Paleoenvironmental basis of cognitive evolution in great apes

A bias favoring tree-dominated habitats and ripe-fruit frugivory has persisted in great ape evolution since the early Miocene. This bias is indicated by fossil ape paleoenvironments, molar morphology, dental microwear, the geographic pattern of extinctions, and extant apes' reliance on wooded settings. The ephemeral aspect of high-quality fruit has placed a premium on cognitive and social means of finding and defending food sources, and appears related to great apes' affinity since the Miocene for wooded, fruit-rich environments. These habitats have, however, undergone a severe withdrawal toward the low latitudes of Africa and Southeast Asia since the late Miocene, corresponding to a decline in the diversity of great apes beginning 9.5 million years ago. Plio-Pleistocene records imply that wooded settings of Africa and SE Asia were prone to substantial fragmentation and coalescence. Once apes were confined to equatorial settings, therefore, habitat instability heightened the spatial/temporal uncertainty of ripe-fruit sources. Prolonged learning, the assignment of attributes to distant places, mental representation, and reliance on fallback foods were all favored in this dynamic environmental context. These abilities helped sustain forest frugivory in most lineages. Fluid social grouping afforded the animals opportunities to locate ephemeral foods in continuous and fragmented forests. Fission-fusion grouping also magnified the problems of object impermanence (of individuals) and dispersion manifested by food sources in the ecological realm. Thus the spatial and temporal dynamics of fruit and wooded habitats since the Miocene are reflected in important components of great ape cognition, foraging, and sociality. In contrast to great apes, cercopithecoid monkeys have increased their plant dietary options and diversified in seasonal environments since the late Miocene. Early hominins eventually severed the habitat bias that characterized the evolution of great apes, and later expanded into diverse environments.     

Paleoenvironmental implications of fixed dune systems in Southern Africa

Extensive systems of fixed linear dunes occur in the Kalahari region of southern Africa, from 28°S to 16°30′S. They provide evidence for large-scale expansion of arid climates in the subcontinent during the Quaternary. On the basis of differing dune morphologies and alignments, three periods of Upper Pleistocene aridity are recognised.Patterns of dune alignments reflect paleosand flow regimes and permit deduction of past winds and circulation patterns, leading to the conclusion that arid episodes were associated with, and probably caused by, greater strength and persistence of the South African anticyclone.A tentative chronology of the arid periods tends to support the hypothesis that subtropical aridity was contemporaneous with glacial conditions in high latitudes.     

Paleoenvironmental reconstruction based on palynofacies analysis of the Aptian–Albian succession of the Sergipe Basin,Northeastern Brazil

Palynofacies analyses were carried out on 272 core samples from two wells (GTP-17-SE and GTP-24-SE) in the Sergipe Basin, with the aim of reconstructing the paleoenvironments of the upper Aptian–middle Albian. For the palynofacies analysis the kerogen categories were counted and subjected to cluster analyses. For detailed environmental analysis, kerogen distribution trends and parameters were applied, based on percentages of kerogen categories. Total organic carbon analysis was also used. The stratigraphic distribution of palynofacies associations that defined eight palynofacies units in well GTP-17-SE and ten in well GTP-24- SE reflects a continuous terrestrial influx throughout the succession. Amorphous organic matter (AOM) and palynomorph groups show moderate to high percentages, especially in well GTP-24-SE. The increase in relative abundance of these groups suggests that a long-term a transgression and/or a decreasing terrestrial influx occurred in the area. From the bottom to top six depositional environments were identified in wells GTP-17-SE and GTP-24, respectively, and they reflect the progressive increase in marine influence as the basin evolved. Brackish lagoon conditions changed to more open marine conditions as sea level changed during the separation of South America from Africa.     

