A New Paleoclimate Classification for Deep Time

Palaeogeography, Palaeoclimatology, Palaeoecology 443 (2016) 98–106 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo A new paleoclimate classification for deep time Laiming Zhang a,b, Chengshan Wang a,b,⁎, Xianghui Li c,KeCaod,YingSonge, Bin Hu a,b,DaweiLuf, Qian Wang a,b, Xiaojing Du a,b,ShuoCaoa,b a State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China b School of the Earth Science and Resources, China University of Geosciences, Beijing 100083, China c State Key Laboratory of Mineral Deposit Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China d The Key Laboratory of Marine Hydrocarbon Resources and Environment Geology, Qingdao Institute of Marine Geology, Qingdao 266071, China e School of Geosciences, China University of Petroleum, Qingdao 266580, China f College of Geological Science and Engineering, Shandong University of Science and Technology, Qingdao 266510, China article info abstract Article history: In deep time, climates are mainly classified by climatically sensitive deposits, paleontological evidences, and Received 26 September 2015 modeling. However, they only have limited applicability in deep time studies. Here, we propose a new Received in revised form 23 November 2015 paleoclimate classification based on the widely used Köppen climate classification. The proposed new classifica- Accepted 24 November 2015 tion is simple and quantitative, but bridges the gap between modern and deep time climate studies. The new Available online 7 December 2015 classification is closely related to but differs from that of Köppen by changing some limits. A world map using fi fi Keywords: the new classi cation shows the same patterns as the world map of the Köppen climate classi cation. Using fi Paleoclimate classification the new classi cation, we are able to solve a long-standing problem about the climates of East Asia during the Deep time Eocene. We found that East Asia shared the same climate type (Ca: Subtropical) at all studied locations, Köppen climate classification supporting the hypothesis of monsoon or monsoon-like climate that prevailed there during the Eocene. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Clearly, a paleoclimate classification should be simple enough to de- scribe the limited climatic data available in deep time studies and be re- Systematic grouping of climates into different types based on partic- lated to modern climates, thus serving as a bridge over the gap between ular attributes brings structure, order and simplicity to a complex cli- modern and deep time climate. More importantly, the paleoclimate matic system, which allows us to set spatial boundaries to conditions classification should be quantitative, with the same measures of modern on Earth's surface (Oliver, 2005). A variety of classifications have been climates when studying geological ages and regions. We need to clarify established for modern climates based on specific applications that there is no natural boundary in the world that is able to distinctive- (Essenwanger, 2001; Farmer and Cook, 2013). However, paleoclimatol- ly define two climate types. Although the boundary between types is ogists have found it difficult to apply these modern climate classifica- quantitatively defined, what the climate classification defines is in fact tions to deep time (pre-Quaternary), and there are no widely accepted to show the overall characteristics. paleoclimate classifications. Here we propose a new classification for paleoclimates in deep time Deep time climates present special problems for classification, be- based on these considerations. The new classification is established cause the instrumental meteorological parameters are totally lacking, based on the widely used Köppen climate classification. However, such as the temperature, precipitation, wind, and air pressure. All we what we need to note is that the ‘extinct climate’ in deep time cannot know about the paleoclimate comes from indirect evidence from the be discriminated in the new climate classification. geologic records, i.e., the proxies. However, interpretations of indirect evidence are limited because of our incomplete knowledge on the mea- surements of proxies and relatively poor understanding of climate dy- 2. Terminology namics in the past. In consequence, paleoclimate information often has no direct relation to climatic variables used for modern climate clas- In this paper, ‘deep time’ refers to the pre-Quaternary, the part of sification, a gap between modern and deep time climate studies. Earth's history that has to be reconstructed from rock, and is older than historical or ice core records (Soreghan, 2005; Montañez et al., 2011). In a narrow sense, climate can be considered as the “average weath- ⁎ Corresponding author at: State Key Laboratory of Biogeology and Environmental ” Geology, China University of Geosciences, Beijing 100083, China. er for 30 years. In a wider sense, climate is the state of all the statistical E-mail address: [email protected] (C. Wang). description of the climate system (Farmer and Cook, 2013). http://dx.doi.org/10.1016/j.palaeo.2015.11.041 0031-0182/© 2015 Elsevier B.V. All rights reserved. L. