Albian Research Articles

The rise of flowering plants in the high southern latitudes of Australia

The Early Cretaceous high-paleolatitude palynofloras from the Otway and Gippsland basins of southeastern Australia contain diverse angiosperm assemblages not described previously. Clavatipollenites hughesii recovered from the early Aptian Upper Cyclosporites hughesii subzone in the Gippsland Basin represents the first record of angiosperm pollen in Australia, coeval to records recovered from the Great Artesian and North West Shelf basins of northern Australia. Tricolpate pollen including Tricolpites variabilis, Rousea georgensis and Striatopollis spp., are first recorded in the late Albian Upper Coptospora paradoxa subzone in southeastern Australia. This represents the second oldest occurrence of tricolpate pollen in Australia, the first occurring in the older middle Albian Lower Coptospora paradoxa subzone in the northern Great Artesian Basin. By the latest Albian Phimopollenites pannosus Zone angiosperms had diversified rapidly in southeastern Australia. The delayed appearance, rise in abundance and diversification of eudicot angiosperms in the high-latitude southern basins of Australia, relative to low- and mid-latitude settings, supports a latitudinally diachronous pattern of angiosperm range expansion from warmer paleoequatorial regions to relatively cooler high-latitude settings. Increasing mean annual temperatures globally in the late Albian likely facilitated the expansion of angiosperms into high-latitude settings in the Southern and Northern hemispheres.

A new species of Lapparentophis from the mid-Cretaceous Kem Kem beds, Morocco, with remarks on the distribution of lapparentophiid snakes

Two isolated trunk vertebrae from the ?uppermost Albian–lower Cenomanian Kem Kem beds of Morocco are described and assigned to Lapparentophis, an early snake genus known from coeval deposits in Algeria. The Moroccan specimens represent a new species, Lapparentophis ragei, which can be distinguished from the type and only known species, Lapparentophis defrennei, by its smaller size, its more elongate vertebrae, the presence of parazygosphenal foramina, and paradiapophyses extending anteroventrally closer to the cotyle. The discovery of Lapparentophis in the Kem Kem beds adds to the relatively diverse snake assemblage previously reported from this formation and extends the geographical range of the genus. The distribution of Lapparentophis and lapparentophiid-grade (?lapparentophiid) snakes is discussed. This poorly known family of terrestrial snakes seems to be restricted to the latest Albian–early Cenomanian of North Africa, with the exception of Pouitella from the early–middle Cenomanian of France. As for many other vertebrate taxa of this period, this distribution is consistent with a dispersal event from Africa to the western part of the European archipelago.

Main Types of Aptian–Cenomanian Sedimentary Rocks on Guyots of the Magellan Mountains, Pacific Ocean

The typical rocks composing the base of the sedimentary cover of the guyots on the Magellan Seamounts are described. The upper part of the volcanic basement of the guyots is overlain by Aptian deposits of shallow reef ecosystems represented by terrigenous (beach) and organic-chemical (coral, shell-and-detritus, and oolitic) carbonate rocks. These deposits encircle the western part of the Fedorov and Ilyichev guyots, and the satellite buildings of the Alba and Pallada guyots in the form of an almost complete ring, extending from the edge of the plateau summit to 2500–3000 m depth. Down the slope they are replaced by planktonic (nanoforaminiferal) sediments and edaphogenic breccias. The appearance of pelagic limestone is associated with a sea-level rise during the Late Albian–Cenomanian eustatic transgression. Exposures of reef and planktonic limestones of up to 300 km2 in area are also recorded on some guyots.

Straight-jawed lacewing larvae (Neuroptera) from Lower Cretaceous Spanish amber, with an account on the known amber diversity of neuropterid immatures

Three larval neuropterans (Insecta: Neuropterida) with straight mandibulomaxillary stylets are described from Lower Cretaceous (late Albian, ~105 Ma) Spanish amber: a third-instar beaded lacewing (Berothidae) from the Peñacerrada I locality (Burgos, Spain), and two specimens from the San Just locality (Teruel, Spain), i.e., a tentative first-instar beaded lacewing and a remarkable specimen considered a berothid-like mantispoid or dilaroid (instar unknown) displaying a combination of potentially plesiomorphic characters and some unique features. These morphotypes are among the oldest straight-jawed neuropteran larvae described. According to the morphology of the specimens and the taphonomy of the amber pieces where they are embedded, the described forms are regarded as active predators of small soft-bodied arthropods, probably living among bark or other vegetation of the resin-producing forest although they could have frequented the soil. An account of the diversity of larval Neuropterida described and/or figured from amber localities worldwide is provided, including reassessments of some specimens. The gathering diversity of fossil immature neuropterans, like that of their adult counterparts, already leans towards reflecting a greater diversity and disparity of the group in deep time ‒particularly during the Cretaceous‒ than in modern days, and it is worthy of increased research efforts due to the evolutionary and palaeobiological potential that it holds.

