Tertiary tectonics of Svalbard

 

Harmon D. Maher Jr., Department of Geography and Geology, University of Nebraska at Omaha

harmon_maher@mail.unomaha.edu

 


Talk outline:


Talk objectives:


Highlights of geologic history:

(from most recent to oldest)

Isostatic response to glacial denudation (Blythe and Kleinsphen, 1998).

Quaternary basaltic volcanism in the northwest part of the islands.

Tertiary transtension, offshore basin and continental margin formation.

Tertiary transpression (65-38 Ma), polyphase development of variably decoupled transpressional welt, foreland basin development.

Late Cretaceous broad uplift and unconformity formation, related to the High Arctic LIP.

Stable platform cover sedimentation until Upper Cretaceous (circa 4-5 km thick).

Carboniferous rifting:

Local Serpukhovian folding and thrusting (Adriabukta event of Birkenmajer, 1981).

Late Devonian Svalbardian contractional phase (Lamar and others, 1986).

Devonian basin development > several kms deep (gravitational collapse basins?).

Basement geology highlights:


Description of Tertiary tectonics on a regional scale.

Three major components:

Fold-thrust belt components:


Debate on timing of fold-thrust development.

Manby and Lyberis in three different articles propose an Upper Cretaceous age, prior to the dextral separation of the Barents Shelf and Greenland. They also suggest a minimum of 80 km of shortening.

Evidence that major fold-thrust development is Tertiary (Maher & others, 1995):

My conclusions:


Plate tectonic setting during the Tertiary:

Basic two stage history:

Stage 1: circa 400 km dextral shear of Greenland and Barents Shelf for anomalies 24-13, some 60-37 Ma.

Stage 2: change in pole of rotation, transtension, formation of continental margin and development of oceanic crust between Greenland and the Barents Shelf.

Are more complicated scenarios, ones that even include minor sinistral movement. Below chart is from Skilbrei (1993). Main point is that fairly complicated history possible, but dextral transpression dominant.

 chron 34-31  84 - 69 Ma  170 km dextral and 20 km extension
 chron 31-25  69 - 59 Ma  35 km dextral and 12 km contraction
 chron 25-24  59 - 55 Ma  42 km of shortening and 16 km sinistral
 chron 24-21  55 - 49 Ma  220 km dextral, 40 km contraction
 chron 21-13   49 - 37 Ma  270 km dextral

Harland gave birth to concept of transpression for Caledonide structures, and Lowell applied it to the Tertiary fold-thrust belt in developing the original formulation of a a positive flower structure.


Description of major Tertiary tectonic elements.

Basement involved antiformal stack structures:

Thin-skinned foreland zone:

Billefjorden and Lomfjorden fault zones:

To the hinterland - Forlandsundet 'graben' and SEDL:

Overview of Tertiary kinematics:



Conclusions as to what influenced this particular case history.

Decoupling of orogen-parallel and perpendicular movements played a major role in this orogen. The pattern of decoupling evolved.

Weak surfaces played a major role in localizing detachments and orogen-parallel motions. Weak surfaces include stratigraphic horizons, basement faults, and structural zones that evolved in the Tertiary (possible foreland migration of orogen-parallel motions with time).

Reactivation and inversion of a Carboniferous rift basin localized antiformal stack, influenced along strike patterns and segmentation.

Foreland basin development played a role as it became a big piggy back basin, and acted as a competent unit forcing propagation underneath it.

Backthrusting and wedge insertion played a critical role in distinct portions of the orogen (Hauser).

This was a low strain rate orogen, manifest by cleavage duplexes, greater degree of basement involved folds, and fold duplexes, and perhaps a larger taper angle.


The end!