Quanta 650f

An edge of the MIP films on glass was removed using a razor and the film was coated with sputtered gold. An FEI Quanta 650F field emission scanning electron microscope (FEI, Hillsboro, OR, USA) was used for imaging of the MIP film section with secondary electrons at a 70° tilt and 10 kV acceleration potential. A thickness of film (H) was estimated based on average height of seeming 90° section measured on SEM image (H′) and the tilt angle:
Thickness values for three films of the same kind were averaged.

Conventional (light) photographs were taken with either a Canon EOS 7D Mark II camera mounted on a BK Lab Plus Lab imaging system (Dun Inc., Charlottesville, VA, USA), a Leica DVM6 microscope (Leica Microsystems GmbH, Wetzlar, Germany), or a Nikon D100 digital camera using a standard copy stand. SEM images were taken with a FEI Quanta 650F variable-pressure field-emission SEM (FEI Company, Hillsboro, OR). The FEI microscope was operated at 15 kV, with a spot size of 2.45 and working distances of about 12 to 15 mm. Notably, the high conductivity of the rocks from McGraths Flat allowed high-resolution SEM imaging without any coating. All microfossils were imaged in situ (i.e., in the matrix) rather than using acid preparation. Micro x-ray fluorescence (μXRF) was undertaken by directly sampling across the surface of a rock containing a fish spine (AM F.146602) using a benchtop M4 Tornado μXRF (Bruker Corp., Billerica, MA). This allowed us to sample both the fossil and matrix for differences in chemistry. The instrument consists of a Rh anode metal-ceramic x-ray tube. The measurement was carried out under vacuum condition (20 mbar). The following parameters were used for elemental mapping analysis: x-ray tube, 45 kV and 600 μA; area mapping point distance, 60 μm; time/pixel, 600 ms; 1 cycle; maximum energy, 40 keV; and maximum pulse throughput, 130 kilo counts per second.