Taxonomy and palaeobiogeography of the early and middle Albian (Early Cretaceous) bivalves and brachiopods from central Serbia (Topola, Oplenac Hill)

Sixteen early and middle Albian bivalve species, belonging to fourteen genera, eleven families and seven orders, and one brachiopod species are systematically described from the Mitrovčić section near Topola (Oplenac Hill), Vardar Zone of central Serbia. Four bivalve species: Acesta subrigida (Roemer, 1836), Acesta cf. dorbignyana (Mathéron, 1843), Neithea (Neithea) sexcostata (S. Woodward, 1833), “Cardium” cottaldinum d'Orbigny, 1844, and one terebratulide species, Praelongithyris rogeri Gaspard, 1974 are recorded from the lower and middle Albian rocks of central Serbia for the first time. The section comprises reddish ferruginous calcareous sandstones that are assigned to the lower Albian as indicated by the presence of the ammonite Douvilleiceras mammillatum (Schlotheim), while yellowish sandy wackestones/packstones located below the late Albian Mortoniceras (M.) inflatum (J. Sowerby), are middle Albian in age. Most of the identified bivalve taxa have a Tethyan affinity and seem to be closest to faunas from western and eastern Europe. This indicates that these regions were close to Serbia during the early–middle Albian. The occurrences of some of these Tethyan bivalves at the northern and western Pacific coast of South America and southern coast of North America is explained by dispersal through the opening of the North Atlantic Ocean during the Albian (Proto-North Atlantic Ocean). Meanwhile, the occurrence of some other Albian taxa along the eastern coast of South America (South Atlantic) was probably a result of the opening of the equatorial Atlantic gateway during that time. The faunas are not endemic, indicating that the larvae were long-lived and possessed a high dispersal potential, facilitated by seaways during the Albian.

Change from rimmed to ramp platform forced by regional and global events in the Cretaceous of the Friuli-Adriatic Platform (Southern Alps, Italy)

Carbonate platforms are sedimentary archives recording the evolution of the global carbon cycle. Their stratigraphic architecture depends on the regional tectonics, controlling subsidence rates and geometries, as well as the paleoceanography and evolutionary trends, controlling the different organisms thriving at their margins, such as frame-building corals or mound-building microbes. We present an integrated bio- and chemostratigraphic study of the Aptian to Santonian interval of a base-of-slope section located in the Southern Alps of northeastern Italy that we correlate with the classic section representing the Friuli-Adriatic Carbonate Platform, one of the largest isolated platforms of the low latitude Tethys. We show the effects of the end of the passive-margin stage and the interaction between foreland flexuring due to the growing Alps, to which the study area represented the retroforeland, and the approaching prowedge of the Dinarides. The Friuli-Adriatic platform margin shows an abrupt change from reef rimmed to ramp, where abundant microbial mounds provided the habitat for the rudists to thrive. This change occurred around the late Albian and likely correlates with the Oceanic Anoxic Event (OAE) 1d. The previous OAE's did not change the structure of this platform, whose margins were mostly rigid and colonized by corals and calcareous sponges. Late Albian was a time of important changes in paleoceanography in Tethys and North Atlantic Oceans. We propose that the paleooceanographic changes related to the OAE- 1d had more profound impacts on the Friuli-Adriatic Platform than the previous Cretaceous OAE's since they co-occurred with the tectonic transition from passive margin to foreland ramp. The increased subsidence rates, in conjuction with the important late Albian paleoceanographic changes, created favourable conditions for a dramatic change in the platform margin physiography and ecology.

