Temperature and salinity of the Late Cretaceous Western Interior Seaway (original) (raw)
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Isotopic evaluation of ocean circulation in the Late Cretaceous North American seaway
Nature Geoscience, 2011
During the mid-and Late Cretaceous period, North America was split by the north-south oriented Western Interior Seaway. Its role in creating and maintaining Late Cretaceous global greenhouse conditions remains unclear. Different palaeoceanographic reconstructions portray diverse circulation patterns 1-3. The southward extent of relatively cool, low-salinity, low-δ 18 O surface waters critically distinguishes among these models, but past studies of invertebrates could not independently assess water temperature and isotopic compositions. Here we present oxygen isotopes in biophosphate from coeval marine turtle and fish fossils from western Kansas, representing the east central seaway, and from the Mississippi embayment, representing the marginal Tethys Ocean. Our analyses yield precise seawater isotopic values and geographic temperature differences during the main transition from the Coniacian to the early Campanian age (87-82 Myr), and indicate that the seaway oxygen isotope value and salinity were 2 and 3 lower, respectively, than in the marginal Tethys Ocean. We infer that the influence of northern freshwater probably reached as far south as Kansas. Our revised values imply relatively large temperature differences between the Mississippi embayment and central seaway, explain the documented regional latitudinal palaeobiogeographic zonation 4,5 and support models with relatively little inflow of surface waters from the Tethys Ocean to the Western Interior Seaway 2,3. Global greenhouse conditions during the Late Cretaceous indicate small latitudinal temperature gradients for open ocean surface waters 6,7 , but equivocal surface water conditions in the North American Western Interior Seaway (WIS). Consequently, the role of the WIS in ocean circulation and promoting high-latitude warmth remains unknown. Latitudinal palaeobiogeographic zonation 4,5 indicates meridional variations in one or more environmental conditions (for example, temperature, salinity and sedimentation rate). Direct investigation of WIS temperatures and seawater compositions using shell carbonate δ 18 O (δ 18 O CO3 ; refs 8-10), however, does not independently discriminate seawater temperature (T W) and isotopic composition (δ 18 O W); one must be assumed whereas the other is calculated. Typically assumed δ 18 O W values for Cretaceous oceans (≥ −1.25 ; ref. 7) can result in grossly inaccurate T W (up to 60 • C), and inverse latitudinal and water column temperature gradients (data from refs 8-10). To infer δ 18 O W and temperatures in the east central WIS and southern Mississippi Embayment (Fig. 1), we analysed stable oxygen isotopes of diagenetically resistant vertebrate fossils. We then evaluated competing palaeoceanographic models for Late Cretaceous transgressions, especially the degree to which northern boreal versus Tethyan surface waters flowed across the WIS, potentially affecting circulation and biogeographic zones.
Earth and Planetary Science Letters, 2013
We apply the carbonate clumped isotope thermometer (D 47) to macrofossils from the Baculites compressus ($ 73.5 Ma) and the Hoploscaphites nebrascensis ($ 67 Ma) ammonite zones of the Western Interior Seaway (WIS) of North America, and nearby coeval terrestrial and open marine environments. The carbonate clumped isotope thermometer is based on a single-phase isotope exchange equilibrium that promotes the 'clumping' of two heavy isotopes together within a single carbonate molecule as temperature decreases. Due to the thermometer's isotopic independence from water, coupled measurements of D 47 and the bulk oxygen isotopic composition of a carbonate (d 18 O c) enable the reconstruction of both paleotemperature and the isotopic composition of the water in which the organisms grew. Before applying the technique to the aragonite shells of fossil marine organisms (mostly ammonites, but also some gastropods, bivalves, and one belemnite), we measure the clumped isotopic composition of modern nautilus and cuttlefish, two of the nearest living relatives to the Cretaceous ammonites. Modern cephalopods exhibit disequilibrium isotope effects with respect to D 47 , but not d 18 O c , therefore a simple correctional scheme is applied to the Late Cretaceous macrofossil data before reconstructing paleotemperatures. Diagenesis is also assessed by visual preservation and previously measured Sr concentrations (Cochran et al., 2003). Temperatures reconstructed for the Late Cretaceous Western Interior Seaway range from 16.4 7 3.5 1C for an offshore Interior Seaway environment from the H. nebrascensis zone to 24.2 7 0.4 1C for the B. compressus ammonite zone. The seaway itself has an isotopic composition of approximately À 1% (relative to VSMOW), the expectation for an ice-free global ocean average, while a nearby freshwater environment has an isotopic composition approaching À 20%. We compare the attributes of the reconstructed climate to predictions based on Late Cretaceous climate models and previous reconstructions of the seaway, and also assess the sensitivity of our results to the modern cephalopods correction by comparisons to suitable modern analogs. Finally, our clumped isotope data are consistent with cooling between the Late Campanian and Maastrichtian, as also seen in benthic foraminfera d 18 O.
