Article

Lilliput effect in late Maastrichtian planktic foraminifera: Response to environmental stress

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Abstract

The Lilliput effect marks morphologic and intraspecies size reductions in response to environmental stresses commonly associated with the aftermath of mass extinctions. This study shows that the Lilliput effect is a universal biotic response associated with greenhouse warming, mesotrophic or restricted basins, shallow marginal settings and volcanically active regions during the late Maastrichtian. Sedimentary sequences analyzed from Tunisia, Egypt, Texas, Argentina, the South Atlantic and Indian Ocean reveal that the biotic stress response appears uniform, regardless of the cause, varying only with the degree of biotic stress. Overall, late Maastrichtian environments span a continuum from optimum conditions to the catastrophic (mass extinctions) with a predictable set of biotic responses relative to the degree of stress induced by oxygen, salinity, temperature and nutrient variations as a result of climate and sea level changes and volcanism. Early stages of biotic stress result in diversity reduction and the elimination of large specialized species (k-strategists) leading to morphologic size reduction via selective extinction/disappearances and intraspecies dwarfing of survivors. Later stages of biotic stress result in the complete disappearance of k-strategists, intraspecies dwarfing of r-strategists and dominance by low oxygen tolerant small heterohelicids. At the extreme end of the biotic response are volcanically influenced environments, which cause the same detrimental biotic effects as observed in the aftermath of the K–T mass extinction, including the disappearance of most species and blooms of the disaster opportunist Guembelitria.

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... Instances of impoverished and dwarfed assemblages are plenty across the Cretaceous-Paleogene (K-Pg) boundary (e.g., Punekar et al., 2014;Patra et al., 2024) and the Permian-Triassic (P-Tr) boundary (e.g., Song et al., 2011;Zhang et al., 2016). However, such adaptations may also J o u r n a l P r e -p r o o f result from a wider range of environmental stress conditions linked with global physicochemical changes in the global oceans (Keller and Abramovich, 2009). ...
... The "Lilliput effect" (Urbanek, 1993) involves a decrease in the average test size of organisms , and is a well-documented response to adverse environmental conditions (Keller and Abramovich, 2009). The dwarfed individuals show fully developed morphologies like normalsized adults and can only be identified through morphometric analyses of populations and estimating the average size (MacLeod et al., 2000;Falzoni et al., 2018). ...
... The dwarfed individuals show fully developed morphologies like normalsized adults and can only be identified through morphometric analyses of populations and estimating the average size (MacLeod et al., 2000;Falzoni et al., 2018). A practical estimate to track dwarfing through geologic time is population studies of different size fractions-an increase in the population of a species in the smaller (sieve) size fraction linked with a decrease in its population in the larger size fraction (Keller and Abramovich, 2009). However, low magnitude size changes may not be discernible through this approach, necessitating a more rigorous morphometric study of individual tests of a population, and populations through geologic time (e.g., Wade and Olsson, 2009). ...
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Anthropogenic CO₂ levels have increased by nearly 40% from preindustrial levels, with about 30% absorbed by the ocean leading to ocean acidification (OA). The associated carbonate undersaturation can critically affect marine calcifying communities. Major disruptions in the marine carbonate cycling are common throughout the Phanerozoic stratigraphic record, and often coincide with major mass extinctions and faunal turnover events. The anthropogenic OA is progressing at a rate nearly ten times faster than similar events of the past 300 million years. This makes OA research of high priority, and entails a rigorous evaluation of OA events from deep time for perspective. Such efforts are contingent upon reliable proxies. This review compiles geochemical and foraminifera-based proxies, offering a critical assessment of their fidelity, ease of use, and application scope. This study evaluates the scope and utility of documented observational and analytical proxies based on factors like the nature of data, and the time, effort and advanced analytical facilities involved. Foraminifera-based observational proxies like morphological and community responses to OA are effective but demand taxonomic expertise. They are further complicated by vital effects, metabolic trade-offs, the influence of stressors other than ocean acidification, and paleogeographic variability in both the magnitude of stress and the organisms' response to it. Well-calibrated analytical (geochemical) proxies offer the potential for rapid, high-resolution records across various sites. All proxies face challenges from diagenetic alterations, which can affect their reliability. However, this review offers the pros/cons and practical recommendations for proxy utility, emphasing the need for a multi-proxy approach to enhance accuracy and cross-verification. Future research must urgently address plankton community responses, OA-tolerant taxa, and localized calcification environments to grasp the full impact of acidification. It is critical to refine lesser-known proxies (e.g., S/Ca) and to rapidly expand datasets on carbonate system parameters across Phanerozoic OA events to advance our understanding and mitigation strategies.
... Independent evidence of biotic stress in planktic foraminifera from the Deccan benchmark interval leading up to the K/Pg boundary mass extinction can bolster the Deccan-linked ocean acidification hypothesis. In general, environmental stress due to climate, trophic and/or palaeoceanographic change is reflected in fossil planktic foraminifera assemblages as altered community structures, low diversity assemblages, dominance of opportunist species, malformed tests and dwarfing (Abramovich and Keller, 2003;Coccioni and Luciani, 2006;Keller and Abramovich, 2009;Tantawy et al., 2009;Gertsch et al., 2011). Changes in marine carbonate chemistry (acidification) can have variable effects on planktic foraminifera of different sizes and carbonate demands, based on open ocean observations, culture experiments and modelling studies (Barker and Elderfield, 2002;Marshall et al., 2013;Henehan et al., 2017). ...
... Species analyzed for average test size include Globotruncana arca, Globotruncana mariei, Planoglobulina brazoensis, Planoheterohelix globulosa (Heterohelix globulosa sensu Ehrenberg, 1840), Pseudoguembelina carsayae, Pseudoguembelina hariaensis, Pseudoguembelina palpebra, Pseudoguembelina costulata, Pseudotextularia elegans, and R. rugosa. This preliminary test-group spans the Cretaceous planktic morphospace, and includes species of different inferred life strategies (k-and Rstrategies; Keller and Abramovich, 2009). Specimens of each target species in a representative population of 300 tests (per stratigraphic level) are analyzed. ...
... The dissolution and/or fragmentation processes tend to favour the preservation of environmentally-sensitive yet architecturally-robust planktic foraminifera (Manda and Punekar, 2020). Caution must be exercised while interpreting the timing and nature of biotic stress from such assemblages, especially in the context of the K/Pg boundary mass extinction (Keller and Abramovich, 2009). ...
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The late Maastrichtian witnessed substantial surges in Deccan volcanism, prompting the hypothesis that these voluminous pulses may have instigated repeated episodes of ocean acidification during this period. The Cretaceous-Palaeogene (K/Pg) boundary at Bidart (France) is preceded by a ∼0.5 m thick interval with geochemical and taphonomic vestiges of an ocean acidification event linked with Deccan volcanism. New planktic foraminifera census and morphometric data now confirm biotic stress conditions related to acidification in the Deccan benchmark interval. The absolute abundance data of larger (>150 μm) heavily calcified planktic morphogroups show fluctuating populations throughout zone CF1 (spanning the final ∼225 ky), lowest peaks within the Deccan benchmark, and a demographic collapse (>90%) at the K/Pg boundary. The analyzed species are generally reduced in size, with thinner test walls in this ∼0.5 m interval, indicating the likelihood of calcification stress as a contributor to the overall biotic stress. At the K/Pg boundary, maximum biotic stress is recorded in all the tested faunal proxies. A preliminary graphic correlation of zone CF1 at Bidart with the auxiliary GSSP at Elles (Tunisia) constrains the Deccan benchmark interval of high biotic stress to the final ∼58 ky of the late Maastrichtian, culminating in the K/Pg mass extinction. The volcanogenic Hg peaks coincident with faunal and taphonomic evidence of ocean acidification strengthen the Deccan-related ocean acidification hypothesis.
... The faunal changes indicate continued and even increasing high-stress environments during the CF3 zone [56,57]. The top of the CF3 zone is marked by the extinction of Globotruncana linneiana (d'Orbigny) (at level 66.96 Ma) according to ref. [4]. ...
... Through the event of the CF6 zone, a gradual increase in the relative abundance of Gublerina rajagopalani Govindan ranging between 0.03 and 6.7%, Planoheterohelix planata (Cushman) ranging between 2.7 and 9.3%, and other heterohelicids to 30% (Figure 8) have been shown the tolerate and thrive in a wide range of environmental conditions as in high-stress environments affected by temperate, salinity, nutrients, and oxygen variations due to sea-level fluctuations and receiving more meteoric water. These conditions may increase the population, abundance, and stability of life of different organisms [56,57]. ...
... The climate warmed to 2-3°C before and after this cooling and appears correlative with the onset of Deccan volcanism (phase 1) [86]. During the CF4 and CF3 zones, the climate warm events are accompanied by decreased planktic foraminiferal diversity and increased dissolution effects [57,[71][72][73]. ...
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The studies of benthic calcareous foraminifera of the Maastrichtian–early Paleocene Dakhla Formation in Gebel Um El-Ghanayem (Western Desert, Egypt), improve reconstruction of depositional environments of these successions. In total, 68 taxa of benthic foraminifera were identified in the studied succession. The late Maastrichtian assemblages (Zone CF3) are dominated by calcareous foraminifera with tapered tests, this tapered taxon Loxostomum applinae, Lox. tegulatum various dentalinid taxa, and Buliminella cushmani dominate in CF3 Biozone. We thus interpret these faunas as being dominated by infaunal morphogroups, suggesting a moderately eutrophic environment. Danian assemblages are characterized by abundant epifaunal trochospiral species, such as Cibicidoides abudurbensis, Cibicidoides farafraensis, and Gyroidinoides girardanus. The infaunal morphogroups make up 25–47% of fauna in the Danian, in contrast to 62–76% in the Upper Maastrichtian. This dominance of the Danian benthic foraminiferal assemblages by epifaunal or mixed epifaunal/infaunal morphogroups suggests that the food supply to the benthos was less abundant than in the latest Cretaceous. The Cretaceous/Paleocene boundary (K/Pg) is within the upper unit of the Lower Kharga Member and marked by a hiatus in at least the top of CF3 Zone of the Upper Maastrichtian to the Lower Paleocene (base Plc Zone). �
... The ecological behaviour of planktic foraminifera can be divided into three group: specialists, generalists, and disaster opportunists (Keller & Abramovich, 2009;Pardo & Keller, 2008;Premoli-Silva & Sliter, 1999) (Tables 1 and 2 Constrained clustering based on wards method were carried out on the planktic foraminiferal species matrix to identify distinct changes in assemblages. These assemblages were also analysed using non-parametric Non-metric Multidimensional Scaling (NMDS) to find possible similarity/differences. ...
... The K-strategists (= Specialist species), have large, complex tests and can only tolerate a narrow range of environmental variables(Ashckenazi-Polivoda et al., 2011;Harper et al., 1990;Mateo et al., 2017). The R-strategists (generalist and disaster opportunist species) are known to have relatively small, simple tests and are able to occupy a wide range of ecological niches(Harper et al., 1990;Keller & Abramovich, 2009;Premoli-Silva & Sliter, 1999). The R-strategists often thrive under severe biotic stress environments ranging from mesotrophic to eutrophic in shallow continental shelves and upwelling areas(Ashckenazi-Polivoda et al., 2014;Keller & Abramovich, 2009;Punekar et al., 2014).In addition, the planktic foraminiferal species are also categorized based on their ecological niches that they occupy at various depths within the water column; they are accordingly grouped as thermocline, intermediate, and mixed-layer dwellers, following the categorization of Petrizzo, Huber, Falzoni, & Macleod (2020, and references therein) (Table 2).The deep-surface (D/S) ratio [thermocline dwellers/(thermocline dwellers + mixed layer dwellers)] is used to evaluate changes in thermocline depth, where higher values indicate more stable conditions with a deeper and wider thermocline (well-stratified)(Abramovich et al., 2010;Ashckenazi-Polivoda et al., 2014;Falzoni et al., 2014;Petrizzo et al., 2020).Species diversity (both number of taxa and Shannon H), as well as species evenness and relative abundance changes for each depth group, were determined and used to evaluate changes in water mass stratification, as well as stressful conditions, where higher values are suggestive of a stable environment and lower values are indicative of stressful conditions (seeAbramovich & Keller, 2003 and references therein). ...
... The R-strategists (generalist and disaster opportunist species) are known to have relatively small, simple tests and are able to occupy a wide range of ecological niches(Harper et al., 1990;Keller & Abramovich, 2009;Premoli-Silva & Sliter, 1999). The R-strategists often thrive under severe biotic stress environments ranging from mesotrophic to eutrophic in shallow continental shelves and upwelling areas(Ashckenazi-Polivoda et al., 2014;Keller & Abramovich, 2009;Punekar et al., 2014).In addition, the planktic foraminiferal species are also categorized based on their ecological niches that they occupy at various depths within the water column; they are accordingly grouped as thermocline, intermediate, and mixed-layer dwellers, following the categorization of Petrizzo, Huber, Falzoni, & Macleod (2020, and references therein) (Table 2).The deep-surface (D/S) ratio [thermocline dwellers/(thermocline dwellers + mixed layer dwellers)] is used to evaluate changes in thermocline depth, where higher values indicate more stable conditions with a deeper and wider thermocline (well-stratified)(Abramovich et al., 2010;Ashckenazi-Polivoda et al., 2014;Falzoni et al., 2014;Petrizzo et al., 2020).Species diversity (both number of taxa and Shannon H), as well as species evenness and relative abundance changes for each depth group, were determined and used to evaluate changes in water mass stratification, as well as stressful conditions, where higher values are suggestive of a stable environment and lower values are indicative of stressful conditions (seeAbramovich & Keller, 2003 and references therein). ...
