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Climate and Flora of the Puercan in the Denver Basin, CO Laurel Butterworth, Khalil Flowers, Blen Abamecha, Aeon Way-Smith Abstract: The Denver Basin has historically been of great interest to all sorts of

Findings: In the flora, ~60% of the morphotypes were smooth. This resulted in a MAT of 19.5 ± 4.7 :C or 67.1

paleontologists due to its unique position in time, immediately after the K-Pg extinction in an age called the Puercan, and to the fascinating fossils it contains. Recent discoveries in the Denver Basin that help to address lingering questions regarding how plants and animals recover from catastrophic disasters have attracted world renowned experts and Teen Science Scholars (TSS) alike. Museum staff and TSS have spent the last several months focused on the Corral Bluffs region of the Denver Basin, collecting and analyzing fossils to flesh out what the first million years after the K-Pg extinction looked like, essentially bringing it to life. To do this, the paleobotany TSS team excavated leaf fossils in Corral Bluffs. These fossils were brought back into the lab where the scholars identified, classified, photographed, and measured the leaves in order to determine mean annual temperature (MAT) and mean annual precipitation (MAP). The scholars found a MAP value of 525 cm of rain per year and a MAT value of 19.5 :C (67.1 :F). These values, along with the presence of palms in the flora, suggest the environment was similar to that of a modern day moderate rain-forest with plenty of rain, no frost, and warm temperatures. In the context of vertebrate fossils, which includes crocodiles, turtles, and an abundance of mammals, leaf data confirms that the environment was warm, lush, and wet. Understanding these environmental characteristics broadens the understanding of post-K-Pg North America and how the world’s ecosystems recovered from one of the greatest extinctions in the history of life on Earth.

± 8.5 :F. Approximately 38% of the leaves were Noto, 48%, Meso, and 23% Macro size class. This resulted in an estimate of 525 cm of rain per year. In addition to MAT and MAP the flora contained 10 unique dicot morphotypes and 23 morphotype in total, with a sample size of 144 leaves.

Geology: The Late Cretaceous and Early Paleocene sequence in the Denver Basin began to form ~70 million years ago. It centered in Eastern Colorado with sites in Colorado Springs, Denver, and other cities. The Denver Basin is made up of terrestrial sedimentary rock layers that were deposited in ancient swamps, rivers, and lakes. A feature of the Corral Bluffs area is its numerous braidedstream channels and floodplain ponds. These depositional environments allowed for excellent fossil preservation but washed away the K-Pg iridium layer.

Monocots Dicots

No. of Morphotypes

No. of Specimen

% of Morphotypes

% of Specimen

2

2

0.083

0.014

11

113

0.458

0.784

Ferns

6

24

0.25

0.167

Other Plant Organs

2

3

0.083

0.021

Other

2

2

0.083

0.014

24

144

Count for all Morphotypes

Above (Table 1): This table breaks down the specimen and morphotypes into their different taxonomic categories by both number and percentage of total dataset. Right (Table 2): This table is used for calculating both MAT and MAP. It includes morphotype number (column 1), organ of the plant (column 2), number of samples per species (column 3), and whether or not the leaf is toothed (column 4). This data is used for the calculation of MAT. Columns 5-11 break down the different morphotypes into size categories to calculate MAP.

Morph-type #

Organ

# of specs

Toothed (0) Smooth (1)

