Early Barremian Research Articles

Systematic of a Massively Constructed Specimen of Iguanodon galvensis (Ornithopoda, Iguanodontidae) from the Early Barremian (Early Cretaceous) of Eastern Spain

Styracosternan ornithopods are plenty abundant in the Lower Cretaceous fossil record of Europe. In particular, Iguanodon, the second genus of dinosaurs described worldwide, has been found in UK, Belgium, France, Germany, and Spain, evidencing a wide geographical distribution. Currently, the genus Iguanodon comprises two species, the type species I. bernissartensis from the late Barremian–Aptian of Europe and I. galvensis from the early Barremian of Teruel, Spain. The latter species is well known mainly from perinate and juvenile specimens. Here, axial and appendicular fossils of an adult, large and massively constructed ornithopod from the lower Barremian (Lower Cretaceous) Camarillas Formation of Galve (province of Teruel, Spain) are described. Fossil dimensions and some osteological evidence reveal that the specimen was a large (roughly 10 m long) ornithopod. An autapomorphic feature in the ischium and other characters allow us to ascribe this specimen to I. galvensis. In addition, postcranial co-ossification and fusion of the neurocentral suture indicate that the specimen was skeletally mature. Part of the material studied here was unknown in adults of I. galvensis, providing a better knowledge of the axial and appendicular region of this species.

Filling the gap in the evolution of the genus Echinochara Peck (Clavatoraceae, Charophyta)

Echinochara is a poorly known charophyte genus of the extinct family Clavatoraceae that thrived in the Middle Jurassic–Early Cretaceous of North America, Europe, and North Africa. It represents the most ancient and plesiomorphic genus of this family. However, the fossil record of Echinochara is discontinuous, showing several gaps, one of them especially significant in evolutionary terms between the Kimmeridgian and the early Barremian. The new species Echinochara pontis sp. nov., described here from the late Berriasian of the Maestrat Basin (NE Spain), bridges, in part, this gap, shedding light on the evolution of the genus during the earliest Cretaceous. The fructification (utricle) has bilateral symmetry, formed by two superimposed series of bract cells that abaxially cover the gyrogonite. The inner series has three long cells that are born by a short basal cell and reach the oospore apex. The outer series shows a central fan of bract cells, composed of a small basal cell, triangular in shape, that bears three long cells growing upwards, which are in turn flanked by two long bract cells on each side. The central basal cell and these two lateral cells are directly attached to the base of the utricle. The thallus is corticated with cells twisting at an angle of 30°. The utricle of Echinochara pontis displays a combination of features present in Echinochara peckii (Bathonian?–Kimmeridgian) and Echinochara lazarii (Barremian–early Aptian). For instance, the bilateral symmetry of the utricle and the morphology of the inner bract-cell series allow comparison with E. lazarii, whilst the morphology of the outer bract-cell series is closer to E. peckii. Moreover, the thallus of the new species shows cortical cells with a twisting angle intermediate between that of Echinochara peckii (40°–45°) and Echinochara lazarii (not twisted). The unique combination of morphological characters in the utricle of Echinochara pontis fits well with its intermediate chronostratigraphic position between the two former species. Echinochara pontis formed monospecific meadows in brackish settings. A preference for brackish settings is also observed for Echinochara peckii and in the older populations of Echinochara lazarii, suggesting that this habitat is probably a basal character in the evolution of the genus Echinochara.

Evidence of theropod dinosaurs in the upper hauterivian–lower barremian of Jebel Kebar (central Tunisia): Paleobiogeographic implications