Article
Based on quantitative changes in the Maastrichtian planktic foraminiferal species distribution patterns from the Elles section (central Tunisia), δ13C, δ18O-based palaeotemperature and inferred proxies (species diversity, ecological associations, and depth ranking), the palaeoenvironment is inferred. Based on Constrained Clustering and corroborated by Non-metric Multidimensional Scaling (NMDS), four statistically significant intervals are identified. Interval 1 (lower–middle part of CF5 Zone) is marked by a warm, oligotrophic, stable, and well-stratified upper water column. Interval 2 (upper part of CF5 Zone), here designated as the pre-Mid-Maastrichtian Event (MME) event, is marked by stressed, warmer, moderately mesotrophic, and weakly stratified surface waters with an unstable upper water column. Interval 3 (CF4 Zone) encompasses the MME and is marked by warm, stable, mesotrophic surface waters with a moderately well-stratified upper water column. The upper part of Interval 3, designated as post-MME, is also marked by mesotrophic conditions, but with increased surface water warming, unstable and stressed conditions. Interval 4 (CF3–CF1 zones) shows the effects of the Indian Deccan volcanism, and is marked by warmer surface waters, mesotrophic, unstable, stressed environmental conditions, with a weakly-stratified upper water column.
... The faunal changes indicate continued and even increasing high-stress environments during the CF3 zone [56,57]. The top of the CF3 zone is marked by the extinction of Globotruncana linneiana (d'Orbigny) (at level 66.96 Ma) according to ref. [4]. ...
... Through the event of the CF6 zone, a gradual increase in the relative abundance of Gublerina rajagopalani Govindan ranging between 0.03 and 6.7%, Planoheterohelix planata (Cushman) ranging between 2.7 and 9.3%, and other heterohelicids to 30% (Figure 8) have been shown the tolerate and thrive in a wide range of environmental conditions as in high-stress environments affected by temperate, salinity, nutrients, and oxygen variations due to sea-level fluctuations and receiving more meteoric water. These conditions may increase the population, abundance, and stability of life of different organisms [56,57]. ...
... The climate warmed to 2-3°C before and after this cooling and appears correlative with the onset of Deccan volcanism (phase 1) [86]. During the CF4 and CF3 zones, the climate warm events are accompanied by decreased planktic foraminiferal diversity and increased dissolution effects [57,[71][72][73]. ...
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Abstract: During the Late Campanian, sea-level fluctuation occurred in the form of two chert bands and the topmost conglomeratic phosphate beds (CF8a zone). A great transgression event occurred associated with the global warming (CF8b zone) trend indicated by large double-keeled foraminifera as Globotruncana aegyptiaca Nakkady of oligotrophic conditions. Through the event of CF6/CF5 zones, a gradual increase in the relative abundance of Gublerina rajagopalani Govindan and Planoheterohelix planata (Cushman) and other heterohelicids have been shown to tolerate and thrive in a wide range of environmental conditions as in high-stress environments. Sea-level fall at the CF6 zone and the overlying CF5 boundary marked a warming climate for the Middle Maastrichtian Event. In the latest CF4 records, the beginning of the decrease in planktic/benthic ratio, globotruncanids, rugoglobigerinids, and heterohelicids indicating a fall in sea level coincided with the CF4/CF3 and the development of dark grey shales in a regressive regime. The observed low abundance of planktic specimens may be due to the presence of pyrite with black shale interval suggesting low oxygen condition. The latest zones CF3, CF2, and CF1 are generally characterized by heterohelicids blooms specially Planoheterohelix globulosa (Ehrenberg), and a gradual decrease in diversity associated with the warming phase before the K/Pg boundary event, implying high biotic stress to even absent of Guembelitria cretacea species through CF3–CF1 zones. Pseudotextularia elegans (Rzehak) occurs in the zones CF4 and CF2 warming of phases 1 and 2 of Deccan Trap Volcanic. The absence of P. elegans (Rzehak) in the zone (CF3) is postulated due to a tectonic cause (maximum cooling of Deccan Trap Volcanic) whereas its absence in the zone (CF1) was due to regression of phase 2.
... The faunal changes indicate continued and even increasing high-stress environments during the CF3 zone [56,57]. The top of the CF3 zone is marked by the extinction of Globotruncana linneiana (d'Orbigny) (at level 66.96 Ma) according to ref. [4]. ...
... Through the event of the CF6 zone, a gradual increase in the relative abundance of Gublerina rajagopalani Govindan ranging between 0.03 and 6.7%, Planoheterohelix planata (Cushman) ranging between 2.7 and 9.3%, and other heterohelicids to 30% (Figure 8) have been shown the tolerate and thrive in a wide range of environmental conditions as in high-stress environments affected by temperate, salinity, nutrients, and oxygen variations due to sea-level fluctuations and receiving more meteoric water. These conditions may increase the population, abundance, and stability of life of different organisms [56,57]. ...
... The climate warmed to 2-3°C before and after this cooling and appears correlative with the onset of Deccan volcanism (phase 1) [86]. During the CF4 and CF3 zones, the climate warm events are accompanied by decreased planktic foraminiferal diversity and increased dissolution effects [57,[71][72][73]. ...
Article
Full-text available
During the Late Campanian, sea-level fluctuation occurred in the form of two chert bands and the topmost conglomeratic phosphate beds (CF8a zone). A great transgression event occurred associated with the global warming (CF8b zone) trend indicated by large double-keeled foraminifera as Globotruncana aegyptiaca Nakkady of oligotrophic conditions. Through the event of CF6/CF5 zones, a gradual increase in the relative abundance of Gublerina rajagopalani Govindan and Planoheterohelix planata (Cushman) and other heterohelicids have been shown to tolerate and thrive in a wide range of environmental conditions as in high-stress environments. Sea-level fall at the CF6 zone and the overlying CF5 boundary marked a warming climate for the Middle Maastrichtian Event. In the latest CF4 records, the beginning of the decrease in planktic/benthic ratio, globotruncanids, rugoglobigerinids, and heterohelicids indicating a fall in sea level coincided with the CF4/CF3 and the development of dark grey shales in a regressive regime. The observed low abundance of planktic specimens may be due to the presence of pyrite with black shale interval suggesting low oxygen condition. The latest zones CF3, CF2, and CF1 are generally characterized by heterohelicids blooms specially Planoheterohelix globulosa (Ehrenberg), and a gradual decrease in diversity associated with the warming phase before the K/Pg boundary event, implying high biotic stress to even absent of Guembelitria cretacea species through CF3–CF1 zones. Pseudotextularia elegans (Rzehak) occurs in the zones CF4 and CF2 warming of phases 1 and 2 of Deccan Trap Volcanic. The absence of P. elegans (Rzehak) in the zone (CF3) is postulated due to a tectonic cause (maximum cooling of Deccan Trap Volcanic) whereas its absence in the zone (CF1) was due to regression of phase 2.
... Marine biota frequently responded to extreme events such as greenhouse warming, eutrophication and volcanic events showing an overall size reduction (Erba et al., 2010;Ferreira et al., 2017;Keller & Abramovich, 2009;Lübke et al., 2015;Mattioli et al., 2009;Salaviale et al., 2018;Tremolada et al., 2008). Also, minor environmental changes such as the shallowing/shrinkage of the basin, were documented to impact the size of marine biota (Keller & Abramovich, 2009). ...
... Marine biota frequently responded to extreme events such as greenhouse warming, eutrophication and volcanic events showing an overall size reduction (Erba et al., 2010;Ferreira et al., 2017;Keller & Abramovich, 2009;Lübke et al., 2015;Mattioli et al., 2009;Salaviale et al., 2018;Tremolada et al., 2008). Also, minor environmental changes such as the shallowing/shrinkage of the basin, were documented to impact the size of marine biota (Keller & Abramovich, 2009). Overall, the marine biota size decrease is related to variation in the oxygen, salinity and nutrients contents as well as change in temperature (Keller & Abramovich, 2009). ...
... Also, minor environmental changes such as the shallowing/shrinkage of the basin, were documented to impact the size of marine biota (Keller & Abramovich, 2009). Overall, the marine biota size decrease is related to variation in the oxygen, salinity and nutrients contents as well as change in temperature (Keller & Abramovich, 2009). This biotic response to such events is referred as "Lilliput effect" (Urbanek, 1993), and accompanied for instance the Oceanic Anoxic Events (Erba et al., 2010) and mass extinction episodes, but was also recorded in other time intervals characterized by environmental conditions loosely defined as "stressed condition" (Ferreira et al., 2017;Violanti et al., 2013). ...
Article
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Dwarfism is a common feature affecting organisms across extreme events that characterized the Earth history, frequently referred as the result of “stressed conditions.” To date, no study addressed the morphological and biometric changes across the Messinian Salinity Crisis (MSC), one of the most recent and impacting event occurred in the Mediterranean Sea, historically interpreted as characterized by hypersaline conditions. Here we focus on morpho/biometric changes affecting calcareous nannofossils (CN) toward the MSC onset in order to better constrain the paleoenvironmental dynamics and the loosely defined “stressed conditions” characterizing this interval. Size characterization and absolute abundance of selected CN taxa were performed in the Perales (Spain, Western Mediterranean) and in the Banengo and Pollenzo sections (Italy, Northern Mediterranean). We also tested whether size changes and orbital cyclicity were related through analyzing size and calcite mass of Reticulofenestra minuta using an automated image analysis system of CN recognition (SYRACO). We recorded a significant size reduction affecting the CN taxa involved in the MSC onset bioevent, related to the restriction of the Mediterranean Basin that resulted in increased productivity and enhanced environmental variability, stimulating CN growth rate and decreasing their platelet sizes. Reticulofenestra minuta size and mass correlate with the orbital cyclicity with minimum values during periods of enhanced environmental variability, coinciding with the diatomite deposition in the Sorbas Basin. Our finding reveals that the size change recorded across the MSC onset coincided with the instauration of a productive and highly variable environment, linked to the restriction of the paleo Gibraltar Strait.
... However, foraminifera may face environmental stress and decreasing abundance at high temperatures (Titelboim et al., 2016). In the late Maastrichtian, Keller and Abramovich (2009) found that foraminifera exhibit the "Lilliput effect" in response to environmental stresses, such as greenhouse warming and mesotrophic or restricted basins. Facing these stresses, foraminiferal individuals may opt to shrink in size and produce additional offspring using the r-strategy (Keller, 2003;Keller & Abramovich, 2009). ...
... In the late Maastrichtian, Keller and Abramovich (2009) found that foraminifera exhibit the "Lilliput effect" in response to environmental stresses, such as greenhouse warming and mesotrophic or restricted basins. Facing these stresses, foraminiferal individuals may opt to shrink in size and produce additional offspring using the r-strategy (Keller, 2003;Keller & Abramovich, 2009). The small individuals (<150 μm) could be ignored in some morphological studies (Lei et al., 2017; F I G U R E 2 The fitted line of foraminiferal parameters (read counts, OTU counts, Margalef index, and Shannon-Wiener index) plotted against temperature (6, 12, 18, 24, and 30°C). ...
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Foraminifera is the most important temperature proxy of the ocean on long time scales. However, the absence of temperature‐controlled experiments at different water depths hinders the advancement of paleotemperature reconstruction with foraminifera from the continental shelf. For the first time, this study investigated the response of benthic foraminifera to temperature change using microcosm culture and metabarcoding. Foraminiferal communities from three continental stations at varying water depths (6.0, 9.2, and 26.0 m) were cultured under five temperature gradients (6, 12, 18, 24, and 30°C), with each treatment performed in triplicate. The foraminifera were fed with microalgae every 4 days, and the filtered seawater (through 0.22 μm pores), acting as a medium, was changed accordingly. The experiment lasted for 80 days, and 47 DNA samples were obtained and analyzed, including three in situ samples. The results showed that foraminifera adjusted its growth rate within the low‐temperature range and adopted an r‐strategy to cope with high‐temperature stress. In addition, the foraminifera from deeper water stations exhibited a pronounced vulnerability to diminishing read counts. The read counts, operational taxonomic units (OTU) counts and Margalef index of foraminifera and the read counts of Rotaliida exhibited a remarkably positive correlation with temperature. The recommended relationships were described as read counts = 1314.75*T + 44754.51; OTU counts = 1.13*T + 44.26; Margalef index =1.13*T + 44.26. This study established the first quantitative relationship between temperature and foraminifera molecular parameters that holds significant implications for long‐time paleotemperature calibration in climate change.
... Urbanek's definition outlines expectations for both the body size and phenotype of Lilliputian species in the aftermath of an extinction and restricts the phenomenon as a process that occurs temporarily within a single species. Since this initial work, the Lilliput effect has been reported in a diverse range of clades, including brachiopods ( (Brom et al. 2015), and the Cretaceous-Paleogene mass extinction (Jeffery 2001;Keller and Abramovich 2009;Berv and Field 2018). The widespread documentation of this phenomenon suggests that the Lilliput effect is a common response to stressful environmental or ecological conditions during biotic crises. ...
... Chen et al. 2005;He et al. 2007;He et al. 2010;Huang et al. 2010;Metcalfe et al. 2011;Schaal et al. 2016;Chen et al. 2019), mollusks(Twitchett 2007;Atkinson and Wignall 2020), ostracodes(Forel et al. 2015); corals(Kaljo 1996), foraminifera(Keller and Abramovich 2009;Song et al. 2011), echinoderms(Jeffery 2001;Twitchett and Oji 2005;Borths and Ausich 2011;Brom et al. 2015), graptolites(Urbanek 1993), and vertebrates(Girard and Renaud 1996;Renaud and Girard 1999;Mutter and Neuman 2009;Huttenlocker and Botha-Brink 2013;Huttenlocker 2014;Sallan and Galimberti 2015;Botha-Brink et al. 2016;Berv and Field 2018;Botha 2020;Xinsong et al. 2020). These body-size reductions also occur during many extinction events and biotic crises, including the Ordovician-Silurian mass extinction(Kaljo 1996;Borths and Ausich 2011), the late Silurian extinction events(Urbanek 1993), the Frasnian-Famennian Mass extinction(Girard and Renaud 1996;Renaud and Girard 1999;Xinsong et al. 2020), the end-Devonian mass extinction(Sallan and Galimberti 2015), the end-Permian mass extinction (EPME)(Chen et al. 2005;Twitchett and Oji 2005;He et al. 2007He et al. , 2010Twitchett 2007;Mutter and Neuman 2009;Huang et al. 2010;Metcalfe et al. 2011;Song et al. 2011;Huttenlocker and Botha-Brink 2013;Huttenlocker 2014;Botha-Brink et al. 2016;Schaal et al. 2016;Chen et al. 2019;Botha 2020), the end-Triassic mass extinction (Atkinson and Wignall 2020), the Cretaceous marine anoxia events ...
