Sr isotopic composition and the highest values, while the younger rocks of the Mashavera and Kura Flows have similar and more "crustal" isotopic signatures. The 87 Sr/ 86 Sr ratios of the Dzhavakheti subalkaline basalts are close to the initial Sr isotopic ratios of the Quaternary and Middle Pliocene dacite lavas from the same territory. Considered together with petrogeochemical and geological data, this suggests that all young rocks in Southern Georgia were produced in similar tectonic and geodynamic envi-

Implications of soils on mid-Miocene-aged drifts in the McMurdo Dry Valleys for ice sheet history and paleoclimate reconstruction

Strongly developed soils on unconsolidated deposits of mid-Miocene age occur in the uplands above 1500 m elevation in the Asgard Range and Quartermain Mountains in the McMurdo Dry Valleys. Inferred from the preservation and distribution of their surfaces, these deposits have been largely unmodified since a widespread glacial erosional event prior to 10 Ma. Composition of the till plays a key role in soil development on these ancient surfaces. Soils derived from dolerite-rich till have significantly greater depths of staining and ghosts, color-development equivalents of the Bw horizon, and extractable Fe than sandstone-rich tills. However, no significant differences were found in depth of visible salts, salt stage, electrical conductivity of the horizon of salt enrichment, and profile quantities of salts, which implies a similar age for the soils. The soils on the Miocene-aged deposits are less developed than soils of early Quaternary and Pliocene age at lower elevation in the Dry Valleys, inconsistent with the conclusion that these are relict Miocene surfaces. We suggest that the lower stage of soil development on the surfaces of Miocene age deposits primarily reflects higher erosion (deflation) rates than soils on Pliocene age deposits at lower elevation. If so, several meters of material may have been removed on 10-million-year timescales and that many of the erosion features ascribed to ancient glacial erosion could simply be the result of subaerial erosion under cold desert conditions. In this case, the soils would only reflect the climate of the last few million years. Although the soils are classified primarily as Typic Anhyorthels and Typic Anhyturbels, some of the soils on doleritic till have saltpans enriched in NaNO 3 or Na 2SO 4 and are classified in petronitric or petrogypsic subgroups.

Tundra environments in the Neogene Sirius Group, Antarctica: evidence from the geological record and coupled atmosphere–vegetation models

The Neogene Meyer Desert Formation, Sirius Group, at Oliver Bluffs in the Transantarctic Mountains, contains a sequence of glacial deposits formed under a wet-based glacial regime. Within this sequence fluvial deposits have yielded fossil plants that, along with evidence from fossil insects, invertebrates and palaeosols, indicate the existence of tundra conditions at 85°S during the Neogene. Mean annual temperatures of c . −12 °C are estimated, with short summer seasons with temperatures up to +5 °C. The current published date for this formation is Pliocene, although this is hotly debated. Reconstructions produced by the TRIFFID and BIOME 4 vegetation models, utilizing a Pliocene climatology derived from the HadAM3 General Circulation Model (running with prescribed boundary conditions from the US Geological Survey PRISM2 dataset), also predict tundra-type vegetation in Antarctica. The consistency of the model outputs with geological evidence demonstrates that a Pliocene age for the Meyer Desert Formation is consistent with proxy environmental reconstructions and numerical model reconstructions for the mid-Pliocene. If so, the East Antarctic Ice Sheet has behaved in a dynamic manner in the recent geological past.

Changes in the Abundance and Diversity of Proteaceae in South‐western Australia: a Review of an Integrated Palaeoenvironmental Study

AbstractSouth‐western Australia is a globally significant hotspot of Proteaceae diversity. This review reports on changes in the abundance and diversity of Proteaceae in south‐western Australia. Using palynology, the data were obtained from three sediment sequences from the Eocene, Pliocene and Holocene, as well as a modern pollen rain study, in the context of a vegetation history framework. The total percentages of Proteaceae pollen in pollen counts indicate that the number of Proteaceae in the vegetation are highest at present, slightly lower, yet still high in the Eocene, reduced by the Pliocene and lowest in the Holocene. It was found that Proteaceous genera can contribute up to 50% of the total modern pollen rain. Sediment from Lake Lefroy showed Nothofagus‐dominated rainforest occurred in the Middle to Late Eocene. Proteaceae species were at least as diverse as today, contributing up to a maximum of 42% of the total pollen rain, and varying across small lateral distances. A laminated Pliocene age sequence from Yallalie confirmed other studies that south‐western Australia was covered by a rich vegetation mosaic consisting of heath and wet rainforest elements. Proteaceae species were a consistent component of the counts, although diversity and abundance (maximum 5%) were low. A Holocene record from Two Mile Lake, near the Stirling Range, recorded little environmental change. Proteaceae species were noted in low abundance, at a maximum of 3.5% of the total pollen count. It is likely that both changing pollination mechanisms and changes in associated vegetation are important in determining the dispersal of Proteaceous pollen.