The fossil record of Mesozoic dinosaurs in Tunisia has long been thought to be restricted exclusively to the southern part of the country. Although tidal and continental environments have been recognized within Cretaceous formations in central Tunisia based on sedimentological analyses, no skeletal remains ascribable to dinosaurs have been found in these deposits. The hypothesis of a possible land connection between central and southern Tunisia during the Early Cretaceous has not been previously explored due to notable lateral variations in facies, marked by the recurrent occurrence of shallow marine deposits separating these domains. The vertebrate ichnological record in the Central Tunisian Atlas was limited to isolated tridactyl footprints exclusively observed in the Albian Kebar Formation. Here, we report the first dinosaur tracks from the pre-Albian Cretaceous (upper Hauterivian–lower Barremian) of central Tunisia. These tracks consist of large tridactyl footprints left behind by medium to large-sized non-avian theropods. They occur within an extensively fractured dolostone bed and exhibit poor morphological preservation. Besides their dimensions, some tracks show morphological features, including broad digit impressions with some terminating in sharp claw traces, low to moderate mesaxony, and a wide divarication angle of the outer digits, reminiscent of the ichnogenus Megalosauripus. However, due to their poor state of preservation and limited number, we refrain from assigning these tracks to the ichnogeneric level and refer to them as indeterminate eubrontid footprints. The occurrence of theropod tracks in the Lower Cretaceous of central Tunisia confirms the sedimentology-based hypotheses about a temporal emergence of parts of this area, which was probably related to tectonic events. We compile previous biostratigraphic, sedimentological, and paleoichnological data to suggest possible periodic connections between the mainland in the south and the tidal flat environments within the central basins. Additionally, two possible scenarios regarding the biogeographic implications of the Jebel Kebar tracks are discussed. The first scenario suggests that a Gondwanan theropod fauna would have been exploring and residing in newly emerged regions of higher latitudes, whereas the alternative scenario posits the existence of a paleogeographic link between the northern margin of Gondwana and Adria, which would have allowed an interchange of theropod faunas between the two landmasses at least in the early Barremian.

Tannoura: A new early Barremian fossiliferous amber outcrop from South Lebanon

A fossiliferous amber outcrop in Tannoura (Rashayya District, Southern Lebanon) is described. This new discovery constitutes the 30th amber outcrop with biological inclusions in Lebanon and enriches and improves our knowledge about the palaeobiodiversity and palaeoenvironment of the North-Eastern coast of Gondwana during the early Barremian. Also, an infrared spectrum of the amber from Tannoura is given and discussed.

Increasing the theropod record of Europe: a new basal spinosaurid from the Enciso Group of the Cameros Basin (La Rioja, Spain). Evolutionary implications and palaeobiodiversity

Abstract A new member of Spinosauridae from the Enciso Group (uppermost Barremian–lower Aptian) from Igea (La Rioja, Spain) is here erected on the basis of axial, pelvic girdle, and hindlimb elements that exhibit a unique combination of characters. Riojavenatrix lacustris gen. et sp. nov. is one of the latest Iberian and European spinosaurid taxa. It retains a triangular pubic boot, like the megalosaurids, and a medial condyle of the femur that shows a transitional stage between the anteroposteriorly oriented long axis of non-spinosaurid theropods and the posteromedially oriented long axis of Spinosauridae. The spinosaurid record of Iberia ranges from the late Hauterivian–early Barremian to the latest Barremian–early Aptian so far, and both the oldest and the most recent evidence comes from the Cameros Basin, where spinosaurid remains are especially abundant in the Barremian deposits. A review of the spinosaurid record has allowed us to dismiss the presence of the genus Baryonyx from Iberia; hence, only Camarillasaurus, Iberospinus, Protathlitis, Riojavenatrix gen. nov., and Vallibonavenatrix are considered to be present in the Early Cretaceous of Iberia. According to this study, Riojavenatrix is one of the youngest baryonychines in the fossil record.

A new genus of Panguoidea in Lower Cretaceous Wealden amber

ABSTRACT The panguid wasps are a ‘primitive’ family found only in the Cretaceous. Herein, a new species and genus, Protopangu valdensis gen. et sp. nov. assigned to the family Panguidae, is described and illustrated from Wealden amber, which represents one of the oldest-known fossiliferous ambers (early Barremian, ~125 Ma). A key to the genera and species of Panguidae is provided. The fossil wasp from the Wealden Group not only represents the oldest record of Panguoidea but also augments the geographic distribution of the taxon during the Cretaceous Period.

