The marine ecosystem has been severely disturbed by several transient paleoenvironmental events (<200 kyr duration) during the early Paleogene, of which the Paleocene-Eocene Thermal Maximum (PETM, ...~56 Ma) was the most prominent. Over the last decade a number of similar events of Paleocene and Eocene age have been discovered. However, relatively little attention has been paid to pre-PETM events, such as the "Latest Danian Event" ("LDE", ~62.18 Ma), specifically from an open ocean perspective. Here we present new foraminiferal isotope (δ13C, δ18O) and faunal data from Ocean Drilling Program (ODP) Site 1210 at Shatsky Rise (Pacific Ocean) in order to reconstruct the prevailing paleoceanographic conditions. The studied five-meter-thick succession covers ~900 kyr and includes the 200-kyr-lasting LDE. All groups surface dwelling, subsurface dwelling and benthic foraminifera show a negative δ13C excursion of >0.6‰, similar in magnitude to the one previously reported from neighboring Site 1209 for benthic foraminifera. δ18O-inferred warming by 1.6 to 2.8°C (0.4-0.7‰ δ18O measured on benthic and planktic foraminiferal tests) of the entire water column accompanies the negative δ13C excursion. A well stratified upper ocean directly before and during the LDE is proposed based on the stable isotope gradients between surface and subsurface dwellers. The gradient is less well developed, but still enhanced after the event. Isotope data are supplemented by comprehensive planktic foraminiferal faunal analyses revealing a dominance of Morozovella species together with Parasubbotina species. Subsurface-dwelling Parasubbotina shows high abundances during the LDE tracing changes in the strength of the isotope gradients and, thus, may indicate optimal living conditions within a well stratified surface ocean for this taxon. In addition, distinct faunal changes are reported like the disappearance of Praemurica species right at the base of the LDE and the continuous replacement of M. praeangulata with M. angulata across the LDE.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Latest Danian Event (LDE, ~ 62.2 Ma) is characterized by global changes in the carbon cycle as indicated by two negative δ
13
C excursions of up to ~ 1‰. These δ
13
C shifts are accompanied by a ...2–3 °C warming of both surface and deep waters based on benthic and planktic foraminiferal δ
18
O measurements, and the LDE has, thus, been considered as a so-called hyperthermal event. The event lasted for 200 kyr and has been identified in various ocean basins and shallow marine settings. Here, we present a compilation of data from three deep-sea cores covering the Pacific, North and South Atlantic oceans as well as a southern Tethyan shelf section to document the response of planktic foraminifera assemblages to ocean warming. In all studied successions, we observe the disappearance of the planktic foraminifer genus
Praemurica
on a global scale that took place close to the onset of the LDE. Moreover, on the long run, praemuricids were contemporaneously replaced by morozovellids. Both the decline of
Praemurica
and a temperature increase started between 200 and 260 kyr before the LDE onset and were punctuated by the LDE itself. In this paper, we propose two mechanisms that have controlled the environmental changes associated with this event, (1) increased activity of the North Atlantic Igneous Province acting on long time-scales, and (2) changes of orbital parameters resulting in insolation changes on shorter time-scales.
In contrast to a proposed muted benthic foraminiferal response, the planktic community has been substantially impacted by the LDE as indicated by changes in planktic foraminifera faunas and calcareous nannofossils. Finally, our quantitative and conventional approaches identifying stratigraphically important planktic foraminifera datum levels justify a revision of the upper Danian to lower Selandian planktic foraminifera biozonation.
The Latest Danian Event (LDE, c. 62.1 Ma) is an early Palaeogene hyperthermal or transient (<200 ka) ocean warming event. We present the first deep‐sea benthic foraminiferal faunal record to study ...deep‐sea biotic changes together with new benthic (Nuttallides truempyi) stable isotope data from Walvis Ridge Site 1262 (Atlantic Ocean) to evaluate whether the LDE was controlled by similar processes as the minor early Eocene hyperthermals. The spacing of the double negative δ13C and δ18O excursion and the slope of the δ18O–δ13C regression are comparable, strongly suggesting a similar orbital control and pacing of eccentricity maxima as well as a rather homogeneous carbon pool. However, in contrast to early Eocene hyperthermals, the LDE exhibits a remarkable stability of the benthic foraminiferal fauna. This lack of benthic response could be related to the absence of threshold‐related circulation changes or better pre‐adaptation to elevated deep‐sea temperatures, as the LDE was superimposed on a cooling trend, in contrast to early Eocene warming.
The cause of the end-Cretaceous mass extinction is vigorously debated, owing to the occurrence of a very large bolide impact and flood basalt volcanism near the boundary. Disentangling their relative ...importance is complicated by uncertainty regarding kill mechanisms and the relative timing of volcanogenic outgassing, impact, and extinction. We used carbon cycle modeling and paleotemperature records to constrain the timing of volcanogenic outgassing. We found support for major outgassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change. Our models show that these extinction-related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide, thus limiting the global warming otherwise expected from postextinction volcanism.