Biochemostratigraphy of an upper Albian–Turonian succession from the southeastern Neo-Tethys margin, SW Iran

A Neo-Tethyan upper Albian–Turonian (hemi-)pelagic carbonate succession (Sarvak Formation), accessible in outcrop in the Zagros, SW Iran, was investigated using sedimentology, microfacies analysis, planktonic foraminifera biostratigraphy, and carbon-isotope stratigraphy. The succession contains six biozones including Thalmanninella (Th.) appenninica, Th. globotruncanoides, Rotalipora cushmani, Whiteinella archaeocretacea, Helvetoglobotruncana Helvetica, and Marginotruncana schneegansi. Some of these biozones show variable stratigraphic positions throughout the Tethyan and Boreal realms that hinder correlation of the studied Iranian section with European reference sections. Therefore, the correlation of the existing biostratigraphic framework was complemented by carbonate carbon-isotope stratigraphy based on bulk carbonate material. Despite the low resolution of the presented carbon-isotope record, pronounced global events including the late Turonian Events, Cenomanian/Turonian Boundary (CTB) Event (OAE 2), and Albian/Cenomanian Boundary (ACB) Event can be distinguished. The δ13C excursions provide global synchronous time-lines for correlation. The distinguished biozones were compared among the sections regarding their stratigraphic positions relative to these time-lines. The correlation tentatively suggests that the biostratigraphic datum marking the ACB is diachronous with an SE–NW trend. First appearance datum (FAD) of Th. appenninica varies from the upper Albian to the lower Cenomanian. The FAD of Th. globotruncanoides is also variable from the upper Albian to the lower Cenomanian. However, the middle Cenomanian–Turonian biozones including Rotalipora cushmani and Whiteinella archaeocretacea zones are synchronous. Elevated pCO2 contributed to the gradual increase of the SST (sea surface temperature) during the Cenomanian, and the dramatic climax at the earliest Turonian. This trend closely correlates with the change from the diachronous ACB-biozones to synchronous CTB-biozones. Possibly, increasing SSTs provided temperature-tolerance range for the species throughout different latitudes, and assisted their rapid distribution. Moreover, the warming raised the sea level from the latest Albian to Turonian that inundated landbridges, resulting in an enhanced marine circulation and faster distribution of planktonic species throughout the Neo-Tethys Ocean.

Arquitetura estratigráfica dos depósitos fluviais albianos da base da Formação São Mateus no norte da Bacia do Espírito Santo

Os depósitos aluviais da Formação São Mateus (Albiano da Bacia do Espírito Santo, Brasil) consistem em importantes reservatórios. Entretanto, existem poucos trabalhos detalhando a estratigrafia deste intervalo estratigráfico. Em decorrência disso, este trabalho teve por objetivo estabelecer um fatiamento estratigráfico de alta resolução da seção basal desta unidade, a qual é constituída por depósitos fluviais. Diante das dificuldades apresentadas para a correlação estratigráfica desses depósitos, a estratégia de correlação utilizada foi a subdivisão da sucessão aluvial em ciclos estratigráficos. Este método se baseia na variação na razão entre as taxas de criação de acomodação e suprimento sedimentar (A:S) que diretamente controla o grau de amalgamação dos corpos arenosos de canais fluviais. Com isso, foram definidos seis ciclos compostos internamente por tratos de sistemas de alta e baixa acomodação. Esses ciclos refletem a estruturação do arranjo da amalgamação dos canais fluviais com os depósitos externos aos canais através da razão entre a taxa de acomodação (A) e a taxa de influxo sedimentar (S) formando ciclos.

Shajia, a new genus of polyconitid rudist from the Langshan Formation of the Lhasa block, Tibet, and its palaeogeographical implications

A new polyconitid rudist Shajia tibetica gen. et sp. nov., of late Aptian to Albian age, is described from the Langshan Formation of Nyima County, northern Lhasa Block, Tibet. Though comparable in size and external morphology with Horiopleura haydeni Douvillé, which is a common endemic species in southwestern Asia, Shajia differs from the latter species in its possession of an inwardly inclined, instead of outwardly facing, posterior myophore in the right valve. In addition, a single specimen from Ladakh, which was previously assigned to Polyconites? sp., on account of a similar myophoral distinction from H. haydeni, is transferred to the new genus. Shajia is considered most likely to have been derived from one of a group of Horiopleura species that lived on the southern margin of the Mediterranean Tethys.The so-called ‘Yasin fauna’ represented by the late Aptian to Albian Horiopleura haydeni/Auroradiolites gilgitensis rudist association, is considered to be restricted to southwestern Asia, including Afghanistan, Kohistan in northern Pakistan and Ladakh in northern India, though those two species in particular have not so far been recorded from the Lhasa Block of Tibet. Nevertheless, S. tibetica co-occurs with Auroradiolites biconvexus (Yang et al.), which probably evolved directly from A. gilgitensis (Douvillé), and the age of the latter association is in accordance with the generally accepted age of the Yasin fauna as late Aptian to Albian. Hence the S. tibetica and A. biconvexus association can be considered a regional variant of the Yasin fauna, which had evidently already dispersed to the Lhasa Block by the late Aptian. So the Langshan Formation can be considered palaeogeographically linked with other mid-Cretaceous shallow-marine carbonate deposits in adjacent southwestern Asian regions. These findings also provide new evidence that the age of the rudist assemblage of the Lhasa Block is late Aptian to Albian, although a slightly younger age cannot be excluded.

