Large igneous provinces and explosive basaltic volcanism - Volcanism and Global Environmental Change - page 6

site. Epiclastic (or volcanogenic) sediments are formed from weathering and
erosion of volcanic rocks, including previously lithi ed volcaniclastic rocks.

Lithi cation can occur as part of volcanic emplacement (e.g. welding) or as a

secondary process of cementation or compaction.

1.3 Spatial and temporal occurrence of mafic volcaniclastic deposits
One of the strengths of ma c volcaniclastic deposits is in the record they preserve

of tectono-volcanic facies and province architecture evolution over time. The recog-
nition that pre-volcanic kilometer-scale doming is not an unequivocal feature of
large igneous provinces, coupled with recent numerical modeling indicating that
large igneous province emplacement can generate substantial and complex patterns
of pre- and syn-volcanic subsidence and/or uplift ( þ / hundreds to thousands

of meters: e.g. Czamanske et al ., 1998 ; Ukstins Peate and Elkins-Tanton, 2009 ;
Elkins-Tanton and Ukstins Peate, 2010 ;Sobolev et al ., 2011 ), suggests that
tectonic evolution may be a signi

-

cant factor controlling the broad-scale distribution
of these deposits. Provinces that contain signi cant volcaniclastics include the

middle-Jurassic Kirkpatrick section of the Ferrar flood basalts in Antarctica, with

tuff-breccias up to 400 m thick (Elliot and Flemming, 2008 ); the Kachchh region in
the northwest of the Deccan flood basalts, with lapilli and lithic blocks (Kshirsagar

et al ., 2011 ); and the Karoo (McClintock et al ., 2008 ). Here, we brie y describe

three additional signi cant examples: the North Atlantic, the Emeishan and

the Siberian.

1.3.1 East Greenland, North Atlantic Igneous Province
Detailed volcanostratigraphic studies in East Greenland illustrate a cyclicity
of phreatomagmatism and subsidence during the initial stages of province
emplacement, recording three phases of subaqueous to subaerial volcanism, with
progressively less hydrovolcanic in

uence (and inferred downdropping) in each
cycle ( Figure 1.1 ; Ukstins Peate et al ., 2003 ). Initiation of volcanism is represented
by subaerially deposited phreatomagmatic lapilli-tuffs with accretionary lapilli
and abundant quartz and feldspar grains ( ~ 50%) sourced from underlying upper

shoreface sandstones and mid-Paleocene fluvial clastic deposits (Larsen et al ., 2003 ).

Overlying these are a series of hyaloclastites and pillow lavas, some forming foreset-
bedded units > 300 m thick (Nielsen et al ., 1981 ), suggesting that water depth
increased dramatically with the initiation of basaltic volcanism. Hydromagmatic
deposits transition to 500 m of compound lava flows, and the entire volcanic

succession forms a shield-like structure with a diameter of ~ 40 km (Ukstins Peate

et al ., 2003 ). This is, in turn, overlain by a sequence of ma c volcaniclastic deposits