Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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LAB 8: INTRODUCTION TO FACIES: PLEISTOCENE SEA LEVEL
CHANGES IN HECATE STRAIT AND MODERN AND ANCIENT TETHYAN
HEXACTINELLID SPONGE REEFS
PART 1: WISCONSINAN HOLOCENE FACIES IN HECATE STRAIT
Read and examine the coastal evolution posters by Hetherington et al and the Barrie et al paper on
Hecate Strait and the Queen Charlotte Region. Note the maps on the posters and other figures
containing sedimentological information (seismic sections and facies strip logs of cores containing
grain size, sedimentary structure, fossil information and 14C age. Pay particular attention to the sea
level changes. Some of this is eustatic (ice versus water on the planet) and some of it is glacial-isostatic
(loading, unloading & flexing the local crust). Answer each question and discuss this with maps or
other illustrations. !0Ka is officially the boundary between the Wisconsinan Ice Age (Latest
Pleistocene) and the Holocene interglacial period. Hear are a pair of maps from near ice maximum and
during the start of the big Holocene recession. The maps are very qualitative from rebound data, dated
glacial versus beach deposits, eclectic information widespread, scant and contoured with a broad
brush. Look at the deglacial poster and the web for more information. Last glacial maximum was
between 25 ka and 21 ka depending on where on the map you are. The exent of ice caps on land is
from grounding lines, outwash fan deltas, deep permafrost (pro ice). Sea ice in the arctic & Atlantic was
likely complete in winter but there may have been katabatic polynya and open leads from upwelling.
Global sea levels were lowered ~130 m at LGM from exposed carbonates far from glaciated areas.
Close to Ice fronts flexure, downwarping, and glacial rebound all play variable roles depending on ice
thickness, crustal thickness and crustal strength. Underneath Arctic and Eastern Canada the crust is
thick and strong and the underlying mantle is cold and stiff with a viscosity of ~1023 poise (dynecm/s2). Queen Charlotte Basin was a rift margin like the Sea of Cortez up until ~10 Ma so the crust is
thin (<20 km) and the mantle is hot and weak of ~1019 poise (dyne-cm/s2). Because of this eastern
and Arctic Canada is still slowly rebounding while it happened fast here in the west over a few
hundred years at most. This leads to some interesting sea level & facies changes as you will see below.
Last Glacial Maximum (Late Wisconsinan in N. America)
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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1. What was the duration (start & end time) of Wisconsinan ice cover in Hecate Strait?
(3 points)
2. Look at the map below and assume that the elevation on the summit of the Coast mountains is
~4000 masl such as -128°W, 54°N. If this ice at LGM extended from there to the continental margin
near Kunghit Island and the the mouth of Moresby Trough, how thick was the average ice at LGM over
central Hecate Strait near -130°W, 52.5°N? (Assume a wedge shaped ice profile and -130 m of sea level
lowering. What was the angle on the top of the ice sheet if this was true?
(5 points)
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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3. Note the location and depth of Goose, Mitchell and Moresby Troughs. From the above map and the
Heatherington poster on the late Pleistocene sea level history: a) Speculate on their origin (1). ______
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b) Examine the reflection seismic profile and core END92A21 off Hotsprings Island. Note the erosional
profile. What type of sediments and depositional environment made the deeper strongly reflective
layers(1)? ________________________________________________________________________________________________________
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c) How does this contrast with the modern water depth and environment(2)? ___________________________
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d) What does this indicate for the original depositional environment at 10.5 Ka (this location currently
at -116 m sub sea level) (1)? ___________________________________________________________________________________
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4. Examine core END87A23 on Cook Bank. What is the significance of the 14C date at 90 cm sub
seafloor? What kind of organism was responsible for this material and would it be found there in
living position today? (2) _______________________________________________________________________________________
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5. Note the Paleo Delta including its bed-forms, geomorphology from reflection seismic and maximum
grain size from the coring information a) What was the approximate water depth of the top-set beds
at the time of deposition between 11.4 and 11.0 Ka? (1) ____________________________________________________
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b) Examine the position of this delta & speculate on the source of the river which likely fed into it. (2)
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c) Has the sea level changed or has the land level changed or both and what might cause either to
happen? (3) ______________________________________________________________________________________________________
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6) Examine the Eastern and Northern shorelines of Rose Spit in Naikoon Provincial Park on Graham
Island in air photo and beach exposures. a) What are the active coastal processes occurring there
today? (2) b) Describe or sketch a cartoon map and cross section of what you think the coastline of
