Immigration of the genus Macrocephalites Spath and the Bathonian biostratigraphy of the Kachchh basin (Western India, South Tethys)

The Bathonian occurrences of Indonesian Macrocephalites from the Kachchh basin (Western India) (and correspondingly the immigration of the genus into the basin) is evaluated in context of improved biostratigraphy and new ammonite data vis-à-vis European and Submediterranean records. The Indonesian Middle Bathonian macrocephalitids [Macrocephalites bifurcatus transient intermedius (Spath) (M), M. bifurcatus transient cf. intermedius (Spath) (M), M. bifurcatus transient aff. bifurcatus Boehm (m) and M. cf. etheridgei Spath (m)], have largely been recorded from a single dome, Jumara (from the basal Yellow bed, bed A4), with additional singular occurrences of M. cf. etheridgei Spath (m) from the adjoining Nara and Jhura domes (Kachchh). In Jumara, the Indonesian macrocephalitids are associated with Micromphalites (Clydomphalites) clydocromphalus Arkell (M), Procerites (Gracilisphinctes) arkelli Collignon (M), P. (G.) intermedius Jain (m), P. hians (Waagen) (M), Wagnericeras sp. (m), Parapatoceras distans (Baugier and Sauzé) (M), Sivajiceras congener (Waagen) (M and m), Macrocephalites triangularis Spath (M and m), Epimorphoceras decorum (Waagen) (M), and Reineckeia sp. A and B (M). This fauna is correlated with the European early Middle Bathonian Progracilis Zone. Both Jumara and the adjoining Jara domes have also yielded characteristic Indonesian Late Bathonian macrocephalitids – M. cf. keeuwensis Boehm (M and m), M. keeuwensis var. aff. forma flexuosa Boehm (m) and M. cf. mantataranus Boehm (M). In light of improved high–resolution stratigraphy, the Kachchh Bathonian fauna is evaluated and an improved biostratigraphy of the basin is proposed

Pliensbachian nannofossils from Kachchh: Implications on the earliest Jurassic transgressive event on the western Indian margin