2.1

SEED

2

N/A

2.2

SEED

1

N/A

0.000

0.000

0.000

0.000

0.000

0.000

0.000

7.1

FERN

10

N/A

0.000

0.000

0.000

0.000

0.000

0.000

0.000

7.2

FERN

5

N/A

0.000

0.000

0.000

0.000

0.000

0.000

0.000

7.3

FERN

5

N/A

0.000

0.000

0.000

0.000

0.000

0.000

0.000

7.4

FERN

2

N/A

0.000

0.000

0.000

0.000

0.000

0.000

0.000

7.5

FERN

1

N/A

0.000

0.000

0.000

0.000

0.000

0.000

0.000

7.6

FERN

1

N/A

0.000

0.000

0.000

0.000

0.000

0.000

0.000

11.1

MONO

1

N/A

0.000

0.000

0.000

0.000

0.000

0.000

0.000

11.2 12.1

MONO LEAF

1 1

N/A N/A

0.000 0.000

0.000 0.000

0.000 0.000

0.000 0.000

0.000 0.000

0.000 0.000

0.000 0.000

13.1

LEAF

1

1

0.000

0.000

0.000

0.000

0.000

0.000

0.000

16.1

LEAF

32

0

0.000

0.000

0.000

1.000

0.000

0.000

0.000

16.2

LEAF

5

0

0.000

0.000

0.000

0.333

0.333

0.333

0.000

17.1

LEAF

5

0

0.000

0.000

0.000

0.500

0.500

0.000

0.000

22.1

LEAF

25

1

0.000

0.000

0.000

0.500

0.500

0.000

0.000

24.1

LEAF

19

1

0.000

0.000

0.000

0.000

0.000

1.000

0.000

30.1

LEAF

3

1

0.000

0.000

0.000

0.000

1.000

0.000

0.000

33.1

LEAF

16

0

0.000

0.000

0.000

1.000

0.000

0.000

0.000

35.1

LEAF

3

1

0.000

0.000

0.000

0.000

1.000

1.000

0.000

35.2

LEAF

3

1

0.000

0.000

0.000

0.500

0.500

0.000

0.000

41.1

N/A

1

N/A

0.000

0.000

0.000

0.000

1.000

0.000

0.000

Unspecified

N/A

1

N/A

million years ago) in the Denver Basin was swampy and forested, moist and warm. The flora was exceptionally diverse and dominated by dicotyledonous angiosperms. It also contained abundant palms, other monocots, ferns, and herbaceous lycopods. The Paleocene flora indicates similar climate conditions but the flora is depauperate, and shows a very low diversity. This is because about 60% of plant species went extinct at the K-Pg boundary.

Leaf Size Lepto

Nano

Micro

Noto

Meso

Macro

Mega

Methods (Lab): After leaf fossils are found they must be identified and catalogued. Using a flow chart of different leaf characteristics, morphotypes are determined and leaves are numbered. Morphotypes are then photographed for further study and display.

Methods (MAT and MAP Calculations): Morphological data and the number of specimen per species are entered into a calculation spreadsheet in order to determine MAT and MAP. MAT is determined by calculating the proportion of smooth leaf morphotypes to toothed leaf morphotypes. MAP is determined by calculating the percentages of morphotypes in seven leaf size groups: Lepto, Nano, Micro, Noto, Meso, Macro, Mega.

Discussion: The MAT and MAP data combined with other calculated and observed characteristics suggest the Puercan climate in the Denver Basin was subtropical and rainy, similar to modern day Costa Rica. It is likely that the Puercan Denver Basin never saw frost during the Puercan as palm fronds are heavily featured in the fossil record. The subtropical climate of the Puercan Denver Basin allowed for palm fronds, medium sized leaves, and some paleobotanical treasures such as pea pods to develop. The quarry

Left: Khalil digs on the quarry. Right: Paleobotany team sits on the quarry with Jeremy Wyman and Allie Skaer

Methods (Field): Due to water, wind damage, and erosion, rocks containing intact leaves are unlikely to be on the surface. In order to obtain them, scientists must dig into the sides of hills to expose the more intact rocks underneath. Scientists use pick axes and shovels to remove the dirt and create a bench like surface called a quarry. Once the quarry is finished, large blocks of solid rock can be removed and cleaved with rock hammers in order to reveal fossilized leaves inside.

View of both quarries, the one to the right was made entirely by TSS

Major Taxonomic Categories

Late Cretaceous and Early Paleocene Flora: The Late Cretaceous period (ca. 66.5

History: In the mid-1800s, The Denver Basin was discovered by F.V Hayden’s survey. The Hayden Survey collected fossil leaves from the Laramie Formation, close to Marshall, CO. In the 1940s, R. Brown discovered the K-Pg boundary on South Table Mountain, Near Golden, CO. This exposure was the first recorded K-Pg boundary, on land, in the world. However, it wasn’t until the Denver Museum team began work in the Basin in the late 1990s, that the precise location of the K-Pg boundary was determined and the large datasets of Puercan leaves were collected.

Kirk Johnson Circa. 2007

Glossary: Flora – Plants from a particular region or time period. Fauna – Animals from a particular region or time period. K-Pg extinction or boundary – The Cretaceous-Paleogene extinction happened 66.043 million years ago and is best known for killing the dinosaurs though it also killed off up to 70% of all life on Earth. The K-Pg boundary refers to the line the extinction makes, separating the Cretaceous from the Paleogene. Note: The Cretaceous and Paleogene are both Geologic times. Morphotype – A group of different types of individuals in the same species. Essentially, a type of biological grouping of individuals. Paleobotany – The study of prehistoric plants. Puercan – A faunal time period lasting 2.7 million years (from 66,000,000 to 63,300,000 years ago). It is a North American Land Mammal Age (NALMA), a time scale based off the presence of certain mammals.