Evidence for long-term uplift on the Canary Islands from emergent Mio–Pliocene littoral deposits

Several islands in the Canarian archipelago show marine deposits with identical fossil faunas, which are generally assigned to different glacioeustatic marine episodes: mainly Pleistocene episodes in Lanzarote and Fuerteventura, and Mio–Pliocene ones in Gran Canaria. Three fossil species ( Saccostrea chili, Nerita emiliana and Strombus coronatus) characterize all the marine deposits from southern Lanzarote, to the west and south of Fuerteventura and northeast of Gran Canaria. Three other species ( Ancilla glandiformis, Rothpletzia rudista and Siderastraea miocenica) confirm the chronostratigraphic attribution of these deposits. Other more occasional fossils (as Chlamys latissima, Isognomon soldanii and Clypeaster aegyptiacus) fit an upper Miocene and lower Pliocene age. This agrees with new K/Ar ages obtained from pillow lavas emplaced into the marine deposits (ca. 4.1 Ma in Gran Canaria, ca. 4.8 Ma in Fuerteventura) and from underlying (ca. 9.3 Ma in Gran Canaria) or overlying (ca. 9.8 Ma in Lanzarote) lava flows. The marine deposits are eroded but large continuous segments are preserved sloping gently towards the coast. Variations in the highest and the lowest elevations of the deposits apsl (above present sea level) indicate post-depositional uplift movements. Glacioeustatic causes are unlikely to be responsible for these variations on the basis of the coastal location of the deposits and their equatorial fauna characteristic of Mio–Pliocene corals. Differential uplift of the deposits across the archipelago is argued to result from the progressive seaward tilting of the islands along the insular volcanic trail marking the westward migration of hot spot head since 20 Ma. Successive westward accretion of younger volcanic edifices resulted in increasing lithostatic load of the crust with progressive (diachronous) tilting of the older edifices and their palaeo-shorelines marked by past coastal deposits.

Rock petrophysics v. performance of protective and consolidation treatments: the case of Mt Arzolo Sandstone

Abstract The petrophysical characteristics of a building stone used in the city of Pavia, northern Italy, are analysed in the light of stone conservation through the application of water repellent and consolidant products. The research focuses on the modification of petrophysical properties as a function of the applied products, and on the critical assessment of the performances of fluorinated and siloxane resins as a function of the variable nature of the same lithotype. The studied material is a calcareous sandstone (Mt Arzolo Sandstone), Late Miocene-Early Pliocene in age, extensively employed as a building material during the 11th and 12th centuries. Experimental investigations on samples from historic quarries were performed before and after application of treatments: i.e. petrographical and fabric analyses; ultrasonic measurements; mercury porosimetry; abrasion resistance measurements; contact angle measurements; capillary and low-pressure water absorptions; water vapour permeability; and colour measurements. Two main lithotypes of Mt Arzolo Sandstone were recognized according to their petrophysical features: the open porosity being similar, differences exist concerning their fabric. These differences influence the physical-mechanical properties of the material and consequently the performances of the applied products. In particular, the difficulties in penetration of products when sandstone of smaller pore size is treated can lead to a significant reduction of the overall performances, which is more evident for products containing organic solvent with high molecular weight.

