Timing and causes of forest fire at the K–Pg boundary

Abstract

We report K–Pg-age deposits in Baja California, Mexico, consisting of terrestrial and shallow-marine materials re-sedimented onto the continental slope, including corals, gastropods, bivalves, shocked quartz grains, an andesitic tuff with a SHRIMP U–Pb age (66.12 ± 0.65 Ma) indistinguishable from that of the K–Pg boundary, and charred tree trunks. The overlying mudstones show an iridium anomaly and fungal and fern spores spikes. We interpret these heterogeneous deposits as a direct result of the Chicxulub impact and a mega-tsunami in response to seismically-induced landsliding. The tsunami backwash carried the megaflora offshore in high-density flows, remobilizing shallow-marine fauna and sediment en route. Charring of the trees at temperatures up to > 1000 °C took place in the interval between impact and arrival of the tsunami, which on the basis of seismic velocities and historic analogues amounted to only tens of minutes at most. This constrains the timing and causes of fires and the minimum distance from the impact site over which fires may be ignited.

Full text

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Timing and causes of forest re
at the K–Pg boundary
A. Santa Catharina1,2, B. C. Kneller1*, J. C. Marques3, A. D. McArthur4,
S. R. S. Cevallos‑Ferriz5, T. Theurer1, I. A. Kane6 & D. Muirhead1
We report K–Pg‑age deposits in Baja California, Mexico, consisting of terrestrial and shallow‑marine
materials re‑sedimented onto the continental slope, including corals, gastropods, bivalves, shocked
quartz grains, an andesitic tu with a SHRIMP U–Pb age (66.12 ± 0.65 Ma) indistinguishable from that
of the K–Pg boundary, and charred tree trunks. The overlying mudstones show an iridium anomaly
and fungal and fern spores spikes. We interpret these heterogeneous deposits as a direct result of the
Chicxulub impact and a mega‑tsunami in response to seismically‑induced landsliding. The tsunami
backwash carried the megaora oshore in high‑density ows, remobilizing shallow‑marine fauna
and sediment en route. Charring of the trees at temperatures up to > 1000 °C took place in the interval
between impact and arrival of the tsunami, which on the basis of seismic velocities and historic
analogues amounted to only tens of minutes at most. This constrains the timing and causes of res
and the minimum distance from the impact site over which res may be ignited.
e consensus is that the Chicxulub bolide impact was at least partially responsible for the Cretaceous–Paleogene
boundary extinction event, e.g.,1–3, and references therein] and associated profound climatic changes, e.g.,4–6.
Schulte etal.7 identied a pattern of decreasing ejecta thicknesses with distance from the impact site consistent
with it being the single source, e.g.,8,9. is interpretation is also supported by the distribution, composition, and
depositional characteristics of the ejecta1,10–13.
Continental margin localities proximal to the impact site and on the North Atlantic margin of North America
show evidence of large-scale mass wasting, e.g.,11,14,15; an iridium anomaly is oen observed immediately above
the mass ow deposits, associated with other ejecta such as spherules and shocked minerals, e.g.,7. ere is also
evidence of global-scale res in the form of soot16,17, though there has been considerable debate over the exact
nature, timing and proximate cause of these res.
e upper Campanian to lower Danian Rosario Formation near the town of El Rosario on the western side of
the Baja California peninsula, c. 300km south of the US/Mexico border (Fig.1)21,22, comprises c. 1200m of deep-
marine sedimentary rocks23,24, and references therein]. It includes several slope channel systems and submarine
landslide deposits within background hemipelagic slope mudstones, little faulted and with very low dips, e.g.
25,26, (Fig.2). is west-facing continental margin in the Upper Cretaceous was oriented similarly to the modern
coastline, with a shoreline approximately 25km east of its current location27, where shallow marine sediments
onlap a Lower Cretaceous arc succession. e study area represents the upper slope, with a slope angle of 3.5 to
7°, estimated from water depth (1500–3000m based on benthic foraminiferal assemblages28); and distance to
the contemporaneous shoreline (c. 25km to NE27).
is sequence includes a previously undocumented ≤ 60m package recording catastrophic re-sedimentation
events. e occurrence of terrestrial material (charred tree trunks) and shallow-water micro and macro fauna
(corals, gastropods, and bivalves) is in marked contrast to the enclosing bathyal succession25,26,28. We rst present
previously undescribed geological, palaeontological, palynological, and geochemical evidence from this relatively
impact-proximal (2500km) setting to show that this represents the K–Pg boundary succession. It demonstrates
the burning of live trees at temperatures consistent with crown res before the arrival of animpact-related tsu-
nami (the rst described from the Pacic margin) that displaced them into deep water on the continental slope.
Finally, we discuss the implications for the timing, causes and distance from impact site of wildres.
OPEN
1School of Geosciences, University of Aberdeen, Aberdeen AB23 3UE, UK. 2ITT Oceaneon, Universidade do Vale
do Rio dos Sinos, Sao Leopoldo 93020-190, Brazil. 3Instituto de Geociências, Universidade Federal do Rio Grande
do Sul, Porto Alegre, RS 90650-001, Brazil. 4School of Earth and Environment, University of Leeds, Leeds LS2
9JT, UK. 5Universidad Autónoma de México, 04510 Ciudad de México, Mexico. 6Department of Earth and
Environmental Sciences, University of Manchester, Manchester M169PL, UK. *email: b.kneller@abdn.ac.uk
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Results
e Maastrichtian/Danian boundary has been mapped in the region as an erosive surface23, and wherever the
Maastrichtian–Palaeocene boundary can be seen in this area it is truncated by km-scale, low-angle slide surfaces,
commonly overlain by slide blocks (Fig.2). e sedimentary package lying above these surfaces and associated
blocks contrasts with the sequences above and below in consisting of pebbly mudstones, locally with shallow-
marine foraminifera, horizons rich in terrestrial and shallow-water fossils, and a tu (Fig.2). ey are immedi-
ately succeeded by hemipelagic Danian deposits. No nannofossils or planktic foraminifera were encountered in
this package, and benthic foraminifera are decalcied.
Unit A (pebbly mudstone with fossil wood). e lowest unit is a ≤ 6m-thick pebbly mudstone (thin-
ning to both NW and SE; Fig.2). Charcoalied sub-cm plant fragments comprise 5% of the deposit in a
clay-rich matrix. Sparse rounded granules and pebbles of crystalline rock occur throughout. It is distinctive in
containing fossilized fragments of tree trunks, including Pinaceae, Cupressaceae and Lauraceae (the new spe-
cies Rosarioxylon bajacaliforniensis Cevallos-Ferriz29). e specimens are ≤ 1.5m in diameter and up to 3m in
length, larger and more common at the base, distributed every few meters horizontally along the outcrop, form-
ing a Lagerstätte. Preservation is exceptional, with nodes and broken branch stumps, bark commonly attached
and visible growth rings (Fig.3A,B). Vascular, epithelial oil/mucilage cells, resin canals and ducts, rays and pits
are also well preserved29.
