Data supporting Maastrichtian paleoclimate variables applying a multi proxy approach to a paleosol profile, Arctic Alaska

We provide the dataset of climate variables related to the research article “Paleoclimate reconstruction of the Prince Creek Formation, Arctic Alaska, during Maastrichtian global warming” [1]. The dataset includes mean annual precipitation (MAP) values determined using two independent proxies, estimates of the oxygen isotope composition of meteoric water (δ18Ow) obtained from smectites and a comparison with previously published siderite data. We also provide the data used to calculate the total flux of CO2 required for the weathering of silicates. This dataset is an example of a multi proxy approach that could add further insight for researchers in the selection of suitable proxies for paleoclimatic interpretations.


Data description
In this article, we report raw data of carbon and nitrogen isotopes (from pollen and bulk organic matter) in Table 1. Data of major elements from a Maastrichtian paleosol profile (n ¼ 7) are reported in Table 2. These data are reported as raw, and as molar proportions, for the A-C*N-K diagram plotted in Ref. [1], using Al 2 O 3 , CaO* þ Na 2 O, K 2 O, according to Ref. [3]. Both, raw and analysed oxygen isotope data from the total clay-size fraction for the NKT paleosol (n ¼ 7) and from the KKT and PFDV bentonites (n ¼ 2) are reported in Tables 3 and 4, respectively. Table 4 and Fig. 1 also report the calculated d 18 O w (‰. VSMOW) of meteoric water using the equation of Sheppard and Gilg [4], and compare the data with d 18 O w from siderite [5]. Fig. 2 is a plot of mean annual precipitation using three equations Specifications Table   Subject Earth and Planetary Sciences: Earth-Surface Processes Specific subject area Paleoclimatology of a Maastrichtian paleosol profile in the paleo-Arctic using geochemical proxies.

Value of the Data
The climatic variables provide information regarding the Cretaceous paleo-Arctic that can be compared with previously published independent qualitative and quantitative data. The data allow assessment of Cretaceous General Circulation Model (GCM) simulations through data-model comparisons.
The carbon isotopic composition (d 13 C), obtained in paleosols from pollen and bulk organic matter, is valuable as a reference to refine proxies used in the identification of carbon cycle perturbations. The oxygen isotopic composition of meteoric water (d 18 O w ) derived from smectite provides information as a paleohydrologic indicator, extending the sampling of high latitude continental deposits to pedogenic clays. The total flux of CO 2 required for silicate weathering is useful to understand the CO 2 sinks in the geological carbon cycle in Maastrichtian arctic paleosols.

Experimental design, materials, and methods
Seventy-five sections of the Prince Creek Formation were measured and described for grain size and sedimentary structures [2]. The NKT site (N 69 45.068 0 ; W 151 30.873 0 ) was selected for paleosol study based on accessibility of outcrop and abundance of paleopedological features. Macroscopic features including color, grain size, ped structure, mottles, nodules, root traces, flora and fauna were described in detail in Ref. [2]. Bulk samples were collected at 15e30 cm intervals and all samples were air-dried. Total organic carbon (TOC) was determined by Weatherford Laboratories, Shenandoah, Texas. Samples were pulverized, sieved, and reacted with concentrated HCl to dissolve carbonates. Samples were dried and combusted in a LECO model C230 combustion furnace, and CO 2 generated by the combustion of organic matter was quantified using an infrared detector to determine TOC. Detailed description of the sampling method is given in Ref. [2], and a detailed description of geochemical processing and analytical methods is given in Ref. [1].

d 13 C analyses of pollen grains
Sediment samples were mechanically disaggregated and treated with 10% HCl to remove carbonate, and with 49% HF to remove silicates. Samples were washed with de-ionized water several times to neutralize the acid. The final wash was through a 250 mm sieve. Sodium polytungstate was used as a heavy liquid to separate the organic fraction from remaining minerals. After freeze-drying, pollen samples were weighed for d 13 C analyses. The C and N analyses (Table 1) were conducted at the Alaska Stable Isotope Facility (ASIF), University of Alaska Fairbanks. d 13 C was measured using EA-IRMS. This method utilizes a Costech Elemental Analyzer (ESC 4010), and Thermo Conflo III interface with a DeltaV Mass Spectrometer [1]. Table 3 Calculated d 18 O (‰ VSMOW) of meteoric water from the total clay-size fraction for the NKT paleosol and the KKT and PFDV bentonites. The last column is the calculated d 18 O of meteoric water using temperatures (À2 C minimum, 6.3 C average, and 14.5 C maximum) determined from CLAMP analysis of paleobotanical specimens [14].

XRF analyses
Samples were prepared by powdering using hardened steel vials from SPEX CertiPrep Group, and pressed into 35 mm diameter pellets using a polyvinyl alcohol binder. Abundances (in wt. %) of the light major oxides (SiO 2 , Al 2 O 3 , Fe 3 O 3 , Na 2 O, MgO, P 2 O 5 , K 2 O, CaO, MnO and TiO 2 ) ( Table 2) were measured from bulk samples using a PANalytical Axios wavelength-dispersive X-ray fluorescence spectrometer (WD-XRF) at the University of Alaska Fairbanks Advanced Instrumentation Laboratory (AIL) [1]. The chemical index of alteration minus potassium (CIA-K) was calculated according to Ref. [11] (Table 2).

d 18 O analyses of clay samples
The total clay (<2 mm fraction) was separated using the hydrometer method. After mixing the slurry in a settling column, we used a settling time of 23 h 16 min for a 30 cm settling column at T ¼ 20 C room temperature. We used a pipette to siphon the supernatant into the centrifuge tubes. Then the <0.2 mm clay fraction was separated by centrifuging for approximately 6 minutes at 11,000 rpm, where the time and speed was calculated with Centriset, a USGS program, which computes settling velocity based on Stokes Law for gravitational procedures. All samples (the <2 mm and <0.2 mm fractions) were freeze-dried for stable isotope analysis. d 18 O values (Table 3) were measured using a Micromass Optima dual-inlet, IRMS in the Laboratory for Stable Isotope Science at the University of Western Ontario, London, Canada [1].

Meteoric water composition data
We determined meteoric water composition (Table 3; Fig. 1) using the relationship that describes the oxygen isotope fractionation between smectite and water [4]. Table 4 and Fig. 1, show the relationship between meteoric water composition and temperature for maximum and minimum smectite d 18 O values and compare these data with previous studies of meteoric water composition calculated from siderite [5] using the equation of [12]. correspond to the meteoric water isotopic composition calculated using pedogenic siderite [5].  Table 3 in Ref. [1]) in the [6,7] Table 5 Depth, after applying a paleosol compaction equation [15], bulk density, and strain (ε) and elemental mass transport (t) for mass balance calculations [8].  . 3. A) NKT paleosol horizons and depth. B) Strain (Ɛ). Volume change during weathering [8] calculated for the NKT paleosol. C) Thickness after applying a paleosol compaction equation at~69 Ma [15]. (DeE) Mass balance cross-plots of strain (ε) vs. elemental mass transport (t) for the NKT paleosol using TiO 2 (blue), Zr (green), and Al 2 O 3 (yellow). The calculations assume immobility of D) TiO 2 , E) Zr, and F) Al 2 O 3 .

Mass balance and total flux of CO 2 data
Mass balance calculations [8] are shown in Table 5 and Fig. 3. Fig. 4 indicates the total CO 2 flux calculated from mass balance [9,10] that was used to determine silicate weathering (the moles of CO 2 that react as carbonic acid to release K, Ca, Mg, and Na base cations).