The oldest rocks within the Kachchh Basin belong to the sediments of Kaladongar Formation exposed in Kuar Bet, Pachchham Island (western India). The Formation’s lowest unit, the Dingi Hill Member has yielded a moderately diversified calcareous nannofossil assemblage that includes the marker species of Lotharingius contractus and Triscutum sullivanii of late Early Aalenian age associated with reworked species of Biscutum finchii, Bussonius prinsii, Crucirhabdus primulus, Crepidolithus pliensbachensis, Discorhabdus criotus and D. striatus suggesting an age spanning NJ4a to NJ7 Zones (Early Pliensbachian, Tethyan ammonite Jamesoni Zone to Middle Toarcian, Variabilis Zone). Additionally, samples from four other Kachchh domal localities (Kachchh Mainland: Jara, Jumara and Habo and the Island belt, Waagad) have also yielded reworked Pliensbachian-Toarcian age (~183 Ma) nannotaxa viz. Crepidolithus granulatus, Diductius constans, Mazaganella protensa, Mitrolithus elegans, Parhabdolithus liasicus, Similiscutum orbiculus, and Triscutum tiziense. This nannotaxa age is much earlier than the ammonite-based Earliest Bajocian date (~171.6 Ma) based on the presence of ammonite Calliphylloceras heterophylloides (Oppel). Additional reworked assemblages have been studied from the Callovian sediments at Jara, the Bathonian-Callovian sediments at Jumara, the Callovian sediments at Habo and the Oxfordian-Kimmeridgian sediments at Wagad. The present data, thus, indicates the presence of a marine connection at least since the Pliensbachian in Kachchh. It is proposed that both global eustatic rise and local tectonics were responsible for this Pliensbachian inundation of the Kachchh Basin. Similar record of Late Pliensbachian age reworked nannofossils have also come from the Masirah Island of the Sultanate of Oman and of ?Aalenian-Bajocian age nannofossils from Kuwait, lending credence to our findings and of the presence of at least Pliensbachian-Toarcian age sediments in Kachchh.Die ältesten Sedimente des Kachchh Beckens gehören zur Kaladongar Formation und sind in Kuar Bet, Pachchham (West-Indien), aufgeschlossen. Aus der untersten Einheit dieser Formation (Dingi Hill Member) konnte eine relativ diverse Vergesellschaftung kalkiger Nannofossilien gewonnen werden, die u.A. die Marker-Taxa Lotharingius contractus und Triscutum sullivanii (oberes unteres Aalenium) enthält sowie umgearbeitete Exemplare von Biscutum finchii, Bussonius prinsii, Crucirhabdus primulus, Crepidolithus pliensbachensis, Discorhabdus criotus und D. striatus, welche eine Zuordnung der Sedimente zwischen NJ4a und NJ7 indizieren (unteres Pliensbachium, Tethys Ammoniten Jamesoni Zone bis mittleres Toarcium, Variabilis Zone). Darüber hinaus wurden in vier andere Lokalitäten des Kachchh Beckens (Kachchh Festland: Jara, Jumara und Habo sowie Inselgürtel, Waagad) ebenfalls umgearbeitete Nannofossilien aus dem Pliensbachium-Toarcium (~183 Ma) gefunden, nämlich Crepidolithus granulatus, Diductius constans, Mazaganella protensa, Mitrolithus elegans, Parhabdolithus liasicus, Similiscutum orbiculus, und Triscutum tiziense. Die Nannofossilien indizieren ein höheres Alter der Sedimente, als die Datierung mit Ammoniten, welche auf der Basis des Vorkommens von Calliphylloceras heterophylloides (Oppel) die Sedimente in das unterste Bajocium (~171.6 Ma) stellt. Um das ungewöhnliche Vorkommen von Nannotaxa aus dem Pliensbachium-Toarcium in Kachchh zu überprüfen, wurden fünf weitere Lokalitäten erfolgreich auf Nannofossilien hin untersucht. Diese Proben stammen aus Sedimenten des Calloviums von Jara und des Bathoniums-Calloviums von Jumara, aus dem Callovium von Habo sowie aus dem Oxfordium-Kimmeridgium von Wagad. Unsere Ergebnisse lassen den Schluss zu, dass in Kachchh mindestens seit dem Pliensbachium eine marine Verbindung existierte. Es ist wahrscheinlich, dass sowohl der weltweite eustatische Anstieg des Meeresspiegels als auch lokale tektonische Aktivitäten für die Überflutung des Kachchh Beckens im Pliensbachium verwantwortlich waren. Ähnliche Vorkommen von umgearbeiteten Nannofossilien aus jungen Pliensbachium sind auch vonder Insel Masirah, Sultanat Oman bekannt. Nannofossilien aus dem ?Aalenium-Bajocium kennt man aus Kuwait. Beide Vorkommen stützen unsere Ergebnisse und bestätigen das Vorkommen von Sedimenten mindestens aus dem Pliensbachium-Toarcium im Kachchh Becken

Relationship of benthic foraminiferal diversity to paleoproductivity in the Neogene of the Caribbean deep-sea

Abstrac

Multiproxy analyses of paleoenvironmental and paleoceanographic changes during the Danian-Selandian in East Central Sinai: An integrated stable isotope and planktic foraminiferal data