Warm Middle Jurassic–Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean
Climate of the Past, 2012
Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed dur ing the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of iso topic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEXs6 back to the Middle Juras sic indicates that relatively warm sea-surface conditions (26-30 °C) existed from this interval (~160 Ma) to the Early Cre taceous (~115M a) in the Southern Ocean, with a general warming trend through the Late Jurassic followed by a gen eral cooling trend through the Early Cretaceous. The low est sea-surface temperatures are recorded from around the Callovian-Oxfordian boundary, an interval identified in Eu rope as relatively cool, but do not fall below 25 °C. The early Aptian Oceanic Anoxic Event, identified on the ba sis of published biostratigraphy, total organic carbon and carbon-isotope stratigraphy, records an interval with the low est, albeit fluctuating Early Cretaceous palaeotemperatures (~26°C), recalling similar phenomena recorded from Eu rope and the tropical Pacific Ocean. Extant belemnite S180 data, assuming an isotopic composition of waters inhabited by these fossils of-1 % o SMOW, give palaeotemperatures throughout the Upper Jurassic-Low er Cretaceous interval that are consistently lower by ~1 4 °C than does TEXs6 and the molluscs likely record conditions below the thermocline. The long-term, warm climatic conditions indicated by the TEX86 data would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the M eso zoic Era.
Earth-Science Reviews, 2017
It is well established that greenhouse conditions prevailed during the Cretaceous Period (~145-66 Ma). Determining the exact nature of the greenhouse-gas forcing, climatic warming and climate sensitivity remains, however, an active topic of research. Quantitative and qualitative geochemical and palaeontological proxies provide valuable observational constraints on Cretaceous climate. In particular, reconstructions of Cretaceous sea-surface temperatures (SSTs) have been revolutionised firstly by the recognition that clay-rich sequences can host exceptionally preserved planktonic foraminifera allowing for reliable oxygen-isotope analyses and, secondly by the development of the organic palaeothermometer TEX 86, based on the distribution of marine archaeal membrane lipids. Here we provide a new compilation and synthesis of available planktonic foraminiferal δ 18 O (δ 18 O pl) and TEX 86-SST proxy data for almost the entire Cretaceous Period. The compilation uses SSTs recalculated from published raw data, allowing examination of the sensitivity of each proxy to the calculation method (e.g., choice of calibration) and places all data on a common timescale. Overall, the compilation shows http://dx. MARK many similarities with trends present in individual records of Cretaceous climate change. For example, both SST proxies and benthic foraminiferal δ 18 O records indicate maximum warmth in the Cenomanian-Turonian interval. Our reconstruction of the evolution of latitudinal temperature gradients (low, < ± 30°, minus higher, > ± 48°, palaeolatitudes) reveals temporal changes. In the Valanginian-Aptian, the low-to-higher mid-latitudinal temperature gradient was weak (decreasing from~10-17°C in the Valanginian, to~3-5°C in the Aptian, based on TEX 86-SSTs). In the Cenomanian-Santonian, reconstructed latitudinal temperature contrasts are also small relative to modern (< 14°C, based on low-latitude TEX 86 and δ 18 O pl SSTs minus higher latitude δ 18 O pl SSTs, compared with~20°C for the modern). In the mid-Campanian to end-Maastrichtian, latitudinal temperature gradients strengthened (~19-21°C, based on low-latitude TEX 86 and δ 18 O pl SSTs minus higher latitude δ 18 O pl SSTs), with cooling occurring at low-, middle-and higher palaeolatitude sites, implying global surface-ocean cooling and/or changes in ocean heat transport in the Late Cretaceous. These reconstructed long-term trends are resilient, regardless of the choice of proxy (TEX 86 or δ 18 O pl) or calibration. This new Cretaceous SST synthesis provides an up-to-date target for modelling studies investigating the mechanics of extreme climates .
2000
In recent years, a surge in the amount and quality of paleoclimatic data has renewed interest in Cretaceous climate and ocean dynamics. New data have provided a more precise picture of paleotemperatures and climate variations, and research on Cretaceous climate has entered an exciting, multidisciplinary phase in which geological, geochemical, geophysical and paleontological data can be integrated between marine and terrestrial realms and into modeling studies, with the goal of better constraining the controls on climate change during intervals of overall warmth. In July, 2002, the JOI-USSSP/NSF-sponsored Workshop on Cretaceous Climate and Ocean Dynamics held in Florissant, Colorado, brought together a multinational group of more than 90 scientists (including 16 graduate students) with diverse research interests and expertise. The conference objective was to summarize the current state-of-the-art in our understanding of Cretaceous paleoclimate and to discuss future research priorities. Ocean drilling has been crucial in our advances to date and is a critical priority for the future of research in this field.