View of Corral Bluffs

A collection of fossil leaves

Blen with camera setup to photograph leaves

Conclusion: Over the course of the summer the Teen Science Scholars took part in fieldwork, research, and calculations in order to give an accurate answer one essential question: What did the Denver Basin look like the first million years after the K-Pg extinction, also known as the Puercan? In order to answer this, the paleobotany team did research on the climate and temperature of the Denver Basin. While digging in quarries, leaf fossils, palm fronds, and a legume pod were found. Using the data from these fossils, MAT was calculated to be 19.5 :C (67.1:F) and MAP was found to be 525 cm per year. The combination of this warm, wet environment with the palms, ferns, and leaf fossils, paints a picture of the Denver Basin as a green, subtropical environment, even in the midst of post K-Pg recovery. Bibleography: Saupe, S. G., Dr. (2009, January 7). Leaf Margin Analysis, Or, Are Leaves Good Predictors of Climate? Retrieved July 31, 2017, from https://employees.csbsju.edu/ssaupe/biol327/Lab/Leaf_Lab/leaf_climate_lab_phys-ver2.htm C. (n.d.). Preserve Corral Bluffs. Retrieved July 31, 2017, from http://www.corralbluffs.org/

Awknowledgements: TSS Paleobotany would like to thank

Nichols, D. J., & Johnson, K. R. (2008). Plants and the K-T Boundary. New York , NY: Cambridge University Press.

their fellow TSS Earth Science colleagues: Kathleen Laughton, Brynn Wooten, Jairo Fontes, and Leslie Gutierreza, and their mentors, Dr. Ian Miller, Dr. Tyler Lyson, and Kent Hupps. TSS Paleobotany would also like to thank the people who helped them in the field including: Dr. Lou Taylor, Dr. Rich Barclay, Jeremy Wyman, Chris Noll, and Claire Wineman. Additionally, TSS Paleobotany would like to thank those who helped them in the museum and especially in the lab: Geoff Flora, Kristen MacKenzie, Allie Skaer, and Sariah Rushing. Finally, TSS Paleobotany would like to thank the museum at whole and the donors for this incredible opportunity to work with scientists and do impactful research, this has been truly a once in a lifetime experience.

Johnson, K. R., Reynolds, M. L., & Thomasson, J. R. (2003). Overview of the Late Cretaceous, early Paleocene, and early Eocene megafloras of the Denver Basin, Colorado. Rocky Mountain Geology,38(1), 101-120. Raynolds, Robert G., and Kirk R. Johnson. "Synopsis of the stratigraphy and paleontology of the uppermost Cretaceous and lower Tertiary strata in the Denver Basin, Colorado." Rocky Mountain Geology38.1 (2003): 171-81. Print. Wilf, P. (1997). When are leaves good thermometers? A new case for Leaf Margin Analysis. Paleobiology,23(03), 373-390. Wilf, P., Wing, S. L., Greenwood, D. R., & Greenwood, C. L. (1998). Using fossil leaves as paleoprecipitation indicators: An Eocene example. Geology,26(3), 203. Rosen, M. (2017, February 4). Dino Doomsday The Survivors. Science News Magazine Society for Science & The Public, 191(No.2), 22-25. Sumner, T. (2017, February 4). Devastation Detectives. Science News Magazine Society for Science & The Public, 191(No.2), 1621.

Aeon holds a leaf fossil

Johnson, K. R. (2002). Megaflora of the Hell Creek and lower Fort Union Formations in the western Dakotas: Vegetational response to climate change, the Cretaceous-Tertiary boundary event, and rapid marine transgression. Special Paper 361: The Hell Creek Formation and the Cretaceous-Tertiary boundary in the northern Great Plains: An Integrated continental record of the end of the Cretaceous,329-391.

Profile for laurelebutterworth

Paleobotany Poster (Denver Museum of Nature and Science)  

This poster entitled, "Climate and Flora of the Puercan in the Denver Basin, CO" was written, in part, by Laurel Butterworth for the Denver...

Paleobotany Poster (Denver Museum of Nature and Science)  

This poster entitled, "Climate and Flora of the Puercan in the Denver Basin, CO" was written, in part, by Laurel Butterworth for the Denver...