Anu Kaakinen

Holocene climate and landscape evolution East of the Pechora Delta, East-European Russian Arctic

This study presents a multiproxy record of Holocene environmental change in the region East of the Pechora Delta. A peat plateau profile (Ortino II) is analyzed for plant macrofossils, sediment type, loss on ignition, and radiocarbon dating. A paleosol profile (Ortino III) is described and radiocarbon dated. A previously published peat plateau profile (Ortino I) was analyzed for pollen and conifer stomata, loss on ignition, and radiocarbon dating. The interpretation of the latter site is reassessed in view of new evidence. Spruce immigrated to the study area at about 8900 14C yr B.P. Peatland development started at approximately the same time. During the Early Holocene Hypsithermal taiga forests occupied most of the present East-European tundra and peatlands were permafrost free. Cooling started after 5000 14C yr B.P., resulting in a retreat of forests and permafrost aggradation. Remaining forests disappeared from the study area around 3000 14C yr B.P., coinciding with more permafrost aggradation. The retreat of forests resulted in landscape instability and the redistribution of sand by eolian activity. The displacement of the Arctic forest line and permafrost zones indicates a warming of at least 2–3°C in mean July and annual temperatures during the Early Holocene. At least two cooling periods can be recognized for the second half of the Holocene, starting at about 4800 and 3000 14C yr B.P.

Paleosol carbonate multiple isotopologue signature of active East Asian summer monsoons during the late Miocene and Pliocene

East Asian summer monsoon precipitation has a globally unique δ 18 O signature characterized by low δ 18 O values related to the precipitation “amount effect”. We explore the history of this signature using carbonate clumped-isotope thermometry and δ 18 O of paleosol carbonates from northern China. We find that soil water δ 18 O throughout the late Miocene and Pliocene was indistinguishable from present-day summer meteoric water δ 18 O. Additionally, soil temperatures were similar to present-day summer temperatures, as were latitudinal gradients in temperature. Paleosol carbonate δ 13 C values document a pattern of northward-increasing C 4 vegetation during 7–3 Ma, interpreted as marking a paleobiome transition from forest to steppe. The present-day summer monsoons give rise to a similar transition owing to latitudinal gradients in precipitation amount and seasonal duration. Taken together, these lines of evidence point to active East Asian summer monsoons during the warm climates of the late Miocene and Pliocene.

Sedimentation of the Late Miocene Bahe Formation and its implications for stable environments adjacent to Qinling mountains in Shaanxi, China

Abstract An important key site along the Bahe River in the Lantian area, Shaanxi Province, northern China exposes a conformable sedimentary sequence that records the transition from early Late Miocene fluvial sediments into Late Miocene and Pliocene aeolian Red Clay, and finally into Pleistocene loess. Although the Red Clay and Pleistocene loess in northern China have been intensively studied over the years, the Bahe Formation, beneath the Red Clay in the Lantian area, has been less well studied. Here we present the preliminary results of a detailed lithostratigraphical investigation of the Bahe Formation on the northern slopes of the Bailuyuan Plateau and discuss the style of sedimentation during its deposition. The Bahe Formation in the Lantian area, is composed of fluvial and lacustrine deposits laid down in the Weihe Graben during the Late Miocene. Six main facies assemblages have been distinguished: (1) massive or crudely bedded conglomerates, (2) cross-stratified conglomerate and sandstone deposits, (3) minor sandstone deposits, (4) fine-grained deposits, (5) gritty mudstone and sandstone deposits and (6) marl deposits. These assemblages represent the deposits of active channels, crevasse splays, sheet floods, and floodplains with paleosols and lakes. Thick and laterally pervasive units of fine-grained sediments, formed as suspension fall-out on the floodplain, indicating low-energy conditions and a relatively gentle surface gradient in the area, are by far the most common sedimentary component. Channel-related sandstones and conglomerates indicate that the rivers had a low-sinuosity and were braided, to anastomosing types. The Bahe fluvial system operated for several million years in a tectonically inactive setting in a vegetated area under a relatively arid climate. This environmental interpretation is consistent with that derived from the interpretation of the vertebrate fossil fauna recovered from the sediments.