Rise and demise of the Urgonian platform in Switzerland

Abstract Defined in the Provence region of France, the rudist-bearing Urgonian Limestone is typical of northern Tethyan shallow-marine carbonate series, and is dated based on benthic fauna and flora, calcareous nannofossils and ammonites. This contribution reports on recent findings that refine the stratigraphy of the Urgonian Limestone in the western Swiss Jura and the Helvetic Alps of Switzerland. In the former location, the high-resolution facies and isotope analysis of samples permits the identification of major periods of subaerial exposure, while a diverse assemblage of calcareous nannofossils indicates a Barremian age for the Urgonian deposits. In the latter location, biostratigraphical data indicate a Late Barremian–Early Aptian age for Urgonian deposits, while the repartition of facies along a proximal-to-distal transect highlights the Late Barremian progradation of the platform. The detailed understanding of the stratigraphy of Urgonian deposits in these regions inscribes them into a broader context that acknowledges palaeoclimatic and palaeoenvironmental conditions. A warmer and more humid climate prone to continental weathering and transport of nutrients to an epicontinental sea characterized the Early Barremian; this was detrimental to the health of carbonate-producing benthic ecosystems. In the Late Barremian, a reduced nutrient supply allowed Urgonian communities to thrive.

The first Early Cretaceous representative of the fly family Tipulidae from the lower Barremian dysodiles of Lebanon (Diptera).

Leptotarsus reyi sp. nov., first representative of the family Tipulidae from the Lower Cretaceous of Lebanon, is characterised, described and illustrated from the Early Barremian dysodile of Jdeidet Bkassine, South Lebanon.

TAXONOMIC AND BIOSTRATIGRAPHIC REMARKS ON TORINOSUELLA MAYNC, 1959 AND BALKHANIA MAMONTOVA, 1966, LARGER BENTHIC FORAMINIFERA FROM THE LOWER CRETACEOUS OF IRAN (SANGESTAN, TIRGAN FORMATIONS)

The monospecific genera Torinosuella Maync [type-species T. peneropliformis (Yabe & Hanzawa)] and Balkhania Mamontova (type-species B. balkhanica Mamontova) have been reported from the Lower Cretaceous of Iran, respectively the ‘Carbonate Member’ of the Sangestan Formation (Central Iran) and the Tirgan Formation (NE Iran). The literature review reveals a range of late? Tithonian–early Barremian for Torinosuella and late Barremian–early Aptian for Balkhania. In a recent publication dealing with the ‘Taft’ Formation (Central Iran) and the Tirgan Formation (northeastern Iran), both taxa have been lumped together and described as two morphotypes of B. balkhanica based essentially on size differences. This mixing was associated with incorrect phylogenetic, taxonomic, biostratigraphic (e.g., First Appearance Datum) and palaeoecological conclusions that are herein addressed and corrected. Without clarification about the spatial and temporal distribution of individual taxa, the usefulness of larger benthic foraminifera for biostratigraphy, palaeoecology and palaeobiogeography would be distinctly reduced.

An unusual artematopodid beetle from Early Cretaceous Wealden amber (Coleoptera: Elateroidea: Artematopodidae)

Early Cretaceous Wealden amber of the Isle of Wight (early Barremian, ~125 Ma) represents one of the oldest known fossiliferous ambers. Here we describe the first fossil beetle from the deposit, and first British coleopteran amber inclusion, the artematopodid Valdopogon simpsoni gen. et sp. nov. Despite its fragmentary nature, the fossil possesses a puzzling combination of characters unseen in modern Artematopodidae, namely equally long abdominal ventrites I and II, concave sutures between ventrites I–V, and absence of elytral striation. Valdopogon contributes to our understanding of the morphological evolution of this once diverse group of elateroid beetles.

