Presentations by Keck Geology Consortium at the 2019 Annual Meeting of the Geological Society of America
22-25 September 2019, Phoenix, Arizona
Sunday, 22 September 2019; 09:00 AM – 05:30 PM Phoenix Convention Center – Hall AB, North Building
Booth 223: TAPHONOMIC COMPARISON OF VERTEBRATE MICROFOSSIL BONEBEDS FROM THE UPPER CRETACEOUS JUDITH RIVER AND HELL CREEK FORMATIONS OF MONTANA Peter Zimmermann (Oberlin College), Asha Lang (Smith College), Gabriela Roat (Colorado College), Kaylee Velasquez (Union College), Sun Tun (Macalester College), Katherine Irving (Macalester College), Sedalia Gomez (Amherst College), Nolan Clark (Pomona College), Kristina Curry Rogers (Macalester College), Raymond Rogers (Macalester College)
Wednesday, 25 September 2019; 09:00 AM – 06:30 PM Phoenix Convention Center – Hall AB, North Building
Booth 210: CAPTURING A LATE CRETACEOUS PALEOFAUNA: A NEW VERTEBRATE MICROFOSSIL BONEBED IN THE UPPER CRETACEOUS (CAMPANIAN) JUDITH RIVER FORMATION, MONTANA Gabriela Roat (Colorado College), Sedalia Gomez (Amherst College), Sun Tun (Macalester College), Katherine Irving (Macalester College), Asha Lang (Smith College), Nolan Clark (Pomona College), Peter Zimmermann (Oberlin College), Kaylee Velasquez (Union College), Raymond Rogers (Macalester College), Kristina Curry Rogers (Macalester College)
The 2018 Keck Alaska field team was a marine-based project that involved considerable travel by boats in cold Alaskan water. What does this mean for participants of a Keck Project? For one thing it means long days on the cold water, and limited protection from the wind and waves. It also means wearing a pair of Xtra Tuff boots and Grundens. Nice warm weather with no waves is perfect and easy, but when the waves come up and the rain starts, one feels pretty exposed riding on these boats. We have quite a bit invested in a field excursion, so things need to get pretty bad before we take a day off.
Safety matters. We have several important safety features that are built into this field approach. Foremost among them is that we travel with two boats simultaneously, and we are always in radio contact. Working on the cold wet coast typically means that visibility is low. Several years ago we made hi-visibility rain gear required, because gear that is colored black, blue, and green is just too difficult to spot on the boat or on the shoreline. Thus if you were wondering why all participants in the 2018 Keck Alaska project are so brightly colored – it’s for safety. And it works.
We travel long distances using the Zodiac boats, and this field season daily travel between 20 and 50 miles was typical. For the first part of the field season we were moored every evening in the Valdez marina, and almost all outcrops we were working on were at least 6-10 miles out. So daily we did the long run down Valdez Arm, and then we started working on outcrops. We stood out in the Valdez marina because most of the other boats were significantly larger. For the second part of the field season we were based in the remote Unakwick Inlet, and long inlet in northern Prince William Sound, and here our biggest daily challenge was getting to and from the boats with a 12-15 ft tidal range.
Oil and ice don’t mix. The 2018 Keck Alaska field season involved the analysis of rocks in Prince William Sound, in south central Alaska. The first part of our field season was in the Valdez area, and it included rocks in northeastern Prince William Sound, so we were boating daily out of the Port of Valdez – and we typically needed to run the six miles of Valdez Arm to Valdez Narrows before we got to our target rocks. This is complicated choppy water that has special hazards, and distinct tragic history.
The Valdez area is unique for two reasons. One is that Valdez is the terminus of the Alaska Pipeline, which carries oil from the North Slope. Where the pipeline ends, tens of massive on land tanks hold arriving oil for the large double-hulled ocean tankers that make daily runs to deliver this oil to refineries to the south.
These tankers have tug escorts, so the boating activity of a single arrival or departure is a significant event, especially if your perspective is from a 15 ft Zodiac. We used radios to monitor boat traffic and we learned to stay well clear of the tankers. No matter what, these huge boats made us nervous.
The other reason that this area is distinct is that sometimes things don’t go right with the tankers. In 1989 the Exxon Valdez left Valdez arm, turned the corner, and ran aground on Bligh Reef, an exposed shoal made of the Orca Group. The collision resulted in an oil spill of 11 million gallons of crude oil that had a long residence time in the cold pristine waters of Prince William Sound.
This historically has been the largest oil spill in US history, but the 2010 Deepwater horizon has since taken top spot for oil spill disasters in the US. In the Exxon Valdez disaster, over 1300 miles of coastline were oiled, and despite attempts to clean up the oil, it persisted for decades. Part of the issue is that oil takes a long time to break down in cold water.
In our fieldwork we commonly encountered oiled outcrops in our sampling: a sad sight and a reminder of a past ecological disaster that still haunts us. Below is an image of sandstone of the Orca Group with blobs of oil from 1989.
Part of the 2018 Keck Alaska project is focused on understanding the tectonic evolution of the Upper Cretaceous Valdez Group in Prince William Sound, which is part of the Chugach terrane. This unit is typically viewed as a Mesozoic-Tertiary accretionary complex that is well exposed for ~2200 km in southern Alaska and is inferred to be one of the thickest accretionary complexes in the world. The Chugach flysch is mainly comprised of younger deep-water turbidites with sparse fossil localities that indicate Campanian to Maastrichtian deposition. Work this year by Nicholas Gross Almonte (Carleton College) will focus on using U/Pb dating of detrital zircon to better understand that age of deposition and provenance of this important unit in southern Alaska.