Parts of these trunks are charred, with portions of bark and cambium completely charcoalied but still
attached to the rest of the trunk (Fig.3C,D), suggesting very little reworking and rapid burial. e internal
wood below the distinct charring layer appears uncharred/unaltered and shows no evidence of decay prior to
burning. e absence of bio-erosion, such as Teredolites30, also suggests negligible post-mortem residence time
at air/water and water/sediment interfaces.
Around 70% of the palynomorphs are dinocysts and acritarchs, including the Cretaceous markers Dinogym-
nium spp. and Yolkinigymnium spp. (cf31.). e bulk of plant palynomorphs are angiosperm pollens and pteri-
dophyte spores with clear Mesozoic forms (Fig.4A,B. Spore color indicates burial of < 1km. No foraminiferal
tests were found in this unit (Supplementary Information, Fig. S2 and tablesS2-S3).
Unit B (pebbly mudstone). is ≤ 8m thick unit thins towards NW and SE (Fig.2) and overlaps Unit A,
overlying it via a transition over a few cm, containing more silt, less clay (~ 55%) and only sparse sub-dm frag-
ments of plant material. It includes similar granules and pebbles, concretions (≤ 10cm in diameter), convolute
bedding and so-sediment folds.
Shallow-water benthic foraminifera such as miliolids and lagenids (Fig.4C,D), cf. Midway Fauna, Gulf of
Mexico (GoM)32, indicate re-deposition of shelfal and/or upper slope sediments. Unit B yielded few palyno-
morphs; like Unit A, dinocysts are dominant, but fewer acritarchs were observed. Bryophyte, angiosperm and
pteridophyte spores are present.
Figure1. (A) location map of the study area(georeferenced and vectorized from Google Earth Pro (2022):
https:// www. google. com. br/ earth/ about/ versi ons/), using ArcMap 10.7: https:// www. esri. com/ en- us/ arcgis/
produ cts/ arcgis- deskt op/ resou rces); (B) paleogeographic reconstruction of Gulf of Mexico and Baja California
Pacic margintaken from Stéphan etal.18, andHelenes & Carreño19; using ArcMap 10.7:https:// www. esri. com/
en- us/ arcgis/ produ cts/ arcgis- deskt op/ resou rces), with location of this study, Chicxulub crater, and impact-
related slumps, faults, slides, and tsunami deposits (compiled by Vellekoop etal.20).
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Figure2. Log correlation of K–Pg-related deposits; main lithologies, structures, and fossils, within upper
Maastrichtian and lower Danian hemipelagic mudstones. Panel is hung on correlative horizons that are present
in three or more sections. Penecontemporaneous conglomerate deposits are unrelated to the K–Pg event and
form part of channel systems that are ubiquitous in this stretch of the Pacic margin. Base map generated
from: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN,
Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors,
and the GIS User Community. Map produced using ArcMap 10.7: https:// www. esri. com/ en- us/ arcgis/ produ cts/
arcgis- deskt op/ resou rces.
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Unit C (bioclast‑rich pebbly mudstone). is ≤ 2m thick, erosively-based unit of silty mudstone con-
tains a high concentration of randomly oriented, 1–5-cm coral fragments (Flabellum sp. And Lithostrotionella
sp.), gastropods (Turritella sp., Retipirula sp. And Pyropsis sp.) and bivalves (Calva sp.) throughout (e.g., Fig.4F–
H). Preservation is excellent, with little abrasion (few fragmented edges, shell ornamentation intact), and bivalves
frequently found still articulated with closed valves, suggesting transport with minimal turbulence in a cohesive
ow. Reworked fossil wood fragments occur throughout, along with concretions, both ranging from a few cen-
timeters to 1m. Palynomorph recovery and preservation were poor in this unit.
Unit D (pebbly mudstone). is ≤ 15m thick unit has a sharp, at contact, and is indistinguishable from
Unit B, apart from its lower organic content. e palynomorph assemblage, however, comprises more than 80%
fungal spores (Fig.4B) that indicate the presence of a terrigenous component, possibly remobilized soil.
Unit E (tu). is ≤ 20m thick unit of lapilli crystal vitric tu has an erosive base, and its lower half incor-
porates crystalline pebbles and fossil tree trunks from the underlying units. Its margins are not seen, but it thins
overall towards both NW and SE. Busby etal.27 described the proximal equivalent to this unit c. 25km to the NE.
e tu is of intermediate composition (70% vitreous groundmass, 15% labradorite, 5% quartz, 6% biotite, 3%
hornblende, with subordinate lithic fragments, oxides, and zircon), and includes rare, shocked quartz ≤ 150µm
(Fig.4I). It nes upwards overall, with bands of coarse ash alternating with pumice lapilli (≤ 5cm diameter in
this section and bombs ca. 35cm in the area 25km to the NE). Our SHRIMP U–Pb dating of zircons yields an
age of 66.12 ± 0.65Ma (Supplementary Information, Fig.S2 and TableS4). Within error, the tu age we obtained
is indistinguishable from the 65.5 ± 0.6Ma Ar–Ar biotite age of the proximal tu27, both coeval with that pro-
posed for the Chicxulub impact, 66 Ma33.
Unit F (pebbly mudstone). e ≤ 18m thick unit above the tu (Fig.2) is similar in texture and composi-
tion to Units B and D, but its largest clasts rarely exceed 2cm in diameter. Poor exposure and surface alteration
Figure3. (A) Fossil wood with medullary rays (1) and growth rings (2), shown by weathering (lens cap 5cm);
(B) Fossil wood with bark preserved indicated by (1) (hammer is 30cm long); (C,D) Charred external portions
of trunks indicated by (1) (hammer is 30cm long).
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obscure any deformation structures. No palynomorphs were recovered from this unit; the few benthic foraminif-
era recovered were etched and fragmented, implying reworking.
Danian mudstones. e mudstones immediately above Unit F contain bathyal benthic foraminifera
(mostly Bathysiphon sp., Fig.4E, and lagenids) and an iridium anomaly (1.2ppb Ir, cf. Units B—0.3ppb, and
D—0.5ppb; Fig.5) comparable to K–Pg boundary interval deposits elsewhere, e.g., Brazos River34,35, where in
proximal and intermediate settings the iridium anomaly oen occurs atop mass ow clastic units, e.g.,7.