New Insights into the Platform-to-basin Anatomy of the Urgonian Bas-Vivarais Domain (Lower Cretaceous; SE France)

This paper offers a new contribution to our ongoing harmonization efforts concerning the chronostratigraphic model of the southern France Urgonian-type carbonate platforms, which surrounded the Vocontian Basin during the Early Cretaceous. A multi-stratigraphic approach on the classical sections of the Ardèche River gorges and the Saint-Remèze Plateau have been used for reconstructing the evolution of the Bas-Vivarais Urgonian domain along an inner-to-outer platform profile; the latter being nearly perpendicular to the eastern Vocontian platform margin. In our transect, the installation and first developments of the Urgonian platform domain occured during the early Barremian Taveraidiscus hugii and Kotetishvilia nicklesi ammonite zones. This first platform stage was interrupted at a brief emersion episode that lasted through the Nicklesia pulchella ammonite zone, and resulted in the deposition of a sedimentary wedge with limited gradual downward, basinward shift in inner platform facies. This was followed by the regional deposition of shallow-water communities dominated by corals, echinoids, and orbitolinids, which passes basinward into open-marine, ammonite-bearing marly deposits in the Saint-Remèze Plateau outcrops. This change in facies was previously referred to as the Serre de Tourre Beds (STB), and dated to the Kotetishvilia compressissima and Moutoniceras moutonianum ammonite zones. The STB are further identified to as the local sedimentary expression of the Mid-Barremian Event recording a brief warming climate pulse testified by the presence of Offneria simplex, a caprinid rudist of Caribbean origin. Above, there is a regional recovery of inner platform Urgonian facies during the early late Barremian showing a striking progradational basinward trend. The latter, and its subsequent developments are in need of investigations. Taken together, the general evolution of the Urgonian Bas-Vivarais domain shows strong similarities with the sedimentary context of the nearby Subalpine Urgonian platform during the early Barremian. The finding of common sedimentary signals is more difficult with the Provence platform domain at that time.

Evolutionary characteristics and key controlling factors of the volcanic rocks in the Lower Cretaceous Changling fault depression, Songliao Basin, China

The Songliao Basin is a large petroliferous basin located in Northeast Asia; the complex structure and volcanic filling are obstructions to the petroleum geological exploration of the Lower Cretaceous strata in the basin. Based on seismic, logging and lithologic data, this paper reveals the tectonic–stratigraphic characteristics of the Changling fault depression in the Songliao Basin, identifies the depression's volcanic rocks and summarizes their distribution patterns and changes, and finally analyzes the main factors controlling volcanic rock development combined with the regional tectonic background. The research shows the fault extension and subsidence caused the Changling fault depression to gradually evolve from an independent fault depression group to a connected large lake basin. The volcanic rocks in the fault depression are mainly “sill–like” volcanic lava and mounded volcaniclastic rocks, and their development can be divided into several stages. In the early Valanginian to Barremian, volcanic rocks show a large range of contiguous bedded and buninoid-structured rocks, which separate several small sedimentary sags; during the early Barremian to the late Aptian, volcanic rocks stopped developing; from the late Aptian to the late Albian, the volcanic rocks in the basin underwent multiple evolutionary periods, and their morphology gradually changed from mats and gentle mounds to high-angle cones and domes. Mantle upwelling caused by plate activity in Northeast Asia is the main driving force of extension and volcanic eruptions in the Songliao Basin, and the deep basement faults that formed by extensional activity control the magma upwelling channel, thus affecting the active periods, scale, morphology and distribution characteristics of volcanic rocks.

Ornithopod tracks and bones: Paleoecology and an unusual evidence of quadrupedal locomotion in the Lower Cretaceous of eastern Iberia (Teruel, Spain)