Naikoon Provincial Park might look like in 50 years and the orientation of any sedimentary features
likely ? (5) ________________________________________________________________________________________________________
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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--------Cross Section --------------------
7. Sketch a simple cartoon map below with an outline of the modern Gwaii Haanas (Queen Charlotte
Islands). a) Show the approximate location of the shoreline circa 10 Ka in a. different colour. (1)
b) Discuss any uncertainties based upon what you know about glacial isostatic (gravitational
equilibrium) loading and global sea level changes. (2) c) Where were the fishing grounds for the Haida
at that time? (1) d) How did the coastline change between 17 Ka and now? (1) (5 points total) _______
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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8. The oldest Salish cultural sites date to about 6 Ka (Tlingit, Haiida, Haisla, Tsimishan). a) Examine
the Sea level curve and speculate on where one might seek older archeological evidence to confirm
oral tradition that the coastal First Nation Haida people have been here longer. (2) b) According to
oral tradition, the Haida have always lived in Gwaii Haanas. Have they always lived at the modern
locations for Kunga, Masset, Skidegate, Cumshewa, Tian, Tanu, Ninstints and Skedans village sites?
Where do you think there might have been village sites prior to 6 Ka presuming they were still shorebased communities? Put some likely dots on your map above. (3) (5 points total) ____________________
1st graph is distal sites far from isostatic effects. 2nd graph is Waelbroeck et al. (2002) from IPCC report
for entire span from Sangamon interglacial through Wisconisinan and Holocene Interglacial.
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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9. Examine the 1st 2 maps in this handout, the posters and the map below. Anthropologists favour the
Beringia hypothesis for the migration of Human populations into North America. Given that the NEhalf of the
Bering Sea and all of the Chukchi seas are shallow <60 m there may have indeed been some land or ice to
walk across. Marine coring and Quaternary sections on land suggests that perplexingly much of Alaska and
Beringia might have been ice free at LGM, while the Eastern Aleutians, Kenai & Seward Peninsulas held an
ice cap. Murray Seamount cores (ODP Leg 145) gave us ~1 km of glacial dropstone diamict with
Alaskan/Yakutat/Wrangell provenance for the Pleistocene section so there were at least calving tidewater
glaciers for substantial periods. .a) Discuss the pros and cons for the Interior versus coastal routes apropos
your findings on the sea level history and changing facies for Later Pleistocene/Early Holocene in Hecate
Strait. (2) b) When and how do you think the Haiida people arrived at Haiida Gwaii given the geological
constraints? (3) (5 total)
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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PART 2A: MODERN HEXATINELLID SPONGE REEFS IN HECATE STRAIT
Hexactinellids are the most ancient group of sponges but while once tropical and more widespread,
their modern distribution is severely restricted to cold, sparsely populated deglacial seabeds in high
latitude oceans. Finding large ~10ka old colonies of them on the floor of Hecate Strait is unique and
noteworthy on a world scale. The oldest demosponge biomarker evidence, ~635 Ma (24-isopropylcholestane, a steroid compound) is from the late Cryogenian (Marinoan glaciation) in Oman (Love et
al., 2009). There are no known Ediacaran spicules, but sponges undoubtedly existed then. There may
be a seawater chemistry/diagenetic explanation for the non-preservation of siliceous spicules, which
are common in most sponges including the presumed basal clades (demosponges). Jim Gehling's
reticulated saucer shaped macrofossils in the late Ediacaran of South Australia are most likely true
sponges (Gehling and Rigby, 1996), despite the lack of preserved spicules. Below is an electron
microscope photograph of a phosphatized casting of a large sand grain sized ancestral sponge called
Otavia antiqua found in Upper Tsumeb Group (Ediacaran, “Post Snowball Earth”, < 635Ma) aged
carbonate and siliciclastic sedimentary rocks from Namibia. This little metazoan probably ate algae
and bacteria. It has a similar colonial structure with filtration and output ports to modern sponges
(Brain et al., 2012). http://www.sajs.co.za/first-animals-ca-760-million-year-old-sponge-fossilsnamibia/brain-c-prave-anthony-hoffmann-karl-heinz-fallick-anthony-botha-andre-herd-donaldsturrock-craig Some of the sponge structures are shown on the right. The present biological division
for recognition of sponges is based entirely on whether they secrete siliceous skeletal material
(Siliceria, e.g. sponges) versus calcareous material (Calcarea, e.g. corals). Probably this makes sense to
sponge biologists like Dr. Henry Reiswig, but the Cambro-Ordovician fossil record contains much
hexactinellid spicule forms (think jacks shapes) parenchymalia principalia which are carbonate either
in their primary form or permineralization and preservation. This seems to be a biochemical detail to
me and would be like calling a clam with an aragonite shell one phylum and a leather clam with a
chitin shell a species in another phylum altogether. By Ordovician, sponges had diversified sufficiently
to become reef formers as opposed to solitary forms. Forming larger commensal structures (bigger
than a solitary cup or boot sponge) invites other animals, plants, bacteria and even diverts currents to
affect food supply much like coral reefs. They also serve to trap and bind sediment.