Pteridophytes spores account for 17% of a palynomorph assemblage dominated by fungal spores (Fig.5;
Supplementary Information, Fig.S2) as well asDanian dinocysts (e.g.,Damassadinium californicum). High con-
centrations of horizontally disposed Bathysiphon sp. also occur, and bioturbation is intense, with sub-centimetric
sand-lled burrows constituting up to 40% of these mudstones.
Discussion and conclusions
e tu age we obtained is identical within error to that proposed for the Chicxulub impact and the K–Pg
Boundary. e apparent absence of spherules and tektites is to be expected given the mixing and dilution within
the large volume debris ows and subsequent alteration to clay minerals similar to the muddy debrite matrix.
e stratigraphic position, architectural characteristics, radiometric ages, shocked quartz, iridium anomaly, and
fungal and fern spore spike all indicate that this was coincident with the K–Pg event (Fig.5).
e occurrence of fossil trees in Unit A, shelfal macrofauna in Unit C, and shallow-water benthic microfauna
throughout, clearly indicate downslope remobilization. Pebbly mudstones such as those in units B, D and F are
common in deep marine settings and are generally regarded as deposits of debris ows; the overall similarity
of these units suggests a single composite event consisting of more or less continuous debris ow punctuated
by faster and more turbulent surges represented by units C and E. Occurrence of exclusively unbioturbated
wood within Unit A unequivocally shows the transport of material from a subaerial setting. Transport of wood
Figure4. (A) Classopollis sp. tetrad, slide coordinates C44-4 (sample LOG-01–002); (B) Cluster of fungal
spores, slide coordinates C43-1 (sample LOG-01 MWD4); (C) Miliolid (sample LOG-05–03); (D) decalcied
Lagenid, (sample LOG-05–21); (E) Bathysiphon sp. (sample MWD-18); F) Isopora sp. corals; (G) Turritella webbi
gastropods, bivalve shells, pebbles, and cobbles; (H) Retipirula crassitesta gastropods; (I) shocked quartz crystal
(sample SF-30).
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(presumably buoyant) into the deep marine environment requires buoyancy less than the yield strength of the
debrite matrix (cf36. and discussion thereof).
Mass failures at many localities around the GoM and the Atlantic margin are attributed to impact-related
seismicity, of likely magnitude M10-11 (e.g.37,). We interpret the observed large-scale and widespread sliding in
the local coastal and slope settings of the Rosario Formation similarly (this study and27). Based on the mappable
extent of the mass failures, we estimate a minimum volume of 15 km3 in the immediate area alone.
Figure5. Generalized section of K–Pg catastrophic deposits in this study, showing lithologic units, the
occurrence of fossilized tree trunks, occurrences of selected abundant palynomorphs, foraminifers and
metazoan taxa, iridium concentrations, shocked quartz crystal occurrence, and absolute age.
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Impact-related tsunamis have been invoked for the onshore-directed transport of material in the US Western
Interior37, and for oshore-directed transport by tsunami backwash around the GoM8,36. Numerical modelling
of the impact-generated tsunami in the GoM, constrained by tsunami-related deposits on the Atlantic margin,
GoM and Caribbean, e.g.,14, appears to rule out propagation of signicant tsunami waves through the still-open
passage from the Caribbean to the Pacic38. We therefore attribute tsunami generation to the observed massive
seismogenic slope failure on the Pacic margin.
With P wave velocities of 6 to 8km s−1, e.g.,39, depending on the ray path, arrival times would have been
between 5 and 7min post-impact. Based on historic seismogenic mass failures, e.g.,40, sliding would have
occurred almost immediately, and the associated tsunami would have arrived within minutes to tens of minutes,
by which time the trees were already charred. e picture is thus one of seismically-triggered landsliding and
large-scale re-sedimentation of terrestrial and shallow-marine material by sediment gravity ows. e tsunami
(the rst of this age recorded from the Pacic margin) is likely to have propagated across the paleo-Pacic to
aect many coastal regions of the Earth within days of the impact.
e global presence of soot in K–Pg sequences has been used to argue either for wildres or for combustion
of mineral sources in sedimentary rocks and fossil hydrocarbons close to the impact site, e.g.,41, and references
therein]. However, uncertainties remain over the total mass of soot, the abundance of burn-related charcoal42,43,
the heat ux required to ignite live or dead vegetation, and the area over which the requisite heat ux could have
occurred, e.g.,44. Also uncertain is the timing of the res, either from the impact plume, e.g.,45,46, from ejecta
re-entering the atmosphere, e.g.,16,47,48, both of which are subject to uncertainties in impact energy, angle, and
trajectory, or due to subsequent lightning strikes over the following days to months in forest dead or dying from
the aer-eects of the impact23.
e presence of charcoal fragments and partially-charred fossilized tree trunks in the Rosario Formation
demonstrates that the adjacent coastal vegetation suered some high-intensity thermal event sucient to cause
combustion. e absence of any signs of decay implies that the trees were live when ignited and that charring of
the trees was specically a result of the impact event. Material that was charred prior to the event is likely to have
shown microbial degradation in the wood structure, so we can be condent that the charring was a consequence
of this event and not a pre-impact wildre. Charcoalied parts still attached to trunks indicate little exposure to
the air–water or water–sediment interface, since charcoal is extremely physically mobile and erodible49. Raman
spectroscopy yields temperatures between 395 and 1022°C, with a median of 716°C.
is high-temperature event occurred before the tsunami, i.e., within minutes to tens of minutes aer impact;
the timing is thus consistent with ignition either by thermal radiation emitted from the plume46 or by ejecta
re-entry48. e context and nature of preservation of charred material at this site suggest that wildres began
almost immediately aer impact and may have begun more easily than suggested by Belcher etal.44. e discrete
charcoal layer on the tree trunks would be consistent with ‘ash-heating’ alone (e.g., radiation) or of the con-
sequent wildre that was rapidly quenched by the tsunami, and therefore unable to alter signicantly the wood
below the outer surface charcoals. However, wildre propagation would have to have been extremely rapid in
the latter case. Further work would be required to dierentiate with certainty between these two possibilities.
Methods
Samples for all analyses presented in this paper were collected along Log 5, at the positions indicated on Sup-
plementary FigureS1, aimed at obtaining a complete prole through the local K–Pg boundary section, with
palynomorphs, foraminifera, macro charcoal, fossil wood, materials for dating, and iridium content, to ascertain
their correct relative stratigraphic position, and to correlate with other K–Pg sections globally. All gures and
tables related to the methods applied are available as Supplementary Information.