Late Quaternary foraminiferal record in Murchisonfjorden, Nordaustlandet, Svalbard

Benthic foraminiferal assemblages from Nordaustlandet, Svalbard, are described for the first time with the objective of reconstructing the palaeoenvironmental conditions in the area during the late Quaternary. Investigations were carried out on marine deposits exposed along the southern shores of Murchisonfjorden. Five foraminiferal assemblages (A1–A5), representing different palaeoenvironmental conditions, were identified from the marine intervals, i.e., the Cassidulina reniforme–Elphidium albiumbilicatum assemblage (A1) from the Early Weichselian, the Islandiella helenae–Cibicides lobatulus assemblage (A2) from the Early Weichselian, the Cibicides lobatulus–Cassidulina reniforme assemblage (A3) from marine isotope stage 3, the Elphidium albiumbilicatum assemblage (A4) from the early Holocene and the Astrononion gallowayi assemblage (A5) from the mid-Holocene. Assemblages A1–A5 are compared with modern and fossil Quaternary assemblages from Arctic regions. Particularly notable is the fact that a well-defined Middle Weichselian assemblage in Svalbard is described for the first time, i.e., the Cibicides lobatulus– Cassidulina reniforme assemblage. All the assemblages from Nordaustlandet represent glacier-distal, inner-shelf environments with an open connection to the ocean. The results reveal the occurrence of three marine intervals (ice-free periods) in the north-western part of Nordaustlandet during the Weichselian, as well as ice-free conditions during most of the Holocene. A comparison of the assemblages from Nordaustlandet with previously published foraminiferal zones from onshore sections elsewhere in Svalbard show some degree of similarity, but also show considerable variation in species compositions, presumably caused by local environmental differences.

Late Miocene large mammals from Ivand (Northwestern Iran)

ABSTRACT Large mammalian fossil fauna of the Ivand locality in northwestern Iran is reported for the first time. This new locality is situated north of the city of Tabriz in the geographical proximity of the famous Maragheh fossil sites. A large hipparion, represented by an almost complete skull and mandibles, is recorded from this locality. The skull, most likely of Hipparion giganteum-Hipparion brachypus lineage, represents significant evidence of the presence of large hipparionine horses in northwestern Iran in the Late Miocene. A small number of horn-cores attributed to Oioceros atropatenes Rodler & Weithofer, 1890 and Gazella sp., in addition to some indeterminate dentition, represent the bovid material in the Ivand fossil assemblage. Postcranial evidence also points to the presence of Deinotherium giganteum Kaup, 1829 and Rhinocerotinae indet., while other material adds carnivorans, giraffes and large porcupine rodents to the list of the fauna. Based on the occurrence of these taxa, the Ivand locality can be correlated with the Middle and Upper Maragheh biostratigraphical intervals, thus demonstrating a middle Turolian age (c. 8–7 Ma).

Floodplain processes in the shaping of fossil bone assemblages: an example from the Late Miocene, Bahe Formation, Lantian, China

Abstract Vertebrate remains are frequently preserved and recovered from floodplain deposits. The composition of such fossil assemblages is expected to vary considerably with the processes active during and after deposition. In this paper, vertebrate fossil assemblages from three separate localities (Late Miocene, Bahe Formation, Lantian County, Shaanxi, China) were studied to assess how fluvial processes may have influenced the shaping of these. Although, the three localities represent floodplain deposits, all were formed in different fluvial subfacies. The localities were logged in detail and the degree of surface exposure of the collected specimens was determined through analysis of their stage of weathering. Combining these data, the following interpretation was made: Locality 31 represents a crevasse splay, an avulsion that instantaneously buried a group of animals. Locality 6 was formed on an overbank area during repeated, unchannelised flooding. This assemblage represents an attritional accumulation, ranging from fresh to reworked remains, accumulated during several events representing a long time period. Locality 42 represents a bone accumulation laid down in a topographic depression. The bulk of this assemblage is likely to represent remains accumulated over a very short time period, along with some reworked remains. The assemblages analysed were all formed in non-exceptional floodplain subfacies, representing a wide range of time periods ranging from instantaneous catastrophic events to long periods of time. This work provides a context for the these remains and contributes to the understanding of the events that gave rise to vertebrate fossil assemblages in the Bahe Formation and fossil accumulations in floodplain environments in general.

