RECOGNITION OF FOSSIL NEBKHA DEPOSITS: CLUES FROM NEOICHNOLOGY AND SEDIMENTOLOGY

ABSTRACT This study includes the first neoichnologic characterization of the burrow systems of Tympanoctomys barrerae (Rodentia: Octodontidae) and also considers sedimentologic features of the modern nebkhas where they occur. Tympanoctomys is a South American solitary and fossorial rodent that has ecomorphofunctional adaptations for living in saline environments and constructs its burrow in nebkhas with halophyte shrubs. The purpose of this work is to identify the ichnologic signatures of T. barrerae burrow systems and to provide combined ichnologic-sedimentologic criteria for identification of Cenozoic nebkha deposits. Tympanoctomys barrerae burrow systems are subhorizontal, typically with ten or more entrances, two or three levels, closed circuits, average complexity of 48, average tortuosity of 3.25, and an average ratio of total chamber volume to total tunnel volume of 0.04. The size of the tunnels averages 85 mm in horizontal diameter and 64 mm in vertical diameter, and cross-section shape ranges from elliptical flattened to plano-convex with incipient bilobed floor. Surface ornamentation is typified by a coexistence of primary (sets of four claw traces forming an arcuate pattern produced during digging) and secondary (numerous arthropod burrows excavated from the burrow lumen) surface ornamentation. Nebkha deposits in upper Cenozoic sequences can be recognized by the combination of ichnologic and sedimentologic features: fossil burrows having the ichnologic features characteristic of T. barrerae burrow systems and presence of rhizoliths of shrubby plants occurring in well-sorted sandy deposits with low-angle crossbedding. These criteria can be potentially applied to fossil sequences dating back to the early Oligocene.

Palynological data on the description of the Gelasian and Calabriane analogues in the strato- type section of the Kuyalnik deposits near Kryzhanivka village (Odessa region)

The state of paleontological study of the Kuyalnik deposits of Odessa region, in particular the stratotype section near Kryzhanivka village was analyzed. Attention is paid to the absence of the palynological description of the Krizhanivka climatolith in the section and the insufficient palynological study of the liman-marine Kuyalnik sediments. The goal of the presented research was to obtain a detailed palynological description of the subaerial Eopleistocene and the liman- marine Kuyalnik sediments of the stratotype section near Kryzhanivka village. Based on the results of the research, the palynological description of rocks of the upper part of the section of the liman-marine Kuyalnik sediments is presented for the first time, as well as the materials to substantiate the correlation of the studied sediments with the Beregove and Siversk climatolyths of the continental Upper Cenozoic section of Ukraine, which correspond to the Gelasian of the International Stratigraphic Scale (ISS). For the first time, palynological description of the Kryzhanivka climatolith correlated with the Calabriane of the ISS is presented for the studied section. Three subcomplexes are described in the composition of the Kryzhanivka complex. The characteristic features of the Kryzhanivka spore-pollen complex (SPC) and the changes in the ecological structure of each subcomplex are determined. Correlation of the established complex with the even-aged SPC of the Kryzhanivka deposits of the southern part of the Ukrainian Shield (the Eastern Azov Sea region). Outstanding questions of stratigraphic division of different facial deposits of the section based on palynological data are outlined. The necessity of further palynological studies of deposits of the section near Kryzhanivka village is substantiated.

Astroniumxylon, Schinopsixylon, and Parametopioxylon n. gen. fossil woods from upper Cenozoic of Argentina: taxonomic revision, new taxon and new records

This paper presents new descriptions of Anacardiaceae fossil woods from the Ituzaingó Formation (late Cenozoic) at the Toma Vieja, Curtiembre, and Arroyo El Espinillo localities, Argentina. We describe eight silicified woods assigned to four different species in three genera, one of which, Parametopioxylon crystalliferum n. gen. n. sp., is new. Similarities between these three genera and the six Anacardiaceae species previously recorded from the late Cenozoic in northeastern Argentina are investigated using multivariate analysis techniques (correspondence and cluster analysis). Our study is based on 33 characters scored for 17 fossil specimens (10 Astroniumxylon Brea, Aceñolaza, and Zucol 2001; five Schinopsixylon Lutz, 1979; and two Parametopioxylon n. gen.) and four extant species (Astronium balansae Engl., Astronium urundeuva Engl., Schinopsis balansae Engl., and Metopium sp.). Our main goal is to determine the wood anatomical features useful for distinguishing among these species. Results of the multivariate analyses support the previous classification where Schinopsixylon is distinguished from Astroniumxylon by having exclusively paratracheal axial parenchyma, ≥30% multiseriate rays, and multiseriate rays that are ≥5 cells wide and commonly 301–400 μm in height. Additionally, we propose that Schinopsixylon heckii Lutz, 1979 is synonymous with S. herbstii Lutz, 1979. A diagnostic key for the fossil species studied is given. Wood anatomy of Anacardiaceae fossil woods from Argentina (late Cenozoic) suggests a warm, dry to semi-humid climate for this region, supporting previous studies.