Global evolution and paleogeographic distribution of mid-Cretaceous orbitolinids

Abstract

Members of the Larger Benthic Foraminiferal (LBF) family Orbitolinidae occurred from the Cretaceous to the Paleogene, however, they were most diverse during the mid-Cretaceous, and dominated the agglutinated LBF assemblages described from limestones of that period. Various orbitolinid species have been used to zone and date lithologies formed in the shallow, warm waters of the Aptian to the early Cenomanian, and many, sometimes inaccurate, generic and sub-generic nomenclatures have been proposed to differentiate the often-subtle morphological changes that orbitolinids exhibit over time. Also, until now, it has not been possible to develop an effective global overview of their evolution and environmental development because descriptions of specimens from Asia have been relatively rare. Following our recent study of over 1800 orbitolinid-rich thin sections of material from 13 outcrops of Langshan limestone, from the Southern Tibetan Plateau, and from the Barito Basin, South Kalimantan, Indonesia, it has been possible to compare the stratigraphic ranges of these orbitolinids with previously described Tethyan and American forms, based on the use of a planktonic zonal (PZ) scheme, itself tied to the most recent chronostratigraphic scale. This has allowed the reconstruction of the phylogenetic and paleogeographic evolution of the orbitolinids from their Valanginian origin in the Tethys. Although the Tethys remained the paleogeographic centre for the orbitolinids, it is inferred here for the first time that a bi-directional paleogeographic migration of some orbitolinid genera occurred from the Tethys to the Americas and also to the Western Pacific region. Our observations and dating suggest that global marine regressions in the Aptian were coincident with, and may well have facilitated, these orbitolinid transoceanic migrations. Migration stopped however after rising sea level in the early Albian appears to have again isolated these provinces from each other. Tectonic forces associated with the subduction of the Farallon Plate and further sea level raises led to the opening of the Western Interior Seaway in North America, which correlates with, and may have been the cause of, the middle Albian (top of PZ Albian 2) extinction of the American orbitolinids. The extinction of the orbitolinids revealed that the Western Pacific province was split into two sub-provinces, with extinction occurring at the end of the early Albian (top of PZ Albian 1) in the Northwest Pacific sub-province, and at the end of the Albian (top of PZ Albian 4) in the subprovince that is today South East Asia (on the margins and west of the Wallace Line). The final near extinction of the orbitolinids occurred at the end of the Cenomanian in the Tethyan province, which coincides with, and may have been caused by, global anoxic oceanic events that correlate with a near-peak Mesozoic eustatic sea level high-stand that led to the overall global collapse of the paleotropical reef ecosystem at that time.

The Geographic, Environmental and Phylogenetic Evolution of the Alveolinoidea from the Cretaceous to the Present Day.

“…The three main alveolinoid provinces were those of the Americas, Tethys, and the Indo-Pacific. We have previously demonstrated that the Cretaceous agglutinated orbitolinids originated in Tethys, but underwent periodic westward trans-oceanic migration to the Americas during periods of global sea-level low-stands (BouDagher-Fadel and Price, 2019). In this study, we have confirmed that the Tethyan province also remained the palaeogeographic centre for the porcelaneous alveolinids, and that they inhabited similar ecological habitats throughout the Cretaceous and Paleogene.…”

“…Likewise, we have seen that once established in the American and Indo-Pacific provinces, local provincial forms evolved, indicating that they were periodically effectively isolated from the Tethyan province. These characteristics have been observed in previous studies of Mesozoic (BouDagher-Fadel and Price, 2019) and Cenozoic LBF, specifically the lepidocyclinids (BouDagher-Fadel and Price, 2010), the miogypsinids (BouDagher-Fadel and Price, 2013), the nummulitoids (BouDagher-Fadel and Price, 2014;Benedetti, 2018) and the orthophragminids (BouDagher-Fadel and Price, 2017;Özcan et al, 2019). The periods of migration from one province to another were often followed by subsequent isolation and development of local provincial linages.…”

“…The inter-provincial migration of a genus is characterised and defined by the contemporaneous occurrence of the same species (although they may have been given different names, which are therefore synonyms) in two previously isolated provinces. In the Cretaceous, for example, we inferred that during a global sea-level low-stand, some orbitolinids (agglutinated foraminifera, members of the Order Textulariida) underwent a westward transoceanic migration from their Tethyan province of origin to the American province (see BouDagher-Fadel and Price, 2019), and that although subsequently the Tethyan province remained the hotspot for the orbitolinid speciation, parallel lineages evolved in the once again isolated American province, but were extremely rare. Later in the Cenozoic, the American province became the hot spot for speciation of other LBF families (including members of the Order Rotaliida, studied previously by BouDagher-Fadel and Price, 2010.…”

The Geographic, Environmental and Phylogenetic Evolution of the Alveolinoidea from the Cretaceous to the Present Day.

“…As described below, our analysis of the evolution and distribution of the alveolinoids will show that our previously developed hypothesis (i.e. that periodic, sea-level low-stands enable interprovincial migration of LBF; BouDagher-Fadel and Price, 2019; is again strongly supported, and that the behaviour and directions of migration of the alveolinoids is resonant with those of the orbitolinids (BouDagher-Fadel and Price, 2019), the orthophragminids (BouDagher-Fadel and Price, 2017), the nummulitoids (BouDagher-Fadel and Price, 2014), the miogypsinids (BouDagher-Fadel and Price, 2013), and the lepidocyclinids (BouDagher-Fadel and Price, 2010).…”

“…The inter-provincial migration of a genus is characterised and defined by the contemporaneous occurrence of the same species (although they may have been given different names, which are therefore synonyms) in two previously isolated provinces. In the Cretaceous, for example, we inferred that during a global sea-level low-stand, some orbitolinids (agglutinated foraminifera, members of the Order Textulariida) underwent a westward transoceanic migration from their Tethyan province of origin to the American province (see BouDagher-Fadel and Price, 2019), and that although subsequently the Tethyan province remained the hotspot for orbitolinid speciation, parallel lineages evolved in the again isolated American province, but were extremely rare. Later in the Cenozoic, the American province became the hot spot for speciation of other LBF families (including members of the Order Rotaliida, studied previously by BouDagher-Fadel and Price, 2010.…”