黄土磁化率及其古环境意义述评

黄土是第四纪时期的重要堆积物,其对于古环境的恢复具有极重大的意义。黄土磁化率对古降水量的推算,以反建立古气候复元的定量模型等都已成为可行。同时,对现代土壤环境与降尘等环境因素的研究是磁化率应用性研究的新领域。     

Paleoenvironmental model and sequence stratigraphy of the Asmari Formation in southwest Iran

The Asmari Formation is a thick carbonate succession of the Oligo-Miocene in southwest Iran (Zagros Basin). The Zagros Basin was a continental margin attached to the eastern edge of Africa throughout the Phanerozoic. The foraminiferal limestone from the Asmari Formation has been studied to determine its microfacies, paleoenvironments and sedimentary sequences. Based on analysis of larger benthic foraminiferal assemblages and microfacies features three major depositional environments are identified. These include open marine, barrier and lagoon-lower intertidal. These three are represented by eleven microfacies. A carbonate ramp platform is suggested for the depositional environment of the Asmari Formation. The inner ramp facies are characterized by wackestone-packstone, dominated by various taxa of imperforate foraminifera. The middle ramp facies represented by packstone-grainstone to floatstone with a diverse assemblage of larger hyaline foraminifera. The outer ramp is dominated by argillaceous wackestone, characterized by planktonic foraminifera and larger hyaline foraminifera. Two third-order sequences are identified based on deepening and shallowing patterns in microfacies, staking patterns and the distribution of Oligocene-Miocene foraminifers.     

The Oldest Beetle and Bee Ichnofossils from Mexico and their Paleoenvironmental Implications

ABSTRACT

Specimens of Fictovichnus gobiensis, Celliforma curvata, Celliforma rosellii, Celliforma germanica and Celliforma isp. were collected from paleosol horizons in a fluviolacustrine succession near Santiago Yolomécatl town, in northwestern Oaxaca, southern Mexico. These ichnofossils represent the oldest evidence of beetles and bees in Mexican localities. K–Ar ages and the record of the equid Miohippus assiniboiensis, an index fossil, indicate that the age of the deposits is late Eocene. Based on the presence of the insect ichnofossils, pedogenic carbonate isotopes and mammal proxies, the inferred type of vegetation present in the study area was scrubland/woodland, within subhumid to subarid conditions.     

甘肃苏苗塬头地点石制品特征与古环境分析

苏苗塬头地点位于甘肃省平凉市庄浪县东北部, 埋藏于章麻河二级阶地的典型马兰黄土中。经剖面清理和地表采集, 2002和2004年在该地点共获得石制品2318件, 本文以集中分布区出土(2166件)和地表采集(48件)共2214件石制品为主要研究对象。该批石制品以石片、碎片和碎屑为主, 有少量石核和工具。剥片技术以砸击法为主, 锤击法为辅, 鲜见第二步加工。石制品原料主要为来自现代河床或阶地底部砾石层的脉石英。炭屑加速器质谱(AMS 14C)年代测试和多环境代用指标分析显示, 苏苗塬头为一处旧石器时代晚期文化地点, 人类活动主要发生于气候干冷的末次盛冰期(约距今2.4—1.8万年), 反映了古人类较强的环境适应能力。     

Paleoenvironmental distribution of microfossils and stromatolites in the Upper Proterozoic Backlundtoppen Formation, Spitsbergen

The Upper Proterozoic (ca. 700-800 Ma old) Backlundtoppen Formation, northeastern Spitsbergen, preserves an abundant and varied record of ancient microbial life. Five distinctive microfossil assemblages occur in five equally distinct sedimentary settings; differences among the assemblages appear to reflect original ecological heterogeneity, although taphonomic circumstance may contribute to some distinctions. Microfossil assemblages occur in: oncolites, oolites, and pisolites; stratiform stromatolites and associated intraclastic rudites; partially silicified micrites; and siltites interbedded with quartz arenites. Individual assemblages contain one to eight differentiable taxa; a minimum of 17 distinct populations is present in the formation as a whole. Additional microbial community diversity an be inferred from the presence of domal, columnar, pseudocolumnar, and coniform stromatolites, none of which contains microfossils. On the basis of macrostructure, four stromatolite types appear to be present, but only three distinct mat-building communities can be inferred from microstructural features. Eohyella elongata n. sp., a euendolithic cyanobacterium found in silicified pisolites, is described as new.     