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Body size has a long history of study in paleobiology and underlies many important phenomena in macroevolution. Body-size patterns in the fossil record are often examined by utilizing size data alone, which hinders our ability to describe the biological meaning behind size change on macroevolutionary timescales. Without data reflecting the biological and geologic factors that drive size change, we cannot assess its mechanistic underpinnings. Existing frameworks for studying ontogeny and phylogeny can remedy this problem, particularly the classic age–size–“shape” space originally developed for studies of heterochrony. When evaluated based on metrics for age, size, and phenotype in populations, proposed mechanisms for size change can be outlined theoretically and tested empirically in the record. Using this framework, we can compare ontogenetic trajectories within and between species and determine how changes in size emerge. Here, we outline ontogenetic mechanisms for evolutionary size change, such as heterochrony, as well as how geologic factors can drive apparent, non-biological size change (e.g., taphonomic size sorting). To demonstrate the utility of this framework in actual paleobiological problems, we apply it to the Lilliput effect, a compelling and widely documented pattern of size decrease during extinction events. However, little is known about the mechanisms underlying this pattern. We provide a brief history of the Lilliput effect and refine its definition in a framework that can be mechanistically tested. Processes that likely produce Lilliput effects include allometric and sequence repatterning (including heterochrony) and evolutionary size-selective sorting. We describe these mechanisms and highlight relevant examples of the Lilliput effect for which feasible empirical tests are possible.
... Though the mechanisms and possible causes of the K-Pg mass extinction are still a matter of discussion (Álvarez et al., 1980;Alegret et al., 2001;Punekar et al., 2014;Richards et al., 2015;Petersen et al., 2016;Schoene et al., 2019;Sprain et al., 2019;Chiarenza et al., 2020;Hull et al., 2020;Keller et al., 2020), there is a broad consensus that drastic biological, oceanic and climatic changes occurred at the K-Pg boundary (e.g. Culver, 2003;D'Hondt, 2005;Koutsoukos, 2006;Keller and Abramovich, 2009;Dameron et al., 2017;Guerra et al., 2021;Carvalho et al., 2021;Krahl et al., 2021). Even since the Campanian-Maastrichtian interval, major paleoenvironmental disturbances occurred (e.g. ...
... However, as previously mentioned, the study of Martínez (1989) focused on the lower (Socuy Member) and the middle part of the Colón Formation, only partially present at Core Diablito-1. This aspect explains why planktonic assemblages at Core Diablito-1 were mainly composed of Guembelitria cretacea and scarce non-keeled taxa, both characteristic of inner platforms and restricted marine settings (Leckie and Olson, 2003;Keller and Abramovich, 2009). A similar deposition setting was observed at the nearby stratigraphic core LL-3E (Fig. 1), where foraminiferal assem- Patarroyo et al. ...
Article
One of the major environmental and biotic turnovers of the Phanerozoic occurred at the Cretaceous-Paleogene (K-Pg) boundary, being the focus of countless scientific studies that addressed the timing, causes and consequences of this global event. Paleoenvironmental conditions that preceded the K-Pg boundary, however, have been less studied, especially at low latitudes. In order to help reconstructing late Maastrichtian marine environments along the equatorial South American margin, we apply micropaleontological and geochemical techniques to a stratigraphic core that recovered the Colón Formation in northern Colombia. Low abundance foraminiferal assemblages were overall dominated by benthic taxa (Maastrichtian local biozones Siphogenerinoides bramletti and Ammobaculites colombiana), and the planktonic species Guembelitria cretacea. Ostracod assemblages were mainly composed of the genera Veenia, Cytherella, Paracypris, and Cythereis. Calcareous nannofossils were typical of Upper Cretaceous low-latitude successions, with low abundance and diversity assemblages dominated by Micula staurophora, Kamptnerius magnificus and Cervisiella operculata. Sediment elemental ratios (Zr/Rb, Fe/Ca and Sr/Ba), as well foraminiferal, ostracod and nannofossils assemblages, indicate a shallowing upward trend, characterized by a transition from inner platform settings to sublittoral conditions. Input of terrigenous sediments and weathering intensity also increased upward in the section, probably related to the uplift pulses of the Andean orogeny. Proportions of benthic infauna, as well the V/Cr ratio and the distribution of redox-sensitive trace metals (Ni, Cu) along the core, mostly indicate suboxic bottom water conditions in the Colón Formation.
... The OI proposed in the present study is a quantitative method for evaluating the conchs of different animals, such as ammonites, bivalves, gastropods, echinoderms, and brachiopods. Existing studies on the morphological evolution of shelled animals rely on counting ornament types and characterizing their shapes Keller & Abramovich, 2009;Vörös, 2010;Ward, 1981), but these are inadequate for quantitatively measuring the strength of ornamentation. Thus, OI can help understand the macroevolution of the morphology of diverse shelled animals, primarily for evolutionary comparisons within a clade, but also for comparisons among clades. ...
... During geological history, several major climatic and environmental events have occurred, including global warming and cooling events (Scotese et al., 2021), oceanic anoxic events (Song et al., 2017), and ocean acidification events (Hönisch et al., 2012). These events have led not only to mass extinctions (Song, Kemp, et al., 2021) but also to remarkable changes in body size (Lilliput effect) and morphology (Calosi et al., 2019;Dai et al., 2021;Feng et al., 2020;Harries & Knorr, 2009;Keller & Abramovich, 2009;MacLeod et al., 2000;Nätscher et al., 2021;Twitchett, 2007). A semi-quantitative study on ammonoid morphology across the Permian-Triassic mass extinction revealed that ammonoid conch exhibited an ornamental simplification . ...
Article
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Morphological complexity reflects the biological structure of an organism and is closely linked to its associated functions and phylogenetics. In animals with shells, ornamentation is an important characteristic of morphological complexity, and it has various functions. However, because of the variations in type, shape, density, and strength of ornamentation, a universal quantitative measure of morphological complexity for shelled animals is lacking. We propose an ornamentation index (OI) derived from 3D scanning technology and a virtual model for quantifying ornamentation complexity. This index is designed to measure the extent of folding associated with ornamentation, regardless of shape and size. Ornamentation indices were measured for 15 ammonite specimens from the Permian to Cretaceous, 2 modern bivalves, 2 gastropods from the Pliocene to the present, and a modern echinoid. Compared with other measurements, such as the fractal dimension, rugosity, and surface-volume ratio, the OI displayed superiority in quantifying ornamentational complexity. The present study demonstrates that the OI is suitable for accurately characterizing and quantifying ornamentation complexity, regardless of shape and size. Therefore, the OI is potentially useful for comparing the ornamentational complexity of various organisms and can be exploited to provide further insight into the evolution of conchs. Ultimately, the OI can enhance our understanding of morphological evolution of shelled organisms, for example, whether shell ornaments simplify under ocean acidification or extinction, and how predation pressure is reflected in ornamentation complexity.
... These coincide with emplacement of the "main phase" of the Deccan Traps Large Igneous Province (LIP) in India (Schoene et al. 2019;Sprain et al. 2019), linked to a period of rapid global climate warming and cooling (Barnet et al. 2018;Hull et al. 2020; also see Dzombak et al. 2020). Shifts in the distribution, richness, and abundance of various groups of marine plankton occur alongside these climate changes before the K/ Pg boundary (Olsson 2001;Thibault 2016;Vellekoop et al. 2019), while morphological changes (dwarfing) and increased fragmentation in some planktonic foraminifera hint at stressful conditions in the oceans (MacLeod et al. 2000;Keller and Abramovich 2009;Henehan et al. 2016;Gilabert et al. 2021). The influence of these environmental changes on ammonoid species has been debated, with some workers suggesting widespread global decline of ammonoids leading into the K/Pg (e.g., Stinnesbeck et al. 2012) and others supporting species' health and even increased abundance during the latest Cretaceous (Landman et al. 2014Witts et al. 2015Witts et al. , 2018Witts et al. , 2021. ...
... Implications of Temporal Stasis for Pre-K/Pg Paleoenvironmental Change.-Size and shape changes documented by other authors in planktonic foraminifera during the latest Maastrichtian, temporally equivalent to the D. iris Zone (Larina et al. 2016;Naujokaitytė et al. 2021;Witts et al. 2021), have been related to environmental stresses associated with the emplacement of the Deccan Traps LIP, before the Chicxulub impact event and K/Pg mass extinction (Keller and Abramovich 2009;Henehan et al. 2016;Gilabert et al. 2021). Morphological changes have been detected in ammonoids before other mass extinction events linked to episodes of environmental change driven by LIP volcanism: for example, Kiessling et al. (2018) documented a reduction in size and morphological complexity in ammonoid assemblages from deep-water limestones correlated to the last 700 kyr of the Permian in Iran, coincident with the onset of Siberian Trap LIP volcanism and disruption to the global carbon cycle, but preceding the main phase of the end-Permian mass extinction. ...
Article
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We examine temporal and spatial variation in morphology of the ammonoid cephalopod Discoscaphites iris using a large dataset from multiple localities in the Late Cretaceous (Maastrichtian) of the U.S. Gulf and Atlantic Coastal Plains, spanning a distance of 2000 km along the paleoshoreline. Our results suggest that the fossil record of D. iris is consistent with no within-species net accumulation of phyletic evolutionary change across morphological traits or the lifetime of this species. Correlations between some traits and paleoenvironmental conditions as well as changes in the coefficient of variation may support limited population-scale ecophenotypic plasticity; however, where stratigraphic data are available, no directional changes in morphology occur before the Cretaceous/Paleogene (K/Pg) boundary. This is consistent with models of “dynamic” evolutionary stasis. Combined with knowledge of life-history traits and paleoecology of scaphitid ammonoids, specifically a short planktonic phase after hatching followed by transition to a nektobenthic adult stage, these data suggest that scaphitids had significant potential for rapid morphological change in conjunction with limited dispersal capacity. It is therefore likely that evolutionary mode in the Scaphitidae (and potentially across the broader ammonoid clade) follows a model of cladogenesis wherein a dynamic morphological stasis is periodically interrupted by more substantial evolutionary change at speciation events. Finally, the lack of temporal changes in our data suggest that global environmental changes had a limited effect on the morphology of ammonoid faunas during the latest Cretaceous.
... Schulte et al., 2010;Morgan et al., 2022) and intense volcanic activity, producing greenhouse gases in the atmosphere (e.g. Courtillot, 1990;Keller, 2005;Keller and Abramovich, 2009), resulted in one of the largest mass extinction events in Earth history (e.g. D 'Hondt, 2005;Sepkoski, 2016). ...
Article
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The Península Vald´es es-1 well exhibits the most complete stratigraphic record of an important Danian Atlantic marine event in Patagonia, Argentina. Biostratigraphic analysis of organic-walled dinoflagellate cysts (dinocysts) along with sporomorphs, calcareous nannofossils and foraminiferal complementary data allowed the identification of three stratigraphic intervals of earliest Danian, early to middle Danian and late Danian ages. Diagnostic palynomorph events were recognized including the highest occurrences of the dinocysts Danea californica and Senoniasphaera inornata; the highest common occurrences of Trithyrodinium evittii and Trithyridinium verrucosum. A basal spike of the Cheirolepidiaceae pollen Classopollis provides further evidence of the flourishing of this opportunistic taxon in disturbed ecosystems related to the K/P mass extinction event. The nannofossil zones NP1 to NP4 were identified throughout the section, as well as the foraminifera zones P1b–P1c in the middle and upper part. The microfossil composition reveals fluctuating proximal and neritic environments, as well as a maximum flooding episode; the latter, indicated by the outer neritic Spiniferites, the oceanic taxa Impagidiniumr, along with a glauconitic level. Two warm-sea surface temperature episodes were identified; the oldest, in the early Danian, indicated by the thermophilic dinocysts Trithyrodinium, Hafniasphera and Cordospheridium; and the youngest, in the late Danian, marked by Glaphyrocysta, Hafniasphaera, Tectatodinium pellitum and Pierceites spp. together with frost-intolerant sporomorph taxa and the warm-water foraminifer Boltovskoyella paleocenica. This study contributes to the Argentina paleogeography, achieving a refined marine reconstruction model for the early Paleocene.
... These include global warming, ocean anoxia, a reduced primary productivity and salinity shifts (Twitchett 2007). Being not necessarily limited to unique or catastrophic events, they are reflecting high-stress environments (Keller & Abramovich 2009). Ecological parameters (climate, nutrients, salinity, oxygen and others) triggered the size evolution. ...
Article
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Marine sequences on Wollaston Forland, North‐East Greenland have provided rich belemnite assemblages of Barremian (Early Cretaceous) age. Most common are belemnites of Boreal affinities, closely related to northwest European faunas. Remarkable are the findings of 47 rostra of Duvalia , a genus of Tethyan origin. In addition to Duvalia grasiana , Duvalia arctica sp. nov., Duvalia aff. silesiaca and Duvalia sp. have been recognized. Duvalia grasiana is well known from the Barremian–Aptian of the western Tethys. The other three taxa differ, however, morphologically from contemporaneous Duvalia species common in the Barremian of the Tethys. Our findings suggest a migration of D . grasiana to North‐East Greenland in the early Barremian and a subsequent in situ evolution of D . arctica in the Greenland Norwegian Seaway. Duvalia aff. silesiaca , second in abundance, most probably also evolved from a Tethyan precursor species ( Duvalia silesiaca ). The taxonomic affinities of Duvalia sp. remain unclear. Duvalia arctica , D . aff. silesiaca and Duvalia sp. are all characterized by small size, indicating an endemic evolution and adaptation to a well‐confined position in the food chain. The niche occupied by these small‐sized Duvalia species must have differed substantially to that occupied by co‐occurring Boreal belemnites, which have robust, stout rostra. The findings make North‐East Greenland part of a migration route from the Tethys via the north Atlantic to the high Boreal. The Duvalia Event corresponds stratigraphically to the middle Barremian warming.
