Leinstranda

Wednesday, July 23rd.  Today, we sailed to Leinstranda.  My group is the reporting group for today.

Leinstranda is tucked away behind the northern tip of Prins Karls Forlund.  This locality keeps it in a inter-fjord area, meaning that Leinstranda did not directly interact with any major ice streams, which Kongsfjordhallet and St. Jonsfjorden certainly did.  Leinstranda was our first "protected" area.  

If you've had sedimentology, or even just physical, you know that geologists have many different descriptors for lithologic units.  Diamicton is one of those terms, and it includes all manner of unsorted, different sized, varying lithology sediment within a mud or otherwise fine grained matrix.

So.  Glacial fun fact.  When a glacier grounds into the sea floor, we can directly evidence its grounding position by locating a till.  Till is diamicton that is deposited directly by glacial activity.  That is what separates it from diamicton.  

Witness my first ever till!

Here, Kaleb explains what group 2 noticed in their findings.  Boulder sized particles, red till.  We generally differentiate till from diamicton by the presence of striated clasts.  Striations typically form as a direct result of a big, weighty glacier sitting on top of a rock, scratching the crap out of it.  Here's a better look at the till (Unit 2b), underlain by a diamicton (Unit 2a), and overlain by glaciomarine mud (dark brown, unlabeled).  Unit 1 is the continuation of a sandy unit that group 3 discovered.

Much thanks to Kaleb for annotating this image!

Anyways, TILL!  I've read about them many times, but this was my first up close encounter.

More things besides till happened -- here's a quick overshot of where we were sectioning:

 

 

 We go pretty much in a diagonal -- group 1 at the top NW, then group 2 in the center, group 3 more easterly (I demand that this is a word!), easily identified by Liz's green jacket. 

My group was in charge of sectioning the sand deposits.

  

Jon is cleaning the "party" layer.  Here's an up close shot:

 

We think this bedding looks heterolithic -- wavy, to be specific.  Wavy bedding consists of alternating sand and mud (or clay) layers, and generally occurs in tidally influenced areas.  After this layer, we had the "business" layer, so called because it had less cool structures.

Cool structures like this sediment deformation!

 

Very cool stuff -- we're looking at the continued retreat of one of the glaciers -- there were at least three acting on the area during the pullback.  Just one remains visible now:

 

We ended the day with jumping shots, which I forgot to be in because I was busy taking them.

Group 1!  Iceland, Denmark, Norway, and the American behind the camera.