Engineering geological map of the urban area of Kastoria, NW Greece

In the present work, the engineering geological conditions of the urban area of Kastoria were examined. More specifically a geotechnical assessment of subsoil and rock outcrops within a minimum depth of 20 m bellow surface is made, for urban planning purposes. Landslide potential of the studied area including mainly rock falls and ground subsidence was also evaluated. Eleven engineering geological units were identified and mapped at 1:5.000 scale, which constitute the foundation ground of the old Kastoria town, as well as of its new areas of built-up extension. The identified ground units consist of six soil and five rock types. Soil units comprise one fill formation of variable composition and consistency with a ranging thickness between 2 m and 6 m and five loose to cohesive deposits, Holocene to Upper Pliocene in age, with high variation in grain size, density and plasticity factors. Rock lithologies range from highly to moderately weathered, closely fractured serpentinites and schists to fresh, widely fractured limestones. The old city of Kastoria is founded mainly on stable rocky ground and does not show any remarkable geotechnical problems. However, the need of built-up extension however and improvement of infrastructures, led to configurations of the marshy areas and to the use of foundation ground with poor mechanical properties, which locally need a special treatment to become stable.

A Shelduck (Anatidae: Tadorna) from the Pliocene of South Australia

SummaryA complete fossil humerus referable to a shelduck (Anatidae: Tadorna sp.) is reported from an uncertain locality in the ‘Bookmark cliffs’ on the River Murray, a few kilometres upstream from Berri and Lyrup southwest of Renmark, in the Riverland region of South Australia. The fossil was embedded in a piece of pale grey, clean coarse sandstone having a siliceous cement. This is interpreted as being Parilla Sand, of late Pliocene age, which outcrops along the Murray River from Renmark to Loxton.

Preliminary geology and paleontology of new hominid-bearing Pliocene localities in the central Afar region of Ethiopia

The Woranso-Mille paleontological study area is located in the central Afar region of Ethiopia, about 360 km northeast of the capital, Addis Ababa. Some parts of this area have been paleontologically known since the 1970s. However, most of the fossiliferous areas were discovered by surveys conducted in the region between 2002 and 2004. By the end of the 2006 field season, a total of 17 vertebrate localities had been designated, and more than 1000 vertebrate fossil specimens collected. Among these specimens, there are more than 20 fossil hominid craniodental and postcranial remains, including one partial skeleton, of Pliocene age (3.5–3.8 Ma). Research at this study area has thus far focused on the geology and paleontology of the early Pliocene deposits along the Mille river and adjacent areas located between the towns of Mille and Chifra. Exposed sediments in the new fossiliferous area are mostly silty sand and silty clay horizons interbedded with a number of volcanic tuffs and basaltic flows suitable for 40Ar/39Ar radioisotopic dating. The total stratigraphic section is about 50 m thick with a minimum age of ~3.5 Ma. The study area also has deposits of early to middle Pleistocene age, although no locality has been designated to date. The new Woranso-Mille paleontological study area provides a crucial temporal window into the time during which Australopithecus anamensis (3.9–4.2 Ma) appears to have given rise to Australopithecus afarensis (3.0–3.6 Ma). Radiometric dates have thus far yielded a minimum age of 3.5 Ma for the hominid localities and this conforms well with a biochronological age estimate of 3.6–3.8 Ma. The associated fauna, particularly the abundance of fossil cercopithecids and presence of diverse aquatic fossil vertebrates, indicates a relatively closed, wooded habitat probably associated with a paleo-Mille river.

Distribution and chronology of submarine volcanic rocks around Santorini and their relationship to faulting

Abstract Seismic reflection profiles from the marine areas around Santorini in the south Aegean arc show the distribution of active faults and the occurrence of submarine volcanic rocks interfingering with stratified basinal sediment. Santorini is located at the intersection of fault sets of different ages. To the west, active faults trend east–west, whereas to the east, active faults trend ENE–WSW and a slightly older set of faults trends NE–SW. Subsurface submarine volcanic rocks can be dated using ages estimated for the stratified basin sediments elsewhere in the Milos–Christiani Basin. Volcanic horizons off Santorini correlate with the main (young) Akrotiri (0.65–0.55 Ma) and old Akrotiri (1.6 ka) volcanic episodes, respectively. Off Christiani, the upper unit of volcanic rocks is of similar age to the young Akrotiri episode and the lower volcanic unit is likely to be of latest Pliocene age. Late Neogene basin subsidence and volcanism are a consequence of changing patterns of faulting resulting from the collision of the African and Aegean–Anatolian plates.