Calcareous nannoplankton proxies for palaeoenvironmental reconstruction of the Albian–Cenomanian succession in North-western Israel (Mount Carmel Region)

Abstract We present data on the calcareous nannofossil distribution in the Albian–Cenomanian borehole CT8 obtained from the Carmel area, NW Israel. The nannofloral assemblage consists of 113 species, with Watznaueria spp. dominating the entire succession. The detailed calcareous nannofossil biostratigraphy of this section is established, and seven nannofossil (sub)zones are recognised. For the first time the age of the Tavasim Tuff (V2) is biostratigraphically identified as Late Albian. The quantitative analysis of the calcareous nannofossils suggests warm, open marine or coastal, mainly oligotrophic conditions throughout the entire succession of borehole CT8, with evident fluctuations of temperatures and fertility and a general trend towards cooling in the uppermost part of the sequence (Middle–Late Cenomanian). Temperature and nutrient variations correspond to those in the western Tethys, thus suggesting at least a supra-regional extent of processes detected in the Carmel Region. The biostratigraphy shows no evidence of hiatuses in the studied section, but the absence of positive carbon isotope anomalies associated with the Oceanic Anoxic Event (OAE) 1d and Mid-Cenomanian Event elsewhere suggests that the OAE 1d is possibly missing in the studied section due to a hiatus around the Isfiye Fm./Arqan Fm. boundary.

Albian–Cenomanian Orogenic Belt and Igneous Province of Pacific Asia

Geological data and about 300 precision geochronological and geochemical determinations are analyzed to identify the Albian–Cenomanian continental-margin orogenic belt and simultaneous igneous province of Pacific Asia. The orogenic belt represents a newly formed region of continental lithosphere that resulted from the deformation of mainly Jurassic–Early Cretaceous epioceanic terranes. The igneous province is made up of volcanic and intrusive complexes of mostly Albian age, which are syn-orogenic within the belt and post-orogenic beyond it. The igneous rocks include A-, I-, and S-type granitoids; adakites; and VAB- and OIB-type basalts and their intrusive analogues. Both the orogenic belt and the igneous province were formed in a tectonic setting of a transform continental margin between 110 and 95 Ma. The interval of 103–97 Ma became the peak of orogenic and magmatic activity caused by upwelling of the hot asthenospheric mantle through destructed stagnant slabs of the pre-Albian subduction. The Albian–Cenomanian age of the large gold, copper, tungsten, tin, and other ore deposits argues in favor of recognition of the corresponding metallogenic province. The first age data (100–97 Ma) are reported for the granite from the Malmyzh deposit within the Sikhote-Alin Ridge.

How Do Continents Deform During Mantle Exhumation? Insights From the Northern Iberia Inverted Paleopassive Margin, Western Pyrenees (France)

AbstractExtreme crustal thinning associated with subcontinental mantle exhumation characterizes the distal domain of some current, magma‐poor continental passive margins. Since these domains lie at abyssal depths and are hardly accessible, their internal structure and the finite strain of the stretched crust are not directly observed and are only inferred. A detailed field study was conducted on exceptionally preserved Cretaceous distal margin analogs in two key areas of the western Pyrenees (North Pyrenean Zone): the Urdach and Saraillé ultramafic massifs in the Chaînons Béarnais range. A tight sampling allowed us to characterize the conditions of the ductile deformation of the continental crust exhumed together with the mantle. New 40Ar/39Ar dating on muscovite constrains the timing of the last deformation of the continental crust in relation with mantle exhumation to the late Albian. We propose a new reconstruction for the distal part of the North Iberian paleopassive margin based on the following constraints: (i) post‐Silurian Paleozoic rocks are never found in the distal domain; (ii) lower crustal levels are not found in the exhumed crustal units; (iii) extension in the pre‐Silurian series is accomplished by lenticular deformation and pervasive ductile flattening through anastomosing extensional mylonitic shear zones at temperatures of 350–450 °C; and (iv) at the final step of exhumation, only pre‐Silurian crustal lenses remained welded on the exhumed mantle. Finally, we discuss the importance of the crustal structure inherited from previous Paleozoic and Mesozoic tectonic events and we state that mantle exhumation was partially achieved before the Cretaceous North Pyrenean rifting.

