Name/Title
Fossil CycadEntry/Object ID
05.58.141Description
Assemblage Zone: sandstone sediments
Chemical Composition: Si O2
Crystal System: Hexagonal
Description: Order: Cycadeoidales
Family: Cycadeoidiaceae
Common name: Fossil Cycad
Age: Jurassic
Location data: Morrison Formation, Arizona USA
Description: Outer side shows the texture of the plant in shades of browns, the polished end shows a crystalline center surrounded by black to dark browns
Type of Fossils Present: Plants
Fracture: conchoidal
Grain Size: Fine
Hardness: 7 Quartz
Lithofacies: Fluvial System
Luster: Glassy
Occurrence: The fossil cycad produced during the Jurassic period Brushy Basin Member of the Morrison Formation hodgepodge of lithologies, consisting mostly of fine-grained volcaniclastic mudstones with supporting sequences of fine- to coarse-grained sandstones, conglomerates, calcretes, and even lacustrine limestones. This was a time of felsic volcanic activity, river sediments were laden with ash from these eruptions and the lakes may have been alkaline or even saline during certain times of the year. Flooding deposited coarser-grained sediments and occasionally uprooted, transported, and buried trees. Most cycads are associated with these high-energy sequences.
Fossilization occurs when the plant is buried and minerals dissolved in the groundwater, over millions of years, replace the original plant tissues. Fossilized cycads may occur as leaves or trunks. The trunks somewhat resemble overgrown pineapples turned to stone because of the armor of old leaf bases which protected them in life. Leaves are usually found as carbonized impressions in the rock.
Pressure: Low-Moderate
Rock Color: Medium
Rock Origin: Post-depositional
Rock Type: Sedimentary
Specific Gravity: 2.6
Surface Process: Not apparent
Streak: white
Temperature: Low
Texture: Mircrocrystalline
Variety: The cycads are a group of very primitive ligneous plants bearing a superficial resemblance to palms, although they are not at all related. Cycad are often refer to as a "living fossils," since this group of plants had reached its highest point of evolution during the early Jurassic about 200 million years ago since then cycads have been declining without showing any appreciable changes in their evolution. Present cycads have many characteristics similar to the fossil cycads of 240 million years ago; thus, the name living fossils. Apparently, during the Triassic and Jurassic periods, the cycads enjoyed an abundant distribution, because nowadays, although often very localized, the existing species appear in places such as Polynesian, Madagascar, Japan, South Africa, tropical Africa, Australia, Mexico, Cuba, and Central and tropical America, which gives us an idea of the world-wide distribution that they had in the past.Collection
Petrified Wood CollectionAcquisition
Accession
05.58Source or Donor
Petrified Wood CollectionAcquisition Method
DonationOther Names and Numbers
Other Number
Other Number: 2005.58.141Dimensions
Width
2 inDepth
2-3/4 inLength
3-1/2 inDimension Notes
Dimension taken at widest pointsLocation
Location
Container
RightDrawer
BottomShelf
LeftCabinet
Case#104Wall
East WallBuilding
Mentzer Hall: Petrified Wood RoomCategory
PermanentLocation
Shelf
Top far right, Top far rightWall
EasternRoom
Petrified WoodBuilding
Mentzer Hall: Petrified Wood RoomCategory
Permanent