Paleoenvironmental interpretation of the mid‐late Holocene of Corrientes province,Argentina

The objective of the present paper is to recognize and reconstruct, from the analysis of pollen recovered from sedimentary cores, the predominant plant communities and their variations during the Holocene in Corrientes Argentina, in order to infer changes in climatic conditions, vegetation and paleoenvironmental evolution in the northeast of Argentina. For this study, lakes located in the central region of Corrientes province were selected, comprising part of the western margin of the Iberá Wetland. The palynological analysis of the paleocommunities shows, in a first stage of the mid Holocene, the predominance of marsh grasslands and hygrophilous communities that indicates humid to sub‐humid environmental conditions. In a later stage of the mid Holocene, the paleocommunities show a characteristic association of wetlands, which together with the presence of Typha sp., would indicate sub‐humid to humid conditions and waterlogged or flooded soils with slow‐moving water. For the late Holocene, the paleocommunities show, initially, the presence of a grass‐dominated herbaceous steppe, indicating environmental disturbances, which in the fossil record could reflect the combination of intense wind action under a dry climate. In a later stage, the frequency and variety of species characteristic of humid environments increase, dominated by marshy‐herbaceous species, in addition to the development of the hygrophilous forest. Consequently, since the mid Holocene, the main climate factors responsible for the observed changes in wetland conditions were the location and intensity of the Atlantic and Pacific anticyclones in addition to changes in sea level. These forces mainly affected the distribution of precipitation, causing significant changes in the vegetation communities.     

Large-Diameter Burrows of the Triassic Ischigualasto Basin,NW Argentina: Paleoecological and Paleoenvironmental Implications

Large-diameter ichnofossils comprising three morphotypes have been identified in the Upper Triassic Ischigualasto and Los Colorados formations of northwestern Argentina. These burrows add to the global record of the early appearance of fossorial behavior during early Mesozoic time. Morphotypes 1 and 2 are characterized by a network of tunnels and shafts that can be assigned to tetrapod burrows given similarities with previously described forms. However, differences in diameter, overall morphology, and stratigraphic occurrence allow their independent classification. Morphotype 3 forms a complex network of straight branches that intersect at oblique angles. Their calcareous composition and surface morphology indicate these structures have a composite biogenic origin likely developed due to combined plant/animal interactions. The association of Morphotypes 1 and 2 with fluvial overbank lithologies deposited under an extremely seasonal arid climate confirms interpretations that the early appearance of burrowing behavior was employed by vertebrates in response to both temperature and moisture-stress associated with seasonally or perpetually dry Pangean paleoclimates. Comparisons of burrow morphology and biomechanical attributes of the abundant paleovertebrate fauna preserved in both formations permit interpretations regarding the possible burrow architects for Morphotypes 1 and 2. In the case of the Morphotype 1, the burrow constructor could be one of the small carnivorous cynodonts, Ecteninion or Probelesodon. Assigning an architect for Morphotype 2 is more problematic due to mismatches between the observed burrow morphology and the size of the known Los Colorados vertebrates.     

Paleoenvironmental model for Eocene foraminiferal limestones of the Adriatic carbonate platform (Istrian Peninsula)

The foraminiferal limestones from the Middle Eocene Central Istrian region illustrate progressive deepening of depositional gradients. Shifting of Lower Cuisian to Upper Lutetian microfacies can be described in terms of a ramp model. The Orthophragminae-bearing parts of the foraminiferal limestones are interpreted in terms of larger foraminiferal faunal associations, planktonic foraminiferal relative abundance, limitations of algal endosymbionts, foraminiferal lamellar thickness and flattening of test shapes. Microfacies I contains the most diverse larger foraminiferal association with a predominance of large, thick nummulitids, assilinids, and asterocyclinids. Microfacies II is characterized by a gradual increase of Orthophragminae diversity and abundance. Nummulitids, equally abundant, are dominated by lenticular and subspherical specimens. The reduction in number of nummulitid specimens with characteristic biconical radiate morphologies, and relative abundance of flattened orthophragminids, characterizes Microfacies III. Scattered biodestructed orthophragminid tests and planktonic foraminifera constitute Microfacies IV, indicating the end of a long-lasting, shallow-marine Adriatic Carbonate Platform regime.     