Evolving ideas about the Cretaceous climate and ocean circulation
Cretaceous Research, 2008
The Cretaceous is a special episode in the history of the Earth named for a unique rock type, chalk. Chalk is similar to modern deep-sea calcareous ooze and its deposition in epicontinental seas occurred as these areas became an integral part of the ocean. The shelf-break fronts that today separate inshore from openocean waters cannot have existed during the Late Cretaceous probably because the higher sea level brought the base of the wind-mixed Ekman layer above the sea floor on the continental margins. A second peculiarity of the Cretaceous is its warm equable climate. Tropical and polar temperatures were warmer than today. Meridional and ocean-continent temperature gradients were lower. The warmer climate was a reflection of higher atmospheric levels of greenhouse gasses, CO 2 and possibly CH 4 , reinforced by higher water vapor content in response to the warmer temperatures. Most of the additional energy involved in the meridional heat transport system was transported as latent heat of vaporization of H 2 0 by the atmosphere. Poleward heat transport may have been as much as 1 Petawatt (20%) greater than it is today. C 3 plants provided for more efficient energy transport into the interior of the continents. Circulation of the Cretaceous ocean may have been very different from that of today. It is impossible for large areas of the modern ocean to become anoxic, but episodes of local anoxia occurred during the earlier Cretaceous and became regional to global during the middle of the Cretaceous. The present ocean structure depends on constant wind systems, which in turn depend on stability of the atmospheric pressure systems forced by polar ice. During most of the Cretaceous the polar regions were ice free. Without polar ice there were seasonal reversals of the high-latitude atmospheric pressure systems, resulting in disruption of the mid-and high latitude wind systems. Without constant mid-latitude westerly winds, there would be no subtropical and polar fronts in the ocean, no well-developed ocean pycnocline, and no tropical subtropical gyres dominating ocean circulation. Instead the ocean circulation would be accomplished through mesoscale eddies which could carry warmth to the polar regions. Greater knowledge and understanding of the Cretaceous is critical for learning how the climate system operates when one or both polar regions are ice free.
2019
Climate plays a significant role in determining the style of depositional processes at different latitudes, which in turn influences the location of hydrocarbon systems. Results of climate modelling may therefore provide important information for predicting the presence or absence of suitable hydrocarbon plays. The critical step is to validate the model results against proxy data where they are available, to determine whether the models provide realistic results. Paleoclimate proxy data are most often derived from more accessible low to mid latitude regions and are biased towards warm climate states. However, General Circulation Models (GCMs) have traditionally been biased to colder temperatures, in particular at high latitudes, struggling to maintain the high latitude regions warm enough to sustain forests that were present during greenhouse periods, such as the mid-Cretaceous (~110-90 Ma), without exaggerated warming of the equatorial regions. To
Palaeogeography, Palaeoclimatology, Palaeoecology, 2003
Well-preserved fossils of the Late Cretaceous Western Interior Seaway (WIS) of North America have been analyzed for Sr concentration and Sr and O isotopes in order to decipher paleosalinities and paleotemperatures. The samples are from four biofacies within the Seaway (late Maastrichtian): offshore Interior (Pierre Shale), nearshore Interior (Fox Hills Formation), brackish (reduced salinity; Fox Hills Formation) and freshwater (Hell Creek Formation). Samples were also obtained from the Severn Formation of Maryland (considered to be representative of the open ocean). All biofacies (except the freshwater) are demonstrably within the Jeletzkytes nebrascensis ammonite zone (6 1 Ma duration). The 87 Sr/ 86 Sr ratios show significant and systematic decreases from marine (mean þ 1 S.D. = 0.707839 þ 0.000024) to brackish facies (mean þ 1 S.D. = 0.707677 þ 0.000036), consistent with dilution by freshwater with a lower 87 Sr/ 86 Sr ratio than seawater. Such variation disallows using the 87 Sr/ 86 Sr ratios of fossil shell material to assign ages to fossils from the Late Cretaceous WIS without knowledge of the salinity in which the organism grew. The Sr isotope ratios for scaphitid ammonites within a single biofacies are similar to each other and different from those for scaphites in other biofacies, implying that these organisms are restricted in their distribution during life. The 87 Sr/ 86 Sr values of freshwater unionid mussels range widely and are not compatible with the freshwater endmember 87 Sr/ 86 Sr ratio required by the trend in 87 Sr/ 86 Sr vs. biofacies established from the other samples. Paleosalinities for the biofacies are estimated to range from 35x in the open marine to a minimum of 20x in the brackish, based on the presence of cephalopods in all four facies and the known salinity tolerance of modern cephalopods. Producing reasonable 87 Sr/ 86 Sr values for the freshwater endmember of a 87 Sr/ 86 Sr vs. 1/[Sr] plot requires a Sr concentration 0.2^0.5 that of seawater for the dominant freshwater input to the WIS. Such high Sr concentrations (relative to seawater) are not observed in modern rivers, and we suggest that the brackish environment in the WIS arose through the mixing of freshwater and seawater in a nearshore aquifer system. Reactions of the solution with aquifer solids in this 'subterranean estuary' [Moore, Mar. Chem. 65 (1999) 111^125] produced brackish water with the Sr concentration and isotopic composition recorded in the brackish biofacies. N 18 O values of the fossils