Inorganic geochemical characterisation of the Velenje lignite in the representative P-9k/92 borehole profile (Slovenia)

The study is based on 30 lignite, 6 footwall and 3 hanging-wall interval samples. Lignite seam of the Pliocene age is 101 m thick in the treated profile. Minor element geochemistry is evaluated by the contents of 11 standard oxides, among which SiO2, Al2O3, Fe2O3 and CaO form the bulk composition. Trace-element characterization is based on contents of 46 elements. Stot., Ctot., Corg. and loss on ignition (LOI) at 1000 °C were analysed in addition. Ali analyses (by ICP-AES, ICP-MS, Leco) were carried out on the “whole lignite”/“whole rock” samples in the Acme Analytical Laboratories (Canada). Recalculation to the “pure inorganic matter” basis was carried out in order to obtain realistic relations between contents of minor element oxides. Contents of the minor element oxides in the inorganic matter are dependant on the ash content, and, an ash content of 20-25 % was found out as an important “geochemical threshold”. SiO2+ Al2O3 together with positively corelated K2O and TiO2increase with increasing ash content. On the contrary, CaO, MgO and Fe2O3, they increase with decreasing ash content. Affinity of organic binding of Ca, Mg, and (probably) of Fe is ascertained by negligible contents of Cinorg., Abundances of the great majority of trace elements are mostly lower and/or normal in comparison to the world coals. However, As, U, and Mo are typomorphic for the treated lignite. In spite of that, they are not critical. Widespread areas of different lithologies with higher contents of these elements are known throughout the world as well as in Slovenia.

Plio-Pleistocene climatic transition and the lifting of the Teton Range, Wyoming

Fine-grained lacustrine, riverine and ash-fall sediments of the Shooting Iron Formation, whose late Pliocene age is established by Blancan gastropods and vertebrates, yield a pollen flora that is essentially similar in composition to the modern pollen rain in the Jackson Hole area. The Pliocene assemblage suggests a climate like that of the Jackson valley and foothills today. These spectra also resemble a Pliocene pollen flora from Yellowstone Park dated at ∼ 2.02 Ma. However, the underlying Miocene Teewinot sediments differ by containing pollen of four exotic deciduous hardwoods (Tertiary relicts) that suggest a summer–moist climate, unlike that of today. The Shooting Iron sediments lie with an angular unconformity on and above the Miocene lake sediments of the Teewinot Formation. Both of these deposits probably preceded the main uplift of the Teton Range based on the absence of Precambrian clasts in the Tertiary valley deposits. Because the Pliocene floras were modern in aspect, a Plio-Pleistocene transition would be floristically imperceptible here. The sequence denotes a protracted period of relative stability of climate during Teewinot time, and a shift in vegetational state (summer–wet trees drop out) sometime between the latest Miocene and latest Pliocene. The Pliocene spectra suggest a dry, cooler climate toward the end of Shooting Iron time.

Tectonic subsidence v. erosional lowering in a controversial intramontane depression: the Jiloca basin (Iberian Chain, Spain)

The Jiloca basin is a large intramontane, NNW–SSE-trending topographical depression in which the relative role of tectonic subsidence and erosional lowering is currently a matter of discussion. Geometry and facies of the sedimentary infill at its central sector have now been characterized from compiled borehole data, which allows discussions of how the evolutionary model is constrained. The central Jiloca depression contains a Late Pliocene to Pleistocene sedimentary sequence made up of alluvial fan, pediment mantle and episodic palustrine deposits, overlying a carbonate unit that could represent an early lacustrine stage of Late Miocene–Early Pliocene age. The geometry of these units is partially controlled by NW–SE-striking normal faults. Both the morphological depression and the sedimentary basin truncate previous folds, whose traces beneath the Neogene–Quaternary infill have been interpreted from the geology of the basin margins, borehole data and hydrogeological criteria. The northern and southern sectors of the Jiloca depression are bounded by faults showing measurable hectometric-scale throws (Calamocha and Concud faults). Moreover, in the central sector, the ∼ 350–400 m tectonic uplift of Sierra Palomera has been interpreted from a morphostructural reconstruction of the tilted block which separates the Teruel and Jiloca graben, being similar to the height of the Sierra Palomera mountain front. All these features are consistent with a tectonic basin developed within the framework of the Neogene–Quaternary extensional evolution of eastern Spain. In contrast, they are hardly compatible with genetic models based on erosional deepening, either topographic lowering by numerous nested Tertiary erosion pediplains, or sub-alluvial Pliocene–Quaternary karstic corrosion.