... The fossil record indicates size selectivity among benthic foraminifera during the P-T mass extinction event, with larger foraminifera exhibiting a higher susceptibility to extinction (15)(16)(17)(18). Similarly, during the K-Pg mass extinction, larger planktonic foraminifera exhibited a trend of preferential extinction (19). In contrast, fusulinoidean foraminifers did not exhibit size-selective extinction during the Guadalupian-Lopingian (G-L) extinction event (20). ...
Article
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There is a strong relationship between metazoan body size and extinction risk. However, the size selectivity and underlying mechanisms in foraminifera, a common marine protozoa, remain controversial. Here, we found that foraminifera exhibit size-dependent extinction selectivity, favoring larger groups (>7.4 log 10 cubic micrometer) over smaller ones. Foraminifera showed significant size selectivity in the Guadalupian-Lopingian, Permian-Triassic, and Cretaceous-Paleogene extinctions where the proportion of large genera exceeded 50%. Conversely, in extinctions where the proportion of large genera was <45%, foraminifera displayed no selectivity. As most of these extinctions coincided with oceanic anoxic events, we conducted simulations to assess the effects of ocean deoxygenation on foraminifera. Our results indicate that under suboxic conditions, oxygen fails to diffuse into the cell center of large foraminifera. Consequently, we propose a hypothesis to explain size distribution–related selectivity and Lilliput effect in animals relying on diffusion for oxygen during past and future ocean deoxygenation, i.e., oxygen diffusion distance in body.
... It is essential to consider that these small individuals may also represent the influence of some adverse factors. Facing these stresses, foraminiferal individuals may become smaller (Keller, 2003;Keller and Abramovich, 2009). Therefore, it is important to recognize that the results and conclusions drawn from this study are more representative of foraminiferal behavior under optimal conditions. ...
... The decrease of the size at the end Frasnian affected different orders (McNamara and Feist, 2016), reflecting a probable "Lilliput effect" in trilobites. This trend to smaller body size corroborates the existence of strong environmental stresses, such as oxygen depletion or shortage of primary productivity (Twitchett, 2007;Keller and Abramovich, 2009). Size reduction in the late Frasnian also affected other marine clades (Xinsong et al., 2020;Zhuravlev and Sokiran, 2020). ...
... Disruption of food chains are prone to drive size reduction in various organisms (Rita et al., 2019;He et al., 2010), leading to the so-called "Lilliput effect" after major crises (e.g. Keller and Abramovich, 2009;Urbanek, 1993). Such an effect might have overridden the TSR in driving Palmatolepis size evolution during the Kellwasser period. ...
... We interpret this signal as a significant perturbation of the deep-sea atelostomate assemblages in conjunction with the K-Pg Boundary Event-an analogue to the contemporaneous size decrease observed in shelf Atelostomata [59]. Smaller deep-sea Atelostomata are in line with food depletion [60][61][62] and dwarfism ("Lilliput effect") after the K-Pg Boundary Event, as it is well-recorded from all trophic levels in marine and terrestrial realms, e.g., within planktonic foraminifera [63], calcareous nannoplankton [64], marine molluscs [65], lamniform sharks [66] and in terrestrial trace fossil records [67]. Curiously, the Lilliput effect is also observed in other echinoderms (crinoids) in the aftermath of Palaeozoic extinction events [68]. ...
Article
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Deep-sea macrobenthic body fossils are scarce due to the lack of deep-sea sedimentary archives in onshore settings. Therefore, hypothesized migrations of shallow shelf taxa into the deep-sea after phases of mass extinction (onshore-offshore pattern in the literature) due to anoxic events is not constrained by the fossil record. To resolve this conundrum, we investigated 1,475 deep-sea sediment samples from the Atlantic, Pacific and Southern oceans (water depth ranging from 200 to 4,700 m), providing 41,460 spine fragments of the crown group Atelostomata (Holasteroida, Spatangoida). We show that the scarce fossil record of deep-sea echinoids is in fact a methodological artefact because it is limited by the almost exclusive use of onshore fossil archives. Our data advocate for a continuous record of deep-sea Atelostomata back to at least 104 Ma (late early Cretaceous), and literature records suggest even an older age (115 Ma). A gradual increase of different spine tip morphologies from the Albian to the Maastrichtian is observed. A subsequent, abrupt reduction in spine size and the loss of morphological inventory in the lowermost Paleogene is interpreted to be an expression of the “Lilliput Effect”, related to nourishment depletion on the sea floor in the course of the Cretaceous-Paleogene (K-Pg) Boundary Event. The recovery from this event lasted at least 5 Ma, and post-K-Pg Boundary Event assemblages progress—without any further morphological breaks—towards the assemblages observed in modern deep-sea environments. Because atelostomate spine morphology is often species-specific, the variations in spine tip morphology trough time would indicate species changes taking place in the deep-sea. This observation is, therefore, interpreted to result from in-situ evolution in the deep-sea and not from onshore-offshore migrations. The calculation of the “atelostomate spine accumulation rate” (ASAR) reveals low values in pre-Campanian times, possibly related to high remineralization rates of organic matter in the water column in the course of the mid-Cretaceous Thermal Maximum and its aftermath. A Maastrichtian cooling pulse marks the irreversible onset of fluctuating but generally higher atelostomate biomass that continues throughout the Cenozoic.
... This sharp change towards blooming and dwarfing of disaster species implies swift, excessive biotic stresses and environmental instability (Fig. 11; e.g. Keller and Abramovich, 2009;Keller et al., 2020). Decreased Mn/Al and slightly increased V/Al ratios suggest less oxic conditions at the K-Pg boundary. ...
Article
The Žilina-Hradisko borehole in Slovakia intersects a succession from the Cretaceous Hradisko formation to the Paleocene Hričovské Podhradie formation. In this paper, we mainly focus on the Cretaceous–Palaeogene (K–Pg) boundary interval, which is marked by an abrupt change in planktonic biota and magnetic properties. Micropalaeontological findings suggest a rapid change from a stable, oxygen-rich, oligotrophic environment during the Maastrichtian to an unstable, cooler environment with reduced oxygenation and evidence of biotic stress in the lowermost Danian strata. An abrupt change in the magnetite concentration in the same interval indicates increased detrital input and probably biogenic (soft) magnetite production. Evidence recorded in borehole with enhanced Hg input into the Maastrichtian Ocean suggests that the Deccan eruptions mostly occurred prior to the K–Pg boundary, whereas no volcanic Hg input was detected at the K–Pg boundary itself. Double peaks in multiple magnetic properties mark the Danian hyperthermal Dan-C2 event, which was characterised by a series of environmental changes, including enhanced terrigenous input, oxygen deficit, increased nutrient supply, high benthic productivity, and Parasubbotina acme. Prior to the Latest Danian event, foraminiferal assemblages were significantly affected by dissolution and oxygen depletion, followed by warming, water column stratification, and diversification of calcareous plankton groups. An increase in detrital input and nutrient export drove the productivity of deep-dwelling subbotinids and globanomalinids and were correlated with the mid-Paleocene biotic event (MPBE). The seafloor biota associated with the MPBE implies oxygen deficiency and the prevalence of benthic infauna. The Selandian–Thanetian strata markedly differ from planktonic foraminifera of older formations, with their rich content of large, diversified, and heavily calcified morozovellid and igorinid foraminifera, revealing the existence of water column stratification with surface-water productivity and meso- to oligotrophic conditions. The microfauna of ornate morozovellids and benthic biota from the lowermost formation implies the onset of environmental stress and CaCO3 dissolution during the Paleocene-Eocene Thermal Maximum (PETM).
... We suspected that the decrease in weight is the response strategy of reduced energetic costs of calcification under OA (Spalding et al., 2017;Liu et al., 2020) and the phenomenon of dwarf is due to growth retardation (Dong et al., 2020). Overall, our results demonstrated that shell weight reduction and size reduction were two simultaneous processes under OA, indicating a dual effect of OA on the calcification process of benthic foraminifera (Keller and Abramovich, 2009;Feng et al., 2020). This offers robust experimental evidence to explain the dwarf and thin shell of foraminifera found in the geological record. ...
... A similar trend was also reported in planktic foraminifera (Thiede, 1971). The change of size in foraminifera usually reflects the subjected stress and has certain selectivity in evolution (Keller and Abramovich, 2009). The previous study showed that the larger foraminifera was susceptible to extinction (Cotton and Pearson, 2011;Song et al., 2011). ...
Article
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Foraminifera are sensitive to climate change and their species composition, shell chemical element composition and morphological characteristics are useful paleoenvironmental proxies. Coiling direction is a distinctive and easily identifiable morphological feature in trochospiral foraminifera and has been used for paleoceanographic reconstruction. Here, we conducted a field survey in a low intertidal zone in Yellow Sea for 13 months and performed a culture experiment under three temperatures and four salinities for the benthic foraminifera to seek the relationship between coiling direction and environmental factors. Our results showed that the dominant benthic foraminifera Ammonia aomoriensis (Asano, 1951) preferred sinistral direction under high temperature and had no preference with salinity. Statistical analysis showed that the ratio of sinistral/dextral in A. aomoriensis was significantly positively correlated with temperature (r = 0.5017, p = 0.0011 for field survey and r = 0.5117, p = 0.0014 for culture experiment), but had no evident relationship with salinity (p > 0.05). The ratio of sinistral/dextral was significantly negatively related with the abundance of A. aomoriensis (p < 0.05) and the ratio of sinistral/dextral was significantly positively related with the size (p < 0.05). This was the first study on the coiling direction of benthic foraminifera combining the field survey and culture experiment. Our findings suggested that the ratio of sinistral/dextral in A. aomoriensis could be used to indicate the change of temperature. This study offered new evidence for the reliability of the coiling direction as a temperature proxy and made us rethink the significance of the morphological change in biological adaptation and evolution.
... The significant decrease of microfossil body size across the Ediacaranearly Cambrian, cause of which is still ambiguous, needs a more precise and enormous size body database to reveal the long-term size trends. The Lilliput effect is also universal in the foraminifera as a response to catastrophic events, including global warming, ocean anoxia, which together have influenced the survival of foraminifera (Keller and Abramovich, 2009;Feng et al., 2020). For such purposes, FossilMorph may be improved for automatic measurement and statistical analysis of more complex microfossil dimensions in the future. ...
... The significant decrease of microfossil body size across the Ediacaranearly Cambrian, cause of which is still ambiguous, needs a more precise and enormous size body database to reveal the long-term size trends. The Lilliput effect is also universal in the foraminifera as a response to catastrophic events, including global warming, ocean anoxia, which together have influenced the survival of foraminifera (Keller and Abramovich, 2009;Feng et al., 2020). For such purposes, FossilMorph may be improved for automatic measurement and statistical analysis of more complex microfossil dimensions in the future. ...
Article
Quantifying morphological features of fossils represents a major methodology in palaeontological researches. However, an overwhelming number of fossil images trap researchers in the dilemma of laborious manual measurements which is not only time-consuming, but also prone to errors. Here we present FossilMorph, a user-friendly and open access software that offers rapid measurement and statistical analysis based on fossil images. Routine steps of image processing technologies and algorithms designed for three types of organic-walled microfossils (i.e., spheroidal type, filamentous type, and broken type) have been introduced in detail in order to illuminate the rationale of FossilMorph. In addition, two case studies on the form genera Leiosphaeridia and Siphonophycus have been provided to test the feasibility of FossilMorph on the study of micropalaeontology, especially the Proterozoic spheroidal acritarchs. Future development of FossilMorph will focus on fossils with complex morphology and massive preservation to make the software a convenient, efficient, full-featured tool for automatic measurement and statistical analysis in the field of palaeontology. Abstract We present FossilMorph, a user-friendly and open access software that offers rapid measurement and statistical analysis based on fossil images. Routine steps of image processing technologies and algorithms designed for three types of organic-walled microfossils (i.e., spheroidal type, filamentous type, and broken type) have been introduced in order to illuminate the rationale of FossilMorph. Two case studies on the form genera Leiosphaeridia and Siphonophycus are used to test the utility of FossilMorph on the study of micropalaeontology, especially the Proterozoic spheroidal acritarchs. Future development of FossilMorph may be extended to deal with complex morphology and community-type preservation for wider applications.
... Mounting evidence suggests that the K-Pg extinction event triggered convergent patterns of life-history evolution [7]. For example, some lineages experienced a transient "Lilliput effect" in which average body sizes became smaller, likely through faunal sorting, dwarfing, or miniaturization [8][9][10][11][12]. While great effort has been devoted to investigating extinction patterns among various groups across the K-Pg boundary [1, 5,13], the impact of the end-Cretaceous mass extinction event on the genomes of surviving lineages has received little attention. ...