Paleoenvironmental proxies and what the Xiamaling Formation tells us about the mid‐Proterozoic ocean

The Mesoproterozoic Era (1,600–1,000 million years ago, Ma) geochemical record is sparse, but, nevertheless, critical in untangling relationships between the evolution of eukaryotic ecosystems and the evolution of Earth‐surface chemistry. The ca. 1,400 Ma Xiamaling Formation has experienced only very low‐grade thermal maturity and has emerged as a promising geochemical archive informing on the interplay between climate, ecosystem organization, and the chemistry of the atmosphere and oceans. Indeed, the geochemical record of portions of the Xiamaling Formation has been used to place minimum constraints on concentrations of atmospheric oxygen as well as possible influences of climate and climate change on water chemistry and sedimentation dynamics. A recent study has argued, however, that some portions of the Xiamaling Formation deposited in a highly restricted environment with only limited value as a geochemical archive. In this contribution, we fully explore these arguments as well as the underlying assumptions surrounding the use of many proxies used for paleo‐environmental reconstructions. In doing so, we pay particular attention to deep‐water oxygen‐minimum zone environments and show that these generate unique geochemical signals that have been underappreciated. These signals, however, are compatible with the geochemical record of those parts of the Xiamaling Formation interpreted as most restricted. Overall, we conclude that the Xiamaling Formation was most likely open to the global ocean throughout its depositional history. More broadly, we show that proper paleo‐environmental reconstructions require an understanding of the biogeochemical signals generated in all relevant modern analogue depositional environments. We also evaluate new data on the δ⁹⁸Mo of Xiamaling Formation shales, revealing possible unknown pathways of molybdenum sequestration into sediments and concluding, finally, that seawater at that time likely had a δ⁹⁸Mo value of about 1.1‰.     

Paleoenvironmental reconstruction of middle Miocene paleosols bearing Kenyapithecus and Victoriapithecus, Nyakach Formation, southwestern Kenya

Paleosols in the middle Miocene (15 Ma) Nyakach Formation at Kaimogool, near Sondu, southwestern Kenya have yielded specimens of the early cercopithecoid Victoriapithecus macinnesi and the early kenyapithecine Kenyapithecus africanus, and can be used as evidence for the environmental mosaic occupied by these primates. Five distinct types of paleosols (pedotypes) are recognized in the Nyakach Formation section at Kaimogool South. The most common paleosols are reddish brown, silty calcareous profiles with blocky structure and large root traces (Ratong pedotype) which are interpreted as soils of well-drained, dry bushland or thicket (nyika). Weakly developed paleosols associated with paleochannels (Dhero pedotype) represent wooded grassland early in the ecological succession from streamside flooding. One of these paleosols has yielded a fossil flora of grasses and small-leaved dicots like those of modern semi-arid wooded grassland. Crumb structured, calcareous paleosols with iron-manganese nodules (Yom pedotype) are interpreted to represent seasonally waterlogged, wooded grassland (dambo or vlei). Thick, red clayey, calcareous paleosols with blocky ped structure and large root traces (Tut pedotype) are interpreted as soils of well-drained dry woodland. Other blocky-structured, gray to brown calcareous paleosols with iron-manganese nodules (Chido pedotype) are interpreted as soils of seasonally waterlogged, riparian dry woodland. Fossil soils, plants and gastropods are evidence of an unusually dry (300-500 mm mean annual precipitation) habitat for apes, consisting of a vegetational mosaic dominated by dry woodland, bushland and thickets with few areas of seasonally waterlogged grassland. Fossils of V. macinnesi are rare from Nyakach, but were found in paleosols representative of bushland and thicket habitats (Ratong). Fossils of the ape K. africanus were found within paleosols indicative of dry woodland (Tut). Other paleosol types representative of seasonally dry dambo grassland (Yom), colonizing grassland (Dhero) or riparian woodland (Chido) are also represented, but have not yet produced primate fossils.     

Ichnofossils of the Psilonichnus Ichnofacies and Their Paleoecological and Paleoenvironmental Significance in the Scottish Middle Jurassic

