Tiny witnesses of time

Most of us have heard about fossils like ammonites, Nautilus, Propalaeotherium or the Neanderthals. In one of the Chicxulub-cores a fossil can be seen on the screen where high resolution images are displayed:

bmatyssekecord_iodp_foraminifera
This is the shell of the marine foraminifera-microfossil

Heather Jones and Jan Smit are members of our onshore science party of Expedition 364 Chicxulub K-Pg Impact Crater in MARUM, Bremen. Jan Smit has been looking at Foraminifera (“forams“) since the seventies, and Heather started some years ago – one of her teachers was, as Heather puts it, “addicted to nannofossils“. These are even smaller! This teacher-student relationship opened the door for a career in paleontology for Heather. Chris Lowery is in Bremen for paleontology too.

 

bmatyssekecord_iodp_coccolith
The calcareous coccoliths are between 3 and 15 micrometer big (a pin head has a diameter of 2000 micrometer) – see scale! Star-shaped calcareous coccolith, one of several structures encapturing the body of coccolithophorid.

 

bmatyssekecord_iodp_microfossil_literature
Researcher use high resolution pictures to find species under the microscope, but the individuals might look a little bit different due to their orientation.

 

Microfossils’ size is less than three millimeters and nanofossils’ size is less than 50 micrometer, but these are only guidelines. Micro- and nanofossils are used in geosciences because they carry important biostratigraphic information. Looking out for Foraminfera or Coccolithophoridae in the cores that were drilled at Chicxulub Heather and Jan want to figure out how life came back after the great impact event at Chicxulub.

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Methylene blue-dyed foraminifera seen under the microscope

 

There can be hundreds of thousands individuals per gram. Even the smallest sample quantities of drill cores allow to obtain this information. The microfossils are highly responsive to minimal environmental changes.

“Foraminifera“ are tiny little species with small chambers and different symmetry forming beautiful individuals and species. “Fora“ (latin) mean little hole and “fera“ is derived from greek “pherein“ which means to bear, so they are “hole bearers” (compare also phosphorous, Lucifer). These amazing tiny creatures are made of calcite and have beautiful sounding names such as “Globigerinoides sacculifer”. The substance these microorganisms are made of calcium carbonate.

Foraminifera inhabit marine habitats from the coast to the deep sea. Some of these animals colonize the seabed (benthic). A large part of them live planktonic. Half of the dried samples are colored with methylene blue to make it easier to spot the tiny details under the microscope. Adhering foreign particles like clay and sand are removed in an ultrasonic bath. The solution is filtered, then washed with a laboratory eyewash, and then dried. Ready to study!

Jan has found small Foraminifera in the Eocene 53 million years ago, but not the bigger ones that normally live in deeper water. It could be that 53 million years ago the sea water from the Gulf of Mexico spilled over the crater rim of Chicxulub and allowed only the near-surface, small Foraminfera into the crater – we are curious of what is yet to be discovered!

 

By Barbara Matyssek

All Images: BMatyssek@ECORD_IODP

 

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