Preprint
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Complex patterns of genome and life-history evolution associated with the end-Cretaceous (K– Pg) mass extinction event limit our understanding of the early evolutionary history of crown group birds. Here, we assess molecular heterogeneity across living birds using a technique enabling inferred sequence substitution models to transition across the history of a clade. Our approach identifies contrasting patterns among exons, introns, untranslated regions, and mitochondrial genomes that reflect distinct regimes of molecular evolution. Up to fifteen shifts in the mode of avian molecular evolution map to rapidly diversifying clades near the Cretaceous-Palaeogene boundary, demonstrating a burst of genomic disparity early in the evolutionary history of crown birds. Using simulation and machine learning techniques, we show that shifts in developmental mode or adult body mass best explain transitions in the mode of nucleotide substitution. These patterns are related, in turn, to macroevolutionary shifts in the allometric scaling relationship between basal metabolic rate and body mass. In agreement with theoretical predictions, we show that this scaling relationship became weaker across the end-Cretaceous transition. Ultimately, our study provides evidence that the Chicxulub bolide impact triggered integrated patterns of evolution across avian genomes, physiology, and life history that structured the evolutionary potential of modern birds.
... 3) in situ and indicative of high-stress environments (Keller and Abramovich, 2009), such as restricted and/or diluted marine environments Corbí et al., , 2020. However, the paleoecological significance of dwarfism in foraminifer tests is not well understood and, given its potential implications for the Lago-Mare environment, it needs to be explored in greater detail. ...
Thesis
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The Messinian Salinity Crisis (MSC; 5.97– 5.33 Ma) is one of the most controversial geological events that influenced the evolution of the Mediterranean Basin in the late Miocene, leaving behind an immense volume of evaporites known as the Mediterranean Salt Giant (MSG). Today, more than 90% of the MSG evaporitic deposits are located offshore, buried below thick sediments that are Pliocene to Quaternary in age, and have thus been studied mainly by marine seismic reflection imaging. The Balearic Promontory (BP), a prominent topographic high in the Western Mediterranean basin, contains a unique and tectonically poorly deformed MSC record that resembles the evaporitic record of other peri-Mediterranean marginal and intermediate basins. This PhD thesis was performed in the framework of the SaltGiant European Training Network (ETN), a cross-disciplinary project whose objective is to understand the formation of the MSG. The work of the thesis is focused on the MSC deposits of the BP. Multi-disciplinary approach was applied to answer some of the still open questions concerning the MSC event. As a first step, seismic interpretation of a wide seismic reflection dataset in the Western Mediterranean in general and in the BP in particular was performed, with the aim of refining the mapping of the Messinian units covering the area. To restitute the depositional history of the MSC evaporites of the BP, a detailed comparison with the Messinian evaporitic units of the Sicilian Caltanissetta Basin was carried out, in which a discussion on how this history matches the existing 3-stages chrono-stratigraphic ‘consensus model’ is illustrated. The next step consisted in the restoration of the paleo-bathymetry of the BP at the beginning of the MSC, focusing on the relatively less-deformed basin located in the central part of the BP and called the Central Mallorca Depression (CMD). To achieve this restoration, structural interpretation in the CMD area was done where the main post-MSC tectonic-related vertical movements that altered the MSC paleo-bathymetry were identified. Then 2D and pseudo-3D backstripping analysis were applied in collaboration with other colleagues from the SaltGiant project, to restore the paleo- bathymetry. In the final step, the paleo-bathymetry was used to model the deposition of the MSC evaporite volumes observed in the CMD using physics-based models built on strait hydraulic-control theory. The results show that the MSC units of the CMD could constitute an undeformed analog of those outcropping on-land in the Sicilian Caltanissetta Basin. Moderate post-MSC deformation acted along MSC strike-slip corridors in the CMD following the MSC evaporites deposition, thus altering only locally the paleo-bathymetry. A high amplitude xix drawdown (>850m) is required during the halite stage of the MSC. The results rise a series of doubts about the current consensus model, still widely accepted. Doubts concern the synchronous onset of salt at the basin scale, the maximum depth of deposition of the Primary Lower Gypsum (PLG) and the timing of formation of the Resedimented Lower Gypsum (RLG). All the results and discussions hint to the need of revision of the current MSC consensus model, as well as the importance of initiating drillings offshore over the BP area, which would help revealing many of the mysteries still buried with the MSG.
... The Lilliput effect is difficult to assess for any extinction because it requires an excellent fossil record that brackets the extinction event [19]. For this reason, the Lilliput effect has been best documented in marine groups like planktic foraminifera [20], mollusks [21] and lamniform sharks [22], but has also been reported in terrestrial environments [23]. While the incomplete terrestrial fossil record for many clades currently precludes an analysis of the Lilliput effect across end-Cretaceous ecosystems, it is well documented that large-bodied species go extinct at the K-Pg (e.g. ...
Article
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The Cretaceous–Palaeogene (K–Pg) mass extinction was responsible for the destruction of global ecosystems and loss of approximately three-quarters of species diversity 66 million years ago. Large-bodied land vertebrates suffered high extinction rates, whereas small-bodied vertebrates living in freshwater ecosystems were buffered from the worst effects. Here, we report a new species of large-bodied (1.4–1.5 m) gar based on a complete skeleton from the Williston Basin of North America. The new species was recovered 18 cm above the K–Pg boundary, making it one of the oldest articulated vertebrate fossils from the Cenozoic. The presence of this freshwater macropredator approximately 1.5–2.5 thousand years after the asteroid impact suggests the rapid recovery and reassembly of North American freshwater food webs and ecosystems after the mass extinction.
... The early Paleocene (P1c) was time of warming that correlates with the onset of the Deccan Volcanism Phase-3 (Keller et al., 2015). The warming was accompanied by decreased planktic foraminiferal diversity and increased dissolution effects (Keller and Abramovich, 2009;Punekar et al., 2014a;Keller et al., 2015). ...
Article
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The present authors used the scanning electron microscopy and energy dispersive spectroscopy methodology as a standard approach for micropaleontological studies to detect test internal morphological and compositional features of agglutinated foraminifera grains collected from Maastrichtian-Paleogene of the Dakhla Oasis of Egypt. Five main morphogroups dominate Lower Kharga Member,the mixture of infaunal and epifaunal morphogroups indicating mesotrophic conditions during that time.All evolving new species found in the Early Paleocene are small and species richness remains low with small simple test morphologies resembling the under zone CF3 with a new appearance of morphogroup epifaunal flattened planispiral. Zone CF3 of Lower Kharga Member is characterized by the appearances of small-sized Trochammina which are associated with stressful environmental conditions. Zone P1c of the Upper Kharga Member is characterized by high percentages of calcareous agglutinated foraminifera and abundance of granular calcite and hyaline tests, which explained a sufficient quantity of calcium carbonate dissolved in the water and warm water basin. The strong decrease in diversity and heterogeneity of the assemblages, as well as the drastic drop in the number of infaunal elongated morphogroup coincident with the hiatus between CF3 and P1c (Maastrichtian/Danian boundary), indicate a dramatic decrease in the food supply to the sea-bottom floor.
... The MI values tended to increase with increasing patch size, indicating that the proportion of groups with high CP values increased, and they were important indicators of the undisturbed and unstressed soil environment (Resch et al., 2019). This result proves that the environment inside the large patch tends to be stable and that the soil nematode community advances to a relatively mature level (Keller and Abramovich, 2009). Compared with CK, the PPI value was reduced by experimental treatment. ...
Article
Interactions between aboveground and belowground ecosystems components modulate ecosystem functions. However, few studies have focused on the response of soil nematodes to plantation reconstruction. In this study, Cinnamomum longipaniculatum was planted in the gap of a Pinus massoniana plantation. Based on the size, center and edge of C. longipaniculatum patches, the characteristics of the soil nematode community were studied after 8 years of plantation reconstruction. The effect of the C. longipaniculatum plantation on the soil nematode community was related to patch size. The soil nematode community did not change significantly with increasing patch size above 30 m × 30 m. The soil recovered better in the patch center than at the edge, but the edge increased the diversity of soil nematodes with low C-P values. The experimental treatment increased the dominance of soil plant parasite nematodes and bacterivores, decreased the trophic diversity index, and increased the channel ratio, maturity index, enrichment index and structure index of soil nematodes, indicating that soil nutrient cycling improved and the diversity of the soil food web increased. After P. massoniana plantation gaps were replanted with C. longipaniculatum, the main soil properties that affected the soil nematode community were organic carbon, pH, water content and soil aggregate degree. In the soil nematode community, fungal nematodes had the strongest influence on omnivorous-predatory nematodes. Our study showed that the soil environment changed with vegetation and affected soil nematode groups, and soil nematodes effectively reflected soil ecological restoration after P. massoniana plantation gaps were replanted with C. longipaniculatum.
... Neogloboquadrina pachyderma is dominant in subpolar and polar conditions Volkmann, 2000). A decrease in species diversity and richness often occurs in regions of high environmental stress (Keller and Abramovich, 2009) which is the case in the Labrador Sea. The elevated abundance of N. pachyderma in the region can also be explained by the good preservation of these thick-shelled species as that is more resistant to dissolution than T. quinqueloba and G. uvula (Berger, 1973;Boltovskoy and Wright, 2013). ...
Article
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The subpolar North Atlantic (SPNA) Ocean has complex hydrography, and moderates the global climate through the Atlantic Meridional Overturning Circulation (AMOC). The surface water mass dynamics in SPNA and the upper limb of AMOC, govern the plankton distribution. Specifically, the habitat of modern planktic foraminifera is strongly affected by the SPNA hydrography. In the present study, 25 surface sediment samples from the Labrador Sea to the Iceland-Faroe-Shetland Channel (IFSC) were examined for planktic foraminifera distribution along a latitudinal transect at 59.50°N. The planktic foraminifera distribution followed the transition in water mass structure in the study area from the Sub-Arctic water in the west to the warm North Atlantic water in the east. Temperature and salinity are two dominant ecological factors controlling planktic foraminifera assemblages in the region. This hydrographic contrast was also reflected in the ratio of Neogloboquadrina pachyderma/Neogloboquadrina incompta along the transect. Based on the cluster analysis, the planktic foraminifera assemblages could be assigned to three groups. A cold/polar group in the Labrador Sea, a mixed (both cold and warm) group in the Irminger Sea and IFSC, and a warmer temperate group in the eastern part of the transect were represented by different planktic foraminifera assemblages. Additionally, a decrease in Globorotalia inflata in the eastern transect and an increase in Turborotalita quinqueloba in the Iceland basin and Irminger Sea was observed in our study when compared with the published dataset. From this, we suggest a shift in planktic assemblages in the SPNA. The present study on the distribution of modern planktic foraminifera can help paleoceanographic reconstructions in the SPNA ocean.
... The CF6 zone shows a gradual increase in the relative abundance of Gublerina spp. range between 0.01 and 3.9% and heterhelicids to 26% that shows the tolerate and thrive in a wide range of environmental conditions as in high-stress environments affected by temperature, salinity, nutrients and oxygen variations due to sea-level fluctuations (Keller & Abramovich, 2009;Pardo & Keller, 2008). ...
Article
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The late Campanian/Maastrichtian succession exposed at Pondicherry area affords one of the finest exposed marine sections in Cauvery Basin is examined for their foraminiferal contents. The biostratigraphic distribution of 71 species of planktonic foraminifera has been used to diagnose 11 planktonic zones and subzones and correlated to the worldwide bioevent. During the late Campanian, a great transgression event occurred associated with the global warming (CF8b zone) trend indicated by large double-keeled foraminifera (Globotruncana aegyptiaca Nakkady) of oligotrophic conditions. The latest zone CF4 records a sharp decrease in Planktonic/Benthic (P/B), globotruncanids, rugoglobigerinids and heterohelicids implying a fall of sea level.
... Differential origination with respect to body size during recovery intervals could demonstrate the contrasting efficiency of physiological systems, as taxa with higher metabolic rates and buffered physiology fare better in these conditions [55]. The preferential origination of smaller genera during recovery can help to explain the common observation of smaller-bodied fossils in the aftermath of mass extinction events [30][31][32][33][56][57][58], sometimes referred to as the 'Lilliput effect' [59,60]. The ability to cope physiologically with environmental conditions might have been an important factor of body size origination during recoveries. ...
Article
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Whether mass extinctions and their associated recoveries represent an intensification of background extinction and origination dynamics versus a separate macroevolutionary regime remains a central debate in evolutionary biology. The previous focus has been on extinction, but origination dynamics may be equally or more important for long-term evolutionary outcomes. The evolution of animal body size is an ideal process to test for differences in macroevolutionary regimes, as body size is easily determined, comparable across distantly related taxa and scales with organismal traits. Here, we test for shifts in selectivity between background intervals and the ‘Big Five’ mass extinction events using capture–mark–recapture models. Our body-size data cover 10 203 fossil marine animal genera spanning 10 Linnaean classes with occurrences ranging from Early Ordovician to Late Pleistocene (485–1 Ma). Most classes exhibit differences in both origination and extinction selectivity between background intervals and mass extinctions, with the direction of selectivity varying among classes and overall exhibiting stronger selectivity during origination after mass extinction than extinction during the mass extinction. Thus, not only do mass extinction events shift the marine biosphere into a new macroevolutionary regime, the dynamics of recovery from mass extinction also appear to play an underappreciated role in shaping the biosphere in their aftermath.
... 3.3a). This succession of climatic changes matches the warming/cooling/warming/cooling succession that occurred during Maastrichtian times(Li and Keller, 1998;Keller and Abramovich, 2009). Those interpretations were based on planktic and benthic foraminifera-stable isotope data from two DSDP 525 sites drilled in the South Atlantic at a similar latitude to the Salta Rift basin in sediments temporally equivalent to the middle through upper sections of the Yacoraite Formation.The cold periods occurred between 68-69.5 Ma and between 66.25-66 Ma(Keller et al., 2016).Similar climate variations during the Late Cretaceous were observed in sediments at northern latitudes and indicate that climate variations occurred at a global scale, probably triggered by changes in ocean circulation(Linnert et al., 2011). ...