Palynology. Seventeen samples were collected through Log 5 (Supplementary Fig.S1) and were prepared at
the Marleni Marques Toigo Laboratory of Palynology at UFRGS, Porto Alegre, Brazil, using the methodology in
Supplementary TableS1. Counts of two hundred palynomorphs per slide were made where possible. Biostrati-
graphic determinations were made utilizing rst occurrence, last occurrence, and acme zones previously dened
onshore and oshore Mexico31,50 and the USA51–55 to help determine the relative age. In addition, the color of
abundant spore Stereisporites spp. was recorded using the standard spore color index methodology56.
e lowermost samples, collected from a blue-gray mudstone (Unit A) demonstrate a diverse assemblage
of Maastrichtian palynomorphs, including pollen (e.g., Classopollis spp., Tricolporopollenitesspp.), spores (e.g.,
Biretisporites spp. and Todisporites spp.), and dinoagellate cysts, including the Cretaceous markers Dinogym-
nium spp. and Yolkinigymniumspp., with representatives of y-four genera of both marine and terrestrial forms
(Supplementary Fig.S2).
Above the bioclastic debrite, the abundance and diversity are severely reduced, with only seven genera and
the sample dominated by fungal spores (Fig.S2). 18m of section above the lapilli tu is barren of palynomorphs,
but rich in degraded humic debris. At the top of the study interval, a spike in fern spores is observed (e.g., Bacu-
latisporites comaumensis and Laevigatosporites spp.), along with diminutive Danian dinocysts (e.g., Damassa-
dinium californicum) and a distinct absence of any Cretaceous palynomorphs. e count data are presented in
Supplementary TableS2, where general groups of palynomorphs are also presented to demonstrate the wider
variation in oral abundance.
Foraminifers and macro charcoal quantication. Separation of foraminifera tests and macro char-
coal fragments was carried out concomitantly. Fieen samples were collected through Log 5 (collocated with
samples for palynology, as shown in Fig.S1). Preparation and identication were conducted following standard
procedures, e.g.,57, but the friable nature of the material simplied and shortened the process: 200g fractions
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(and in some cases 400g, for samples where recovery was poor) of each sample were immersed in a container
with distilled water. Aer a few minutes, the samples were gently disaggregated manually and ltered in a 63m
sieve to remove the clay minerals. e remaining material was then dried in an oven at a controlled temperature
of 40° Celsius.
Selection of specimens was conducted using a Leica S6D stereoscopic microscope, and identication of the
foraminifers was conducted using the ACEMAC Nano Scale Electron Microscopy and Analysis Facility at the
University of Aberdeen, with the Carl Zeiss Gemini SEM 300—high resolution Field Emission Scanning Elec-
tron Microscope (FESEM). Two hundred foraminifera specimens were counted and identied for each sample
when possible, and the data are presented on TableS3. Macro charcoal particles were counted, and their total
volumetric estimates were established based on the original volume of each sample.
Fossil wood. e material consists of three trunks collected from Log 5 site (Supplementary Fig.S1, location
map in Fig.2) that represent monopodial trees preserved as silica permineralization. Due to the size of these
trunks, the sampling method implemented consisted in removing a fragment of its outermost wood and col-
lecting dispersed wood fragments. Subsequently, the samples were transferred to the Paleobotany Laboratory of
the Institute of Geology, UNAM, where they were cut to obtain sections in the three cutting planes (transverse,
radial and tangential) used for wood anatomical studies. Conventional thin section techniques were applied.
e photomicrographs were obtained with a Canon PowerShot A640 camera and a Carl Zeiss AxioCam ICc 5.
Subsequently, they were assembled into photographic plates aided with Illustrator CS4 program.
e recognition of the anatomical characters was based on58–62. For quantication, 20 measurements were
obtained per attribute, and for ray height, 35 measurements were made. Subsequently, for each characteristic,
its average minimum and maximum values were obtained, expressed as follows: average (minimum–maximum)
unit. Regarding the measurement and quantication of the tracheid radial pitting, the contiguity index (Cp) and
seriation index (Si) of63 were followed.
For the taxonomic identication of fossil woods at genus level, we followed61,62,64–66. For species level identi-
cation, comparisons were made with conifer wood of extant species based mainly on59,67,68; while comparisons
with fossil wood articles describing wood of the same or similar taxa were also used, e.g.,69–73.
Raman spectrometry. Raman spectra were obtained through random sampling of individual charcoal
fragments (n = 50) with no additional treatment. Charcoal sampling surfaces were selected for high reectivity
where possible to ensure an adequate spectral response. A laser power of < 0.3mW was applied over 3 accumula-
tions, totalling 15s exposure per sample. No combustion damage was observed on laser-irradiated surfaces post-
exposure. All spectra were deconvolved within Renishaw WiRE 3.4 soware, applying smoothing and a cubic
spline interpolative baseline, and bands D and G t solely. For geothermometric purposes, parameter FWHMRa
(D- and G-band width ratio) was utilised within the following equation74
See also Supplementary Information, TableS4, Fig.S3. Statistical analyses were conducted in IBM SPSS v. 25
via histogram and boxplot presentation (Supplementary FiguresS4 and S5, TableS5).
SHRIMP U–Pb zircon dating. For SHRIMP U–Pb zircon analyses, 1.5kg of a rock sample of the tu
(SF-30, indicated in Fig.S1) were crushed, powdered, and sieved. Heavy mineral concentrates were obtained by
panning, and puried using heavy liquid procedures. Grains were set in epoxy resin mount (together with the
Temora zircon standard) and polished. Backscattered electron and cathodoluminescence images were obtained
for better spot targeting using a FEI-QUANTA 250 scanning electron microscope equipped with secondary-
electron and cathodoluminescence (CL) detectors. e analyses were performed in a SHRIMP (sensitive high-
resolution ion microprobe) IIe/MC at the Center of Geochronological Research of the University of Sao Paulo
(CPGeo-USP) following the procedures described by75. 206Pb/238U ratio was calibrated using the standard
Temora76. Measured 204Pb was applied for the common lead correction77.
Data reduction, plots and calculated ages were carried out using Excel spreadsheets with the support of Squid
2.078 and Isoplot 3.079. A more detailed description can be found in80. Twenty-eight grains were analyzed, and
the data are presented in Supplementary TableS6. Supplementary FigureS6-A shows all results in the concordia
diagram; three analyses were interpreted as from detrital or inherited older grains (in green), and one analysis
was considered an outlier (in blue). e 24 remaining analyses yielded a 66.12 ± 0.65Ma concordia age (2 sigma
error) (Supplementary Fig.S3-B) and the same result was obtained from 206Pb/238U weighted mean age (2 sigma
error) (Supplementary Fig.S3-C).