Forty-three planktic foraminifera samples from the Themed section (East Central Sinai; Egypt) spanning the Zone Parvularugoglobigerina eugubina (Pα) to the Subzone Acarinina subsphaerica (P4b) have been studied. Data from δ13C, δ18O, and planktic foraminifera-based species diversity, depth habitat, preference for warm and cool surface waters, and nutrients (oligotrophic, mesotrophic, and eutrophic conditions) are used to infer paleoenvironmental changes throughout the Danian‒Selandian duration. Based on quantitative multivariate analyses (hierarchical cluster and principal component), three distinct intervals were recognized, Interval 1 (Pα‒P1b), Interval 2 (P1c‒P3a), and Interval 3 (P3a‒P4b). Interval 2 is further subdivided into three subintervals, 2a (part P1c), 2b (part P1c), and 2c (P2‒P3a). Two δ13C events are identified, Dan-C2 and Latest Danian Event (LDE) and elaborated concerning paleoenvironmental changes. During the earliest Danian planktic foraminiferal Pα Zone, moderately shallow and eutrophic conditions prevailed with cool surface waters and a shallow thermocline. Comparable conditions were still prevailing during P1a‒P1b, but with slightly deeper and mesotrophic conditions and a somewhat deeper thermocline and reduced stratification. P1b‒P1c exhibits a major shift from Eoglobigerina to Subbotina‒ Parasubbotina with cooler surface waters and moderate mesotrophic conditions. For Subzone P1c (upper part), slightly mesotrophic conditions were inferred, whereas for P2‒P3a (lower part), surface water warming and thermocline shallowing events have inferred with increased oligotrophic conditions. The Latest Danian Event (mid-P3a) is marked by a dramatic negative δ13C excursion, warm waters, increased mesotrophic conditions, and enhanced stratification. The dominance of Morozovella, Acarinina, and Igorina specify warm and oligotrophic conditions for subzones P3b‒P4b

The Arkelli Chronozone: A new early Middle Bathonian standard ammonite zone for Kachchh, western India (southern Jurassic Tethys)