Thesis
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This dissertation was carried out as part of the international and interdisciplinary graduate school StRATEGy. This group has set itself the goal of investigating geological processes that take place on different temporal and spatial scales and have shaped the southern central Andes. This study focuses on claystones and carbonates of the Yacoraite Fm. that were deposited between Maastricht and Dan in the Cretaceous Salta Rift Basin. The former rift basin is located in northwest Argentina and is divided into the sub-basins Tres Cruces, Metán-Alemanía and Lomas de Olmedo. The overall motivation for this study was to gain new knowledge about the evolution of marine and lacustrine conditions during the Yacoraite Fm. Deposit in the Tres Cruces and Metán-Alemanía sub-basins. Other important aspects that were examined within the scope of this dissertation are the conversion of organic matter from Yacoraite Fm. into oil and its genetic relationship to selected oils produced and natural oil spills. The results of my study show that the Yacoraite Fm. began to be deposited under marine conditions and that a lacustrine environment developed by the end of the deposition in the Tres Cruces and Metán-Alemanía Basins. In general, the kerogen of Yacoraite Fm. consists mainly of the kerogen types II, III and II / III mixtures. Kerogen type III is mainly found in samples from the Yacoraite Fm., whose TOC values are low. Due to the adsorption of hydrocarbons on the mineral surfaces (mineral matrix effect), the content of type III kerogen with Rock-Eval pyrolysis in these samples could be overestimated. Investigations using organic petrography show that the organic particles of Yacoraite Fm. mainly consist of alginites and some vitrinite-like particles. The pyrolysis GC of the rock samples showed that the Yacoraite Fm. generates low-sulfur oils with a predominantly low-wax, paraffinic-naphthenic-aromatic composition and paraffinic wax-rich oils. Small proportions of paraffinic, low-wax oils and a gas condensate-generating facies are also predicted. Here, too, mineral matrix effects were taken into account, which can lead to a quantitative overestimation of the gas-forming character. The results of an additional 1D tank modeling carried out show that the beginning (10% TR) of the oil genesis took place between ≈10 Ma and ≈4 Ma. Most of the oil (from ≈50% to 65%) was generated prior to the development of structural traps formed during the Plio-Pleistocene Diaguita deformation phase. Only ≈10% of the total oil generated was formed and potentially trapped after the formation of structural traps. Important factors in the risk assessment of this petroleum system, which can determine the small amounts of generated and migrated oil, are the generally low TOC contents and the variable thickness of the Yacoraite Fm. Additional risks are associated with a low density of information about potentially existing reservoir structures and the quality of the overburden.
... Such areas are characterized by a very high nutrient supply that may cause an expansion of the OMZ into the water column, leading to stress conditions for the foraminiferal community (e.g., Ashckenazi-Polivoda et al., 2011). Under optimum environmental conditions, planktonic foraminifera generally produce large tests, but as biotic stress increases, large and specialized species are eliminated or tend to reduce their test size (r strategists; Keller and Abramovich, 2009;Keller and Pardo, 2004;Rillo et al., 2020;Schmidt et al., 2004). Today, near active upwelling systems, the planktonic assemblages are characterized by specimens with smaller test size and by specific minute species (Rutherford et al., 1999;Schmidt et al., 2004). ...
Article
The recent growing interest in Late Cretaceous biserial planktonic foraminifera (heterohelicids) has greatly enhanced their use as paleoceanographic and biostratigraphic markers. Pseudotextularia nuttalli, one of the most common cosmopolitan planktonic foraminifera, has an exceptionally long evolutionary range (Turonian-Maastrichtian). The image processing procedure we developed in this study enabled us to document changes in the growth pattern of Ps. nuttalli over time and between different oceanic provinces, and to identify possible speciation events within this lineage. The analysis was complemented by morphometric measurements of the penultimate chamber and test. The morphometric analyses do not indicate an early speciation event within this lineage, and thus, do not support splitting to Planoheterohelix praenuttalli (Turonian-Coniacian) and Pseudotextularia nuttalli (Coniacian-Maastrichtian). Our results indicate a gradual phyletic increase in mean test size from the Santonian through the Maastrichtian, along with increasing morphological diversification. This trend seems to coincide with the global cooling that culminated in the Late Cretaceous. Comparing between Ps. nuttalli from different oceanic provinces reveals that the Southern Tethys specimens are significantly less developed than their counterparts from the two tropical oceanic localities. This adaptive responsiveness suggests a negative correlation between test size and high productivity conditions in the upper water column. The case of Ps. nuttalli lineage exemplifies how extraordinary long-range species (>30 My) can evolutionarily change over time from “primitive” to “developed” forms, without showing a morphological gap. Such species may also show adaptive morphological diversification in response to different environments and, thus, are valuable for palaeoceanographic and paleoecologic reconstructions.
... Notwithstanding this issue, it is noteworthy that Kucera and Malmgren (1996) determined that largest sized tests of C. contusa come from the Caravaca and El Kef section and are around twice the size of those reported at higher latitudes sites. Although they did not perform biometric analysis, Keller and Abramovich (2009) provided examples of the Lilliput effect in late Maastrichtian planktic foraminifera and concluded that this was a response to a stressed environment. According to MacLeod et al. (2000), a smaller test size implies stunted growth and early sexual maturity, which maximizes survival rates in highstress environments where survival depends on rapid turnover, as was the case for the LMWE. ...
Article
A global warming episode in the Late Cretaceous, the Latest Maastrichtian Warming Event (LMWE), has been commonly linked to both the onset of massive Deccan Trap volcanism and the start of a planktic foraminiferal mass extinction prior to the Cretaceous/Paleogene boundary (KPB). The mechanisms that drove the LMWE are still under discussion, but radiometric dating of the onset of the main phase of the Deccan volcanism supports a temporal coincidence and permits a potential mechanistic link. Here we evaluate the planktic foraminiferal record, carbonate content and stable carbon and oxygen isotopes in the Caravaca section, in order to characterize paleoenvironmental change related to the LMWE. We identified negative d 13 C and d 18 O excursions in bulk carbonate from 66.35 to 66.14 Ma, i.e.~310 to~100 kyr before the KPB, which can be stratigraphically correlated to the LMWE and a major pulse of Deccan Traps volcanism. Within this warm interval, we identified high values in the fragmentation index of planktic foraminiferal tests, episodes of very high abundance of the low oxygen tolerant genus Hetero-helix, a decrease of thermocline dwellers, dwarfing in Contusotruncana contusa tests, and an increase in the biserial morphotype of Pseudoguembelina hariaensis with elongated terminal chambers. However, the environmental disturbance during the LMWE did not cause changes in the planktic foraminiferal extinction rate. At Caravaca, the warming associated with LMWE was followed by a gradual cooling up to the KPB suggesting no extended interval of perturbed environments before the KPB extinction due to Deccan volcanism.
... Survivor species are generally tolerant of variations in oxygen, salinity, temperature, nutrients and toxicity (e.g., mercury from large volcanic eruptions) (Keller, 2003;Keller et al., 2007, Keller et al., 2020. These species tend to be small, unornamented with simple test morphologies (biserial, triserial, trochospiral) and frequently dwarfed in high-stress environments (Leckie et al., 1998;Keller and Abramovich, 2009). Depending on the degree of biotic stress, foraminiferal assemblages vary from few species in shallow neritic environments to a single survivor in brackish estuarine conditions. ...
Article
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We report the Narmada Seaway began in India during the largest global sea-level transgression and Oceanic Anoxic Event 2 (OAE2) δ¹³C excursion during the late Cenomanian to early Turonian. The transgression progressed eastward during the Turonian-Coniacian and reached Jhilmili by the end of the Maastrichtian. During this time the Narmada and Godavari Seaways may have joined via the Narmada-Tapti rift and formed a Trans-India Seaway. The history of this major seaway is entombed in a fossil-rich marine transgression of the tectonically active Narmada rift zone. We examined this transgression in the western Narmada Basin, Gujarat, to improve age control based on planktic foraminifera and ostracods and evaluate paleoenvironmental changes based on the Cenomanian-Turonian OAE2 δ¹³C excursion, δ¹⁸O records, and mercury concentrations in sediments as index for volcanic eruptions. Results reveal the onset of the OAE2 δ¹³C excursion began in the western Narmada Basin during the late Cenomanian coeval with the sea-level transgression and first influx of planktic and benthic foraminifera in the Nimar Sandstone that overlies Archean rocks. The OAE2 δ¹³C excursion peak was recorded in oyster biostromes followed by fluctuating values of the δ¹³C plateau in the overlying Limestone with oysters beds, and gradual decrease to background values by the early Turonian. We tested the age of the transgression and δ¹³C excursion based on planktic foraminifera and ostracod biostratigraphy and successfully compared the results with the Pueblo, Colorado, Global Section and Stratotype Point (GSSP), and the eastern Sinai Wadi El Ghaib section of Egypt.
... 3) in situ and indicative of high-stress environments (Keller and Abramovich, 2009), such as restricted and/or diluted marine environments Corbí et al., , 2020. However, the paleoecological significance of dwarfism in foraminifer tests is not well understood and, given its potential implications for the Lago-Mare environment, it needs to be explored in greater detail. ...
Article
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The late Miocene evolution of the Mediterranean Basin is characterized by major changes in connectivity, climate and tectonic activity resulting in unprecedented environmental and ecological disruptions. During the Messinian Salinity Crisis (MSC, 5.97-5.33 Ma) this culminated in most scenarios first in the precipitation of gypsum around the Mediterranean margins (Stage 1, 5.97-5.60 Ma) and subsequently > 2 km of halite on the basin floor, which formed the so-called Mediterranean Salt Giant (Stage 2, 5.60-5.55 Ma). The final MSC Stage 3, however, was characterized by a "low-salinity crisis", when a second calcium-sulfate unit (Upper Gypsum; substage 3.1, 5.55-5.42 Ma) showing (bio)geochemical evidence of substantial brine dilution and brackish biota-bearing terrigenous sediments (substage 3.2 or Lago-Mare phase, 5.42-5.33 Ma) deposited in a Mediterranean that received relatively large amounts of riverine and Paratethys-derived low-salinity waters. The transition from hypersaline evaporitic (halite) to brackish facies implies a major change in the Mediterranean’s hydrological regime. However, even after nearly 50 years of research, causes and modalities are poorly understood and the original scientific debate between a largely isolated and (partly) desiccated Mediterranean or a fully connected and filled basin is still vibrant. Here we present a comprehensive overview that brings together (chrono)stratigraphic, sedimentological, paleontological, geochemical and seismic data from all over the Mediterranean. We summarize the paleoenvironmental, paleohydrological and paleoconnectivity scenarios that arose from this cross-disciplinary dataset and we discuss arguments in favour of and against each scenario.
... Finally, the abundance of dwarf forms of Heterohelix spp. and low diversity of planktonic foraminifera, suggest that upper and intermediate waters were highly stressed and poorly oxygenated (Keller and Abramovich, 2009). Based on our observations, deoxygenation rather than driven by eutrophication was driven by poor ventilation of the La Luna Sea (a consequence of the paleogeographic situation) and, to some extent, submarine and subaerial volcanic activity. ...
Article
Epicontinental seas were important features of the paleogeographic landscape during the Cretaceous; however, the role they played as sinks of organic carbon is still poorly understood. The La Luna Formation (Albian-Coniacian) is a series of organic-rich limestones deposited in northwestern South America on an epicontinental sea (the La Luna Sea). This formation offers a forty-million-year continuous record of environmental change characterized by periods of oceanic anoxia in an epicontinental sea. The La Luna Sea, may have played an important role –although so far unexplored– in carbon cycling through the ocean during the Cretaceous, specifically during short-term, global-scale disruptions in the carbon cycle known as oceanic anoxic events (OAEs). To evaluate the role of the La Luna Sea in global carbon cycle perturbations, we conducted a detailed lithological and chemostratigraphic analysis of two stratigraphic sections from the Upper Magdalena Basin of Colombia, both of which encompass the Oceanic Anoxic Event 2 (OAE2) at the Cenomanian–Turonian boundary. Compared to deposits in the modern ocean, the La Luna Formation has high total organic carbon (TOC) before, during, and after OAE2. Foraminifera and nannoplankton assemblages also imply a stressed upper water column during OAE2. Geochemical and paleontological evidence suggests that the sediment-water interface was anoxic across the late Cenomanian and early Turonian. Strata deposited just after OAE2, however, contain inoceramid bivalves, consistent with short-lived re‑oxygenation of the benthic layer. Estimates of primary productivity, the covariation of Mo and U enrichment factors, and relations between Cd, Mo, Co, and Mn also reveal that the La Luna Sea was biogeochemically similar to the modern Cariaco Basin. Despite high concentrations of organic carbon found in the La Luna Formation, mass-accumulation rates of organic carbon are low, a finding that can be explained by a reduction in the accumulation rate of sediments caused by the peak of sea-level transgression that took place at the Cenomanian–Turonian transition. Based on the areal extent of the La Luna Sea and mass-accumulation rates of organic carbon, 1.7 Eg of C were removed from the ocean over 500 ky and deposited in the La Luna Sea. Interestingly, although the La Luna Sea was one-third the size of the Western Interior Seaway (WIS), the amount of organic carbon buried in the WIS during OAE2 was similar (1.4 Eg of C). In these two epicontinental seas, 3.1 Eg of C were removed from the ocean during OAE2, accounting only for 3.4% of the total C needed to cause a perturbation of the carbon cycle similar to that observed during OAE2. The low amount of organic carbon buried in the La Luna Sea and the WIS suggests that neither of these inland seas were responsible for the efficient removal of organic carbon from the ocean during OAE2. This conclusion challenges the explanation that epicontinental seas were major sinks of organic carbon—and therefore they did not play a significant role in the carbon cycle during the Mesozoic OAEs and other disruptions of the carbon cycle in Earth's history.
... Finally, the abundance of dwarf forms of Heterohelix spp. and low diversity of planktonic foraminifera, suggest that upper and intermediate waters were highly stressed and poorly oxygenated (Keller and Abramovich, 2009). Based on our observations, deoxygenation rather than driven by eutrophication was driven by poor ventilation of the La Luna Sea (a consequence of the paleogeographic situation) and, to some extent, submarine and subaerial volcanic activity. ...