In the Bathonian (Middle Jurassic) Kilmaluag Formation, Great Estuarine Group, on the Isle of Skye, northwest Scotland, are ichnofossils that can be attributed to the burrowing activity of semi-terrestrial crab-like animals. The ichnofossils are preserved within supralittoral breccia-conglomerates and littoral calcareous mudstones and micrites deposited in a closed and shallow, low-salinity to freshwater coastal-lagoon setting. The dominant ichnofossil assemblage is preserved in the supralittoral rocks and comprises variable burrow types forming an ichnocoenosis and assigned to the Psilonichnus ichnofacies. These ichnofossils potentially provide the earliest known record of crab activity and their physiological adaptation to survive in a semi-terrestrial environment. Burrow characteristics include enlarged funnel-shaped apertures, unlined walls, absence of branching or biogenic reworking, inclined to vertical, U- and L-shaped forms and possible basal dwelling chamber. The ichnofossil assemblage preserved in the littoral rocks is attributed to the activity of either semi-terrestrial crabs or shrimps. Ichnofaunal characteristics reveal unique aspects of the paleoenvironments and paleoecology of the tracemaking community, including climatic conditions, substrate characteristics, the possible influence of paleowater table levels, paleoshoreline position, spatial variation in burrow morphology and possible gregarious and territorial behavior.     

Fossil Diatoms in No.47 Borehole of Jianghan Plain and Their Significance to Paleoenvironmental mental Analysis

The No. 47 borehole is located at Jiangling County in the Jianghan Plain, Hubei Province, China. There are abundant sedimentary diatoms (about 26 genera and 148 taxa) in the upper section (46.6 – 2.2 m) of the borehole. Most of them belong to the existent freshwater diatoms, being mainly epiphytic, littoral and shallow-water-inhabitant species. Among them some gerera are rich in taxa such as Navicula (28 taxa), Cymbella (23 taxa),Achnanthes (15 taxa), Gomphonema (14 taxa) and Eunotia (13 taxa). The dominant species are Gomphonema tropic& var. nonpunctatum, Cyclotella comta, Cocconeis placentula var. lineata and Stephanodiscus dubius, etc. From the lower to the upper section of the sediment, species number (Sp./strat. ) and amount ( Ind./g dry sed. ) of the diatoms underwent a change from scantiness to plenty, then gradually decline to final disappearance. The change of the diatoms obviously reflects a paleoenvironmental change of water bodies in this area, i. e. :at the early stage, this area was possibly a river (might have been an obsolete course of the Yangtze River), then it gradually became a side bank in the river, which later turned into a depression retaining water perphaps in the form of a lake or a swamp in a flood plain. Then it gradually became deepened and widened with final disappearance of the retained water. According to the diatom assemblages in different sedimentary phases, it may be inferred that the pH range in these water bodies were basically stable, ranging from neutral (pH = 7) to slightly alkaline (pH > 7). Combining pollen amdysis (mainly the pollens of Pinus and Betula ) and mineral analysis with diatoms,it might be deduced that the paleoclimate of this area during the period of luxuriant growth of diatoms was somewhat colder than the present time. In the sediment, the amount and species number of the diatoms all significantly correlated with the mean grain size of the sediment.     

Paleoenvironmental reconstruction of the Asbole fauna (Busidima Formation, Afar, Ethiopia) using stable isotopes

The Middle Pleistocene environmental and climatic conditions at Asbole, lower Awash Valley, Ethiopia were reconstructed using stable carbon and oxygen isotopic composition (¹³C, ¹⁸O) of fossil tooth enamel coupled with faunal abundance data. We analyzed the isotopic composition of a total of 80 herbivorous tooth enamel samples from 15 mammalian taxa, which archive the dietary preferences and drinking behavior from the “Asbole faunal zone”. The carbon isotopic data signify a wide range of foraging strategies, across the entire spectrum of pure C4 to C4-dominated diet, mixed C3/C4 diet and C3-dominated diet. The oxygen isotopic enrichment between evaporation sensitive and insensitive taxa (?_ES-EI) is 3.7‰ which provides an estimate of the mean annual water deficit of the Middle Pleistocene at Asbole of 1470 mm, a value characteristic of modern arid landscapes in this part of the Awash Valley. The isotopic data coupled with faunal abundance data indicate an arid C4-dominated open-vegetated region, with an abundance of forest-dwelling primates that identify the presence of gallery forests flanking tributary streams to the paleo-Awash River. Thus, with these combined methodologies, it is possible to explicate a more detailed character of the “mosaic” of environments characteristic of Neogene savanna ecosystems. These findings, clearly indicate the importance of avoiding oversimplification of Pleistocene environmental reconstructions, based on single proxies at isolated localities.     