Based on the widespread distribution of the nominal and Madagascan ammonite species Procerites (Gracilisphinctes) progracilis arkelli Collignon [M] in Kachchh (western India), a new early Middle Bathonian Arkelli Chronozone is proposed and correlated with the Western European early Middle Bathonian Progracilis Zone. The nominal species is now firmly established as a geographic subspecies of the Western European P. (G.) progracilis Cox and Arkell [M]. The recorded assemblage within the Kachchh Mainland from this chronozone now contain Micromphalites (Clydomphalites) clydocromphalus Arkell [M], Procerites hians Waagen [M], Procerites (Siemiradzkia) cf. verciacensis [m], Sivajiceras congener (Waagen) [M and m], Procerites (Gracilisphinctes) progracilis arkelli Collignon [M and m], P. (G.) progracilis aff. arkelli Collignon [M], P. (G.) intermedius n. sp. [m], Macrocephalites cf. etheridgei Spath [m], M. bifurcatus transient aff. bifurcatus Boehm [m], M. bifurcatus transient intermedius (Spath) [M and m], M. bifurcatus transient cf. intermedius Boehm [M], Macrocephalites triangularis Spath [M and m], Parapatoceras distans (Baugier and Sauzé) [M], Reineckeia sp. A and B [M] and Eutrephoceras sp. [M]. Coeval sediments at the Island Belt had previously yielded the presence of Procerites cf. schloenbachi, Micromphalites (Clydomphalites) cf. clydocromphalus, M. (Clydomphalites) sp. indet., M. aff. hourcqui, Clydoniceras triangulare, C. pachchhamensis, Clydoniceras sp. and Bullatimorphites (s.s.). These finds, thus, now extend the Kachchh non-macrocephalitid records to Saudi Arabia and on to the NW European localities, and for the macrocephalitids, into the High Himalayas and further outside the Indo-Madagascan Province, to the East Indies and into New Zealand. Recent nannofossil data from the same ammonite-yielding bed (the Yellow Bed at Jumara, Kachchh Mainland) is reinterpreted with updated chronology. New data suggests that this condensed Yellow Bed encompasses a 2.6 Ma interval spanning from 168.67 Ma (Late Bajocian; Garantiana Zone) to 166.07 Ma (Middle Bathonian; Morrisi Zone). However, for both Garantiana and Morrisi zones, the ammonite records are lacking in Kachchh, so far. Previous benthic foraminiferal data from the same bed had also yielded a broad Middle Bathonian age. Although, an integrated approach is employed here (using ammonite, foraminifers, nannofossils and lithostratigraphy), but for the Bathonian, among the fauna, the ammonites provide a far better age resolution. Globally, Macrocephalites bifurcatus transient cf. intermedius Boehm [M] is recorded here as the earliest macrocephalitid. Its evolutionary path follows from the Late Bajocian to Early Bathonian Satoceras to Praetulites and on to M. bifurcatus in the early Middle Bathonian. The Macrocephalites entry into Kachchh was possibly facilitated by a transgressive event (the T10 event of Hallam and Haq et al.’s ebbing LZA-2.2). This contribution also discusses the implications of these new records to regional and global biostratigraphy.Auf der Basis des weiträumigen Vorkommens des nominellen und madegassischen Ammonitentaxons Procerites (Gracilisphinctes) progracilis arkelli Collignon [M] in Kachchh (Westindien) wird die Einführung einer neuen Arkelli Chronozone für das frühe Mittel-Bathonium vorgeschlagen und mit der westeuropäischen Progracilis Zone korreliert. Das nominelle Taxon wird als eine geographische Unterart der westeuropäischen P. (G.) progracilis Cox & Arkell [M] interpretiert, welche innerhalb der Arkelli Chronozone im Festland von Kachchh assoziiert ist mit Micromphalites (Clydomphalites) clydocromphalus Arkell [M], Procerites hians Waagen [M], Procerites (Siemiradzkia) cf. verciacensis [m], Sivajiceras congener (Waagen) [M und m], Procerites (Gracilisphinctes) progracilis arkelli Collignon [M und m], P. (G.) progracilis aff. arkelli Collignon [M], P. (G.) intermedius n. sp. [m], Macrocephalites cf. etheridgei Spath [m], M. bifurcatus trans. aff. bifurcatus Boehm [m], M. bifurcatus trans. intermedius (Spath) [M und m], M. bifurcatus trans. cf. intermedius Boehm [M], Macrocephalites triangularis Spath [M and m], Parapatoceras distans (Baugier & Sauzé) [M], Reineckeia sp. A und B [M] sowie Eutrephoceras sp. [M]. Aus altersgleichen Sedimenten des Inselgürtels konnte bereits früher das Vorkommen von Procerites cf. schloenbachi, Micromphalites (Clydomphalites) cf. clydocromphalus, M. (Clydomphalites) sp. indet., M. aff. hourcqui, Clydoniceras triangulare, C. pachchhamensis, Clydoniceras sp. und Bullatimorphites (s.s.) belegt werden. Diese Funde verbinden die Kachchh Nachweise nicht-macrocephaliider Ammoniten mit Saudi Arabien und weiter nach nordwest Europa, und, mit Hinsicht auf die Makrocephalitiden, mit der Himalaya-Hochebene und weiter zur Indo-Madegassischen Provinz, Ostindien und Neuseeland. Nannofossiliendaten aus der Ammoniten-Schicht (dem Yellow Bed bei Jumara, Kachchh Festland) weren neu interpretiert, und eine revidierte Chronologie wird erstellt. Die Ergebnisse deuten darauf hin, dass das kondensierte Yellow Bed eine Zeitspanne von etwa 2.6 Ma representiert, von 168.67 Ma (oberes Bajocium; Garantiana Zone) bis 166.07 Ma (mittleres Bathonium; Morrisi Zone). Allerdings sind aus keiner dieser beiden Ammoniten Zonen bislang Belegammoniten in Kachchh gefunden worden. Analysen benthischer Foraminiferen aus derselben Schicht deuten ebenfalls auf ein mittel-Bathonisches Alter hin. Obwohl dieser Arbeit ein integrativer Ansatz basierend auf Ammoniten, Foraminiferen, Nannofossilien und Lithostratigraphie zugrunde liegt, läßt sich feststellen, dass für das Bathonium die Ammoniten die beste Altersauflösung geben. Macrocephalites bifurcatus trans. cf. intermedius Boehm [M] wird als der früheste Vertreter der Macrocephalitiden vorgestellt. Seine Evolutionsgeschichte geht von Satoceras aus dem Ober-Bajocium und Unter-Bathonium über Praetulites zu M. bifurcatus im frühen Mittel-Bathonium. Die Einwanderung von Macrocephalites nach Kachchh wurde vermutlich durch ein Transgressionsereignis (das T10 event von Hallam & Haq et al.s ebbing LZA-2.2) ermöglicht. Die Bedeutung der neuen Funde und Erkenntnisse für die regionale und globale Biostratigraphie wird diskutiert