Iridium analysis. ree samples were collected for iridium content analysis by NiS Fire Assay-Instrumental
Neutron Activation Analysis (INAA) (indicated in Supplementary Fig.S1): two (Logs 5–7 and Logs 5–21) from
the pebbly mudstones of the K–Pg deposits and one (MWD-18) of the hemipelagic mudstone immediately
above. ey were pulverized to a nominal 2mm, mechanically split to obtain a representative sample and then
pulverized to at least 95% passing—105m or smaller. Samples were subsequently transferred to the ACTLAB
facilities in Ontario, Canada, and analyzed following the procedures described in81,82.
25g of each sample, along with 2 blanks, 3 certied standards and 3 duplicates, were re assayed using nickel
sulde (NiS) re assay procedure. e nickel sulde button was then dissolved in concentrated HCl, and the
Formation temperature
(◦C)=
[FWHMRa]
−
3.1765
−0.0016
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residues of this reaction, containing all the iridium (and other PGE) were then collected on a lter paper. is
residue was then submitted to two irradiations and three separate counts to measure all the elements.
Iridium concentrations for the three samples analyzed and used in this paper are presented in TableS7, along
with detection limits of the method used.
Data availability
All data generated or analyzed during this study are included in this published article (and its supplementary
information les). Samples collected and prepared for all laboratory analyzes are available upon request.
Received: 23 May 2022; Accepted: 22 July 2022
References
1. Claeys P., Kiessling W., & Alvarez, W. Distribution of Chicxulub ejecta at the Cretaceous Tertiary boundary, in Catastrophic events
and mass extinctions: Impacts and beyond (eds. Koeberl, C., & MacLeod, K. G.) Geol. Soc. Am. Spec. Pap. 356, 55–68. https:// doi.
org/ 10. 1130/0- 8137- 2356-6. 55 (2002).
2. Nichols D. J., & Johnson, K. R. Plants and the K-T Boundary. Cambridge University Press, 292. https:// doi. org/ 10. 1093/ aob/ mcp052
(2008).
3. Morgan, J. V., Bralower, T. J., Brugger, J. & Wünnemann, K. e Chicxulub impact and its environmental consequences. Nat. Rev.
Earth Environ. https:// doi. org/ 10. 1038/ s43017- 022- 00283-y (2022).
4. Alvarez, L. W., Alvarez, W., Asaro, F. & Michel, H. V. Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science 208,
1095–1108. https:// doi. org/ 10. 1126/ scien ce. 208. 4448. 1095 (1980).
5. Keller, G. e Cretaceous-Tertiary mass extinction, Chicxulub impact, and Deccan volcanism, in Earth and Life (ed. Talent, J.A.)
Springer, 759–793. https:// doi. org/ 10. 1130/ 2014. 2505(03) (2012).
6. Henehan, M. J. et al. Rapid ocean acidication and protracted Earth system recovery followed the end-Cretaceous Chicxulub
impact. Proc. Nat. Ac. Sci. USA 116(45), 22500–22504. https:// doi. org/ 10. 1073/ pnas. 19059 89116 (2019).
7. Schulte, P. et al. e Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary. Science 327(5970),
1214–1218. https:// doi. org/ 10. 1126/ scien ce. 11772 65 (2010).
8. Smit, J., Roep, B., Grajales-Nishimura, J.M., & Bermudez, J. Coarse-grained, clastic sandstone complex at the K/T boundary around
the Gulf of Mexico: Deposition by tsunami waves induced by the Chicxulub impact? in e Cretaceous-Tertiary event and other
catastrophes in Earth history (eds. Ryder, G., Fastovsky, D., & Gartner, S.) Geol. Soc. Am. Spec. Pap. 307, 151–182. https:// doi. org/
10. 1130/0- 8137- 2307-8. 151 (1996).
9. Schulte, P., & Kontny, A. Chicxulub impact ejecta from the Cretaceous-Paleogene (K-P) boundary in northeastern Mexico. in
Large meteorite impacts, III (eds. Kenkmann, T., Hörz, F., & Deutsch, A.) Geol. Soc. Am. Spec. Pap. 384, 191–221. https:// doi. org/
10. 1130/0- 8137- 2384-1. 191 (2005).
10. Morgan, J. V. et al. Analyses of shocked quartz at the global K-P boundary indicate an origin from a single, high-angle, oblique
impact at Chicxulub. Earth Planet Sci. Lett. 251(3–4), 264–279. https:// doi. org/ 10. 1016/j. epsl. 2006. 09. 009 (2006).
11. Gulick, S., Morgan, J., & Mellett, C. L. and the Expedition 364 Scientists. Expedition 364 Preliminary Report: Chicxulub: Drilling
the K-Pg Impact Crater. International Ocean Discovery Program. https:// doi. org/ 10. 14379/ iodp. pr. 364. 2017 (2017).
12. Kring, D. A., Claeys, P., Gulick, S. P. S., Morgan, J. V., Collins, G. S., & the IODP-ICDP Expedition 364 Science Party. Chicxulub
and the exploration of large peak-ring impact craters through scientic drilling. GSA Today, 27(10), 4–8. https:// doi. org/ 10. 1130/
GSATG 352A.1 (2017).
13. Osinski, G. R. et al. Explosive interaction of impact melt and seawater following the Chicxulub impact event. Geology https:// doi.
org/ 10. 1130/ G46783.1 (2019).
14. Smit, J. e global stratigraphy of the Cretaceous-Tertiary boundary impact ejecta. Ann. Rev. Earth Planet Sci. 27, 75–113. https://
doi. org/ 10. 1146/ annur ev. earth. 27.1. 75 (1999).
15. Klaus, A., Norris, R. D., Kroon, D., & Smit, J. Impact-induced mass wasting at the K-T boundary: Blake Nose, western North
Atlantic. Geology, 28, 319–322. https:// doi. org/ 10. 1130/ 0091- 7613(2000) 28< 319: IMWAT K>2. 0. CO;2 (2000).
16. Melosh, H. J., Schneider, N. M., Zahnle, K. J. & Latham, D. Ignition of global wildres at the Cretaceous/Tertiary boundary. Nature
343(6255), 251–254. https:// doi. org/ 10. 1038/ 34325 1a0 (1990).
