The type section of the Codell Sandstone

We formally assign, describe and interpret a principal reference section for the middle Turonian Codell Sandstone Member of the Carlile Shale near Codell, Kansas. This section, at the informally named Pumpjack Road, provides the thickest surface expression (9 m, ~30 ft) of the unit in Ellis County. The outcrop exposes features that typify the Codell throughout the southern Denver Basin and vicinity. At this reference section, the Codell conformably overlies the Blue Hill Shale Member of the Carlile Shale and is unconformably overlain by the Fort Hays Limestone Member of the Niobrara Formation or locally by a thin (<0.9 m, <3 ft) discontinuous mudstone known as the Antonino facies. The top contact of the Codell is slightly undulatory with possible compaction features or narrow (<30.5 m, <100 ft), low-relief (0.3-0.6 m, 1-2 ft) scours, all of which hint that the Codell is a depositional remnant, even at the type section. At Pumpjack Road, the Codell coarsens upward from a recessive-weathering argillaceous medium-grained siltstone with interbedded mudstone at its base to a more indurated cliff-forming muddy, highly bioturbated, very fine-grained sandstone at its top. The unit contains three informal gradational packages: a lower Codell of medium to coarse siltstone and mudstone, a middle Codell of muddy coarse siltstone, and an upper muddy Codell dominated by well-sorted very fine-grained sandstone. The largest grain fractions, all <120 mm in size, are mostly quartz (40-80%), potassium feldspar (7-12%), and albite (1-2%), with some chert (<15%), zircon, and other constituents such as abraded phosphatic skeletal debris. Rare fossil fish teeth and bones also occur. Detrital and authigenic clays make up 9 to 42% of the Codell at the reference section. Detrital illite and mixed layer illite/smectite are common, along with omnipresent kaolinite as grain coatings or cement. As is typical for the Codell, the sandstone at the type section has been pervasively bioturbated. Most primary structures and bedding are obscured, particularly toward the top of the unit where burrows are larger, deeper and more diverse than at its base. This bioturbation has created a textural inversion in which the larger silt and sand grains are very well sorted but are mixed with mud. Detrital zircons from the upper Codell are unusual in that they are mostly prismatic to acicular, euhedral, colorless, unpitted, and unabraded, and have a near-unimodal age peak centered at ~94 Ma. These characteristics suggest they were reworked mainly from Cenomanian bentonites; their ultimate source was likely from the Cordilleran orogenic belt to the west and northwest.

Hjoula: A remarkable mid-Cenomanian Lebanese fossil fish Lagerstätte now promising also for fossil insects

Lebanon is worldwide famous in Palaeontology for its rich Late Cretaceous marine fish deposits in Haqel, Nammoura and Hjoula. Recently, the two latter outcrops yielded surprisingly some complete and none-dislocated fossil insects (Azar et al., 2019; Vršanský & Makhoul, 2013; Nel et al., 2004), indicating a particular depositional marine palaeoenvironment, close to a palaeoshoreline during the mid-Cenomanian.

Issues of species diagnostics of fossil fishes

The article is devoted to the methodological problems of diagnostics of the palaeoich-thyological material from alluvial sediments and to the search for ways of their solu-tion on the example of processing fish remains from late Cenozoic deposits in the south of Eastern Europe. The complexity of such studies (determination to the species level based on skeletal elements) is noted given the limited amount of respective information in the diagnoses accepted in ichthyology. The importance of creation and enrichment of comparative osteological collections is emphasised and possible alternative sources of information for species diagnostics of fossil fish remains from sediments of different age are proposed. Accurate and detailed identification of the palaeoichthyological ma-terial directly depends on the state of its preservation. A set of skeletal structures and features is presented, according to which the author has described extinct species of bony fishes as new to science. The specifics of the use of open nomenclature during the processing of palaeoichthyological material are explained. A new approach to deter-mining the systematic affiliation of fish remains is described and the contradiction be-tween morphological and molecular data is clarified.

A fossil fish assemblage from the middle Miocene of the Cocinetas Basin, northern Colombia

Freshwater fossil fish faunas have been long used to infer past drainage connections, as they are bounded by physical freshwater barriers. Here we study a middle Miocene (15.0-15.5 Ma) fossil fauna (Makaraipao) from the Castilletes Formation in northern Colombia, nowadays west of the Andes. We record the presence of lungfishes (Lepidosiren), pacus (Mylossoma and Piaractus), armored catfishes (Callichthyidae), and red-tail catfishes (Phractocephalus). Extant members of all those groups (except the Callichthyidae, due to lack of taxonomic resolution) are found in Amazonian faunas east of the Andes and are absent from faunas west of the Andes, indicating that the riverine systems of the Guajira Peninsula were connected to Amazonia during the middle Miocene. The similarity of La Venta (west of the Andes) and Rio Acre (east of the Andes) fish faunas during the late Miocene further indicates that the northern Andean uplift was not a complete barrier at least until ~ 11 Myr ago. However, there is a continental-wide structuring of the Miocene fish faunas that is also found in the extant faunas, suggesting that other factors, in addition to the uplift of the Andes, have shaped the biogeographic evolution of South American fish faunas.

Fossil fish species and assemblage are relevant integrative paleo-biogeo-archives in ancient lakes

&lt;p&gt;In paleontological context, fish remains are frequently collected and constitute a large part of the lake macro-fossil assemblages. In the presentation, examples from continental Africa chosen in lakes of different dimension, shape and history (mainly Malawi, Chad and Turkana) will illustrate how fish fossil study potentially provides a wide range of information on the paleoenvironment (water salinity, temperature, oxygenation, seasonality, etc.) and the paleogeography (watershed connections) of the lake and its basin. It is based on the knowledge of the ecology and phylogeny of the species and through dedicated biogeochemical and sclerochronological studies of their bones and teeth that also constitute paleo-bio-archives that recorded certain environmental information. Alongside the results extracted from each dedicated study, their combination provide new information and show the gain of extracting different and independent informations from the same object or from objects from the same assemblage, and notably in the case of lake-fish assemblages. For example, the combination of the knowledge on a fish paleo-ecology in a lake with results of a biogeochemical study of their remains can evidence change in the hydrographical regime between successive lake deposits. Finally, fish study also allow an interpolation of change in paleoenvironments at different time scales and their integrative study as paleoenvironmental proxy should be more widely included in the evolution of lakes in the past. The multi-time scale and proxy study enabled on fossil fish is sensible for transfer to predict modern lake evolution.&lt;/p&gt;