100 meters N
North to South Cross Section across GVSU Campus
fine silty sand (lacustrine)
clay, silt and fine sand (lacustrine)
diamicton (basal till)? Marshall Sandstone
~ 480-510 feet
S distance (meters) N
vertical exaggeration ~16:1
Alluvial Fill Properties
• Upper Fill • Lower Fill
– Texture is variable – Texture is silt and clay
– Organic % is moderate – Organic % is low to
to high moderate
– Carbonate % is low – Carbonate % is high
– Massive and – Mainly massive to
laminated fines and finely laminated.
sorted sand and
Radiocarbon Analyses From Alluvial Wood – Little Mac Ravine
Sample core analysis C-14 Age Calibrated Years
Beta-217917 stream C 180 ± 40 BP 290-260 Cal BP upper fill
(GVSU-1) exposure (1660-1680 AD)
wood near GV-1 220-140 Cal BP
20-0 Cal BP
Beta- 235467 GV-7 C 190 ± 50 BP 310-60 Cal BP upper fill
(GVSU-4) (1640-1890 AD)
Wood 40-0 Cal BP
Beta-231594 GV-3 AMS 320 ± 40 BP 480 to 310 Cal BP upper fill
(GVSU-3) (1470-1640 AD)
Beta-223048 GV-2 C 5070 ± 80 BP 5920-5720 Cal BP lower fill
(GVSU-2) (3960-3770 BC)
C = Conventional radiocarbon method
AMS = accelerator mass spectrometry method
• At least two alluvial fill units are present.
– Older fill - middle Holocene or older?
– Younger fill - Post-settlement ?
• Younger fill is from 0.5 to 2.5 meters thick
over most of the valley.
• Suggests a large change in sedimentation
rates since settlement.
• Thanks to the students in environmental
geology classes who helped with the field
and lab work.
• GVSU Geology students Rhiannon
Mulligan, Sarah Nagorsen and Anthony
Rodriguez who worked on research
projects in past geomorphology classes.