17. Wolbach, W. S., Widicus, S. & Kyte, F. T. A search for soot from global wildres in central Pacic Cretaceous-Tertiary boundary and
other extinction and impact horizon sediments. Astrobiology 3(1), 91–97. https:// doi. org/ 10. 1089/ 15311 07033 21632 444 (2003).
18. Stéphan, J.-F. et al. Paleogeodynamic maps of the Caribbean: 14 steps from Lias to Present. Bulletin de la Société Géologique de
France 8, 915–919. https:// doi. org/ 10. 2113/ gssg ull. VI.6. 915 (1990).
19. Helenes, J. & Carreño, A. Neogene sedimentary evolution of Baja California in relation to regional tectonics. J. S. Am. Earth Sci.
12(6), 589–605. https:// doi. org/ 10. 1016/ s0895- 9811(99) 00042-5 (1999).
20. Vellekoop, J. et al. Rapid short-term cooling following the Chicxulub impact at the Cretaceous-Paleogene boundary. Proc. Natl.
Acad. Sci. USA 111(21), 7537–7541. https:// doi. org/ 10. 1073/ pnas. 13192 53111 (2014).
21. Beal, C. H. Reconnaissance of the geology and oil possibilities of Baja California. Mexico. Geol. Soc. Am. Memoir 31, 138. https://
doi. org/ 10. 1130/ MEM31- p1 (1948).
22. Kilmer, F.H. Cretaceous and Cenozoic stratigraphy and paleontology, El Rosario area. [Ph.D. thesis]. Berkeley, University of Cali-
fornia, 149 (1963).
23. Gastil, R. G., Phillips, R. P. & Allison, E. C. Reconnaissance geology of the state of Baja California. Geol. Soc. Am. Memoir 140,
170. https:// doi. org/ 10. 1130/ MEM140- p1 (1975).
24. Morris, W. R., & Busby, C. J. e eects of tectonism on the high-resolution sequence stratigraphic framework of non-marine to
deep-marine deposits in the Peninsular Ranges forearc basin complex, in Field Conference Guide (eds. Abbott, P.L., & Cooper,
J.D.), AAPG Guidebook 73, Book 80, Pacic Section. SEPM, 381–408 (1996).
25. Morris, W. & Busby-Spera, C. A submarine-fan valley-levee complex in the Upper Cretaceous Rosario Formation: Implication for
turbidite facies models. Geol. Soc. Am. Bull. 102(7), 900–914. https:// doi. org/ 10. 1130/ 0016- 7606(1990) 102% 3c0900: ASFVLC%
3e2.3. CO;2 (1990).
26. Kneller, B. et al. Architecture, process and environmental diversity in a late Cretaceous slope channel system. J. Sediment. Res. 90,
1–26. https:// doi. org/ 10. 2110/ jsr. 2020.1 (2020).
27. Busby, C. J., Yip, G., Blikra, L., & Renne, P. Pacic margin example of catastrophic sedimentation triggered by K/T bolide impact.
Geology, 30, 687–690. https:// doi. org/ 10. 1130/ 0091- 7613(2002) 030< 0687: CLACS T>2. 0. CO;2 (2002).
28. Dykstra, M., & Kneller, B. Canyon San Fernando: A Deep-Marine Channel-Levee Complex Exhibiting Evolution From Submarine-
Canyon Conned to Unconned. in Atlas of Deepwater Outcrops (eds. Nilsen, T.H., Shew, R.D., Steens, G.S., & Studlick, J.R.J.)
AAPG Studies in Geology, 56, 226–230 (2007).
Content courtesy of Springer Nature, terms of use apply. Rights reserved

10
Vol:.(1234567890)
Scientic Reports | (2022) 12:13006 | https://doi.org/10.1038/s41598-022-17292-y
www.nature.com/scientificreports/
29. Cevallos-Ferriz, S. R. S., Santa Catharina, A. & Kneller, B. Cretaceous Lauraceae wood from El Rosario, Baja California, Mexico.
Rev. Palae ob. Palyno. 292, 104478. https:// doi. org/ 10. 1016/j. revpa lbo. 2021. 104478 (2021).
30. Savrda, C. E., Counts, J., McCormick, O., Urash, R. & Williams, J. Log-Grounds and Teredolites in transgressive deposits, Eocene
Tallahatta Formation (Southern Alabama, USA). Ichnos 12, 47–57. https:// doi. org/ 10. 1080/ 10420 94059 09145 07 (2005).
31. Helenes, J. & Téllez-Duarte, M. A. Paleontological evidence of the Campanian to Early Paleocene paleogeography of Baja California.
Palaeogeogr. Palaeoclimatol. Palaeoecol. 186(1–2), 61–80. https:// doi. org/ 10. 1016/ S0031- 0182(02) 00444-3 (2002).
32. Berggren, W. A. & Aubert, J. Paleocene benthonic foraminiferal biostratigraphy, paleobiogeography and paleoecology of Atlantic-
Tethyan regions. Paleogeogr. Paleoclimatol. Paleoecol. 18, 73–192. https:// doi. org/ 10. 1016/ 0031- 0182(75) 90025-5 (1975).
33. Renne, P. R. et al. Multi-proxy record of the Chicxulub impact at the Cretaceous-Paleogene boundary from Gorgonilla Island,
Colombia. Geology 46, 547–550. https:// doi. org/ 10. 1130/ G40224.1 (2018).
34. Ganapathy, R., Gartner, R. S. & Jiang, M. J. Iridium anomaly at the Cretaceous-Tertiary boundary in Texas. Earth Planet Sci. Lett.
54, 393–396. https:// doi. org/ 10. 1016/ 0012- 821X(81) 90055-8 (1981).
35. Gertsch, B. et al. Environmental eects of Deccan volcanism across the Cretaceous-Tertiary transition in Meghalaya, India. Earth
Planet Sci. Lett. 310(272), 272–285. https:// doi. org/ 10. 1016/j. epsl. 2011. 08. 015 (2011).
36. Kruge, M. A., Stankiewicz, B. A., Crelling, J. C., Montanari, A. & Bensley, D. F. Fossil charcoal in Cretaceous-Tertiary boundary
strata: Evidence for catastrophic restorm and megawave. Geochim. Cosmochim. Acta 58(4), 1393–1397. https:// doi. org/ 10. 1016/
0016- 7037(94) 90394-8 (1994).
37. DePalma, R. A. et al. A seismically induced onshore surge deposit at the KPg boundary. North Dakota. Proc. Nat. Acad. Sci 116,
8190–8199. https:// doi. org/ 10. 1073/ pnas. 18174 07116 (2019).