Paleoenvironmental reconstruction of the Early Pleistocene site of Quibas (SE Spain) using a rodent assemblage

In this paper we analyze the rodent assemblage from the Early Pleistocene site of Gruta1 (Quibas karstic complex, Murcia, SE Spain), providing taphonomic comments and paleoecological and paleoclimatic data. The studied assemblage includes 209 identified rodent teeth corresponding to at least four taxa. The karstic source of the site and the low presence of digested remains suggest that the accumulation is scatological in origin, with the influence of predators such as owls; the accumulation also shows certain evidence of slight hydrodynamic sorting. For the area around Quibas/Gruta1 the paleoecological study indicates a predominance of rocky areas (31.7%), forested environments (31.7%) and open dry meadows or shrublands (29.7%), which would indicate a mosaic forest environment, and to a lesser extent the presence of open humid land (5.4%) and areas along streams or ponds (1.5%). The distribution of the bioclimatic spectra yields the highest percentage for a Mediterranean climate (37.5%), while the climatic parameters calculated (MAT = 15 °C, MTW = 25.7 °C, MTC = 4.3 °C, MAP = 390 mm) suggest colder and slightly more humid conditions than today at the time of the deposition of the remains. The data also point to a relative decrease in temperature within the phase in which the site was produced, which possibly occurred during a relative cold period between MIS 36 and MIS 40 according to the age.     

Integrated Paleoenvironmental Reconstruction and Taphonomy of a Unique Upper Cretaceous Vertebrate-Bearing Locality (Velaux,Southeastern France)

The Velaux-La Bastide Neuve fossil-bearing site (Bouches-du-Rhône, France) has yielded a diverse vertebrate assemblage dominated by dinosaurs, including the titanosaur Atsinganosaurus velauciensis. We here provide a complete inventory of vertebrate fossils collected during two large-scale field campaigns. Numerous crocodilian teeth occur together with complete skulls. Pterosaur, hybodont shark and fish elements are also represented but uncommon. Magnetostratigraphic analyses associated with biostratigraphic data from dinosaur eggshell and charophytes suggest a Late Campanian age for the locality. Lithologic and taphonomic studies, associated with microfacies and palynofacies analyses, indicate a fluvial setting of moderate energy with broad floodplain. Palynomorphs are quite rare; only three taxa of pollen grains occur: a bisaccate taxon, a second form probably belonging to the Normapolles complex, and another tricolporate taxon. Despite the good state of preservation, these taxa are generally difficult to identify, since they are scarce and have a very minute size. Most of the vertebrate remains are well preserved and suggest transport of the carcasses over short distances before accumulation in channel and overbank facies, together with reworked Aptian grains of glauconite, followed by a rapid burial. The bones accumulated in three thin layers that differ by their depositional modes and their taphonomic histories. Numerous calcareous and iron oxides-rich paleosols developed on the floodplain, suggesting an alternating dry and humid climate in the region during the Late Campanian.     

Paleoenvironmental study of the Carquefou site (Massif Armoricain, France) from the end of the Sub-boreal

The town of Carquefou, some 10 km northeast of Nantes on the left bank of the river Erdre, occupies a site long associated with human activity. During road construction east of the town, ditches, enclosures and post holes characteristic of the late la Tène were discovered at the locality of “Le Clouet”, which led us to obtain core samples from a nearby peat bog. These investigations indicated the changes in vegetation since 3915±95 uncal B.P., [2828 (2459) 2074 cal B.C.]. The slopes in the surroundings of the bog have been relatively treeless since the Bronze Age, but a very open woodland vegetation composed of Tilia, Corylus and Quercus has been maintained until the present day. In the area around the bog, and Alnus wood with an undergrowth of Cyperaceae was the dominant vegetation, despite some changes probably related to human occupation since the Bronze Age. Beginning at 955±35 uncal B.P. [1004 (1036, 1144, 1146) 1181 cal A.D.], in the Middle Ages, the alders disappeared almost totally, apparently because of clearance or an increase in water level. Human presence led to intensified cultivation of different crops including Cannabis and especially Cerealia. Finally, the presence of a variety of anthropogenic indicator plants (Cichorioideae, Asteraceae, Plantago lanceolata, etc.) suggests that cattle were reared in the vicinity of the site. Received May 22, 2000 / Accepted March 29, 2001