Article
Epicontinental seas were important features of the paleogeographic landscape during the Cretaceous; however, the role they played as sinks of organic carbon is still poorly understood. The La Luna Formation (Albian-Co-niacian) is a series of organic-rich limestones deposited in northwestern South America on an epicontinental sea (the La Luna Sea). This formation offers a forty-million-year continuous record of environmental change characterized by periods of oceanic anoxia in an epicontinental sea. The La Luna Sea, may have played an important role-although so far unexplored-in carbon cycling through the ocean during the Cretaceous, specifically during short-term, global-scale disruptions in the carbon cycle known as oceanic anoxic events (OAEs). To evaluate the role of the La Luna Sea in global carbon cycle perturbations, we conducted a detailed lithological and chemostratigraphic analysis of two stratigraphic sections from the Upper Magdalena Basin of Colombia, both of which encompass the Oceanic Anoxic Event 2 (OAE2) at the Cenomanian-Turonian boundary. Compared to deposits in the modern ocean, the La Luna Formation has high total organic carbon (TOC) before, during, and after OAE2. Foraminifera and nannoplankton assemblages also imply a stressed upper water column during OAE2. Geochemical and paleontological evidence suggests that the sediment-water interface was anoxic across the late Cenomanian and early Turonian. Strata deposited just after OAE2, however, contain inoceramid bivalves, consistent with short-lived re-oxygenation of the benthic layer. Estimates of primary productivity, the covariation of Mo and U enrichment factors, and relations between Cd, Mo, Co, and Mn also reveal that the La Luna Sea was biogeochemically similar to the modern Cariaco Basin.Despite high concentrations of organic carbon found in the La Luna Formation, mass-accumulation rates of organic carbon are low, a finding that can be explained by a reduction in the accumulation rate of sediments caused by the peak of sea-level transgression that took place at the Cenomanian-Turonian transition. Based on the areal extent of the La Luna Sea and mass-accumulation rates of organic carbon, 1.7 Eg of C were removed from the ocean over 500 ky and deposited in the La Luna Sea. Interestingly, although the La Luna Sea was one-third the size of the Western Interior Seaway (WIS), the amount of organic carbon buried in the WIS during OAE2 was similar (1.4 Eg of C). In these two epicon-tinental seas, 3.1 Eg of C were removed from the ocean during OAE2, accounting only for 3.4% of the total C needed to cause a perturbation of the carbon cycle similar to that observed during OAE2. The low amount of organic carbon buried in the La Luna Sea and the WIS suggests that neither of these inland seas were responsible for the efficient removal of organic carbon from the ocean during OAE2. This conclusion challenges the explanation that epicontinental seas were major sinks of organic carbon-and therefore they did not play a signifi ⁎ Corresponding author at: Manuel Paez-Reyes
... Foraminifera develop maximum test size under optimal conditions for important environmental parameters, such as temperature, salinity, food supply, and dissolved oxygen (Caron et al., 1987;Kaiho, 1998;Kaiho et al., 2006;Keller & Abramovich, 2009;Keating-Bitonti & Payne, 2016). Culture and field studies reported that the mean proloculus size of A. aomoriensis is negatively correlated with salinity (Nigam & Rao, 1987;Yu et al., 2016;Lei et al., 2017b). ...
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This study explored the response to salinity of intertidal foraminiferal assemblages from the Yellow Sea by culturing them for 100 days at six constant salinity levels (17, 22, 27, 32, 37, and 42 psu) in laboratory microcosms with four replicates each. A total of 7,471 live (stained) foraminiferal specimens were obtained and analyzed. The diversity parameters of foraminiferal assemblages (species richness, Margalef index, Shannon-Wiener index, and Fisher's alpha) declined significantly when the salinity was increased or decreased from the field value, but foraminiferal abundance was highly resistant to salinity. In addition, salinity exerted different effects on foraminifera from different orders. Specifically, the proportion of species from Order Miliolida significantly increased whereas that of species from Order Rotaliida decreased with increasing salinity. High salinity-tolerant species Ammonia aomoriensis, Cribrononion gnythosuturatum, Ammonia tepida, and Quinqueloculina seminula could fill unoccupied ecological niches when the proportion of salinity-sensitive species has declined. Furthermore, our morphometric results showed that foraminiferal test size was significantly negatively correlated with salinity, and numerous abnormal specimens appeared in foraminiferal assemblages when salinity deviated from the field value. Our study revealed that intertidal foraminiferal assemblages had high adaptability at different salinities because of the existence of high salinity-tolerant dominant species. In addition, salinity variation can significantly alter foraminiferal morphology in test size and abnormality.
... . Luciani, 2004, 2005;Premoli Silvaet et al., 1999 ) . Luciani, 2004, 2005;Macleod et al., 2000) ( Keller and Abramovich, 2009;Coccioni and Luciani, 2004;MacLeod et al., 2000 ) . ( Keller and Pardo, 2004;Kroon and Nederbragt, 1990;Barrera and Keller, 1990;Leckie, 1987 Fanning et al., 1989) ) . ...
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The Cenomanian-Turonian boundary interval (93-94 Ma) was a time of rapid oceanographic change in the U.S. Western Interior Sea ("Greenhorn Sea"). Previous studies documented changes in δ180 in carbonates and shifts in macrofossil (molluscan) populations indicating the incursion of a subsaline surface-water mass into the region and dysoxic to anoxic benthic conditions across wide areas of the seaway. These changes were accompanied by an expanding oxygen minimum zone in concert with global-scale burial of organic matter, which was driven in part by elevated rates of marine productivity. The oceanography of the southern seaway was undoubtedly complex with signals of a global anoxic event overprinted by regional influences of water mass stratification, mixing, productivity, changes in relative sea level, and biotic turnover. Our studies of planlctic and benthic foraminiferal assemblages and clay-mineral distribution in calcareous mudrocks and dark marlstones from the southwestern side of the Greenhorn Sea provide further constraints on the paleoceanography of this region. Specifically, there is a major change in planktic foraminiferal population structure ("Heterohelix shift") coupled with an influx of kaolinite and illite at both a neritic site (Lohali Point, Arizona) and a distal basin site (Rock Canyon, Colorado). These characteristics are not observed at a proximal basin site (Mesa Verde, Colorado) in between the other locales. The distinctive clay mineral assemblages suggest two disparate sources. One of these sources most likely was from the Sevier orogenic belt along the western side of the seaway, and another was either the southwestern comer of the seaway or the southern part of the stable craton. The distribution of clay mineral and planktic foraminiferal assemblages provide information on circulation of the upper water column. The benthic foraminiferal assemblages of Lohali Point and Mesa Verde are very similar and have northern affinities, suggesting the influence of cool bottom waters along the western side of the seaway. We suggest that a submerged tectonic forebulge or bathymetric high near Mesa Verde caused "edge-effect" mixing and upwelling of cool water masses originating from the north. To the west, a foredeep shelf in northe.tern Arizona and southcentral Utah provided a conduit for northward-flowing, warmer surface water m.ses over the southward-flowing, cooler waters. These southern waters were bifurcated by the Mesa Verde high. The resultant oceanographic front, or mixing zone, caused the contrast in ecological and sedimentological patterns at the sites. With rising sea level came the incursion of oxygen-poor Tethyan intermediate waters into the Greenhom Sea during latest Cenomanian early Turonian time and the development of widespread, low diversity benthic foraminiferal assemblages dominated by Neobulimina.
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The eastern Tethys, from Israel to Egypt, experienced unusually adverse environmental conditions for planktic foraminifera during the last two million years of the Maastrichtian, as evident by very low species richness, blooms of opportunistic Guembelitria species in surface waters, dominance of low-oxygen-tolerant heterohelicids in subsurface waters, and near absence of deeper dwelling globotruncanids. Comparison of southern Israel (Mishor Rotem section) with central Egypt (Gebel Qreiya section) reveals that adverse conditions intensified towards the south with foraminiferal assemblages mimicking stress conditions of the early Danian, dominated (75-90%) by Guembelitria blooms. Faunal assemblages indicate an expanded oxygen minimum and dysoxic zone throughout the region, though at the greater depths represented by localities of southern Israel, bottom waters remained aerobic. Primary productivity was extremely low as indicated by stable isotopes and low total organic content in sediments. These adverse environmental conditions are likely related to the regional paleobathymetry of the tectonically active Syrian Arc that spans Syria to Egypt. The paleorelief of intra-shelf and intra-slope basins of the Syrian Arc, with their differential rates of subsidence and sedimentation, active folding and faulting, likely controlled the intensity of circulation, upwelling, watermass stratification and the extent of the oxygen minimum zone. The late Maastrichtian rapid climate and sea level changes exacerbated these conditions.
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In the 1990s the Chicxulub impact was linked to the K-T boundary by impact spherules at the base of a sandstone complex that was interpreted as impact-generated tsunami deposit. Since that time a preponderance of evidence failed to support this interpretation, revealing long-term deposition of the sandstone complex, the K-T boundary above it and the primary impact spherule ejecta interbedded in Late Maastrichtian marls below. Based on evidence from Mexico and Texas we suggested that the Chicxulub impact predates the K-T boundary. Impact-tsunami proponents have challenged this evidence largely on the basis that the stratigraphically lower spherule layer in Mexico represents slumps and widespread tectonic disturbance, though no such evidence has been presented. The decades old controversy over the cause of the K-T mass extinction will never achieve consensus, but careful documentation of results that are reproducible and verifiable will uncover what really happened at the end of the Crectaceous. This study takes an important step in that direction by showing (1) that the stratigraphically older spherule layer from El Peñon, NE Mexico, represents the primary Chicxulub impact spherule ejecta in tectonically undisturbed sediments and (2) that this impact caused no species extinctions.
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Climatic and oceanographic variations during the last 2 m.y. of the Maastrichtian inferred from high-resolution (10 k.y.) stable isotope analysis of the mid-latitude South Atlantic Deep Sea Drilling Project Site 525 reveal a major warm pulse followed by rapid cooling prior to the Cretaceous-Tertiary boundary. Between 66.85 and 65.52 Ma, cool but fluctuating temperatures average 9.9 and 15.4 °C in intermediate and surface waters, respectively. This interval is followed by an abrupt short-term warming between 65.45 and 65.11 Ma, which increased temperatures by 2 3 °C in intermediate waters, and decreased the vertical thermal gradient to an average of 2.7 °C. This warm pulse may be linked to increased atmospheric pCO2, increased poleward heat transport, and the switch of an intermediate water source from high to low-middle latitudes. During the last 100 k.y. of the Maastrichtian, intermediate and surface temperatures decreased by an average of 2.1 and 1.4 °C, respectively, compared to the maximum temperature between 65.32 and 65.24 Ma.
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Spatial and temporal patterns in test size and shape (test conicity and spiral roundness) and absolute abundance (accumulation rate) of the planktonic foraminifer Contusotruncana contusa were studied in the South Atlantic Ocean (DSDP sites 356, 516, 525 and 527) during an interval corresponding to the last 800 kyr of the Cretaceous. The variation in absolute abundance of C. contusa was characterised by alternating periods of high and low abundance; some of these periods were traceable across the entire mid-latitude South Atlantic Ocean. While the mean spiral roundness did not show any interpretable patterns, a sudden increase of the mean test size and mean test conicity occurred between 65.3 and 65.2 Ma (based on linear interpolation within the Cretaceous part of Subchron C29R) at all sites studied, indicating a poleward migration followed by rapid withdrawal of the low-latitude C. contusa morphotypes from the mid-latitude South Atlantic Ocean. We suggest that this event was caused by a short period of surface-water warming in the southern mid-latitudes corresponding to the brief high-latitude warming event and associated faunal migrations in the Boreal and Austral realms.
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Fluctuations in oxygen (delta18O) and carbon (delta13C) isotope values of benthic foraminiferal calcite from the tropical Pacific and Southern Oceans indicate rapid reversals in the dominant mode and direction of the thermohaline circulation during a 1 m.y. interval (71 70 Ma) in the Maastrichtian. At the onset of this change, benthic foraminiferal delta18O values increased and were highest in low-latitude Pacific Ocean waters, whereas benthic and planktic foraminiferal delta13C values decreased and benthic values were lowest in the Southern Ocean. Subsequently, benthic foraminiferal delta18O values in the Indo-Pacific decreased, and benthic and planktic delta13C values increased globally. These isotopic patterns suggest that cool intermediate-depth waters, derived from high-latitude regions, penetrated temporarily to the tropics. The low benthic delta13C values at the Southern Ocean sites, however, suggest that these cool waters may have been derived from high northern rather than high southern latitudes. Correlation with eustatic sea-level curves suggests that sea-level change was the most likely mechanism to change the circulation and/or source(s) of intermediate-depth waters. We thus propose that oceanic circulation during the latest Cretaceous was vigorous and that competing sources of intermediate- and deep-water formation, linked to changes in climate and sea level, may have alternated in importance.
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We present new isotopic and micropaleontological data from a depth transect on Shatsky Rise that record the response of the tropical Pacific to global biotic and oceanographic shifts during the mid-Maastrichtian. Results reveal a coupling between the upper ocean, characterized by a weak thermocline and low to intermediate productivity, and intermediate waters. During the earliest Maastrichtian, oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the North Pacific. Isotopic shifts through the early Maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the Southern Ocean. Although the cooler water mass remained dominant through the remainder of the Maastrichtian, it was displaced intermittently at shallow intermediate depths by North Pacific intermediate water. The globally recognized "mid-Maastrichtian event" ˜69 Ma, manifested by the brief appearance of abundant inoceramid bivalves over shallow portions of Shatsky Rise, is characterized by an abrupt increase (˜2°-3°C) in sea surface temperatures, a greater flux of organic matter out of the surface ocean, and warmer (˜4°C) intermediate waters. Results implicate simultaneous changes in surface waters and the sources/distribution patterns of intermediate water masses as an underlying cause for widespread biotic and oceanographic changes during mid-Maastrichtian time.
