49
salt marsh, it is incorporated into the sediment and can stay there, intact, for many
thousands of years. Palynologists can look at a pollen grain using a microscope and
determine what species of plant it came from (don’t judge them, after all it is no
worse than learning to identify species of foraminifera – and a case in point of how
seemingly extravagant, esoteric occupations and fascinations can underpin our
knowledge of broader issues with great socio-economic importance). This is another
example of reasoning by analogy. The natural landscape of forests that existed in
eastern North America in pre-colonial times was disturbed by the arrival of
Europeans who set about efficiently altering the landscape to grow crops and raise
livestock. This shift is preserved in the pollen record and if you know when a particular location was cleared (for example from historical accounts) then observed
changes in down-core pollen can be assigned an age.
All the approaches briefly explained above enable us to determine the age of the
sediment. When this is coupled with our analysis of the sea-level proxy (e.g., foraminifera), a detailed relative sea-level history is produced because we now know the
height of relative sea-level in the past and when it was there.
Fig. 3.10 A Tufts
University student and
professor (Jack Ridge)
collecting a sediment core
in a Boston salt marsh for
an undergraduate senior
thesis project. Some of
these marshes are heavily
impacted by people; we
once hit a buried radiator
when coring here that
someone had dumped
years before. (Image by
A.C. Kemp)
3 Time and Tide Wait for No Man
salt marsh, it is incorporated into the sediment and can stay there, intact, for many
thousands of years. Palynologists can look at a pollen grain using a microscope and
determine what species of plant it came from (don’t judge them, after all it is no
worse than learning to identify species of foraminifera – and a case in point of how
seemingly extravagant, esoteric occupations and fascinations can underpin our
knowledge of broader issues with great socio-economic importance). This is another
example of reasoning by analogy. The natural landscape of forests that existed in
eastern North America in pre-colonial times was disturbed by the arrival of
Europeans who set about efficiently altering the landscape to grow crops and raise
livestock. This shift is preserved in the pollen record and if you know when a particular location was cleared (for example from historical accounts) then observed
changes in down-core pollen can be assigned an age.
All the approaches briefly explained above enable us to determine the age of the
sediment. When this is coupled with our analysis of the sea-level proxy (e.g., foraminifera), a detailed relative sea-level history is produced because we now know the
height of relative sea-level in the past and when it was there.
Fig. 3.10 A Tufts
University student and
professor (Jack Ridge)
collecting a sediment core
in a Boston salt marsh for
an undergraduate senior
thesis project. Some of
these marshes are heavily
impacted by people; we
once hit a buried radiator
when coring here that
someone had dumped
years before. (Image by
A.C. Kemp)
3 Time and Tide Wait for No Man