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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The generic anatomy of sponges is given below. Use the cartoon on the left to name particular
features in your specimens from Hecate Strait. Examine the living cartoon on the right to understand
how this is a colonial animal with differentiated cells that control the functions and structures. Also go
to Sally Leys website to see the Dye test and observe how exciting it is to watch a sponge eat and poop!
Hexactinellid sponge reefs are know from the Triassic and Jurassic margins of the Tethys and from
modern refugia on sediment-starved, high-latitude continental shelves in cold waters like Canada’s
West Coast, and more recently off Antarctica. Hexactinellid sponges are primitive sponges which filter
feed on dissolved organics and small bacteria, in contrast to most modern sponges which have well
developed cilia and feed on phytoplankton. The two dominant (abundant) species are Aphrocallistes
vastus (Cloud sponges, thin, fragile, transparent) and Heterochone calyx (Finger goblet, thicker, more
opaque). Both species are present in Georgia Strait, Haro Strait and the Saanich Inlet but only
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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Aphrocallistes is present in the bioherms (organic reef of mound-like form built by a variety of
marine invertebrates, including corals, echinoderms, gastropods, mollusks, and others) in Hecate
Strait. Other species like Ferrea occa while not so abundant are important as 1st colonizers and often
provide a better substrate for other species to nucleate upon. Sponges like the rosellid “boot sponges”,
e.g. Rhabdocarpus dawsoni are solitary, do not form reefs and just collapse to a mat of spicules when
they die. Examine the two sponge reef posters by Conway et. al. and the extant (modern) and fossil
organisms provided and perform the following tasks:
Heterochone calyx see video clips on link http://www.geog.uvic.ca/viwilds/ve-glassreefs.html for
equivalent sponge reefs (bioherms) in Georgia Strait between 90 and 270 m water depth. Deeper
facies are shown here. The photo on the right is Aphrocallistes vastus and in reality 4-5 X bigger than
the other sponge.
1. a) Draw and label Heterochone calyx (Finger Goblet or Chalice Sponge) labeling the filter feeding
inlet pores (see diagrams above), osculum (exit current port), wall structure & overall appearance
when held up to the light. (6) b) Explain how this organism maximizes its surface area to feed. In the
video clips above, how do you tell the difference between living & dead sponges? (2) (8 total)
2. a) Draw and label Aphrocallistes vastus (cloud sponge) labeling infiltration ports and osculum. (2)
b) How does this species maximize its surface area? (1) Carefully examine the structure of the inner
wall in the atrium/coel (body cavity of the colony). Take a fragment of this and one of Heterochone
calyx from the jars provided and draw and label this and describe how can you tell these 2 sponges
apart. (3) (6 points total).
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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3. Examine the side-scan sonar and reflection seismic images on the poster and compare the sidescan
image to the geological map. Note the rough, dark, reflective character of the glaciated seabed (linear
iceberg furrows) compared to the sponge mounds. a) Speculate on why these features are so nonreflective (acoustically transparent)? (Hint sound bounces or echoes off of hard surfaces which are
denser or have a faster speed of sound.) Assuming that the speed of sound in sea water is 1500 m/sec
and that the sound has to go both down from the sea surface and back up, how thick are the thickest
bioherms surveyed here? (3) Approximately how long did it take these bioherms to grow this large?