First direct age determination for the Baltic Ice Lake/Yoldia Sea transition in Finland

The drainage of the Baltic Ice Lake (BIL) to the Yoldia Sea level occurred at around 11 600 years ago and can be considered as one of the most important events in the Late-Glacial Baltic Basin history. Distinctive sandy deposits were formed as a result of the water-level fall. These deposits form a marker horizon at the Pleistocene–Holocene boundary, which has been used as the 0-varve in Finnish clay varve chronology. These sandy deposits have not been dated, and in general, there is lack of direct age determinations from the Pleistocene–Holocene transition. Sediments from three localities: backshore, beachface and upper shoreface environments, interpreted to be connected with BIL drainage, were sampled and dated with an optically stimulated luminescence (OSL) method. Only the beachface deposit appeared to be the suitable material, giving the expected dates of 11 400 ± 1100 and 11 200 ± 1300 years BP for the water-level fall. The other samples were interpreted as only partially bleached, or they represented a mixture of different age generations. This is the first direct dating of a Yoldia shore deposit in Finland and provides a reference for shore displacement studies in Finland. The results also verify the potential of the OSL method in dating ancient shorelines or land uplift history.

Depositional evidence of water-level changes of the Baltic Ice Lake in southern Finland during the Younger Dryas/Holocene transition

Two natural clay sections were described from southern Finland. The sites, Jokela and Koria, are located 5-10 km south of the 1st Salpausselkä end moraine. Six sedimentary units were identified and interpreted: (1) Baltic Ice Lake (BIL) varved sediments – interbedded, laminated clay and silt with load structures and sand layers in places; (2) homogenous, partly deformed clay; (3) BIL varved sediments, deposited in slightly shallower water – interbedded, laminated clay and silt; (4) BIL drainage from Billingen and the 25-m base-level fall 11 600-11 700 BP – homogenous clay with sand pods and discontinuous sand layers; (5) freshwater varves – clay and silt couplets with lenticular and flaser bedding and load structures and (6) brackish water varves – thick clay and thin silt couplets. These units can be associated with previously described units of the Finnish clay-varve chronology. The results confirm the importance of the drainage unit as a basin-wide key horizon and illustrate the differences in sedimentation in different parts of the Baltic Sea basin. This is evidenced by the diachronous nature of the incursion of brackish water and associated facies change in sediments.

Here be dragons: Mesowear and tooth enamel isotopes of the classic Chinese "hipparion" faunas from baode, Shanxi province, China

In this study, we synthesize available data from isotopes, sedimentology and climate modelling together with an extensive mesowear analysis of North Chinese “Hipparion” faunas of Baode. We build on previous research and enlarge the range of analysed localities. Our results show that climate during accumulation of the older localities (7.5 Ma) was more humid than that of the youngest locality (5.7 Ma), while the intermediate localities (∼6.5 Ma) accumulated under variable climatic conditions. Our results generally confirm those of previous studies, but highlight temporal and spatial variation within localities. We suggest that this is caused by variation in monsoon strength as evidenced by various proxy records.

Tectonic controls of the onset of aeolian deposits in Chinese Loess Plateau – a preliminary hypothesis

ABSTRACT Previous studies show that the thick aeolian dust deposits in the Chinese Loess Plateau (CLP) have accumulated since the early Miocene or even late Oligocene. They are considered to provide the best terrestrial record for the onset of Asian interior aridification and the evolutionary history of the Asian Monsoon. However, large variability in the basal ages of aeolian deposits makes the aeolian dust depositional history and the controlling dynamics controversial. Here, we present a preliminary hypothesis for the tectonic controls of aeolian dust deposition in the CLP by connecting the two main uplift events of the Tibetan Plateau and the regional tectonic events with the aeolian dust accumulation history. Regional tectonic events in the Ordos Block (the basement of the CLP) during the late Cenozoic are less recognized as controlling aeolian dust accumulation by sculpting the surface landscape. The stable tectonic environment of the Ordos Block since the late Miocene might have been the main controlling factor that enabled the widespread deposition of the aeolian red clay after ~8 Ma. Here, we hypothesize that because the large-scale monsoon system and central Asian aridity had existed since at least the early Miocene, the accumulation and preservation of aeolian deposits within the CLP are actually largely controlled by the regional tectonic environment and less by climatic factors.