Dinosaur tracks and osteological remains in the El Castellar Formation (upper Hauterivian–lower Barremian) in the Peñagolosa subbasin, southwest sector of the Maestrazgo Basin (Teruel Province, Spain), are scarce and fragmentary, respectively. Here, we report several unexpected, well-defined natural casts of large ornithopods from several sites of the El Castellar Formation. Moreover, an unusual manus-pes track set preserved as convex hyporelief has been found in the lowermost sandstone level of the Camarillas Formation, the first evidence of dinosaur for the base of this unit at the Peñagolosa subbasin. The ichnological comparison allows us to ascribe the studied tracks to Caririchnium. Their trackmakers were large styracosternans related to Iguanodon, and the presence of a manus-pes track set verifies that some of them may have a quadrupedal locomotion. This associated manus-pes track set constitutes one of the oldest ichnological pieces of evidence of quadrupedalism in large ornithopods from the Lower Cretaceous of Iberia and increases the limited record of this kind of track in the Lower Cretaceous of Europe. In addition, we describe some osteological fossils of these dinosaurs from the El Castellar Formation. These skeletal remains are related to medium to large-sized styracosternans, some of which closely resemble those of other European styracosternans such as Iguanodon. The evidence provided here verifies that these dinosaurs were frequent components in the coastal wetland, and fluvial to deltaic systems developed, during the late Hauterivian–early Barremian, in the Peñagolosa subbasin, possibly because these may have had a source of fresh vegetation and may have provided protection.

Organic-walled marine microplankton from the Hauterivian and early Barremian of the North Sea Region - biostratigraphy and taxonomy

Organic-walled marine microplankton from the Hauterivian and early Barremian of the North Sea Region - biostratigraphy and taxonomy

The Aptian-Cenomanian ostracod "Conchoecia?"/Neorichterina: Taxonomic review and its paleoecological, paleobiogeographic, and biostratigraphic significance

Though primarily a recent genus, Conchoecia Dana 1853 has had a number of Cretaceous forms dubiously attributed to it since the description of Conchoecia cretaceaPokorný, 1964. Recently, most of these species were reassigned to the genus NeorichterinaTóth and Cséfán, 2018, considered a Cretaceous representative of Family Entomozoidae. However, there are still taxonomic uncertainties regarding this assignment, and much is still unknown about the paleoecology, paleobiogeography, and biostratigraphic significance of these taxa. This paper provides a revision of the taxon based on available literature on Neorichterina and the Cretaceous forms attributed to “Conchoecia”. Considering several problems with the taxonomic description of Neorichterina, we propose the removal of the genus from Family Entomozoidae, and identify two potential new species, which are left in open nomenclature. The earliest occurrence of the genus is the late Hauterivian–early Barremian of the Haha Basin, Morocco. After that, Neorichterina spread to the South Atlantic and Tethys oceans during the late Aptian–late Albian, and became extinct in the lower Cenomanian. Neorichterina was likely a planktonic genus with a preference for warm neritic environments, and was able to tolerate fluctuating oxygenation levels. It frequently occurred in association with blooms of Favusellid foraminifera, and was particularly abundant in the South Atlantic Ocean. Although Neorichterina has a broad stratigraphic range, it occurred only for a small time interval during the late Aptian of the Santos Basin, Brazil, suggesting that it could be a useful regional biostratigraphic marker in the southeastern Brazilian margin.

Structural Restoration of Cretaceous Inversion Events in the Bjørnøyrenna Fault Complex, Western Barents Shelf

Inversion structures including folds, reverse faults are observed along the Bjørnøyrenna Fault Complex in the western Barents Sea, although the fault complex is extensional in origin and developed in mid-Jurassic to Early Cretaceous. Subsidence along the fault complex was interrupted in Early Cretaceous (Valanginian to early Barremian) because of syn-rift localized tectonic inversion, itself related to the uplift of the Loppa High. The Early Cretaceous inversion caused dextral transpression along the boundary faults adjacent to the Loppa High. The second phase of inversion is interpreted to be Late Cretaceous (mid-Cenomanian) in age, coeval to the deposition of the Kolmule Formation in the Bjørnøyrenna Fault Complex. The later phase of compression is of regional significance and related to NW‒SE directed far field stresses in Late Cretaceous which caused head-on inversion in the study area. The aim of present study is to identify and decipher eventual Cretaceous inversion structures in the Bjørnøyrenna Fault Complex by means of structural restoration. To these aims, 2D MOVETM, structural modeling and analysis software by Midland Valley Exploration Ltd (Glasgow, Scotland), is used and three key seismic lines crossing the central and northern segments of the Bjørnøyrenna Fault Complex are restored. Key profiles 1 and 2 reveal null point positions at the base of the Cretaceous (Hekkingen Formation). Null point positions show progressive compressional inversion of syn-rift Early Cretaceous deposits (Knurr Formation). Below and above null points the geometries of the restored faults show normal and reverse faulting respectively. The results of the restored key profiles 1 and 2 confirm reverse faulting at the Lower Cretaceous triggered by inversion of the study area. The restored sections also show positive inversion features associated with folding of the hanging wall of the base of the Upper Cretaceous (Kolmule Formation). The reconstruction of the amount of eroded material on the footwall block also suggests reverse faulting of the base of the Upper Cretaceous. In key profile 3 the footwall block is eroded up to the base of the Upper Cretaceous (Kolmule Formation) due to the uplift of the Loppa High. The corresponding restored section shows a compressional anticline associated with both Early and Late Cretaceous inversion events.