Organic facies and hydrocarbon potential of the early-middle Albian Kharita Formation in the Abu Gharadig Basin, Egypt, as demonstrated by palynology, organic petrology, and geochemistry

During the past decades, exploration activities carried out in the Western Desert of Egypt by several oil companies revealed the oversimplified approach to the study of sedimentary basins in this region. The current study evaluates and discusses the palynology and palynofacies of the clastic succession of the Kharita Formation (Albian) in one of the most petroliferous, deep seated, fault controlled basins in the Western Desert of Egypt, the Abu Gharadig Basin. Although the focus is on the palynofacies association, the hydrocarbon potential of the Kharita Formation will also be addressed by means of organic petrology and Rock-Eval pyrolysis. Marine Cretaceous source rocks have generated substantial quantities of oil and gas in the Abu Gharadig rift Basin. Moreover, Abu Gharadig Basin is characterized by containing not only oil/gas generating source rocks but also reservoir rocks with appreciable porosities and permeabilities. Palynological, TOC/Rock-Eval pyrolysis, and vitrinite reflectance (VRo%) data from 26 cuttings samples recovered from the Kharita Formation in the BED 2-1× well, are presented. The palynological age dating (AL-2 Palynozone) confirmed early to middle Albian age based on the first downhole appearance of the marker Concavisimisporites punctatus. The optical and visual characterization of the palynofacies associations showed two distinct palynofacies associations that alternated with each other. Kerogen type III to III/II was recorded based on the dominance of phytoclasts and opaque organics. Some intervals showed a slight dominance of amorphous organic matter (AOM). Thermal Alteration Index (TAI) values of 2+/3-measured on the psilate trilete spores, in combination with vitrinite reflectance (VRo) values in the range from 0.51 to 0.62%, and the yellow to dull-yellow colors of the liptinite macerals exhibited under UV light excitation indicate immature to the early stage of the oil window. Tmax values from Rock-Eval pyrolysis range from 426 to 438 °C also confirm the low maturity of the organic matter. Thin coal stringers were recorded within the Kharita Formation having slightly higher VRo,ran values (0.64 to 0.76%), which is possibly the result of differences in mineral matrix variations within the Kharita Formation. Based on the low TOC (avg. 0.71 wt%), S2 (avg. 0.97 mg HC/g rock), and HI (avg. 149 mg HC/g TOC) values from pyrolysis, the hydrocarbon potential of the Kharita Formation in the studied well is considered to be low.

The paralic Albian–Cenomanian Puy-Puy Lagerstätte (Aquitaine Basin, France): An overview and new data

The Puy-Puy quarry at Tonnay-Charente (Charente-Maritime, SW France) is a sand quarry exposing a 9-m-thick series of latest Albian–earliest Cenomanian (mid-Cretaceous) age. The uppermost Albian deposits consist of lignitic clay containing fossiliferous amber. The lowermost Cenomanian sand deposits alternate with clay intercalations containing plant remains. One of these clay levels, named P1, shows an outstanding accumulation of conifer and angiosperm macrofossils including delicate reproductive structures such as flowers. Plant remains are associated with invertebrates such as insects (Odonata, Dictyoptera, Diptera), crustaceans (Mecochirus sp.), putative brachiopods (aff. Lingula sp.), and worms. A few vertebrate remains such as shark egg capsules (Palaeoxyris sp.) and a feather are present in the fossil assemblage, as well as an enigmatic specimen tentatively interpreted as a cephalochordate or a petromyzontiform. Various ichnofossils occur in abundance, such as crustacean coprolites and burrows (Ophiomorpha isp.), insect coprolites (Microcarpolithes hexagonalis), and leaf herbivory, galls and mines. The sediments have been deposited in a coastal, calm and brackish area.

Regional upper Albian–lower Cenomanian sequence boundaries, Texas Comanche shelf: Is timing related to oceanic tectonics?