Earth-Science Reviews, 2018
Deoxygenation is a critical problem facing the ocean as the world warms, and has the potential to effect coastal upwelling zones, shelf areas influenced by high runoff and nutrification, and restricted and semi-restricted basins. The mechanisms that drive deoxygenation in these diverse environments are still not fully understood, in part because the modern record of redox change is short and anoxia is still relatively rare in the modern ocean. Here, we address this problem of scale by studying deoxygenation in the geologic past. We summarize decades of individual studies of benthic foraminifera to generate a record of bottom water oxygen change in the Cretaceous Western Interior Sea (WIS) of North America over ~13 myr (Cenomanian-Campanian), spanning two major sea level cycles. The WIS was prone to major changes in dissolved oxygen content throughout its long history, sometimes directly antiphase to trends in the global ocean. Presented as maps, our data show that bottom water oxygen within the WIS was controlled by a combination of water mass source and mixing moderated by sea level and basin restriction. Areas flooded by cool Boreal (northern-sourced) waters in the northern and western parts of the seaway were better oxygenated than the eastern and southern portions of the seaway, which were flooded by warmer Tethyan (southern-sourced) waters. Beyond east-west differences explained by water mass, the entire seaway was better oxygenated during periods of transgression, and more poorly oxygenated to anoxic during periods of peak transgression/highstand and regression. We suggest that this pattern was due to the formation and downwelling of Western Interior Intermediate Water by the mixing of Tethyan and Boreal waters. During transgressions, an increasing volume of these watermasses entered the 3 seaway, mixed, and downwelled well-oxygenated surface water to the seafloor. During late transgression/highstand, partial stratification and the encroachment of low oxygen waters from the open ocean caused dissolved oxygen levels to drop at the seafloor, but continued downwelling prevented anoxia. During the subsequent regression, a decline in the volume of outside watermasses entering the seaway caused a reduction in mixing and weakened downwelling which led to stratification and seafloor anoxia. As a model for other semi-restricted basins, the trends observed in the WIS show that local changes in relative sea level, mixing, and circulation are critical in controlling oceanic deoxygenation in these environments, in clear contrast to continental margins impinged by oxygen minimum zones, like the contemporaneous Demerara Rise in the southern Caribbean. Although the WIS is larger than most semi-restricted basins, it is characterized by quasi-estuarine circulation driving the interaction of normal marine and brackish watermasses, and thus serves a model for similar shallow epicontinental basins of any size. Understanding how these processes vary in different environments is key to predicting susceptibility of regional water bodies to deoxygenation in the future with a warming world.
To address the limited temporal and spatial context of earlier paleogeographic studies of the Western Interior Seaway (WIS), we provide a broad overview of the paleogeographical history of this epeiric sea and the basin it filled by synthesizing available data from detailed analyses of lithostratigraphic sections, isopach maps, as well as biostratigraphic and biogeographic distributions. The Early Cretaceous to Paleocene WIS connected the Arctic Ocean with the Gulf of Mexico and was likely episodically linked to the Atlantic Ocean via the Hudson Seaway. The paleogeography of the WIS primarily reflects the interplay between sea level and physiography, which were controlled by eustasy, tectonics, and pre-existing topographic features. The Western Interior Foreland Basin (WIFB) initiated in the MiddleLate Jurassic with the subduction of Panthalassan crust beneath the North American plate which resulted in a continental margin arc-trench system and the Cordilleran Orogenic Belt. The deformation front of the Cordillera migrated progressively eastward forcing a cratonward (i.e., eastward) shift in marine sedimentation throughout its history. Several punctuated Albian marine transgressions in the WIFB were restricted to the northern part of the basin due to low sea level compounded by its physiography. The first marine connection of the WIS linking the Arctic Ocean and the Gulf of Mexico occurred during the late Albian as a response to a eustatic rise, together with increased basin subsidence. The sea's north-south connectivity was lost during lower sea levels, but, once established in the middle Cenomanian, persisted at least until the early Maastrichtian and possibly into the Paleocene. The onset of the Laramide Orogeny that broke the WIFB into a series of smaller intermountane basins along with a drop in sea-level caused the final withdrawal of the WIS from North America during the Paleocene.