Early Berriasian to Early Barremian Calcareous Nannofossils Biostratigraphy and Paleoecology of Baghamshah Formation (Esfandiar Section, Tabas Block), Eastern Iran

The Baghamshah Formation was previously assigned to Jurassic age in Iran, based on stratigraphic distribution of ammonites. But, recent studies of calcareous nannofossils in the Lut Block show that the age of this formation should be assigned to the Early Cretaceous (early Berriasian to early Barremian). This study analyzed stratigraphic distribution of calcareous nannofossils of the Baghamshah Formation in the Esfandiar section located in the southeast of the Tabas Block (close to the type section). Examinination of samples identified 39 calcareous nannofossil and 6 didemnid ascidian spicules species belonging to 19 genera, corresponding from CC1 to CC5 biozones with the age of early Berriasian to early Barremian. Index nannofossil species in the succession indicate that the sedimentary basin of the Baghamshah Formation in the Esfandiar section was located in low latitudes of the Tethyan realm with warm surface water toward the top of the section. Also, the oceanic basin was an oligotrophic type with low-fertility, as its nutrient supply dropped toward the top of the section. The oligotrophic paleoenvironment during the late Berriasian to early Valanginian in the study area in eastern Iran may have corresponded to a global low sea-level.

Ain Zhalta: A new early Barremian fossiliferous amber outcrops from central Lebanon

Lebanon has an extraordinarily high proportion of Mesozoic amber outcrops, some (19 outcrops) from the Kimmeridgian, Upper Jurassic (Azar et al., 2010b; Nohra et al., 2013; Maksoud & Azar, 2020); and others (more than 450 outcrops) from the lower Barremian (Granier et al., 2016; Maksoud et al., 2017; Maksoud et al., 2022), Lower Cretaceous (Maksoud & Azar, 2020). The latter number is still endlessly growing (for a very small country with a total surface of 10,452 km2). To date 28 outcrops yielding biological inclusions are known (Maksoud et al., 2019, 2020, 2021a, b, c; Maksoud & Azar, 2022).

Sedimentary processes and deformation styles of the Mesozoic sedimentary succession in the northern margin of the Mohe basin, NE China: Constraints on the final closure of the Mongol–Okhotsk Ocean