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 443 (2016) 98–106 99 Climate classification is a systematic arrangement, gathering cli- results of numerical modeling may contradict the geological proxies, mates into groups or categories using boundaries definedbysimilar as is the case with the ‘cold continental interior’ paradox for the Late conditions and meteorological elements. In this study, the discussion Cretaceous (DeConto et al., 1999). Such model-data discrepancies may of classifications is limited to global and regional climates. be due to incorrect assumption in the initial boundary conditions, poor model resolution, or incomplete representation of the relevant 3. Previous paleoclimate classifications physics (Huber, 2012). In many previous studies, paleoclimates have been classified by 4. A new paleoclimate classification for deep time climatically sensitive deposits, paleontologic evidence, and by numerical modeling. 4.1. Method Since the middle of the last century, many researchers have attempted to reconstruct climate zones in deep time by analyzing the We modify Köppen climate classification to adapt it to deep time. To distribution of climatically sensitive deposits (Strakhov, 1967; accomplish this, we used the following steps: 1) determining the Bárdossy, 1982; Hallam, 1984, 1985). Deposits indicative of special con- paleoclimate parameters that are available in deep time studies; 2) in- ditions, such as evaporites, calcretes, tillites, laterites and bauxites, are vestigating the relation of these paleoclimate parameters to the modern widely distributed both in time and space. They have been used to clas- climate types recognized in Köppen climate classification; 3) redefining sify paleoclimates in the early Phanerozoic before the rise of land plants the climate types and their boundaries by these paleoclimate parame- or animals (Boucot et al., 2013), and younger times (Chumakov, 2004; ters; and 4) testing and verifying the new paleoclimate classification. Winguth and Maier-Reimer, 2005; Guo et al., 2008; Dera et al., 2009; In the new climate classification, the threshold values for the bound- Boucot et al., 2013). Most of these indicators are qualitative, although aries are determined based on the principle that the threshold value can some of them can be interpreted as semi-quantitative (Tabor and minimize the misallocation of observed Köppen climate at each station Poulsen, 2008; Craggs et al., 2012). However, climate classifications into the new groups. based on these commonly have no more than 5 climatic zones on a global scale, and even fewer on regional scales. Such low-resolution classifi- 4.2. Köppen climate classification cations cannot always provide enough climatic information for paleoclimate studies. In the late 19th century Köppen proposed the first quantitative clas- Palynological and macro-plant materials have been extensively used sification of world climates (Kottek et al., 2006), and it remains the most to evaluate ancient climatic conditions (Parrish, 1998; Royer, 2012; widely used (Rubel and Kottek, 2011). It is based on the idea that the Boucot et al., 2013). The abundance, diversity and distribution of vege- vegetation is the best expression of long-term climate conditions. The tation types (Larsson et al., 2010), morphology and structure of the boundaries are a hierarchical system related to vegetation distributions plant, especially the leaf physiognomy (Wolfe, 1995; Wilf, 1997; Wilf that reflect major climate variables. Köppen climate classification com- et al., 1998; Spicer, 2012) are valuable climate indicators. It is generally bines average annual/monthly temperatures, average annual/monthly assumed that the conditions under which a plant lived were similar to precipitation, and seasonality of precipitation (Kottek et al., 2006; Peel those of its nearest living relatives (NLRs) (Vakhrameev et al., 1991; et al., 2007). Iannuzzi and Rösler, 2000; Sun and Wang, 2005; Fernández et al., The classification is a hierarchy that starts by recognizing five major 2007; Iglesias et al., 2011). climates, denoted by letters: A = Tropical; B = Arid; C = Temperate; Many studies have used the distribution of invertebrates to define D =

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