38. Scotese, C., & Golonka, J. Paleogeographic Atlas: Progress Report 20-0682, PALEOMAP Project, University of Texas at Arlington,
Texas & Mobile Exploration & Production Services. https:// doi. org/ 10. 13140/ RG.2. 1. 1058. 9202 (1992).
39. Rosalia, S., Widiyantoro, S., Nugraha, A. D. & Supendi, P. Double-dierence tomography of P-and S-wave velocity structure beneath
the western part of Java. Indonesia. Earthq. Sci. 32, 12–25. https:// doi. org/ 10. 29382/ eqs- 2019- 0012-2 (2019).
40. Løvholt, F., Schulten, I., Mosher, D., Harbitz, C. & Krastel, S. Modelling the 1929 Grand Banks slump and landslide tsunami. Geol.
Soc. Lond. Spec. Publ. 477(1), 315–331. https:// doi. org/ 10. 1144/ SP477. 28 (2019).
41. Lyons, S. L. et al. Organic matter from the Chicxulub crater exacerbated the K-Pg impact winter. Proc. Nat. Acad. Sci. 117(41),
25327–25334. https:// doi. org/ 10. 1073/ pnas. 20045 96117 (2020).
42. Belcher, C. M., Finch, P., Collinson, M. E., Scott, A. C. & Grassineau, N. V. Geochemical evidence for combustion of hydrocarbons
during the KT impact event. Proc. Nat. Acad. Sci. 106(11), 4112–4117. https:// doi. org/ 10. 1073/ pnas. 08131 17106 (2009).
43. Robertson, D. S., Lewis, W. M., Sheehan, P. M. & Toon, O. B. K-Pg extinction: Reevaluation of the heat-re hypothesis. Journ.
Geophys. Research: Biogeos. 118(1), 329–336. https:// doi. org/ 10. 1002/ jgrg. 20018 (2013).
44. Belcher, C. M. et al. An experimental assessment of the ignition of forest fuels by the thermal pulse generated by the Cretaceous-
Palaeogene impact at Chicxulub. J. Geol. Soc. 172(2), 175–185. https:// doi. org/ 10. 1144/ jgs20 14- 082 (2015).
45. Toon, O. B., Zahnle, K., Morrison, D., Turco, R. P., & Covey. C. Environmental perturbations caused by the impacts of asteroids
and comets. Rev. Geophys. 35(1), 41–78. https:// doi. org/ 10. 1029/ 96RG0 3038 (1997).
46. Svetsov, V. V. & Shuvalov, V. V. ermal radiation and luminous eciency of superbolides. Earth Plan. Sci. Lett. 503, 10–16. https://
doi. org/ 10. 1016/j. epsl. 2018. 09. 018 (2018).
47. Kring, D. A., & Durda, D. D. Trajectories and distribution of material ejected from the Chicxulub impact crater: Implications for
postimpact wildres: J. Geophys. Res. 107(E8), 50–62. https:// doi. org/ 10. 1029/ 2001J E0015 32 (2002).
48. Morgan, J., Artemieva, N. & Goldin, T. Revisiting wildres at the K-Pg boundary. J. Geophys. Res. Biogeos. 118(4), 1508–1520.
https:// doi. org/ 10. 1002/ 2013J G0024 28 (2013).
49. Pyle, L. A., Magee, K. L., Gallagher, M. E., Hockaday, W. C. & Masiello, C. A. Short-term changes in physical and chemical proper-
ties of soil charcoal support enhanced landscape mobility. J. Geophys. Res. Biogeos. 122, 3098–3107. https:// doi. org/ 10. 1002/ 2017J
G0039 38 (2017).
50. Helenes, J. Dinoagellates from Cretaceous to Early Tertiary rocks of the Sebastian Vizcaino Basin, Baja California, Mexico, in
Geology of the Baja California Peninsula (Frizzel, A.) Pacic Section SEPM, 39, 89–106. (1984).
51. Firth, J. V. Dinoagellate biostratigraphy of the Maastrichtian to Danian interval in the US Geological Survey Albany core, Georgia,
USA. Palynology 11, 199–216. https:// doi. org/ 10. 1080/ 01916 122. 1987. 99893 28 (1987).
52. Firth, J. V. Dinoagellate assemblages and sea-level uctuations in the Maastrichtian of southwest Georgia. Rev. Palaeob. Palyn.
79, 179–204. https:// doi. org/ 10. 1016/ 0034- 6667(93) 90022-M (1993).
53. Lucas-Clark, J. Small peridinioid dinoagellate cysts from the Paleocene of South Carolina, USA. Palynology 30, 183–210. https://
doi. org/ 10. 2113/ gspal ynol. 30.1. 183 (2006).
54. Prauss, M. L. e K/Pg boundary at Brazos-River, Texas, USA—An approach by marine palynology. Palaeog. Plaeocl. Palaeoecol.
283, 195–215. https:// doi. org/ 10. 1016/j. palaeo. 2009. 09. 024 (2009).
55. Dastas, N. R., Chamberlain, J. A. & Garb, M. P. Cretaceous-Paleogene dinoagellate biostratigraphy and the age of the Clayton
Formation, southeastern Missouri, USA. Geosciences 4, 1–29. https:// doi. org/ 10. 3390/ geosc ience s4010 001 (2014).
56. Marshall, J. E. A. Quantitative spore colour. J. Geol. Soc. 148, 223–233. https:// doi. org/ 10. 1144/ gsjgs. 148.2. 0223 (1991).
57. Snyder, S. W. & Huber, B. T. Preparation Techniques for Use of Foraminifera in the Classroom. Paleontol. Soc. Pap. 2, 231–236
(1996).
58. Barefoot, A.C., & Hankins, F.W. Identication of Modern and Tertiary Woods. Oxford University Press, 189. (1982).
59. García Esteban, L. Anatomía e identicación de maderas de coníferas a nivel de especie. Madrid, Fundación Conde del Valle de
Salazar, 421. (2002).
60. Metcalfe, C.R. Anatomy of the Dicotyledons Vol. III. Magnoliales, Illiciales, and Laurales (sensu Armen Takhtajan). Clarendon
Press. (1987).
61. IAWA Hardwood Committee. IAWA list of microscopic features for hardwood identication. IAWA Bulletin, 10(3), 219–332.
(1989).
62. IAWA Sowood Committee. IAWA list of microscopic features for sowood identication: IAWA Journal, 25(1), 1–70. (2004).
63. Pujana, R. R., Ruiz, D. P., Martínez, L. C. A. & Zhang, Y. Proposals for quantifying two characteristics of tracheid pit arrangement
in gymnosperm woods. Revista del Museo Argentino de Ciencias Naturales 18, 117–124. https:// doi. org/ 10. 22179/ REVMA CN. 18.