• The depositional age of the Xiufeng Formation was estimated as 159 Ma. • The Mohe Formation has a bidirectional provenance from 150 Ma. • The tectonic setting transformed from compression to extension during 135–128 Ma. • A series of E-W and NE-SW-trending normal faults occurred since the Early Barremian . • The final closure of the Mongol-Okhotsk Ocean has been limited to 150–135 Ma. The Mohe basin is located to the south of the eastern Mongol–Okhotsk suture belt and contains critical stratigraphic records and thrust-nappe structures for understanding the closure of the eastern Mongol–Okhotsk Ocean. This paper discusses the formation ages, provenance, and tectonic setting of the Xiufeng and Mohe formations, and further reveals the timing of the final closure of the Mongol–Okhotsk Ocean and the tectonic evolution of the Mohe basin. The weighted mean 206 Pb/ 238 U ages for the youngest zircon of these samples indicate that the maximum depositional ages of the Xiufeng, Mohe and Tamulangou Formations were conservatively estimated at 159 Ma, 150 Ma and 128 Ma, respectively. From Late Triassic to Late Jurassic (150 Ma), the Mongol-Okhotsk Ocean was consumed by bidirectional subduction expressed by subduction under the Siberian Craton and the Erguna Block, respectively. The intense subduction led to the compression of the continental arc and the basement uplift of the Erguna Block, which provided abundant clastic sediments to the Xiufeng-Ershierzhan Formations. During the Late Jurassic-Valanginian (150–135 Ma), the Mongol-Okhotsk Ocean closed rapidly, which finally caused the collision between the Erguna Block and the Siberian Craton. Meanwhile, the southern margin of the Siberian Craton was uplifted and started furnishing sediments into the Mohe-Kaikukang Formations, which may have a bidirectional provenance. The subsequent crustal shortening associated with collision between the Erguna Block and the Siberian Craton led to nappe structures, syn‐collisional folds, and nearly N-S-trending reverse and oblique-slip faults occurred along the northwestern margin of the Mohe basin. Between 135 and 128 Ma, the Mohe basin entered the stage of tectonic setting transformation, which is the crucial period for the Mohe basin to transform from compression to extension. Since the Early Barremian (ca. 128 Ma), the compressional environment was transformed into a post-orogenic extensional tectonic environment, and a series of nearly E-W and NE-SW-trending normal faults occurred, which might have been controlled by the slab rollback of the Paleo-Pacific Plate and detachment of the Mongol-Okhotsk oceanic plate after the closure of the Mongol-Okhotsk Ocean.

Charophyte communities in Barremian Iberian wetlands

A combined micropalaeontological, taphonomical and sedimentological study was carried out in the non-marine Barremian of the Maestrat Basin (E Iberian Chain) to elucidate the palaeoecology of Barremian charophytes. Understanding the palaeoecology of fossil charophytes is of prime importance for the accurate application of charophyte biozonations, since most species used as biostratigraphic markers and/or biozone index species are restricted to facies formed in a particular environment. Five charophyte biocoenoses were distinguished. (1) Charophyte association from freshwater alkaline lakes receiving low clastic input, mainly composed of Atopochara trivolvis var. triquetra, Clavator harrisii, Ascidiella stellata, and A. triquetra. The thalli known as Munieria grambastii, corresponding to Clavator utricles, were extremely abundant in the shallowest facies of the lake margins, and Hemiclavator-rich populations were also locally dominant. (2) An association characteristic of freshwater alkaline lakes with high clastic input was mainly composed of Echinochara lazarii, Globator maillardii var. trochiliscoides, A. trivolvis var. triquetra, C. harrisii, Hemiclavator neimongolensis var. neimongolensis, and locally also Clavator calcitrapus. (3) Monospecific populations of Porochara maestratica thrived in brackish settings with little clastic influence, whereas (4) monospecific E. lazarii populations thrived in clastic-influenced brackish settings. (5) A charophyte association grew in lakes that developed in mudflat to floodplain environments and was mainly constituted by E. lazarii, A. trivolvis var. triquetra, and C. harrisii var. harrisii and var. reyi. Accordingly, the palaeoenvironmental conditions inferred indicate that most of the charophyte species were controlled by (i) bathymetry, (ii) clastic content in the sedimentary environment and (iii) salinity. The stratigraphic succession studied shows an upwards increase in clastic content from the base to the top, which is associated with the more humid period recorded along the margins of the Tethys and the Boreal realm during the early Barremian–early late Barremian. In consequence, those species restricted to clastic-poor settings are constrained to the lower part of the section, whereas those taxa that were able to thrive in clastic-rich settings persisted throughout the entire section. This observation establishes a link between the changes observed in the charophyte floras recognized and the environmental changes that occurred during the Barremian in western Europe.