Paleoclimate and precipitation seasonality of the Early Eocene McAbee megaflora, Kamloops Group, British Columbia

Abstract

whether they represent the same leaf population, (2) assess whether a combined collection yields 24 more precise climate estimates, and (3) reconstruct paleoclimate to assess the character of 25 regional Early Eocene precipitation seasonality. Combined, the two samples yielded 43 dicot leaf 26 morphotypes. Analysis of leaf size distribution using ANOVA showed no difference between the 27 2 samples and they were combined for climate analysis. Climate analysis using leaf 47Early Eocene fossil floras from British Columbia and Washington State, coined the 48Okanagan Highlands, provide a window into the climate of the Early Eocene at mid-latitudes 49(e.g., Smith et al. 2010Smith et al. , 2012 Archibald et al. 2011 Archibald et al. , 2014, where modelling has identified 50 highly seasonal precipitation in the North American continental interior and ever-wet regimes on 51 the west coast and adjoining area of British Columbia (Huber and Goldner 2012 2005; Smith et al. 2010 Smith et al. , 2012. The Brandon University (BU) collection was made by S.B. 101Archibald in the early 2000s. Neither collection was made within a site stratigraphy (J.F. 102Basinger and S.B. Archibald, pers. comm., Sept. 4, 2015). The McAbee main site (Fig. 2) is an 1978; Greenwoood 1992 Greenwoood , 2007 Steart et al. 2002). These same patterns have been seen 141 in Eocene lake sediment leaf assemblages over short stratigraphic distances of <5 m (e.g., 142Greenwood 1991; Smith et al. 2009, 2012). At Falkland, Smith (2011 Smith et al. 2009 Smith et al. , 2012 by changes in annual precipitation amounts over time (Smith et al. 2009(Smith et al. , 2012 or 'ever-wet' climate regime. 167 Materials and Methods 168 Fossil Flora 169The first of the two fossil samples examined in this study was collected by S.B. 170Archibald in the early 2000s and is currently curated at Brandon University (BU). This collection populations. The TRU collection was not available for analysis. 183 Leaf Morphotyping 184The fossil leaves of both the BU and US collections were separated into distinctive in depth taxonomic analysis of the fossil flora (Ellis et al. 2009;Yang et al. 2011 Yang et al. , 2015. 189Important morphological characteristics considered in this process include: leaf size, margin 190 type, apex shape, base shape, and venation. Each morphotype is defined using the character 191 scores of multiple leaves representative of the morphotype, entered into the MLA pro forma. 192Scores of leaf size class for each leaf morphotype were made using both the leaf size classes Yang et al. 2011Yang et al. , 2015. collections was directly measured using the equation: 203(1) Leaf Area = Length × Width × 0.67 (Cain and Castro 1957; Greenwood 1992). 204The leaf area data was analyzed using two one-way ANOVA tests in Microsoft®-Excel to generate an estimate for MAP. In addition, the smallest and largest specimens from each 229 morphotype were directly measured using equation (1) could not be directly measured were excluded from the analysis, although future work will ...

A review of paleobotanical studies of the Early Eocene Okanagan (Okanogan) Highlands floras of British Columbia, Canada, and Washington, USA

“…Absent to rare in the interior assemblages, but present in the coastal pollen floras, were warm climate indicators such as Sabal granopollenites (Arecaceae, palm), Engelhardia (Juglandaceae), ?Nyssa, and fern spores from the Anemiaceae-Schizeaceae group , table 2). interpreted this pollen data to indicate a cooler more continental climate for the interior Eocene (i.e., Princeton coal basin/Allenby Formation, Horsefly, and Driftwood Creek), than for the coastal sites, but still "a warm mesothermal climate", an interpretation supported by recent quantitative climate reconstructions (e.g., Greenwood et al 2005;Smith et al 2012;Dillhoff et al 2013;Mathewes et al 2016;Gushulak et al 2016).…”

“…Since the works of Dawson and Penhallow, and Rouse through to present researchers, the Okanagan Highlands sites have been recognized as having a cooler climate than the Eocene floras of the coastal lowlands (Rouse 1962;Johnson 1996;Greenwood et al 2005). Several authors have quantified this perception, applying both leaf physiognomy and nearest living relative analysis to reconstruct microthermal (MAT 10-15°C) and wet environments (MAP > 100 cm/year) Smith et al 2009Smith et al , 2012Dillhoff et al 2013;Gushulak et al 2016;Mathewes et al 2016). 2.…”

“…(Denk and Dillhoff 2005), Trochodendron drachukii and associated leaves , and a reproductive structure of unknown affinities named Dillhoffia cachensis (Manchester and Pigg 2008). Both Greenwood et al (2005) and Dillhoff et al (2005Dillhoff et al ( , 2013 provided paleoclimate reconstructions for McAbee (see Gushulak et al 2016), and both Dillhoff et al (2005) and Moss et al (2005) presented pollen count data that indicated a diverse flora. While primarily focused on insects in his study of McAbee, Archibald et al (2010) used rarefaction analysis of a small collection (<200 leaves) to show plant diversity in the Early Eocene comparable to tropical rainforest sites, corroborating an extensive and detailed assessment of insect diversity.…”

“…More recently, a greater emphasis on the paleoenvironments of the Okanagan Highland floras has appeared both in locality studies (Dillhoff et al , 2013Smith et al 2009Smith et al , 2010Gushulak et al 2016;Mathewes et al 2016) and in studies dedicated to broader issues of paleoenvironment (Greenwood and Wing 1995;Wolfe et al 1998Wolfe et al , 2000Greenwood et al 2005;Moss et al 2005;Smith et al 2012;Feng and Poulsen 2016). Archibald et al (2011) provided a preliminary synthesis of the Okanagan Highlands sites, focusing on their potential as Lagerstätten to answer questions in paleoecology incorporating both insects and plants.…”

Eocene paleontology and geology of western North America

“…The papers published in this special issue capture that breadth, with an emphasis on the Okanagan Highlands floras (DeVore and Pigg 2016; Greenwood et al 2016;Gushulak et al 2016;Mathewes et al 2016;Moss et al 2016).…”