Mixed Siliciclastic/Carbonate Systems - Trace Fossils as Indicators of Sedimentary Environments - page 790

areas trace fossils are limited to Palaeophycus , Planolites , Psilonichnus , and
Teichichnus . Within the patch reefs, proper trace fossils are rare, possibly partly
because extensive recrystallization of reef facies may have obliterated trace fos-
sils that were present. However, in one of the patch reefs, bioclast-filled Plano-
lites , Thalassinoides , Skolithos , and Scolicia occur within fine-grained sand-
stone beds within intrareef cavities. Moreover, within the patch reefs occur
numerous hardgrounds, many of which are penetrated by small (0.5-4.0 mm
in diameter), simple tubular borings referred to as Trypanites .
3. TEMPORAL VARIABILITY (STRATIGRAPHIC MIXING)
Many mixed systems are produced by stratigraphic controls; changing relative
sea-level results in changes to sediment sources and concomitant changes in
preservation potential of sedimentary successions within a given area. Diage-
netic processes commonly operate at different scales and temporal intervals
in siliciclastics and carbonates, leading to fundamental differences in preserva-
tion and in substrate consistency. Carbonate systems, particularly those depos-
ited in tropical to subtropical settings, are prone to early cementation and thus
Trypanites assemblages commonly occur (i.e., Blanchon and Perry, 2004; Brett,
1995 ; Brett et al., 2010 ; Knaust et al., 2012; McLaughlin et al., 2008; Tapanila
et al., 2004; Webb, 1994 ). Glossifungites -demarcated discontinuity surfaces
are common in both carbonate and siliciclastics-dominated successions
(i.e., Brett et al., 2010 ; Gingras et al., 2001; Knaust, 2007; McLaughlin et al.,
2008; Rodr´guez-Tovar and Perez-Valera, 2008 ; Yang et al., 2009 ). Within
mixed systems, these substrate-controlled ichnofacies may become juxtaposed
and commonly occur at significant lithostratigraphic or sequence-stratigraphic
boundaries.
3.1 Chase Group (Early Permian), Oklahoma
The Early Permian Chase Group in northcentral Oklahoma, USA, consists of a
series of interstratified mixed siliciclastic/carbonate units interpreted to repre-
sent major transgressive and regressive events ( Chaplin, 1996, 2010 ; Fig. 4 ).
The regressive components consist of clastics-dominated marginal-marine suc-
cessions, mainly of red and green, pedogenically altered mudstone ( Chaplin,
1996, 2010 ). Transgressive components consist of marine and marginal-marine
bioclastic wackestone, packstone, and grainstone ( Chaplin, 1996, 2010 ). The
contact between regressive units and overlying transgressive units comprises
Glossifungites -demarcated discontinuity surfaces characterized by dense, hori-
zontal networks of Thalassinoides ( Fig. 5 B and C) as well as burrowing bivalves
( Pinna ; Fig. 5 A; Chaplin, 1996, 2010 ). Abundant, large Rhizocorallium domi-
nate the top surface of each carbonate succession ( Fig. 5 D and E) . Also present
are rarer Arenicolites , Chondrites , Diplocraterion , Planolites, and Teichichnus
( Chaplin, 1996 ). Although these surfaces represent hiatuses, they are interpreted