Abrupt and short-lived "impact winter" conditions have commonly been implicated as the main mechanism leading to the mass extinction at the Cretaceous-Paleogene (K-Pg) boundary (ca. 66 Ma), marking the end of the reign of the non-avian dinosaurs. However, so far only limited evidence has been available for such a climatic perturbation. Here we perform high-resolution TEX 86 organic paleothermometry on three shallow cores from the New Jersey paleoshelf, (northeastern USA) to assess the impact-provoked climatic perturbations immediately following the K-Pg impact and to place these short-term events in the context of long-term climate evolution. We provide evidence of impact-provoked, severe climatic cooling immediately following the K-Pg impact. This so-called "impact winter" occurred superimposed on a long-term cooling trend that followed a warm phase in the latest Cretaceous.

The Cretaceous/Paleogene (K/Pg) mass extinction was associated with a collapse in the carbon isotopic (δ 13 C) gradient between planktonic and benthic foraminifera and a decrease in bulk carbonate δ 13 C values. These perturbations have been explained by several hypotheses: global collapse of primary productivity (Strangelove Ocean), greatly reduced export but not primary productivity (Living Ocean), little or no reduction in export productivity (Resilient Ocean), and geographic heterogeneity in the change of export productivity (Heterogeneous Ocean). We tested primary versus export productivity changes in the paleoshelf of New Jersey, where δ 13 C values and organic carbon accumulation rates can distinguish among different ocean responses. On the shelf, the K/Pg boundary is associated with a~2.5‰ δ 13 C decrease in bulk carbonate, a~0.8‰ δ 13 C decrease in organic carbon, a collapse of the surface to bottom δ 13 C gradient, and a drop in organic carbon accumulation rates. We interpret an early Danian~1.0‰ planktonic foraminiferal δ 13 C gradient, a~0.75‰ cross-shelf benthic foraminiferal δ 13 C gradient, and a drop in carbon accumulation rates to reflect the presence of active primary but limited export productivity, consistent with the Living Ocean hypothesis. We evaluated interbasinal deep-sea benthic foraminiferal δ 13 C gradients between the Pacific (Site 1210) and Atlantic (Site 1262) oceans as a proxy for changes in export productivity. The interbasinal δ 13 C gradient was reduced after the mass extinction, suggesting a reduction in global export productivity. Although our data support the Living Ocean hypothesis, evidence from paleoupwelling zones shows significant export productivity, indicating spatial heterogeneity in the wake of the K/Pg mass extinction (Heterogeneous Ocean).

The Cretaceous-Paleogene (K/Pg) boundary in the Haymana Basin, Central Anatolia, Turkey, was delineated using planktonic foraminiferal biostratigraphy, microfacies analysis, and sequence stratigraphy. An , 29 m outcrop consisting of limestone and marl was measured, and four planktonic foraminiferal biozones were identified spanning the boundary. Planktonic foraminiferal extinction across the K/Pg boundary was catastrophic and abrupt. The extinction level is overlain by a unit (Zone P0) showing an increase in echinoid fecal pellets and authigenic clay minerals such as glauconite, suggesting low sedimentation rates in the early Danian. Ten microfacies types were identified indicating inner-ramp to basinal paleoenvironments based on the sedimentological characteristics and microfossil and macrofossil assemblages. Maastrichtian carbonates contain large benthic foraminifera, calcareous red algae, bryozoans, fragments of echinoderms and mollusks, and planktonic foraminifera. Overlying Maastrichtian-Danian silty marls and silty limestones have common planktonic and benthic foraminifera. Progradation of carbonates into the basin took place during the highstand systems tract, and deposition of a silty marl succession occurred during the transgressive systems tract. The K/Pg boundary is in the upper part of the transgressive systems tract, below a maximum flooding surface. Sequence stratigraphic analysis of a second section, Campo Pit, New Jersey, USA, showed that the K/Pg boundary occurs within a transgressive systems tract in New Jersey as well, suggesting a global sea-level rise across the K/Pg boundary.

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20We examined iridium (Ir) anomalies at the Cretaceous/Paleogene (K/Pg) 21 boundary in siliciclastic shallow marine cores of the New Jersey Coastal Plain, USA, that 22 were deposited at an intermediate distance (~2500 km) from the Chicxulub, Mexico 23 crater. Although closely spaced and generally biostratigraphically complete, the cores 24show heterogeneity in terms of preservation of the ejecta layers, maximum concentration 25 of Ir measured (~0.1 ppb -2.4 ppb), and total thickness of the Ir-enriched interval (11 -26 119 cm). We analyzed the shape of the Ir profiles with a Lagrangian particle-tracking 27 model of sediment mixing. Fits between the mixing model and measured Ir profiles, as 28 well as visible burrows in the cores, show that the shape of the Ir profiles was determined 29 primarily by sediment mixing via bioturbation. In contrast, Tighe Park 1 and Bass River 30 cores show post-depositional remobilization of Ir by geochemical processes. There is a 31 strong inverse relationship between the maximum concentration of Ir measured and the 32 thickness of the sediments over which Ir is spread. We show that the depth-integrated Ir 33 inventory is similar in the majority of the cores, indicating that the total Ir delivery at 34 time of the K/Pg event was spatially homogenous over this region. Though delivered 35 through a near-instantaneous source, stratospheric dispersal, and settling, our study shows 36 that non-uniform Ir profiles develop due to changes in the regional delivery and post-37 depositional modification by bioturbation and geochemical processes. 38

The age of the beginning of magnetic polarity Chron M0r, a proposed marker for the base of the Aptian Stage, is disputed due to a divergence of published radioisotopic dates and ambiguities in stratigraphic correlation of sections. Our magnetostratigraphy of core DH1 from Svalbard, Norway, calibrates a bentonite bed, dated by U-Pb methods to 123.1 ± 0.3 Ma, to the uppermost part of magnetozone M1r, which is ~1.9 m.y. before the beginning of Chron M0r. This is the first direct calibration of any high-precision radioisotopic date to a polarity chron of the M sequence. The interpolated age of 121.2 ± 0.4 Ma for the beginning of Chron M0r is younger by ~5 m.y. than its estimated age used in the Geologic Time Scale 2012, which had been extrapolated from radioisotopic dates on oceanic basalts and from Aptian cyclostratigraphy. The adjusted age model implies a commensurate faster average global oceanic spreading rate of ~12% during the Aptian–Santonian interval. Future radioisotopic dating and high-resolution cyclostratigraphy are needed to investigate where to expand the mid-Jurassic to earliest Cretaceous interval by the required ~4 m.y.

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