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An outer shelf upper slope tropical Tethyan pelagic environment existed over southern Israel during Maastrichtian time. Planktic foraminifera in the >63 and >149 mum size fractions from four sections in this area were studied quantitatively for a high-resolution ecostratigraphic analysis of the pre Cretaceous-Tertiary (K-T) paleoenvironment. During the Maastrichtian, 41% of the planktic foraminifera species became extinct, mostly keeled Globotruncanidae, which also became quantitatively reduced near the end of the Maastrichtian from as much as 35% to only 5% of the planktic foraminifera population. Evolutionary replacement of extinct species by new forms nearly ceased in that interval. Two major opportunistic blooms of Guembelitria took place, associated with reduced abundances of keeled forms and the dominant species Heterohelix globulosa. The first bloom occurred within the upper Gansserina gansseri to lower Abathomphalus mayaroensis Zones and the second within the Plummerita hantkeninoides Zone. The extinctions, concomitant changes in faunal dominance, and opportunist blooms indicate that the pelagic ecosystem in the Negev area experienced multiple stresses during the Maastrichtian. The planktic foraminiferal assemblages were taxonomically impoverished and in decline prior to the K-T boundary crisis.
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The sedimenlology and sequence stratigraphy of deposits spanning the Cretaceous-Palaeogene boundary on the Brazos River are described and reinterpreted. A channelled erosion surface (channels up to 1.5 m deep), locally burrowed, at the summit of the Corsicana Clay is identified as a putative sequence boundary, was formed by very late Maastrichtian sea-level fall. The erosion surface is overlain by a transgressive lag conglomerate which incorporates phosphatized hiatus concretions and clasts derived from the Corsicana Clay, set in a shelly, glauconitic sand matrix. As transgression continued, fining-upward sands infilled the channels and progressively onlapped onto the basal disconformity with the Corsicana. The sands have features diagnostic of storm deposition and up to five discrete beds can be identified. Between storm events, the surfaces of successive sands were colonized by infauna to create dwelling burrows, including Ophiomorpha, Thalassinoides and Planolites. Burrows were subsequently truncated by storm-generated erosion. The highest transgressive deposits are calcareous silts, which are overlain by a burrowed omission surface that coincides with the micropalaeontologically defined K-T boundary. The lowest Danian sediments are silty clays deposited during a highstand. Thus, the Brazos succession, rather than representing a single depositional event generated by a tsunami, as has been claimed, was the product of normal shelf processes under the control of sea-level change. Evidence for bolide impact in the Late Maastrichtian here is provided by the occurrence of pseudomorphs after microspherules (presumably microtektites) in the basal conglomerate of the Kincaid Formation, and positive excursions in iridium content close to the micropalaeontological K-T boundary. However, these levels are separated by at least six discrete burrowed horizons which represent a considerable period of time, and it is therefore impossible that the microspherules and iridium were products of the same impact event. Thus, the succession, exposed on the Brazos River, alongside broadly similar successions exposed in northern Mexico, has implications for the currently accepted K-T boundary impact scenario.
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Concern about the effects of global change on our planet's future has driven much research into the last few thousand years of earth history. In contrast, this volume takes a much longer viewpoint to provide a historical perspective to recent and future global change. Over 40 international specialists investigate the reaction of life to global environmental changes, from Cretaceous times to the turn of the century. During this time earth's climate has changed from a very warm, 'greenhouse' phase with no significant ice sheets to today's 'ice-house' world. A wide spectrum of animal, plant and protistan life is discussed, encompassing terrestrial, shallow-marine and deep-marine realms. Each chapter considers a particular taxonomic group, looking first at the general picture and then focusing on more specialized aspects such as extinctions, diversity and biogeography. This volume will form an invaluable reference for researchers and graduate students in paleontology, geology, biology, oceanography and climatology.
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Investigation of Campanian-Maastrichtian planktic foraminifera in north Tunisia reveals that the late Maastrichtian not only ends with a mass extinction, but also attains maximum species diversity during their evolutionary history. Maximum species diversity is reached during global cooling in the early late Maastrichtian over a 600 kyr interval (69.1-69.7 Ma) when species richness nearly doubled with the evolution of many rugoglobigerinids and globotruncanids. No species extinctions occur at this time and there is little change in the relative abundance of existing species, whereas new species did not evolve into numerically large populations during the succeeding late Maastrichtian. This suggests that species originations did not result in major competition and that the early-late Maastrichtian climatic cooling may have resulted in increased habitats and nutrient supply for marine plankton. The onset of the permanent decline in Cretaceous species richness began at 65.9 Ma and accelerated during the last 50-100 kyr of the Maastrichtian, culminating in the mass extinction of all tropical and subtropical taxa at the end of the Maastrichtian. Climate changes appear to be responsible for both the rapid evolutionary activity in the early late Maastrichtian, as well as the gradual decline in species richness near the end of the Maastrichtian, although the additional stress imposed on the ecosystem by a bolide impact is the likely cause for the final demise of the tropical and subtropical fauna at the K-T boundary.
Article
Maastrichtian sediments exposed in the Bay of Biscay region at coastal sections at Zumaya and Sopelana, northern Spain, and Hendaye and Bidart, France, yield the most diverse Upper Maastrichtian ammonite faunas yet recovered. Thirty-two species/subspecies referred to 21 genera are described, one of which, Anapachydiscus terminus is new. The ranges of all taxa are fully documented and provide the basis for a four-fold division of the uppermost Campanian and Maastrichtian, with zones of Pseudokossmaticeras tercense (oldest), Pachydiscus (P.) epiplectus, Anapachydiscus fresvillensis, and A. terminus (youngest). This represents the most refined, and first properly documented, ammonite zonation for the Maastrichtian of western Europe, and can be directly correlated with the belemnite zonation developed for the white chalks of northern Europe. The extinction of the last ammonites, documented here, occurred at relatively high standing diversity and appears to have been sudden and catastrophic. -Authors
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A series of iridium anomalies and microtektite-bearing layers indicative of extraterrestrial impact events have been found in late Eocene sediments in the deep sea. Previously, these deposits had been reported to be approximately synchronous with major extinction events in groups of both terrestrial and marine organisms. Highresolution biostratigraphic studies, though, have failed to find any direct evidence for association between impact-derived materials and species extinctions in individual stratigraphic sequences. In addition, stable isotopic studies of the deep-sea record reveal abundant evidence for an episode of major climatic change beginning in the middle Eocene and continuing through the Oligocene. A new analysis of patterns of taxic richness, extinction rates, and origination rates in 17 Eocene through Oligocene planktic foraminiferal biozones indicates that relatively high numbers of planktic foraminiferal taxic extinctions are not confined to the Eocene/Oligocene boundary, or to biozones containing impact ejecta (e.g., microtektite layers, Ir anomalies). Instead, virtually all middle Eocene through middle Oligocene biozones are characterized by broadly comparable numbers of taxic extinctions. However, analysis of relative abundances of individual species and patterns of morphometric variation in middle and late Eocene populations of planktic foraminifera suggest that impacts may have had substantial and long-lasting effects on the dynamics of local populations within areas of direct environmental perturbation. In order to understand the local biotic effects and potential evolutionary role of events such as extraterrestrial impacts, it is important that detailed analyses of species- and population-level patterns of morphological variation and faunal turnover proceed in concert with coarser grained investigations so that patterns of variation can be compared on a wide variety of taxonomic and stratigraphic scales (e.g., species-level versus family-level taxonomic resolution, biozone-level versus stage-level stratigraphic resolution).
Article
A number of studies concerning shell-size changes of bivalves in time and space are reviewed from an ecological viewpoint. Although various environmental factors may influence the body size of organisms, recent knowledge of deep-sea and submarine cave faunas indicates that food supply is of prime importance as a factor controlling the adult size and adaptive strategy of bivalves. Significant shell-size reduction of bivalves seems to have occurred at the same time with P/Tr and T/R mass extinctions, probably because large-sized species (or groups) were more or less selectively eliminated. I present here a hypothesis that oligotrophic conditions (especially reduction of primary production on a global scale) are responsible for these mass extinctions, even if such a condition may arise from various geologic and astronomical events.
Article
One of the richest and best preserved late Campanian-Maastrichtian ammonite faunas of the world occurs within the Lopez de Bertodano Formation on Seymour Island. The excellent exposure of this sequence has offered an opportunity for detailed stratigraphic study of the fauna, providing a stratigraphic control unavailable for most other Southern Hemisphere strata of similar age. Ammonites are restricted to the Cretaceous portion of the Lopez de Bertodano Formation, becoming more abundant and increasing in diversity within a 600-m interval below the Cretaceous-Tertiary boundary. The ammonite-rich levels are divided into three zones (from oldest to youngest: Pachydiscus ootacodensis, P. riccardi and P. ultimus zones), extending from the late Campanian-Maastrichtian to the latest Maastrichtian. The taxonomic study of this fauna shows a predominance of endemic taxa of the family Kossmaticeratidae, including the species Maorites tuberculatus Howarth, M. seymourianus (Kilian and Reboul), M. densicostatus (Kilian and Reboul), M. weddelliensis n. sp., Grossouvrites gemmatus (Huppe) and Gunnarites bhavaniformis (Kilian and Reboul). These taxa, together with the members of the family Desmoceratidae Kitchinites ( Kitchinites ) darwini (Steinmann) and K. ( K. ) laurae n. sp., are mostly restricted to the margins of the Late Cretaceous Weddellian Province that extended from southern South America to Australia. Cosmopolitan genera described in this work become more abundant up section and include the species Anagaudryceras seymouriense n. sp., Zelandites varuna (Forbes), Pseudophyllites loryi (Kilian and Reboul), Diplomoceras lambi Spath, Pachydiscus ( Pachydiscus ) ootacodensis (Stoliczka), P. ( P. ) riccardi n. sp. and P. ( P. ) ultimus n. sp.
Article
Inoceramus gradually declined in abundance over a narrow stratigraphie interval of the Maastrichtian Stage and apparently went extinct synchronously across a wide range of depths and facies near the Globotruncana ganserril Abathomphalus mayaroensis planktonic foram zonal boundary, well before the K/T boundary. This conclusion is based largely on the observed numeric density of prismatic shell fragments of Inoceramus through eight stratigraphie sections. If care is taken to minimize the possibility of contamination through physical and biological reworking, prism density seems to follow Inoceramus density and could be a powerful new biostratigraphic tool.
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In the Gulf of Mexico area, Cretaceous-Tertiary sections are characterized by a rather unusual depositional sequence. The lithological units, which are not all present in all sections, are a bed of spherules containing rare glass particles, succeeded by a sandstone, with a rather thick series of marly ripple beds at the top. Ir and Ni-rich spinels, markers derived from extraterrestrial material, are found only in the uppermost part of the sequence. The clear stratigraphical separation of the units and the late deposition of the cosmic markers are not easily explained by a single collisional event. Tentatively, we propose a multiple collision process resulting from the fragmentation of a single-incident bolide, colliding with the Earth at grazing incidence, with ricochet and rebound of fragments.
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The evolution of planktonic foraminifers in the Cretaceous shows pulses of diversification and stasis interrupted by brief extinction events and faunal turnover. The overall record shows a threefold pattern; from the early Valanginian to the latest Aptian/ Albian boundary, then to the latest Albian, and finally, to the end of the Cretaceous. The pattern of evolution in the first and second intervals is similar and is characterized by increasing diversity, size, and morphologic complexity. The third interval differs in pattern and shows short periods of rapid diversification and turnover separated by longer periods of stasis. We equate these evolutionary changes to parallel changes in the physical and chemical structure of the Cretaceous ocean. The first and second intervals represent the progression from a mixed, eutrophic, upper-water column to the development of a thermocline, stratification, and nichepartitioning in an oligotrophic column. The third interval is more complex and is characterized by periods of mixing and stability above the thermocline probably controlled by climatic conditions and nutrient runoff, and by the development of welldefined latitudinal bioprovinces in the Campanian and Maastrichtian. This overall record is interrupted by five events of paleoceanographic significance. Three of the events, the Selli Event in the early Aptian, the Aptian/Albian boundary event, and the Bonarelli Event in the latest Cenomanian, are defined by the deposition of organic carbon-rich sediment. The fourth, or Santonian event, precipitated the largest foraminiferal turnover during the Cretaceous, affecting all planktonic foraminiferal trophic groups. This event also ushered in a Cretaceous ocean with modern attributes. The fifth event was the catastrophic extinction at the end of the Cretaceous that terminated the Mesozoic Era. Each of these events shows evidence of upper-water column disruption likely related to increased upwelling.
Article
The Cretaceous/Tertiary boundary interval in east-central Texas contains a nannofossil succession that indicates continuous deposition from the late Maastrichtian to the Paleocene. Along the Brazos River the Kemp Clay contains nannofossils characteristic of the uppermost Maastrichtian Micula murus Zone. The overlying Kincaid Formation contains a rapid succession of basal Paleocene assemblages initially dominated by Thoracosphaera, then followed by Braarudosphaera bigelowii. Both are probably disaster forms. Next follows a serial introduction and dominance of the Paleocene species--Biscutum romeinii, Cruciplacolithus primus, Biscutum parvulum and Toweius petalosus. This succession is virtually identical with that found in Cretaceous/Tertiary boundary intervals judged to be continuous. In the nearby Littig Quarry section continuous deposition cannot be demonstrated, however. The Brazos River section speaks against a major sea level change at the Cretaceous/Tertiary boundary; the floral turnover occurs in uniformly marly sediments which lack evidence for any change in sedimentary regime such as would be associated with a significant sea level drop. The zonal succession in east-central Texas correlates well with the hemipelagic successions in Spain and in Tunisia, but less perfectly with holopelagic or the high latitude sections. A potential marker, Prediscosphaera quadripunctata, is particularly well developed in Texas and in the corresponding interval of the El Kef section of Tunisia.