A number of short warming events occurred during Paleocene and Eocene, of which the “Paleocene-Eocene Thermal Maximum” (PETM, 56 Ma) is the most severe and most investigated event. The less known ...“Latest Danian Event” (LDE) at 62.2 Ma represents a 200 ky-lasting warming phase, superimposed on a long-term cooling trend after the Early Paleocene. South Atlantic ODP Site 1262 data, covering ~1 myr, indicate a warming of the entire water column by 1.5–2.6 °C, accompanying a prominent negative carbon isotope excursion (~0.9–1.1‰) and a long-term re-organization of the planktic foraminiferal fauna associated with the LDE. This study unravels a different paleoceanographic evolution of the upper ocean structure compared to results from Pacific ODP Site 1210. Unlike the Pacific, the Atlantic site lacks an apparent change of stratification as well as an overall dominance of thermocline dwelling planktic foraminifera species and a low abundance of surface dwelling photosymbiotic foraminifera. Within the LDE, indications for a slightly enhanced stratification of the upper water column and transient warming were indicated when surface dwelling planktic foraminifera became temporarily more abundant. The long-term evolution in planktic foraminifera with the disappearance of Praemurica at the LDE onset and a contemporaneous rise in Morozovella is similar to the trends reported from Shatsky Rise ODP Site 1210.
•Paleocene planktic foraminifera faunas from deep-sea ODP Site 1262 (Walvis Ridge)•Some faunal changes and δ13C, δ18O excursions can be directly linked to the LDE.•But other faunal changes are already initiated well below the LDE•Comparison to Pacific site revealed a different evolution of upper ocean structure.
The early Paleogene is characterized by numerous hyperthermals, transient (<200kyr) ocean warming events, of which the Latest Danian Event (LDE, ~62.1Ma) is one of the first. Although the LDE appears ...to be controlled by similar processes as early Eocene hyperthermals, the first open ocean benthic foraminiferal record across the LDE at Walvis Ridge revealed little faunal response. Here, we studied benthic foraminifera from the uppermost abyssal (2000–2500m) ODP Site 1210, Shatsky Rise, Pacific Ocean, to provide a broader view of faunal response to the LDE. Late Danian oligotrophic background conditions are characterized by a Nuttallides umbonifera dominated assemblage. Yet, ~200kyr before the LDE, benthic foraminiferal assemblages, with increased relative abundance of endobenthic morphotypes and benthic foraminiferal accumulation rates indicate a slightly enhanced food flux. A temperature increase ~40kyr before the first carbon isotope excursion (CIE) of the LDE (= LDE1) is associated with a rise in abundance of Tappanina selmensis, suggesting episodic input of fresh phytodetritus. At the start of LDE1, and through the second CIE (= LDE2), the seafloor returned to more oligotrophic conditions. Between 220 and 430kyr after the onset of the LDE, a second phase of episodic fresh phytodetritus input is suggested by a renewed dominance of T. selmensis. Although the patterns of faunal change during hyperthermals relate to local conditions (circulation patterns), the magnitude of faunal change is probably more related to an absolute temperature threshold.
•Nuttallides umbonifera dominates Paleocene assemblages at Site 1210, Shatsky Rise.•Rising food flux ~200kyr before LDE indicated by benthic foraminiferal numbers•~40kyr pre-LDE warming characterized by opportunistic Tappanina selmensis•Oligotrophic LDE core, with high abundances of Bolivinoides huneri•200kyr of dominance of opportunistic Tappanina selmensis after LDE
The Scratchell's Bay and southern Alum Bay sections, in the extreme west of the Isle of Wight on the Needles promontory, cover the stratigraphically highest Chalk Group formations available in ...southern England. They are relatively inaccessible, other than by boat, and despite being a virtually unbroken succession they have not received the attention afforded to the Whitecliff GCR (Geological Conservation Review series) site at the eastern extremity of the island. A detailed account of the lithostratigraphy of the strata in Scratchell's Bay is presented and integrated with macro and micro biostratigraphical results for each formation present. Comparisons are made with earlier work to provide a comprehensive description of the Seaford Chalk, Newhaven Chalk, Culver Chalk and Portsdown Chalk formations for the Needles promontory.
The strata described are correlated with those seen in the Culver Down Cliffs–Whitecliff Bay at the eastern end of the island that form the Whitecliff GCR site. This provides an overall correlation for the Upper Coniacian to Upper Campanian Chalk strata on the island.
The influence of the Purbeck–Wight Structure (Sandown and Brighstone periclines) on the Chalk Group strata is discussed and the conclusions drawn demonstrate that movement on this structure is diachronous across the island.
The Paleocene and early Eocene (~66–40 Ma) is characterised by a number of transient warming events, also named hyperthermals. A more recent candidate for a hyperthermal of Paleocene age is the ...Latest Danian Event (LDE, ~62.2 Ma). So far, the LDE was only poorly explored in few deep-sea records and Tethyan shelf settings. Planktic data characterizing the surface ocean were almost completely missing. In this thesis, it was studied whether the LDE satisfies the requirements for a hyperthermal and the impact on the planktic foraminfera fauna. Samples from three late Danian deep-sea cores (ODP Sites 1210 and 1262, IODP Site U1407) and one Tethyan shelf section (Qreiya 3, Egypt) were investigated in rather high resolution, which, for the first time, allowed to unravel the impact of the LDE, the evolution of the ocean structure and planktic foraminiferal species abundances on an almost global scale. δ18O paleothermometry revealed a temperature rise of 2–4°C affecting the entire water column in all three depth habitats (sea floor, subsurface and surface ocean) and a contemporary negative carbon isotope excusion of 0.6–0.9 ‰ indicates carbon cycle perturbations. Changes in the planktic foraminiferal assemblages indicate a global biotic response to the LDE.
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