reflecting global eustatic sea level changes, probably
related to glaciations in Brazil; and (d) the reefs reflected
back-stepping events to the east during sea level
highstands, and westward retreat at lowstands. The
Frasnian is generally characterized by a lower diversity
reef ecosystem than seen in the preceding Middle Devonian, with the Devonian reef ecosystem collapsing stepwise toward the end of the Frasnian Mass Extinctions
(Copper, 2002) (Figures 1 and 2).
The Banks reef builders were dominated by exquisitely
preserved stromatoporoid sponges as massive, platy forms
meters thick, and in large domal forms that inhabited the
open ocean, high energy fore-reef zone. In the back-reef
lagoons, or off-reef deeper waters, stromatoporoids and
corals grew as branching structures (Copper and Edinger,
2009). The corals and sponges probably had photosymbionts, as do many modern reef dwellers. The digitate
stachyodid and slender matchstick-sized amphiporid
Banks Island: Frasnian (Late Devonian) Reefs In Northwestern Arctic Canada, Figure 3 The carbonate platform levels B, C and D
of the Frasnian Mercy Formation as seen from the air looking northwest along the East Mercy River branch. The B level reef is in
the upper left background, and C-D levels in the foreground.
Banks Island: Frasnian (Late Devonian) Reefs In Northwestern Arctic Canada, Figure 4 D-level upper 11A and 11B reefs in the
Mercy Fm along the M’Clure River, northeast coast Banks Island: these reefs rest on top of siliciclastics and are buried by deltaic
siliciclastics (NTS 88C/14, N74
0.371
0
, W117
, 0.727
0
).
BANKS ISLAND: FRASNIAN (LATE DEVONIAN) REEFS IN NORTHWESTERN ARCTIC CANADA
95
related to glaciations in Brazil; and (d) the reefs reflected
back-stepping events to the east during sea level
highstands, and westward retreat at lowstands. The
Frasnian is generally characterized by a lower diversity
reef ecosystem than seen in the preceding Middle Devonian, with the Devonian reef ecosystem collapsing stepwise toward the end of the Frasnian Mass Extinctions
(Copper, 2002) (Figures 1 and 2).
The Banks reef builders were dominated by exquisitely
preserved stromatoporoid sponges as massive, platy forms
meters thick, and in large domal forms that inhabited the
open ocean, high energy fore-reef zone. In the back-reef
lagoons, or off-reef deeper waters, stromatoporoids and
corals grew as branching structures (Copper and Edinger,
2009). The corals and sponges probably had photosymbionts, as do many modern reef dwellers. The digitate
stachyodid and slender matchstick-sized amphiporid
Banks Island: Frasnian (Late Devonian) Reefs In Northwestern Arctic Canada, Figure 3 The carbonate platform levels B, C and D
of the Frasnian Mercy Formation as seen from the air looking northwest along the East Mercy River branch. The B level reef is in
the upper left background, and C-D levels in the foreground.
Banks Island: Frasnian (Late Devonian) Reefs In Northwestern Arctic Canada, Figure 4 D-level upper 11A and 11B reefs in the
Mercy Fm along the M’Clure River, northeast coast Banks Island: these reefs rest on top of siliciclastics and are buried by deltaic
siliciclastics (NTS 88C/14, N74
0.371
0
, W117
, 0.727
0
).
BANKS ISLAND: FRASNIAN (LATE DEVONIAN) REEFS IN NORTHWESTERN ARCTIC CANADA
95