(1) (Hint: refer to your sea level and deglaciation history.) (4 total)
4. Are these bioherms comprised entirely of Hexactinellid spongess or is the ecology more complex?
(Review video link above). a) Discuss this and list evidence for other organisms. (2) b) Discuss how
well you think these bioherm communities would withstand bottom trawls or oil spills from diluted
bitumen from ruptured tankers and the Enbridge Pipeline? (2)
5. a) Speculate on how these animals could be responsible for trapping sediments (like carbonate
packstones, boundstones or bafflestones) or for growing high porosity reefs that might one day make
it into the geologic record. (2) b) Where else on the planet might bioherms like this occur, or where
might we go to explore for more of them? (2)
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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PART 2B: ANCIENT HEXATINELLID SPONGE REEFS AND OTHER FOSSILS
6. a) Examine, draw and label the sponge structures on the large flat fossil Hexactinosa from the
Yatova Formation in Eastern Spain and note the two species of ammonites found with it covering this
Tethyan sponge reef. (4)
7. a) Examine and draw the small (palm sized), thick microbolite encrusted Hexactinellids from the
Swabian Alb (this is an area located in Southern Germany). Be sure to label primary sponge anatomy
and distinguish this from the microbolite overgrowth texture. (Recall or refer back to microbolite mats
and photos in the Burgess lab.) (4) b) Note the overall thickness of the sponge reefs in the German
photos and comment on how they compare to those in Hecate Strait today. (2) (6 total)
8. Note from the map of the Tethys in Europe on the sponge reef poster, that all of the primitive sponge
bioherms occurred inside sediment-starved transform margins (no high mountain source areas). a)
Compare modern thicknesses in Hecate Strait Sponge Bioherms to those in the rock record from the
Oxfordian (Upper Jurassic) of Spain and Germany. (3) b) Speculate on sedimentation rates, longevity,
biological cycle, compaction effects and preservation. (5) c) What has happened to turn the European
sponges and reefs into rocks? (2) d) What are the replacive (diagenetic) minerals there compared to
the primary silica skeletons? What happened to turn these sponges into rocks? (3) (13 total)
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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9. a) Draw and compare the Oxfordian (Jurassic) coiled ammonites from Spain (Tethys) to the
Maastrichtian (Upper Cretaceous) Baculites (orthocone) from southern Alberta epicontinental
Cannonball Sea (these may be found in the hallway directly across from the Geoscience lab – see straight
horn ammonites aka Devil’s Walking Stick). (6) b) What has happened to this family of cephalopods in
the intervening 100 Ma? How can you tell their relative ages from their gross morphologies and
evolutionary changes? (3) (9 total)
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Geoscience 240 – Lab 8: Introduction to Facies Pleistocene Sea Level Changes in Hecate Strait and
Modern and Ancient Hexactinellid Sponge Reefs
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10. a) Draw and describe the Quartz-Crystal Fan (west cabinet in hall) which came from a mound
several meters high and many meters across in Namibia between the underlying Marinoan (Late
Proterozoic-Snowball Earth) glacial marine deposits and the overlying Cap Carbonates. (3) b) Also
examine the thin sections from this rock and from cnidaria in the sediment thin section box and
sketch and label any obvious biological structures. (3) c) The oldest known solitary sponge fossils are
40 Ma later than this “crystal fan”. Do you think this is a fossil “sponge” or not from your observations
and explain why? (2) d) Examine the modern boot sponge (Rhabdocalyptus dawsonii) and discuss
the relative merits of these more primitive forms for trapping sediment and building bioherm
structures compared to robust Hexactinellids (Precambrian to Recent). (2) (10 points total) Maiberg
Formation Ediacaran Carbonates with Aragonite Crystal Fans, Namibia photo by Marcus Kunzman and
(Pruss et al, 2008) Late Proterozoic Aragonite Crstal fans from the johnnie Formation Death Valley CA.
Modern boot sponge on right.
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