PALYNOMORPHS

by Dr. Paul F. Ciesielski Univeristy of Florida

I. Introduction to palynomorphs

Palynology- The study of acid resistant organic walled microfossils

A. Types of Palynomorphs

Spores: reproductive bodies of non-flowering "lower" plants (algae, fungi, mosses, ferns)

Range: Silurian to Recent

Pollen: male germinant bodies of seed plants (microgametophytes) and gymnosperms.

Range: Penn. to Recent

Dinoflagellates: biflagellate, unicellular algae

Range: Permian to Recent

Acritarchs: microscopic fossil cysts, probably primative ancestors to dinoflagellates.

Range: PreCambrian to Recent

Chitinozoans: unknown systematic position

Range: Ordovician to Devonian

B. Common characterstics

undergo rapid diversification
excessively resistant to geologic obliteration
easy to process
numerous
facies indicators
sensitive to oxidation
metamorphic threshold- greenshist facies

C. Preservation

strong oxidation destroys them (e.g. beach sediments are barren)
long periods of transportation (and oxidation) destroys them
alkaline environments cause soaponification (transformation of sugars to soap)

D. Color of palynomorphs

appear glassy in limestones
appear brown or amber in shales because of polymerizing by radioactivity

E. Color and Metamorphism

The organic walls of palynomorphs change color with increasing burial temperature and can be used to interpret post-depositional geothermal gradients. Progressive color changes are as follows:

yellow to glassy
yellow
orange
brown
black-brittle-graphitized

F. Alteration of palynomorphs

the larger of overburden the greater the compression
at 1000' spores will flatten and remain so to 6000'
at 6000' they will under metamorphism
do not metamorphose in chert or as rapidly in shale because of incompressibility
usually broken in sandstone
unconformities usually barren
water of high alkalinity destructive
resistance of spores proportional to the amount of sporopollinine

G. Lithologies and Preservation

Better preservation in siltstones, shales, and marls
Poorer preservation in quartzite, porous sandstone, recrystallized limestone or dolomite, dolomite

II. POLLEN

A. General information

generally 20-80 microns but rarely <10 or >200 microns
from anthers of angiosperms (flowering plants) and microsporangia of gymnosperms (pines, spruce, firs)
first gymnosperm pollen- Carboniferous
first angiosperm pollen- Cretaceous

B. Classification

shape most important
sculpture next in importance

III. SPORES

A. General Inforamtion

reproductive bodies of non-flowering "lower" plants (algae, fungi, mosses, ferns)
spheroidal, tetrahedral or elongate
generally biconvex or planoconcave
surface sutures- surface sutures,scars or laesurae

monolete- Pennsylvanian
trilete- Lower Silurian to Recent
alete (no suture)

heterospores (Devonian)- two types by some plant of different size

microspores- male (<200 microns)
megaspores-female; many 500-2000 microns

IV. Chitinozoans

A. General Information

an extinct group of unknown taxonomic affinity
hollow, organic walled
radially symmetrical about longitudinal axis
range: Ordovocian-Devonian

B. Morphology

flask-shaped chamber

shoulder
flank
oral tube
neck
base with central pore and concentric ribs
basal margin, sometimes with appendices

C. Classification

colonial tendancy
shape
nature of basal margin
internal structure
size

D. Biostratigraphy

less abundant than age-equvalent palynomorphs such as acritarchs
1-20 tests/ gram
many remain identifiable in strongly metamorphosed rock

V. ACRITARCHS

A. MORPHOLOGY

varied: fusiform, discoid, spheroidal, polygonal
with or without spines and processes
size and chemical composition only common features
classified into non-Linnaean groupings and 13 subgroups without type genera
apparently unicellular
test of organic substances, enclosing a central cavity
surface sculpture: smooth, granular, punctate, or perforate. Sculpturing <5 microns, generally <2 microns
spines and other processes many be present: ridges, flanges, wings, spines. Such processes >10-20% of central body diameter.
process differences important in classification

B. BIOSTRATIGRAPHY

found in the PreCambrain

Gunflint Chert (2 billion years old)
provide some limited stratigraphic use in PreCambrian of Scotland and Russia

among palynomorphs, second only to Chitinozoans in stratigraphic importance for Ordovician, Silurian, and Devonian
remain abundant in Upper Paleozoic and Lower Mesozoic but less varied in morphology
a restricted number of types are present from the Upper Mesozoic to Recent. Known from Quaternary marine and non-marine record

VI. DINOFLAGELLATES

A. GENERAL

unicellular algae
biflagellate
5 microns to 2mm
autotrophic, photosyhthesis
have a vegetative stage and a encysted stage or resting cyst

B. BIOSTRATIGRAPHY

oldest in the Silurian of Tunisian
not certainly found again until the Permian
insignificant in abundance until the Lower Jurassic
assume considerable importance in the Middle Jurassic
earliest calcareous dinos from Upper Jurassic
some siliceous ones appear in Early Tertiary

C. ECOLOGY-PALEOECOLOGY

phytoplankton
prefer constant light conditions, undergo diurnal migration
greatest concentration at 18-90m, 1-10m in turbid water
never >200m
must have sufficient water depth to undergo diurnal migration
dominant phytoplankton of the upper layer of ocean
greatest concentration above diatoms and coccolithophores
reduced abundance in with reduced salinity
oceans divided into floral provinces
cysts with thick walls indicate unstable, near-shore conditions
thinner walls found in open marine environment and have more elaborate processes (for flotation)
note that spores and pollen most common palynomorphs near shore with increasing acritarchs and dinos further from shore. Dominance of acritarchs and dinos in open marine environment