455 (2016).
64. Bamford, M. K. & Philippe, M. Jurassic-Early Cretaceous Gondwanan homoxylous woods: a nomenclatural revision of the genera
with taxonomic notes. Rev. Palaeobot. Palynol. 113, 287–297. https:// doi. org/ 10. 1016/ s0034- 6667(00) 00065-8 (2001).
65. Philippe, M. & Bamford, M. K. A key to morphogenera used for Mesozoic conifer-like woods. Rev. Palaeobot. Palynol. 148, 184–207.
https:// doi. org/ 10. 1016/j. revpa lbo. 2007. 09. 004 (2008).
66. Metcalfe, C. R. & Chalk, L. Anatomy of the Dicotyledons, Vol. 2. Clarendon Press, 557. (1957).
67. Greguss, P. Identication of living gymnosperms on the basis of xylotomy. Budapest, Akadémiai Kiadó, 263. (1955).
68. García Esteban, L., de Palacios, P., Guindeo Casasús, A. & García Fernández, F. Characterisation of the xylem of 352 conifers.
Investigación Agraria: Sistemas y Recursos Forestales 13, 452–478. https:// doi. org/ 10. 5424/ srf/ 20041 33- 00846 (2004).
69. Knowlton, F. H. New species of fossil wood (Araucarioxylon arizonicum) from Arizona and New Mexico. US National Museum
Proceedings 1888(11), 1–4 (1889).
Content courtesy of Springer Nature, terms of use apply. Rights reserved

11
Vol.:(0123456789)
Scientic Reports | (2022) 12:13006 | https://doi.org/10.1038/s41598-022-17292-y
www.nature.com/scientificreports/
70. Kräusel, R. Die fossilen Koniferhölzer (unter Ausschluß von Araucarioxylon Kraus). Palaeontographica Abteilung 62, 185–275
(1919).
71. Vaudois, N. & Privé, C. Révision des bois fossiles de Cupressaceae. Palaeontographica Abteilung B Band. 134, 61–86 (1971).
72. Richter, H. G. Lauraceae. in Anatomy of the dicotyledons (ed. Metcalfe, C.R.) 2nd ed., vol. III, Magnoliales, Illiciales, and Laurales.
Clarendon Press, 152–173 (1987).
73. Mantzouka, D., Karakitsios, V., Sakala, J. & Wheeler, E. A. Using idioblasts to group Laurinoxylon species: A case study from the
Oligo-Miocene of Europe. Int. Assoc. Wood Anat. J. 37, 459–488. https:// doi. org/ 10. 1163/ 22941 932- 20160 147 (2016).
74. eurer, T., Naszarkowski, N., Muirhead, D., Jolley, D. & Mauquoy, D. Assessing modern calluna heathland re temperatures using
Raman spectroscopy: Implications for past regimes and geothermometry. Front. Earth Sci. (2022).
75. Williams, I. S. U--Pb geochronology by ion microprobe, in Applications of Microanalytical Techniques to Understanding Min-
eralizing Processes (eds. McKibben, M.A., Shanks, W.C., & Ridley, W.I.) Rev. Econ. Geol., 7, 1–35. https:// doi. org/ 10. 5382/ Rev. 07.
01 (1998).
76. Black, L. P. et al. TEMORA 1: A new zircon standard for Phanerozoic U-Pb geochronology. Chem. Geol. 200, 155–170. https://
doi. org/ 10. 1016/ S0009- 2541(03) 00165-7 (2003).
77. Stacey, J. S. & Kramers, J. D. Approximation of terrestrial lead isotope evolution by a two-stage model. Earth Planet. Sci. Lett. 26(2),
207–221. https:// doi. org/ 10. 1016/ 0012- 821x(75) 90088-6 (1975).
78. Ludwig, K. SQUID 2: A User’s Manual. Berkeley Geochronology Center, Special Publication 5, 110 (2009).
79. Ludwig, K. R. Isoplot 300: A geochronological toolkit for Microso Excel: Berkeley Geochronological Center. Special Publication
4, 70 (2003).
80. Sato, K. et al. Sensitive High Resolution Ion Microprobe (SHRIMP IIe/MC) of the Institute of Geosciences of the University of São
Paulo, Brazil: analytical method and rst results. Geologia USP. Serie Cientíca 14, 3–18. https:// doi. org/ 10. 5327/ Z1519- 874X2
01400 030001 (2014).
81. Homan, E. L., Naldrett, A. J., Van Loon, J. C., Hancock, R. G. V. & Manson, A. e determination of all the platinum group ele-
ments and gold in rocks and ore by neutron activation analysis aer preconcentration by a nickel sulphide re-assay technique on
large samples. Anal. Chim. Acta 102, 157–166 (1978).
82. Homan, E. L. Instrumental neutron activation in geoanalysis. J. Geochem. Explor. 44(1–3), 297–319 (1992).
Acknowledgements
ASC, JM and AM acknowledge support from BG/Shell Brasil through ‘BG05 UoA-UFRGS-SWB Sedimentary
Basins’ and ‘DMS Tools’ projects at Universidade Federal do Rio Grande do Sul, and strategic support by Agência
Nacional do Petróleo, Brazil, through the R&D Brazilian levy regulation. Conselho Nacional de Desenvolvimento
Cientíco e Tecnológico (CNPq) is also acknowledged for scholarship to ASC (211796/2013-1) during her thesis
at University of Aberdeen, and for research fellow support to JM (316460/2021-4). We also acknowledge Kei Sato
from Universidade de São Paulo for assistance with U-Pb determination.
Author contributions
A.S.C. undertook eldwork and micropaleontological and all subsequent data analysis and interpretation as part
of her doctoral thesis and draed the initial manuscript. B.K. conceived of and supervised the study, contributed
to the interpretation, and co-authored the manuscript. J.M. performed the isotopic analyses and interpretation.
A.Mc.A. carried out the palynological analyses and interpretation. A.Mc.A., I.K., and J.M. contributed to the eld
supervision. S.C.-F. performed the paleobotanical analysis and contributed to the interpretation. T.T. and D.M.
conducted and interpreted the Raman spectroscopy analysis. All authors edited the nal manuscript.
Competing interests
e authors declare no competing interests.
Additional information
Supplementary Information e online version contains supplementary material available at https:// doi. org/
10. 1038/ s41598- 022- 17292-y.
Correspondence and requests for materials should be addressed to B.C.K.
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