The Albian–lower Cenomanian Comanchean Series on the Comanche Shelf, Texas and northern Mexico is a laboratory to calibrate the numerical ages of mixed carbonate-siliciclastic cycles. The stratigraphic contacts of the long-term cycles formed during subaerial exposure followed by marine drowning. Correlation of these cycle contacts in different basins tests their synchroneity and the hypothesis of eustasy. Petrographic and geochemical evidence of Early Cretaceous meteoric diagenesis differs across the shelf because the Comanche Shelf spanned the subtropical arid belt and the mid-latitude warm humid zone. The contact between the Fredericksburg and Washita groups is Al SB Wa1, which is a composite subaerial unconformity and transgressive drowning surface that is traced from southeastern Oklahoma to El Paso and down-dip to the shelf margin.Chronostratigraphy of the Comanchean Series Fredericksburg and Washita groups is constrained by multiple biostratigraphic data of ammonites, caprinid rudists, and foraminifers. The lower upper Albian Al SB Wa1 is dated by the Dipoloceras cristatum Zone below and the Mortoniceras pricei Zone above. Caprinid zones in carbonate facies are integrated with ammonites and foraminifers to provide a complementary correlation criterion. This contact is coeval with a condensed interval in Europe and flooding sequences in western Asia and northern Africa.Depleted carbon isotope ratios indicate subaerial exposure below sequence boundaries at base of Washita Group, at base of the lower Cenomanian Del Rio Formation and base of the Cenomanian Woodbine-Eagle Ford groups. These contacts are coeval with sequences in Europe, Africa, Asia, and South America. Late Albian–early Cenomanian sea-level changes provide a chronologic scale for significant oceanic plate reorganization dated at about 100 Ma.

New stratigraphic data for the Lower Cretaceous Tirgan Formation, Kopet-Dagh Basin, NE Iran

In this contribution, we describe a section through the Lower Cretaceous shallow-water platform sediments (Tirgan Formation) from the Kopet-Dagh basin (northern Tethys), which is located near Tirgan village, NE Iran. We used benthic foraminifera and planktonic organisms for biostratigraphy associated to the carbon isotope chemostratigraphy to constrain the age of the succession. Microfossils are grouped around the Feurtillia gracilis range zone (Upper Valanginian), the Campanellula capuensis range zone (Upper Hauterivian-Barremian), the Orbitolinid assemblage zone (Lower to Upper Aptian) and the Planktonic assemblage zone (Upper Aptian) as well as several genera and species are reported from the Kopet-Dagh for the first time (e.g., C. capuensis, Colomiella sp., Cuneolina composaurii, F. gracilis). The new biostratigraphic data allow us to date the lower part of the section as Berriasian (?), Valanginian, and Hauterivian, which is older than the age range previously assumed for the Tirgan Fm. (Barremian-Aptian). Our age determinations are consistent with those obtained by the carbonate carbon isotope chemostratigraphy and the resulting age model allows to assign a Berriasian (?)-Valanginian to Albian age to the Tirgan Fm. Furthermore, a prominent positive excursion near the base of the section can be correlated with the Weissert Episode, and likely also the Faraoni Episode is registered in this succession. The Tirgan Fm. displays an explicit onlap pattern to the west, which explains the diachrony in ages of the base of the formation. This suggests the effect of a long-term subsidence in the Kopet-Dagh during the Early Cretaceous, following the Cimmerian phase of orogenesis.

Exquisitely-preserved, high-definition skin traces in diminutive theropod tracks from the Cretaceous of Korea

Small theropod tracks, ichnogenus Minisauripus, from the Jinju Formation (Cretaceous) of Korea reveal exquisitely preserved skin texture impressions. This is the first report for any dinosaur of skin traces that cover entire footprints, and every footprint in a trackway. Special sedimentological conditions allowed footprint registration without smearing of skin texture patterns which consist of densely-packed, reticulate arrays of small (<0.5 mm) polygons, preserved as both impressions and casts, the latter essentially foot replicas. The skin texture resembles that reported for two Lower Cretaceous avian theropods (birds) from China which had quite different foot morphologies. This is also the oldest report of Minisauripus from Korea predating five reports from the Haman Formation of inferred Albian age. Minisauripus is now known from six Korean and three Chinese localities, all from the Lower Cretaceous. This gives a total sample of ~95 tracks representing ~54 trackways. With >80% of tracks <3.0 cm long, Minisauripus is pivotal in debates over whether small tracks represent small species, as the database suggests, or juveniles of large species.