Changes in Caribbean paleoproductivity, diversity and benthic foraminiferal test size caused by the Neogene closing of the tropical Atlantic-Pacific ocean gateway

The purpose of this study was to test 3 hypotheses: (a) that late Miocene to early Pliocene constriction and complete closure of the Central American Seaway (CAS), connecting tropical Atlantic and East Equatorial Pacific (EEP) oceans, caused decreased productivity in the Caribbean, due to reduced coastal upwelling and an end to the connection with high-productivity Pacific waters, (b) reduced paleoproductivity resulted in decreased diversity in the Caribbean and, (c) this decreased availability of food (reduced paleoproductivity) was responsible for larger mean test size in the three most common benthic foraminiferal species Epistominella exigua, Oridorsalis umbonatus and Globocassidulina subglobosa. These are tested by applying correlation analysis to 7 groups of paleoceanographic proxies, 3 indices of diversity measures and mean test size data from the Caribbean Ocean Drilling Project Site 999, to 47 core samples for the interval between 8.3-2.5 Ma. Results are compared with published Caribbean and Pacific deep-sea records. The Caribbean, between 8.3-7.9 Ma, experienced reduced current velocity and lower ventilation of bottom waters. Thereafter, until 4.2 Ma, the seasonality of phytodetritus input increased and ventilation further reduced. From 4.2-2.5 Ma, paleoproductivity decreased, current velocity reduced, ventilation improved, and the seasonality of phytodetrital input decreased dramatically. The benthic foraminiferal diversity followed the same trend as paleoproductivity. Individual correlation analysis between mean test size of benthic foraminiferal species Epistominella exigua, Oridorsalis umbonatus and Globocassidulina subglobosa and paleoceanographic proxies yielded a positive and significant relationship with paleoproductivity. However, a combined datasets of all 3 species yielded a negative and significant relationship with species abundance. Thus, the study concludes that (a) the gradual closure of the CAS led Caribbean diversity and paleoproductivity to decrease abruptly at 7.9 Ma, when the nutrient-rich Pacific deep waters were cut off, and then, again with the complete closure of the seaway at 4.2 Ma, (b) diversity and paleoproductivity are positively correlated in the Caribbean and (c) that the availability of food is an overriding factor that influences mean test size; lower availability of food and decreased abundance leads to larger test size

Callovian and Kimmeridgian fossils and stratigraphy of the Blue Nile Basin (central western Ethiopia)

A refined, stratigraphic and biostratigraphic framework for Ethiopia has a strong bearing on the Jurassic sedimentary evolution, not only for the Horn of Africa, but also for the North African region. The present contribution provides an updated Callovian-Kimmeridgian stratigraphy and biostratigraphy, on the basis of the occurrences of age-diagnostic ammonites from Dejen (Blue Nile Basin; central western Ethiopia). Here, the late Callovian (Lamberti Zone) ammonite Pachyceras cf. lalandeanum (d'Orbigny) is associated with the nautiloid Paracenoceras cf. giganteum (d'Orbigny). The early Kimmeridgian Orthosphinctes aff. tiziani (Oppel) is associated with the nautiloids Paracenoceras cf. kumagunense (Waagen) and P. cf. ennianus (Dacqué) and a large gastropod Purpuroidea gigas (Étallon). The previously recorded middle Callovian ammonite Erymnoceras cf. coronatum (Bruguiere) is associated with the now recorded P. gigas (Étallon). Additionally, the age of the Antalo Limestone Fm is also reassessed on the basis of the ammonite records from the three basins - Ogaden, Blue Nile and Mekele. The Ogaden Basin strata span from the late Callovian to the late Tithonian (from ammonite records), the Blue Nile Basin from the early Callovian to the late Tithonian (calcareous nannofossils) and the Mekele Basin from the uppermost middle Oxfordian to the early Kimmeridgian (ammonite records). However, the upper age assignments should be considered tentative, as much of the previously recorded Oxfordian-Kimmeridgian ammonite fauna needs taxonomic re-evaluation and precise resampling. Contextually, it should be mentioned that in all the three sedimentary basins, the top part of the Antalo Limestone Fm did not yield any ammonites