Early Cretaceous gymnolaemate bryozoans from the early to middle Albian of the Glen Rose and Walnut formations of Texas, USA

AbstractGymnolaemate bryozoans are common encrusters on bivalve shells from the early to middle Albian parts of the Glen Rose and Walnut formations of southcentral and northcentral Texas. Here, we report for the first time the presence of seven gymnolaemate bryozoans, all of which represent new species. They include the bioimmured ctenostomeSimplicidium jontoddin. sp., and the cheilostomesRhammatopora glenrosan. sp.,Iyarispora ikaanakiteehn. gen. n. sp.,Iyarispora chiassn. gen. n. sp.,Charixa bispinatan. sp.,Charixa sexspinatan. sp., andCharixa emanuelaen. sp. The Glen Rose bryozoans slightly antedate the commencement of an explosive bryozoan radiation and the first appearance of neocheilostomes in the late Albian. Although the diversity of cheilostomes in the Glen Rose and Walnut formations is similar to that of cyclostomes, cheilostomes are more abundant and produced larger colonies. These formations therefore yield the oldest known bryozoan assemblage dominated in terms of biomass by cheilostomes. The genus concept ofCharixais discussed and amended.UUID:http://zoobank.org/d9e8f1a4-ae6a-4455-abb3-3b0a75a7d294

Diversity and homologies of corystosperm seed-bearing structures from the Early Cretaceous of Mongolia

New discoveries of corystosperm seed-bearing structures from the Tevshiin Govi locality, Mongolia, which is of Early Cretaceous (Aptian–Albian) age, show that the individual seed-bearing units of Umkomasia mongolica were borne in a cone, as also documented for the very similar reproductive units of Doylea tetrahedrasperma. New material from the Tevshiin Govi locality also documents two additional species of Umkomasia – U. corniculata sp. nov. and U. trilobata sp. nov. – that most likely grew in a different environment to U. mongolica. The occurrence of three different Umkomasia species in the Early Cretaceous of Mongolia, together with other records from the Early Cretaceous of the Northern Hemisphere, indicate that previous concepts of corystosperms, based mainly on material from the Southern Hemisphere, need to be revised. The consistent reproductive architecture of the seed-bearing structures in all three corystosperm species, with a bract subtending a variously modified axis bearing ovules, is similar to the situation in Ginkgo and conifers. These underappreciated architectural commonalities among the reproductive structures of major groups of seed plants are likely significant for a deeper understanding of seed plant evolution and require further exploration.

Thermal maturation assessment of multiple organic-rich intervals in the Khatatba Formation and its influences on hydrocarbon potentiality, North East Abu Gharadig Concession, elucidated by 1D basin modeling approach

ABSTRACTHydrocarbon generation and expulsion simulations of multiple organic-rich intervals with diverse kerogen types in the Khatatba Formation were performed. Generally, the organofacies exhibit an excellent generation potential for liquid hydrocarbons, gas plus oil and/or gas. The 1D forward approaches have been executed for the complex tectonic and basin-fill history. The spatial distribution of the Khatatba organofacies and allocation of significant discoveries from the Khatatba Formation are aligned perpendicular to the NE-SW Jurassic Fault System. The organic-rich intervals underwent several heating episodes throughout its burial history predominantly during the Cretaceous Rifting phase. Likewise, the organofacies underwent episodic expulsion of gas derived from either primary cracking (kerogen type III) or secondary cracking of oil (kerogen type II). The oil prone type II kerogen entered the oil window at JD-4 well close to the Albian whilst the wet-gas window since late Albian. Conversely, gas prone type III kerogen attained the dry-gas window from the time of early Oligocene at the JD-4 well prior to the wet-gas window of the JG-2 well (late Oligocene). Nevertheless, gas prone type III kerogen never reached the dry gas window at JG-2 well due to its low thermal maturation level. The burial effect, attributable to the thick basin-fill sediments (Masajid, Alam El Bueib, Abu Roash and Khoman formations), accelerated the thermal maturation at the JD-4 well. However, the organofacies revealed neither thermogenic gas generation nor gas secondary cracking at the JG-2 well and nix expulsion. The expelled hydrocarbon assumed to migrate laterally and near vertically from the southeastern part towards the north western part.